Vol. XV No.2                                                                                                 JULY 1997

Scientific Journal of

MEDICAL & VISION RESEARCH FOUNDATIONS

18, COLLEGE ROAD, CHENNAI - 600 006, INDIA

Editorial

Perspective — Therapeutic Contact Lenses — Dr Ravindranath Shenoy U and Jothi Balaji

Perspective — Complications of Local Anaesthesia — Dr. Bhanulakshmi Indermohan and
Dr. Ian Sundaraj

Clinical and Biochemical Heterogeneity in Gyrate Atrophy of the Choroid and Retina and
Possible Role of Polyamines — Dr K N Sulochana, Dr S Ramakrishnan, Dr Lakshmi Mahesh, V. Bhooma and R. Punitham

Medulloepithelia Masquerading as Congenital Glaucoma -
Report of A Case with Review of Literature — Dr Jyotirmay Biswas, Dr Rajesh Fogla and
Dr Mahesh P Shanmugam

Model Eye for Nd YAG Laser Capsulotomy — Dr Rajesh Fogla and Dr Srinivas K Rao

Last Page — Correction of Astigmatism using the Excimer Laser — Dr Srinivas K Rao

 
          

Gross photograph of the globe showing corneal oedema, multiple ciliary staphylomas.

            Showing the globe filled with the tumour arising from the ciliary body causing multiple ciliary staphyloma.  Note secondary retinal detachment behind the mass (haaematoxylin and eosin, X 1)

 

Editorial

Ophthalmology has shown the way research should be conducted in the field of medicine, by devising classical case control, randomized studies, such as the Early treatment of diabetic retinopathy study, Diabetic retinopathy study, and the Macular Photocoagulation study. Most of these multicenter studies have originated from the United States. These studies are funded and colloborated by the National Eye Institute, part of the National Institutes of Health, Maryland. We had the opportunity to hear it’s director Dr.Karl Kupfer address crucial issues such as prevention of cataract blindness in the developing countries and conducting research projects. Excerpts from his speech, appear in this editorial as they concern all of us, the ophthalmologists.

As per Dr.Kupfer, the backlog of cataracts in our country, exists due to (i) underutilisation of man power. If 50% of the ophthalmologists were to operate on 1000 cases a year, we should be able to wipe out the cataract backlog. (ii) Underutilisation of hospital resources due to lack of incentives is another reason cited by Dr.Kupfer. Better maintenance of hospital and infrastructure with appropriate incentives to personal will go a long way in increasing the number of cataract surgeries done. (iii)Need for better management. Medical staff are not trained to perform managerial functions. Trained managers capable of setting up and running cataract programs can achieve targets better.

 

Currently the number of cataract surgeries performed in any cataract program is the measure of it’s success. More important than the number of surgeries is the surgical outcome- the number of persons successfully rehabilitated after surgery. This should be the aim of any blindness prevention program. The emphasis on the type of surgery - ICCE / ECCE + IOL is misplaced. Whatever may be the type of surgery, doing it well is all that matters ultimately - as this is what decides if the patient is going to see or not.

Cataract patients should be diagnosed and operated upon at a younger age, according to Dr. Kupfer. This would mean that we take care of the patient before he really goes blind and the patient is of the age when he can still be gainfully employed. This would also reflect in his paying for his surgery thereby making the program cost effective.

Dr. Kupfer also elaborated on the way clinical studies should be conducted. Any study before beginning, should be assessed if it will yield an informative answer, an answer capable of dispelling uncertainty about the statement in question. For a study to do this, it should be a case control, randomised study conducted ethically, avoiding bias.

Dr. Kupfer has said what we already know - but seldom practise. Simple lessons that have been reemphasised.

                           Dr Mahesh P Shanmugam                                                          Editor

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Perspective:
Therapeutic Contact Lenses

Ravindranath Shenoy U M.S., Jothi Balaji, Dip. Opt.
Therapeutic contact lenses are used in the management of the diseased or post surgical cornea. Due to the advent of contact lens technology, new materials have been developed thus covering not only the correction of optical errors but also for a variety of therapeutic purposes.1,2

In general, therapeutic contact lenses are used to

1.Facilitate wound healing

2. Provide mechanical support to the corneal surface

3. Reduce dis comfort from corneal surface abnormalities.

4. Help to maintain proper surface hydration

5. deliver medications to the cornea.

The appropriate use of a contact lens for therapeutic purposes requires a clear understanding of the therapeutic goal as well as the physiologic changes induced by the placement of a bandage lens on the corneal surface.

With this knowledge the ophthalmologist can successfully utilize bandage lenses as an important therapeutic adjunct.

HISTORY:

In 1969, Ridley1,2 used rigid polymethyl methacrylate scleral lenses to treat bullous keratopathy.

In 1970, Gasset, Kaufman, Gould1,2 used successfully therapeutic soft contact lenses in a variety of corneal disorders.

Since then advancements in lens material, production and fitting techniques have expanded the applicability of

therapeutic soft contact lenses.

LENS PARAMETERS:

Therapeutic lenses may be fabricated from hydrogels, silicone or collagen. Most lenses are hydrogels that consist of a acrylic polymer matrix and an aqueous component. Initially hydroxy ethyl methacrylate (HEMA) was the hydrogel material used for therapeutic lenses.

More recently other polymers like poly HEMA, vinyl pyrrolidone, polymethyl methacrylate, glyceryl methacrylate and diacetone anylamide are being used. In most of the cases, BCL is of plano power2.

TYPES OF LENSES:

1. thick, high water content lenses

2. intermediate thickness & moderate water content lenses

3. ultrathin or membrane lenses

Depending on the clinical state, a loosely fit, high water content lens or snug ultra thin lens can be used. Recently silicone rubber has been utilized for the manufacture of therapeutic contact lenses. Silicone is highly oxygen permeable and thin. But it is hydrophobic, tends to form protein and mucous deposits, absorbs lipids such as meibomian secretions and may tighten with continuous wear.

LENS SELECTION, FITTING AND MANAGEMENT:

SELECTION:

1. For support - high water content
(descemetocoele) lens

2. Epithelial defect - low water content (in a relatively lens
dry eye)

3. Minimal lens - low water content
movement is lens
desired

4. Co-existent - high water content
corneal or lens
anterior segment
inflammation

5. Aphakic and - high water content
pseudophakic lens
bullous
keratopathy
(to prevent
epithelial
micro trauma)

FITTING:

Base curve and diameter are important considerations in fitting the lens, since they help to determine centration, movement and tear exchange2.

Since keratometry may not be possible or may give irregular mires in diseased cornea, trial fitting is most appropriate. Lens fit should be examined initially, 60 min. later (as fit may be altered with a change in hydration) and after 24 hours1.

Flared edges may cause discomfort, while adherent edges may indicate a tight lens. A BCL should undergo 1 mm excursion with blinking to allow tear exchange and clearance of debris. Thin membrane type lenses may move less than 1mm and still fit well1,2.


FLAT FIT:

Achieved by : Decreasing the diameter
                      of the lens or increasing
                      the radius of curvature.

Results in : More lens movement,
                    Higher oxygen delivery.
                    Increased tear exchange
                    under the lens

STEEP FIT

Achieved by : Increasing the diameter
                        or decreasing the radius
                        of curvature.

Results in : Lesser lens movement,
                    Better centration
                    Greater lens stability
                    Minimal deformation of
                    the apex of the lens with
                    blinking.

EXTREME : Early decentration.
FLAT FIT Lagging with blinking or
                    gaze.

EXTREME : Blanching of the limbal
STEEP FIT vessels
                      Air bubble is trapped                                                 underneath                                                                Redness and discomfort                                             Cannot be moved with finger pressure.

Both these extreme fits should be avoided. A minimum change of 0.3 mm in base curve or 0.5 mm in diameter is required to significantly flatten or steepen a lens1,2.

AFTER CARE:

There is an increased risk of microbial keratitis with the use of BCL. Some authors advocate the use of prophylactic broad spectrum antibiotic when the lens is in place, others recommend the use of antibiotics to be limited to cases with epithelial defect and dry eye fitted with BCL. However using an antibiotic appears to be a prudent safeguard3,4.

Topical medications like phenylephrine can cause lens damage and discolouration. Fluorescein and rose bengal should not be used in eyes with BCL.

Hypertonic medications (sodium chloride) cause dehydration and a steep fit. Medications formulated as suspensions may lead to discomfort, build up of particulate matter and lens intolerance. Medications formulated as gels or oils may cause lens deposits.

Coexistent ocular conditions should be treated in order to optimize the environment of the bandage lens and achieve the therapeutic goal.

The BCL has to be removed cleaned and disinfected every month. It has be replaced every 3 months.

INDICATIONS:

1. Recurrent Corneal Erosions: It is seen in corneal epithelial dystrophies, diabetes mellitus, cystinosis, post traumatic cornea. The BCL provides a mechanical protective effect shielding the epithelium and corneal nerves from the shearing action of the lids. They also facilitate reestablishment of basement membrane complexes with concomitant healing and firm attachment of the epithelium1,5

BCL is used depending on

- the severity of the symptoms

- the failure of other measures

- the chronicity of the disease

2. Filamentary Keratitis: It is encountered in patients with keratitis sicca, recurrent erosions, prolonged patching, neurotrophic or neuroparalytic keratitis, ptosis, topical medication toxicity, herpes simplex keratitis, superior limbic kerato conjunctivitis or following penetrating keratoplasty. In recurrent or refractory filamentary keratitis BCL is an effective mode of treatment1,5

3. Thygeson's Superficial Punctate Keratitis: It is a lesion of unknown cause characterised by recurrent episodes of fine corneal epithelial lesions. BCL can provide symptomatic relief and promote healing, without protracting the length of the disease.

4. Epithelial Disorders Secondary to Endothelial Failure: Pain from epithelial breakdown is a prominent symptom in these patients and may become disabling. Other symptoms include glare, blepharospasm, lacrimation and photophobia. Causes include Fuch’s endothelial dystrophy, aphakic or pseudophakic bullous keratopathy etc. BCL helps to maintain epithelial integrity, flatten the bullae and protects the epithelium and corneal plexus of nerves from the shearing action of the lids. It has a dehydrating effect on the epithelium. Patients with bullous keratopathy fit with BCL are prone to complications and require close follow up1,5.

5. Persistent Epithelial Defects: Bandage contact lenses are often an effective alternative to other treatment modalities to promote epithelial healing, stop progressive stromal thinning and promote stromal healing.

In exposure keratitis and neurotrophic keratitis tarsorrhaphy is the ideal treatment. In an one eyed patient, BCL can be considered as an alternative.

6. Trophic Ulcers (Herpes simplex and Herpes zoster): When the epithelial

basement membrane is damaged by recurrent infection and ulceration, a persistent epithelial defect may result. In these cases in trophic ulcers secondary to corneal anaesthesia resulting in epithelial breakdown as in herper zoster, BCL helps in promoting the healing.

7. Chemical Injury: BCL helps in promoting epithelialization and protects the corneal surface, thus preventing collagenolytic activity with progressive stromal ulceration. It is an adjunct in the management of chemical injuries.

8. Corneal Perforation and Descmetocoele: A BCL alone or preferably with cyanoacrylate adhesive can be used to support weakened and thinned (descemetocoele) or perforated ( upto 2 mm) areas of the cornea and prevent the need for immediate grafting. Stromal healing is thus facilitated.

9. Peripheral Corneal Ulceration: Seen in immune mediated disorders and often are sterile. Thinning or perforation associated with these disorders requires BCL wear with cyanoacrylate glue.

10. Superior Limbic Kerato Conjunctivitis: It is associated with hyperaemia and papillary hypertrophy of the upper palpebral conjunctiva, inflammation and thickening of upper bulbar conjunctiva, keratitis and micropannus involving the superior third of the cornea. BCL can be very effective in this disorder along with other measures6.

11. Ocular Cicatricial Disorders: Role of BCL in these disorders is highly controversial. Patients with these disorders are at increased risk for infection and close observation is required. It can be used as a desperate measure to promote epithelialization in the face of persistent epithelial defects. Kaufman7 advocates the use of BCL to separate the bulbar and palpebral conjunctiva in order to prevent

symblepharon and other cicatrices.

12. Lid Abnormalities: In trichiasis, distichiasis and entropion, BCL may act as a temporary physical barrier protecting the already compromised corneal surface from these mechanical forces until lid abnormalities are corrected.

13. Post Surgical: BCL can be used after kerato refractive surgery like LASIK, after certain surgical procedures like vitreoretinal surgery which requires epithelial removal, for intra operative corneal protection during oculoplastic procedures. There are reports regarding use of large diameter BCL for shallow anterior chamber and leaking filtration bleb following trabeculectomy8.

14. DrugDelivery: BCL or collagen shields soaked in medication and then placed on the cornea produce very high ocular levels 9.

COMPLICATIONS:

It is important to differentiate lens - induced complications from the course of the base line disease.

1. Sterile Infiltrate and Hypopyon: It is due to mechanical micro trauma, hypoxia or an excessively tight lens. In all the cases infective etiology should be ruled out by micro biological investigations. BCL discontinuation, cycloplegics help resolve this problem.

2. Infectious Keratitis: The compromised nature of the cornea requiring BCL, microtrauma, anoxia contribute to the infection. In most of the cases it is due to gram positive bacteria3,10.

3. Corneal Edema: BCL can cause intracellular epithelial edema as a result of hypoxia and toxic endothelial dysfunction due to lactate accumulation. Extended wear of BCL can cause morphologic changes in the epithelium. In these cases alteration of the lens fit is indicated.  

   
4. Corneal Neovascularization: It is due to hypoxia and microtrauma. BCL wear can lead to superficial as well as deep stromal neovascularization. It regresses with cessation of lens wear.

5. Giant Papillary Conjunctivitis: It is associated with lens deposits and may lead to lens intolerance. Use of high water content BCL, more frequent lens removal with cleaning, frequent replacement, altering the lens fit, use of antiallergy medications are indicated.

6. Lens Deposits: These deposits which consist of lipid, calcium, protein, lysozyme. They form spots or sheets of gray or white material and may lead to irritation, conjuctival congestion and lens intolerance. They are common in patients with dry eye and blepharitis. Enzymatic cleaning or in some cases replacement is required.

7. Tight Lens Syndrome: Patient presents with acute, morning onset of pain, photophobia, decreased vision and lacrimation. A tight lens with no movements, conjunctival congestion and edema, an imprint ring on the perilimbal conjunctiva is seen.11

Guidelines before using a BCL:

1. Avoid BCL in a case of infection and dry eye.

2. Give importance to water content of the lens and the lens fit as per the requirement of the pathology for which it is indicated.

3. Any infiltrate or hypopyon following BCL wear, unless proved otherwise, should be considered as infective.

4. Cleaning and disinfection of the lens should be done atleast once in a month.

5. Do not allow the same lens in place for more than 3 months.

6. Donot use phenylephrine, fluorescein, rosebengal, hypertonic saline, suspensions, and gels when the BCL is in place.

7. It is preferable to use a broad spectrum prophylactic antibiotic.

8. Explain the side effects of BCL wear to the patient and to report if any of them occur. Frequent follow up is absolutely necessary.

9. After fitting a BCL, look for proper fit after 1 hr and 24 hrs.

REFERENCES:

1. Smolin G, Thoft RA, Therapeutic contact lenses, The cornea, Scientific foundations and clinical practice, Third edition, New York Little, Brown and company 1994, 723 - 737.

2. McDermott ML, et al, Therapeutic uses of contact lenes, Surv. Ophthalmol,33(5):381-94, 1989.

3. Ormerod LD, smith RE, Contact lens associated microbial keratitis Arch ophthalmol, 104: 79, 1986.

4. Binder PS, Worthen DM, A continous wear hydrophilic lens. Prophylatic topical antibiotics Arch Ophthalmol, 94, 2109, 1976.

5. Smiddy WE et al, Therapeutic contact lenses, Ophthalmology, 97 (3): 291 - 5, 1990.

6. Mondino BJ et al, Use of pressure patching and soft contact lenses in superior limbic kerato conjunctivitis, Arch ophthalmol, 100 (12). 1932 - 4, 1982.

7. Kaufman HE, Thoma EL, Prevention and treatment of symblepharon, Am J ophthalmol 88: 419, 1979.

8. Blok MD et al, Use of the megasoft bandage lens for treatment of complications following trabeculectomy. Am J ophthalmol, 110 (3): 264 - 8, 1990.

9. O’ Brien et al, Use of collagen shields versus soft contact lenses to enhance penetration of topical tobramycin. J Cataract Refract Surg. 14 (5): 505 - 7, 1988.

10. Schein OD et al, Microbiology of contact lens related keratitis, Cornea, 8 (4), 281 - 5, 1989.                           11. Bonchard CS, Lemp MA, Tight lens syndrome - a case report. CLAO J, 17 (2), 141 - 2 1991.

 Perspective:
Complications of Local Anaesthesia

Dr. Bhanulakshmi Indermohan and Dr. Ian Sundaraj

 
Ninety percent of all Ophthalmic surgeries can be done under local anaesthesia. Patients who would otherwise be a poor risk for general anaesthesia can be operated under regional anaesthesia with minimal intra or postoperative complications. The added advantage of having a conscious patient who can communicate his problems, should any arise during surgery, so that early recognition and treatment can be instituted in time, need not be over emphasized.

The technique of administering a painless perfect block with prolonged analgesia is truly an art that every Anesthesiologist and Ophthalmic surgeon must learn. For this, knowledge not only of local anaesthetic technique but also the anatomy of the orbit, pharmocology and the complications of local anaesthetic drugs and the management of complications is a must.

Complications can be due to the following:

1. Local anaesthetic drugs:

a. Overdose - eg. Xylocaine more than 7 mg/kg body weight

b. Toxicity

c. Tachyphylaxis.

2. Added Preservatives (Allergy)

a. Methyl paraben, Proparaben

b. Sodium metabisulfite. (allergic esp. in asthmatics, Also thought to be neurotoxic)

3. Drugs added

a. To potentiate action - Adrenaline

b. To facilitate its spread / penetration - Hyaluronidase

I LOCAL COMPLICATIONS: -

May occur due to :-

Faulty technique of administration which can result in:

1. Subconjunctival Edema: Chemosis due to large volume of local anaesthetic drug.

2. Bruising (Ecchymosis)1, Skin Bruising: This can be minimised by using blunt needles instead of sharp needles, short instead of long needles.

3. Retrobulbar Hemorrhage:2

Increased bleeding tendencies which can lead to RBH may be due to:-

a. Vascular or hematological disease - purpura, hemophilia

b. Fragile veins - very old patients

c. Preoperative drug therapy: aspirin, NSAIDS, anticoagulants, steroids.

RBH is manifest by increasing proptosis with tight eyelids, subconjunctival and periorbital hemorrhage3. Increase in the intraorbital and intraocular pressure may lead to retinal artery occlusion4. RBH may also initiate an oculo - cardiac reflex5 which is the most common complication of a retro-bulbar block.

Early recognition of RBH is important in the management. Tamponading the vessels with pressure may help stop the hemorrhage. Surgery however has to be deferred by at least a week. Painful proptosis with sudden rise in intraoribital pressure needs decompression which is achieved quickly by a lateral canthotomy.

 

Proptosis, visual acuity, pupils, pain, intraocular pressure and the arterial patency needs to be monitored in the acute phase of severe orbital hemorrhage.6

4. Globe Penetration:

a. Insertion of needle (penetration) or through the globe (perforation)7 are rare complications which are likely to occur in myopic eyes which are longer and more elongated. Globes longer than 26 mm are particularly at risk. Patients who are more prone to this complication are those who come for retinal detachment surgery or radial keratotomy - as both groups of patients are likely to be myopes8.

b. Poor patient co-operation, jerky movements of head, involuntary movements of eye, face or head can also cause globe penetration.

Poor patient co-operation may be due to :

a. Extremes of age: children and elderly patients

b. Language barrier

c. Hearing disorders

d. Mental deficiencies

e. Low pain tolerance

f. Fear

g. Involuntary movements

h. Uncontrolled cough

Simple measures like the proper positioning of arthritic patients, pre-warming local anesthetics to near body temperature and the use of topical anesthesia prior to injections may be beneficial.

Management of intraocular perforation9 :

Most of the cases of accidental perforation are likely to be recognised immediately. If recognised the surgeon should abort the intended surgery and seek

the help of a vitreoretinal surgeon in the management.

With rest, the vitreous hemorrhage may settle down permitting laser photo-coagulation of the retinal breaks in the absence of retinal detachment. If the hemorrhage does not resolve within 7 to 10 days vitrectomy combined with intraoperative treatment of breaks is advocated. Untreated, retinal detachment is likely. Surgery may include lensectomy in phakic eye and total vitrectomy with base excision and membrane peeling. Retinal breaks require laser or cryopexy. Internal tamponade with air or silicone oil may be required, depending upon severity of intraocular damage.10

5. Puncture or Penetration of Optic Nerve Sheath: Spread of local anaesthetic drug through the subarchnoid space to the medullary centres of the brain produces brain stem anaesthesia11, producing signs which vary from mild confusion to marked shivering12 or convulsions, bilateral brain stem nerve palsies13 (including motor nerve blockade of the contralateral orbit with amaurosis14) or hemiplegia, paraplegia or quadriplegia with or without loss of consciousness to apnea15 with cardiovascular instability.

6. Facial Nerve Block: If the main trunk of the facial nerve is blocked at its exit from the stylomastoid foramen it can lead to hemifacial palsy and or dysphagia (temporary) or respiratory difficulty. There are five reports of facial nerve palsy following local anaesthetic block.16 Four patients who had injection in the area of the main trunk and one blocked by O'Brien method, anterior to the tragus of ear.

7. Myotoxicity:17 Extraocular muscle palsies occur causing ptosis or temporary diplopia. High concentration of local anaesthetics are known to cause myotoxicity. Direct injection into the muscle may be another cause.

II SYSTEMIC COMPLICATIONS:

May occur due to:-

Local Anaesthetic toxicity which can result from:-

a. Overdose

b. Intravascular injection

c. Allergy due to the drug or its preservative

d. Following injection of local anaesthetic into the CSF through the cuff of dura around the optic nerve with subsequent brain stem anaesthesia by retrograde spread.

Systemic toxicity is related to the venous blood concentration of the anaesthetic measured from peripheral venous blood which may be lower than the effective concentration to the heart or brain because of the first pass extraction of anaesthetic in the lung.18

SIGNS AND SYMPTOMS:

1. Circum-oral or tongue numbness.

2. Light headedness, delirium or tinnitus.

3. Muscular twitching

4. Signs of visual distrubances (nystagmus) diplopia, extraocular paresis, amaurosis.

5. Nausea, vomiting, dysphagia

6. Bradycardia, hypotension, arrhythmias (Torsade de pointes), especially with Bupivacane (Marcaine)19 which has profound adverse effects on the heart. Resuscitation is then difficult.

7. Respiratory depression - respiratory arrest20,21 occurs at almost twice the concentration required to produce unconsciousness.

8. Convulsions22

9. Unconsciousness

TREATMENT:

In the event of systemic toxicity, the

following measures should be instituted immediately.

1. Ventilatory support with oxygen - Ambu bag, Boyle's Anaesthetic apparatus or Ventilator.

2. I.V. Line should be started with an I.V. Cannula - eg Venflon, (18G/20 G) and run fast ; Ringer lactate if blood pressure is low.

3. Inject through the cannula:

i. Thiopentone (50-100 mg), Diazepam (5-10 mg) or Midazolam (1-2 mg) if convulsions are present. Short acting muscle relaxant - Scoline (1-2 mg/kg)- to secure the airway by endotracheal intubation.

ii. Vasopressor, adrenergic drugs - Mephentine, Ephedrine, Adrenaline and Steroids - Betnesol, Efcorlin if hypotension is present. Pharmacologic circulatory support is indicated only when required.

MONITORING:

a. Monitor blood pressure, pulse rate

b. ECG: Monitor ECG - for rate, rhythm, arrhythmias, ST -T changes.

c. Pulse oximetry (arterial oxygen saturation):23 Monitor SaO2, Ventilate the patient if SaO2 is low (below 90%) - if no improvement, intubate the patient and ventilate with 100% oxygen.

Minimising the toxic effects of local anaesthetics24,25

The toxic effects of local anaesthetics can be reduced by minimising the blood concentration of the drug.

1. Slow -     low volume at the rate of

injection18   1 ml per 10 second. Inject

                    local anaesthetic in divided

                   doses as in parabulbar

                   anaesthesia.

2. Low :  Use O.5 percent for infiltration.

concentration

                                10ml of 2% local                                                          anaesthetic (Xylocaine)                                                     will contain - 200 mg                                                     of Xylocaine (Approx:                                                   Max: dose for adults)                                                        40 ml of 0.5%                      Xylocaine will contain

200 mg of xylocaine.

                         Hence a larger volume                            can be used.

3. Mix different local anaesthetic drugs to reduce the toxicity.25

By mixing 0.5% Xylocaine and 2% Marcaine - Xylocaine hastens the onset of the block and Marcaine prolongs the duration of the block.

4. Reduce the rate of absorption. Also increases the duration of the block.

Adding adrenaline to the local anaesthetic produces vasoconstriction and decreases the rate of absorption from the injected site and the blood concentration is reduced and therefore may decrease the danger of toxic systemic reactions.

5. Increase the threshold for local anaesthetic drugs: Diazepam as premedication increases the threshold for local anaesthethic toxicity.

Don's and dont's of ophthalmic regional anaesthesia:26

DO'S

1. Use primary gaze postion, or consider ' down and out ' or 'down and in'

2. Use a precision technique based on sound anatomical knowledge

3. Measure axial length (thinner sclera with long ovoid myopic eyes)

4. Take extra caution in patients known to have staphyloma, coloboma or scleral buckle.

5. Align needles tangentially to the globe for all injections.

6. Use avascular injection sites

7. Use fine sharp needles in combination with good anatomic knowledge for better tactile discrimination, patient comfort and a lower incidence of tissue trauma and haemorrhage.

8. Avoid extraocular muscles.

9. Use a well-thought out technique, volume and concentration of chosen anaesthetic agent.

10. Maintain verbal contact with the patient.

DONT'S

1. Use the 'up and in' globe position for inferotemporal intraconal blocking

2. Attempt without anatomical knowledge

3. Fail to check axial length

4. Fail to check for globe anomalies or previous surgical intervention

5. Inject with other than tangential alignment to the globe

6. Inject at the orbital apex using long needles

7. Use dull coarse needles

8. Inject into extraocular muscles

9. Use unnecessarily high concentrations of anaesthetic agents.

REFERENCES:

1. Wallace RB, in Maskets (ed) consultation section. J Cataract Retract Surg.; 16:766 -74, 1990.

2. Edge, Nicoll JMV Retrobulbar hemorrhage following 12,500 retrobulbar blocks. Anaesthesia Analgesia; 76: 1091, 1993.

3. Feibel RM, Current concepts in retrobulbar anaesthesia. Surv, ophthalmol ; 30:102-10, 1985.

4. Kraushar MF, Seelenfreund MH, Freilich DB. Central Retinal artery closure during orbital hemorrhage from retro bulbar injection, Trans Am Acad ophthalmol

Central Retinal Artery after retrobulbar corticosteriods. Am J Ophthalmol ; 85: 352-6, 1978.

5. Ellis PP. Occllusion of the Central Retinal Artery after retrobulbar corticosteriods. Am J Ophthalmol; 85: 352-6, 1974.

6. Hamilton RC, Gimbel HV, Javitt JC: The prevention of complications of regional anaesthesia for ophthalmology. Ophthalmol Clin. North Am. 3: 111, 1990.

7. Duker J J, Belmont J B, Benson W E, et al. Inadvertent globe perforation during retrobulbar and peribulbar anaesthesia. Ophthalmology ; 98: 519, 1991.

8. Ramsey RC, Knobloch W H. Ocular perforation following retrobulbar anaesthesia for retinal detachment surgery Am J Ophthalmol ; 86: 61-4, 1978.

9. Rinkoff J S, Doft B H, Lobes L A. Management of ocular penetration from injection of local anaesthesia preceeding cataract surgery. Arch. Ophthalmology ; 109:1421, 1991.

10. Gopal L, Badrinath S S, Parikh S, Chawla G, Retinal detachment secondary to ocular perforation during retrobulbar anaesthesia. India Journal of ophthalmol 43: 13-15, 1995.

11. Javitt J C, Addiego R, Friedgherg H L, Libowati M M, Leach J J, Brain - stem anaesthesia after retrobulbar block. Ophthalmology ; 94: 718, 1987.

12. Lee D S, Kwon N J, Shivering following retrobulbar block, Canadian Journal of Anaesthesia ; 35 : 294, 1988.

13. Rogers R, Orellana J. Cranial Nerve Palsy following retrobulbar anaesthesia, British Journal Ophthalmology ; 72: 78, 1988.

14. Follette J W, Locascio J A, Bilateral amaurosis following unilateral retrobulbar block, Anaesthesiology ; 63:237 - 8, 1985.

15. Morgan G E, Retrobulbar apnea syndrome. A case for the routine presence of an anaesthesiologist ( Letter) Anaesthe.; 15: 107, 1990.

16. Smith R B, Lynn J G , Total Facial Nerve Palsy following modified O'Brien facial nerve block, Ophthalmic surg.; 18; 518, 1987.

17. Foster A N, Carlson B M, Myotoxicity of local anaesthetics and regeneration of the damaged muscle fibres, Anaesth. Analg.; 59: 727, 1980.

18. Gills, Hustead, Sanders, Ophthalmic Anaesthesia ; 93-94, 1993.

19. Thomas R D, Behbehani M M, Coyle D E, Denson D D, Cardiovascular toxicity of local anaesthetics. An alternative hypothesis. Anaesth. Analgesia ; 65: 444 - 50, 1986.

20. Russuvaara P, Setala K, Tarkkanen A, Respiratory arrest after retrobulbar block, Acta Ophthalmologica ; 66: 223-5, 1998.

21. Rosenblatt R M, May D R, Barsoumian K, Cardiopulmonary arrest after retrobulbar block. Am. Journal Ophthalmol ; 90: 425-427, 1980.

22. Nicoll J M V, Acharya P A, Ahlank, et al, Central Nervous system complications after 6000 retrobulbar blocks. Anaesthe. Analg.; 66: 1298 - 1302, 1987.

23. Hamilton R C, Gimbel H V, Strunin L. Regional Anaesthesia for 12,000 Cataract extraction and intraocular lens implantation procedures, Can J Anaesth. ; 35: 615 - 23, 1988.

24. Lichter P R. Avoiding complications from local anaesthesia. (Editorial). Ophthalmology ; 95: 565, 1988.

25. Atkinson W S, Large volume retrobulbar injections. Am. J. Opthal. ; 57: 328, 1964.

26. Smith, Hamilton, Carr, 1996, II Edition . Ophthalmic Anaesthesia.. New York, Oxford University Press, Inc., P.171.

Clinical and Biochemical Heterogeneity in Gyrate Atrophy of the Choroid and Retina and Possible Role of Polyamines

K. N. Sulochana, S. Ramakrishnan, Lakshmi Mahesh, V. Bhooma and
R. Punitham

 
Introduction

Gyrate (Latin: turned round) was originally used to describe this disease because the margin of the retinal atrophy in the early stages of the disease curves as circular segments.

Gyrate atrophy (GA) of the choroid and retina is a chorioretinal degeneration with an utosomal recessive mode of inheritance. Patients report night blindness and loss of peripheral vision between the ages of 10 and 20. Ocular findings include myopia, constricted visual fields, elevated dark adaptation thresholds, very small or absent electroretinographic responses and chorioretinal atrophy distributed circumferentially around the peripheral fundus and often near the disc. In more advanced stages, the areas of peripheral chorioretinal atrophy coalesce and extend posteriorly, and patients develop progressive constriction of the visual field, cataracts, and eventual blindness between the ages of 40 and 50.

It has been reported that affected patients have plasma ornithine concentration, 10-20 fold above normal1,3.

Ornithine plays a key role in the urea cycle and most pathways of its metabolism are well known (Figure). OAT is a pyridoxal phosphate-requiring mito-chondrial transaminase that catalyzes the reversible interconversion of ornithine and alpha ketoglutarate to pyrroline-5-

carboxylate (P5C) and glutamate. The equilibrium is determined by the concentrations of the reacting species in various tissues. OAT has been purified to homogeneity and sequenced from various tissues including the human liver.

The finding of an association between hyperornithinemia and GA in 1974 later led to the discovery of the basic enzymic defect, a deficiency of the enzyme ornithine amino transferase (OAT)2.

The defect in OAT activity is expressed in many tissues and cell types from GA patients, including cultured skin fibroblasts4,5.

As additional cases of GA were reported, clinical heterogeneity became more apparent. It is now best explained in terms of the OAT gene sequences and the amount of OAT protein detectable in the fibroblast of GA patients. Clinical heterogeneity has been documented with respect to responsiveness to vitamin B6 therapy, rate of progression of blindness and expressions of the variable amounts of OAT protein produced by each patient6-8.

It is now generally accepted that demonstration of hyperornithinemia is a prerequisite in clinical cases of GA for the final diagnosis and proper classification of the disease. However, just as there is clinical heterogeneity, it is likely that there could be variation in the chemical pathology too. This is because we found cases with

 

 

 Pathways for Ornithine Metabolism

Gyrate atrophy but without hyper-ornithinemia and vice versa. So it is accepted that chorioretinal degeneration may be due to (i) the toxicity of the accumulated ornithine or (ii) accumulation or deficiency of polyamines which are metabolites of ornithine (iii) deficiency of creatine and creatine phosphate (iv) deficient synthesis of pyrroline-5-carboxylate.

Polyamines are formed by the action of ornithine decarboxylase and have deleterious effects on DNA and proteins. They are also reported to affect the retinal function. Hence in addition to ornithine and OAT, polyamines namely putrescine, spermine, spermidine and cadaverine were also estimated in our studies. Thus this article highlights the clinical and biochemical heterogeneity in some of our patients, who had typical and atypical gyrate atrophy.  

Materials and Methods

Ornithine assay in plasma: ornithine was estimated by two dimensional paper chromatography of plasma treated with sulfosalicylic acid (1:1). The solvents were butanol, acetic and water in the first dimension and pyridine, iso amyl alcohol water in the 2nd dimension. Separated amino acids were stained with ninhydrin. The coloured Ornithine spot was extracted with 50% alcohol and assayed spectro-photometrically at 660nm.

OAT assay in lymphocytes: The lymphocyte cultures were carried out as per the protocol of Hayasaka. Cell extracts of phytohaemagglutinin-transformed lympho-cytes were prepared by the method of Berger9. The enzyme assay was done spectrophotometrically by the method of Katsunuma et al10 using ornithine as

substrate. Protein estimation was done by the method of Lowry et al using BSA as standard11. One unit of enzyme activity is equal to that amount of enzyme which releases 1mM of pyrroline 5 carboxylic acid per mg protein.

Assay of Urinary Polyamines by HPLC12:

A 2 ml aliquot of 24 hr urine sample is hydrolysed in 2ml of 12N HCl for 14-16 hr at 100-120°C.

After the hydrolysis, the sample is adjusted to pH 9.0 and the amines were extracted into n-butanol. The butanol extract was evaporated to dryness and the residue dissolved in 0.1N HCl. After the extraction of polyamines, they are benzoylated. For benzoylation 1ml of 2N NaOH and 10ml of benzoylchloride are added to 200ml of the polyamine aliquots and vortexed for 30 seconds. After a 20 minute incubation at 25°C, 2ml of saturated NaCl is added to the samples, to stop the reaction. The benzoyl-polyamines are extracted in 3ml of diethyl ether (stabilized with about 7ppm. of 2,6, di-tert-butyl-4-methyl phenol). The samples are centrifuged at 3000g for 5 minutes and the ether phase was collected and evaporated over a water bath (60°C) to dryness. The benzoyl polyamines are redissolved and 200ml of this extract is injected into the HPLC column and chromatographed at 25°C. The elution flow rate will be 200ml/min and are detected at 254nm with a UV detector.

Case Reports:

CASE 1: A 27 year old male from Andhra Pradesh was seen at Sankara Nethralaya during July 1993 with complaints of diminished vision at night since the age of 8 years which had been progressive, and subsequently he had difficulty in day vision also. He also gave history of decreased field vision in both eyes and mild hearing difficulty for the last 3 years. He was born of a consanguineous marriage.

He was myopic with correction of -4.00 in the right eye and -2.75 in the left eye. Slit-lamp examination of the anterior segment revealed anterior subcapsular cataract in both the eyes. Fundus examination with indirect ophthalmoscopy revealed pale disks in both the eyes with arteriolar attenuation. There were tongue-shaped lesions of chorio retinal atrophy with advancing and confluent edges sparing the macula, typical of gyrate atrophy in both the eyes. There were pigmented areas due to confluence of tongue-shaped lesions. ERG showed extinguished responses in both the eyes for the photopic and scotopic phases. Field examination with Goldman perimeter revealed tubular fields with a central 10° field of vision. FFA was consistent with GA. Biochemical findings are given in the Table. His cousin has hyperornithinemia but normal vision.

CASE 2: A 35 year old female from Calcutta was examined in Sankara Nethralaya during February 1995 with complaints of defective vision in the right eye since childhood. She was wearing correction of -9.00 DS in both eyes with which her vision was 6/60; 6/36 for distance and N36; N12 for near without glasses in the right and left eyes respectively. Slit-lamp examination showed posterior subcapsular cataract in both the eyes. Fundus examination showed typical features of GA in both the eyes. Biochemical findings are given in the Table. Her ERG showed extinguished responses in both the eyes. She was started on B6 therapy, and was followed-up after three months but her fundus was the same as before and plasma ornithine and OAT also remained the same.

CASE 3: A 25 year old male from Andhra Pradesh had night blindness since the age of 10 years. There were fused tongue-shaped lesions typical of gyrate atrophy. Disc was fairly healthy. Confluent lesions had encroached upon the macula. Retinal vessels were moderately constricted. The biochemical findings are given in the

 

Table. The patient was diagnosed to have gyrate atrophy and was advised pyridoxin treatment. The case was followed-up after 2 years. There were no clinical changes.

Case 4: A 15 year old female from Tamil Nadu was examined here for gradual loss of vision in both the eyes. She had an episode of fever during her 12th year, associated with convulsions. Her parents had married within the family and it was a case of first degree consanguinity. Her visual acuity was 1/60 and 2/60 in right and left eye respectively. The lens and cornea were clear. Fundus examination revealed pale discs, attenuated vessels and unhealthy retinal texture with scalloped margins typical of gyrate atrophy. Biochemical results are given in the Table. Both parents were also investigated clinically and biochemically. They were found to have normal fundus but their plasma ornithine level was elevated.

Case 5: A 15 year old boy from Bangalore was found to have pigments in the post equatorial region. He had no history of night blindness but a family history of retinitis pigmentosa. Two of his maternal grand uncles had severe typical RP. This boy had extinguished ERG and patches of

pigmentation. After clinical and laboratory investigations, he was diagnosed with atypical RP. Interestingly his mother and brothers’ had normal ornithine and OAT levels while the patient had elevated ornithine and lowered OAT levels (Table). His father also had elevated ornithine and lowered OAT levels. All the three members of the family other than the patient had normal fundus.

Case 6: A 54 year old female from West Bengal was examined with complaints of gradual dimension of vision in both the eyes. Her best corrected visual acuity was 6/24 and 6/12 in the right and left respectively. Slit-lamp examination revealed immature cataract. Fundus examination showed evidence of disc pallor with lamellar macular hole in both the eyes. There was also evidence of chorioretinal atrophy involving the inferior hemisphere of the retina suggestive of Gyrate atrophy. Although ERG showed normal responses, the plasma ornithine was elevated (Table). Her younger sister was found to have a normal eye, but elevated ornithine.

Case 7: A 75 year old female from Madras was examined for complaints of gradual painless decrease in vision. Her best

Table: Ornithine, OAT and Polyamines in normals and patients with Gyrate Atrophy

 

corrected visual acuity was 2/60 in the right eye and no vision in left eye. Slit lamp examination revealed posterior and anterior subcapsular and nuclear cataracts. Fundus examination showed Retinitis Pigmentosa like changes in retina. Her plasma ornithine level was highly elevated (Table).

Case 8: A 50 year old male from West Bengal had a complaint of gradual decrease in vision but no night blindness in both eyes. Slit-lamp examination of the anterior segment was remarkable in both the eyes except for a sluggish pupillary defect in the right eye. Fundus examination showed advanced chorio-retinal atrophy in both the eyes, more so in the right eye, with optic atrophy and macular degeneration. Clinical features werre suggestive of GA. There was peripheral pigmentation and attenuation of vessels in both the eyes. His electroretinography showed extinguished responses in both eyes in the scotopic and photopic phases. Serum ornithine was not elevated. OAT also was normal.

Results

The first 4 cases (1 to 4) are typical GA. Their clinical and biochemical manifestations were very similar to reported findings in the literature. Although their ornithine level was elevated, the increase was only 2 to 3 fold while in classical GA it is 10 to 20 fold. The rest of the 3 cases (Case 5 to 7) were atypical GA. It has to be noted that even in some unaffected individuals of families of 1,4,5,6, ornithine levels were elevated and OAT was decreased (Data not given). In all the patients investigated, typical or atypical, there was an increase of ornithine, decrease of OAT and a significant increase of polyamines of ornithine i.e putrescine, spermine and spermidine. Interestingly cadaverine, the polyamine from lysine was found decreased in the patients. The ratio of polyamines from ornithine to polyamine from lysine increased significantly in all

the patients. Regarding case 8, though the clinical picture was very similar to that of Gyrate atrophy, his ornithine and OAT levels did not fit in with those found in other patients. Hence it is doubtful as to whether it is Gyrate atrophy.

Discussion

From our observations in both typical and atypical GA patients, it appears that ornithine alone may not be directly involved in this disease.

A few reports which support our observations and conclusions are as follows.

Low protein (20-35g) and low arginine diet (as arginine is the precursor for ornithine) and B6 (300mg/day) were tried in 3 patients. Although it maintained their plasma ornithine concentrations in the range 30-60% of pretherapeutic levels for about 2 years, no significant improvement in the vision or retinal changes were noted13. If hyperornithinemia is causing the disease, the results should be different.

A neurological study showed that GA is a systemic disease which affects not only the choroid and retina but also the muscle-at least the type-2 fibers. These fibers degenerated more slowly than the ocular structures but as the disease progresses almost complete loss of type-2 fibers takes place14. If this is so, it will support the opinion that a normal synthesis of the high energy compound creatine is necessary for the proper functioning of the eye as well as muscle.

When mice and chicks were given 5-fluoro methyl ornithine, a selective inactivator of OAT over extended periods of time, they had elevated concentrations of ornithine. But ophthalmoscopic findings of the eye and electroretinography were normal. No toxic effects in both the animals were seen15. From this report it is clear that ornithine is not directly involved in GA.  

 
It is unlikely that the high plasma ornithine in GA has resulted from an enzymic deficiency in the Krebs Henseleit urea cycle. Patients with a deficiency of ornithine carbamoyl transferase have shown high levels of blood NH3 and normal plasma ornithine. Other known enzymic defects in the cycle have usually been associated with high levels of blood NH3, and increase in one or more amino acids in the cycle. In contrast, patients with GA have the unusual combination of normal NH3 and high levels of ornithine as well as normal citrulline and arginine16. The high level of ornithine is probably due to some abnormality not involving the urea cycle. None of our patients who reported here had high NH3 or citrulline.

Although the association of high levels of ornithine and GA coincide in many cases, increased levels of ornithine alone do not necessarily lead to this degeneration. A patient with known hyperammonemia and a ten-fold increase in plasma ornithine was found to have a normal fundus appearance and normal electroretinogram. There are cases of GA without hyperornithinemia (vide case 8) and cases of hyperornithinemia without GA17,18.

In a case of GA, excretion of glycine, proline and hydroxy proline has also been reported and OAT activity was normal in fibroblasts. In one of our cases, (not included in the Table), there was also excretion of proline and hydroxyproline. In another report, the ocular disease is reported to progress in juvenile patients despite normal or near normal plasma ornithine concentration19.

The condition of one 45 year old woman with GA was followed up for 12 years and reported. She had ornithinemia. Additional features were massive cysteinemia, massive cysteinuria serum ornithine 740mm/l20. These three acids share the same renal mechanism21. One of our cases (not included in the Table) also had similar findings.

More than ornithine, polyamines, the catabolic products of ornithine and lysine may be the causative factor, especially because ornithine is an innocuous amino acid. Liver in which it is formed continuously is not affected. Ornithine decarboxylase has both ornithine and lysine as substrate. In the case of a deficiency of OAT, ornithine decarboxylase may degrade ornithine to polyamines. The higher the concentration of ornithine, the greater the levels of polyamines viz putrescine, spermine and spermidine. If the decarboxylase has high Km for ornithine and lysine, it would degrade ornithine more than it does lysine, as lysine levels have been reported to be decreased in cases of Gyrate atrophy. Again, the decreased amount of lysine will also be responsible for the low cadaverine formed from it in the disease. This could explain the increase of polyamines from ornithine, decrease of cadaverine from lysine and an increased ratio between polyamines from ornithine and polyamine from lysine.

In this connection it is also of interest to note that spermine and spermidine inhibit OAT22. Thus, polyamines have been shown to inhibit the synthesis of enzyme proteins. They are also reported to destroy cGMP in the rods of the retina23. Hence it is likely that more than ornithine per se, it appears that the polyamines may have greater relevance in the causation of Gyrate atrophy and probably other retinal disorders.

Reference

1. Kaiser KM, Valle D. Clinical, biochemical and therapeutic aspects of gyrate atrophy. in Progress in retinal research (Osbourne N and Chader J eds.) Pergamon, Oxford. pp.179-206; 1987.

2. Takki K. Gyrate atrophy of the choroid and retina associated with hyperornithinemia. Br J Ophthalmol 58:3-23; 1974.         3. Simell O, Takki K. Raised plasma ornithine and gyrate atrophy of the choroid and retina Lancet. 1:1031-1033; 1973

 
4. Trijbels JMF, Sengers RCA, Bakkeren JAJM, Dekori AFM, Dutman AF. L.Ornithine Keto acid transferase deficiency in cultured fibroblasts of a patient with hyperornithinemia and Gyrate atrophy of choroid and retina. Clin Chem Acta 79:371-377; 1977.

5. O’Donnel JJ, Sandman RP, Martin SR. Deficient L.Ornithine-2-oxoacid amino transferase activity in cultured fibroblasts from a patient with Gyrate atrophy of retina. Biochem Biophys Res Commun 79:3696-99; 1977.

6. Khnaway NG, Welber RG, Buist NRM. Gyrate atrophy of the choroid and retina with hyperornithinemia biochemical and histological studies and response to vitamin B6. Am J Hum Genet 44:344-352; 1980.

7. Ramesh V, Mcclatchey AI, Ramesh N, Benoit LA, Berson EL, Shih VE, Gusella JF. Molecular basis of ornithine amino transferase deficiency in B6 responsive and non-responsive forms of gyrate atrophy. Proc Nutr Acad Sci 85:3777-3780; 1988.

8. Shih VE, Mandell R, Berson EL. Pyridoxine effects on ornithine keto acid transferase activity in fibroblasts from carriers of two forms of Gyrate atrophy of the choroid and retina. Am J Hum Genet 43:929-933; 1988.

9. Berger SL. Lymphocytes as resting cells. Methods in Enzymology. New york. 58:486-94; 1979.

10. Katsunuma N, Matsuda Y, Tomino I. Studies on ornithine keto acid transaminase purification and properties. J Bio Chem 56:499-503; 1964.

11. Lowry OH, Rosebrough NJ, Farr AL, Randall RJ. Protein measurement with Folin phenol reagent. J Biol Chem 193:265-75; 1951.

12. Kiriakos K, Maria D, Christakis H, Kalliopi A, Roubelakis A. A narrow bore HPLC method for the identification and quantitation of free conjugated and bound polyamines. Anal Biochem 214:484-489; 1993.

13. Valle D, Walser M, Brusilow W, Kaiser MK. Gyrate atrophy of the choroid and

 

retina. Amino acid metabolism and correction of hyperornithinemia with an arginine deficient diet. J Clin Invest 65:371-378; 1980.

14. Sipila I, Simell O, Rapol J, Sainio K, Tuuteri L. Gyrate atrophy of the choroid and retina with hyperornithinemia tubular aggregates and type 2 fiber atrophy in muscle. Neurology 29:996-1005; 1979.

15. Anglard DG. Biochemical and pathophysiological aspects long term elevation of brain ornithine concentration. Pharmacol Toxicol 73:29-34; 1993.

16. Berson EL, Schmidt SY, Rabin AR. Plasma amino acids in hereditary retinal disease. Ornithine lysine and taurine. Br J Ophthalmol 60:142-147; 1976.

17. Hayasaka S, Mizuno K, Yabata K, Saito T, Tada K. Atypical Gyrate atrophy of the choroid and retina associated with iminoglycinuria. Arch Ophthalmol 100:423-425; 1982.

18. Jaeger W. Differential diagnosis of Gyrate atrophy of the choroid and retina with and without hyperornithinemia. Metabol Pediatr Ophthalmol 3:189-191; 1979.

19. Vannas-Sulonen K, Simell O, Sipila I. Gyrate atrophy of the choroid and retina. The ocular disease progresses in Juvenile patients despite normal or near normal plasma ornithine concentration. Ophthalmol 94:1428-33; 1987.

20. Khan MY, Ibraheim AS, Firoozmand S. Gyrate atrophy of the choroid and retina with hyperornithinemia, cystinuria and lysinuria. Eye 8:284-287; 1994.

21. Kaiser KM, Valle D, Bron AJ. Clinical and biochemical heterogeneity in Gyrate atrophy. Am J Ophthalmol 89:219-222; 1980.

22. Deshnurkh DR, Srivastava SK. Purification and properties of ornithine amino-transferase from rat brain. Experientia 1984; 40:357-359.                            23. Sitaramayya A. Personal communication. Eye Research Institute, Oakland University, MI.

 

 Medulloepithelia Masquerading as Congenital Glaucoma - Report of
A Case with Review of Literature

Dr Jyotirmay Biswas, MD, Dr Rajesh Fogla, MBBS and
Dr Mahesh P Shanmugam, DO
Medulloepithelioma is a congenital tumour usually arising from primitive medullary epithelium prior to its differentiation to various derivatives and the non-pigmented epithelium of the ciliary body. The tumour can contain pure neuroepithelial structures or a mixture of various derivatives of the medullary epithelium. The tumour presents as a mass in the iris, anterior chamber or ciliary body. It is seen typically in children, grows slowly and is locally aggressive. Glaucoma was the presenting feature in 50% of the cases in a large series of medulloepithelioma.1 In a series of 2704 eyes with intraocular tumour, seen at the Oncology service of Wills Eye Hospital, both the patients who had medulloepithelioma had secondary intraocular pressure elevation.2 We report a case of medulloepithelioma presenting with multiple ciliary staphyloma following treatment for congenital glaucoma elsewhere.

CASE REPORT

A 7-year-old girl was brought by her parents with complaints of loss of vision in her left eye. There was history of a brown elevated spot in the left eye, noted 3 years ago. She was diagnosed to have ciliary staphyloma by local ophthalmologist with secondary glaucoma. Patient was treated with anti-glaucoma medication. However pressure remained uncontrolled. She subsequently underwent trabeculectomy at a local medical college. Post operatively the patient developed hyphema with vitreous haemorrhage and cataract and was referred

 

to us. On examination, her vision in the right eye was 6/6; N/6 and in the left eye no light perception. Slit lamp examination revealed no abnormality in the right eye. In the left eye there was corneal oedema, band shaped keratopathy and hyphema. Multiple ciliary staphyloma were seen superiorly as well as on the temporal side (Fig 1). Fundus examination revealed no abnormality in the right eye and the left eye fundus could not be seen. B scan with vector A scan ultrasonography showed a large mass, arising from the ciliary body, almost filling the whole of vitreous cavity and having moderate to high reflectivity. There was no acoustic hollowing or orbital shadowing except for few echolucent areas (Fig 2). Retinal detachment was seen in the inferior portion. Ultrasonographic findings were suggestive of a large ciliary body tumour. Considering that it arose from the ciliary body a suspicion of medulloepithelioma was entertained and the eye was enucleated.

 

Fig 2: Combined B and A scan ultrasound showing a large tumour mass arising from the ciliary body and filling  the vitreous cavity.  Echolucent area seen within the mass lesion.

Fig 3: Showing the globe filled with the tumour arising from the ciliary body causing multiple ciliary staphyloma.  Note secondary retinal detachment behind the mass (haematoxylin and eosin, X 1)

Fig 4: Higher power showing tumour cells invading the sclera causing protrusions of  the ciliary body (haematoxylin and eosin, X 100)

PATHOLOGICAL STUDY

The globe was fixed in 10% neutral buffered formalin. On gross examination the globe was found to be 29 mm ´ 24 mm ´ 23 mm. There was a bulge in the anterior portion of the globe with multiple ciliary staphylomas. No transillumination defect was seen. Globe was opened vertically to incorporate the ciliary staphyloma. Cut sections of the globe revealed whitish tumour mass arising from the ciliary body and extending into the whole of the vitreous cavity measuring 15 mm transversely and 21 mm vertically. Brownish black pigments were seen within the tumour mass. Retina was detached. Underneath the retina a transparent jelly like mass was seen. Microscopic examination revealed dense inflammatory cellular infiltrates underneath the conjunctiva. Cornea showed marked oedema of the basal layer of the epithelium. Fibrous pannus was observed under the epithelium. Bowman’s membrane was broken at places and the stroma was oedematous. Tumour cells were found to be extending into the peripheral part of the cornea. Organized haemorrhage was observed in the anterior chamber. Anterior chamber angle was blocked by the peripheral anterior synechiae and tumour cells . Superior to the limbus, sclera was disrupted with multiple protrusions (Fig.3). Within this scleral outgrowth basophilic tumour cells composed of tubules and cords were seen. The tumour was also noted underneath the conjuntival epithelium. From the ciliary body a large basophilic tumour mass with multiple areas of cystic spaces and condensed vitreous like substances were seen (Fig.4). The tumour cells were arranged in multiple sheets, cords and lobules. Some of the tubules had a central lumen and resembled Flexner-Wintersteiner rosettes. These rosettes were lined by multiple layer of epithelial cells. Although most of the tumour was made up of benign cytologic features, there were foci exhibiting large reticular nuclei with prominent nuclei suggestive of focal

  
malignant trasformation. There was a focus of cartilage formation indicating terratoid medulloepithelioma. Retina was found to be detached with thinning of inner layer, loss of ganglion cells, disorganisation of the cells with marked vacuolar changes. Optic nerve showed loss of anterior tissue, bowing of the lamina cribrosa and atrophy. Pathologic diagnosis of corneal oedema, fibrous pannus, hyphema, secondary angle closure, glaucoma, malignant teratoid medulloepithelioma with extension through sclera, and glaucomatous optic atrophy was made.

DISCUSSION

Medulloepithelioma of the ciliary body, due to its slow growing nature and location often remains undetected. The tumour is remarkably rare. In a review of malignant tumour of the eye and orbit in children between 1919 and 1981 at the Hospital for sick children in Toronto, Gallie et al found 148 retinoblastomas, 14 rhabdomyosarcomas and 4 uveal melanomas but not a single case of medulloeptitheloma indicating rarity of its occurrence.3 In Sankara Nethralaya, Chennai between 1985 to 1996 including this patient, only two cases of medulloepithelioma were seen.4 In four cases of medulloepithelioma reported in Indian literature by Panda et al,5 one patient had ciliary staphyloma, subluxated lens with exudates in anterior chamber while the other three cases had i) white mass in pupillary area with secondary glaucoma, ii) perforated corneal ulcer, and iii) blind eye with fleshy mass with associated haemorrhagic and necrotic changes. In a series of 56 cases reported by Broughton and Zimmerman , most common finding was - a cyst or mass in the iris, anterior chamber or ciliary body (54%), followed by glaucoma (46%) and cataract (25%). Other findings included proptosis, bupthalmos, iritis, rubeosis iridis, retinal detachment, strabismus, retinal mass, and vitreous haemorrhage. Such protean manifestations, with wide range of complications and location of the tumour

tumour makes the diagnosis difficult and is therefore often missed. In our first case the patient had been treated initially with antiglaucoma medications followed by trabeculectomy prior to presentation at our clinic. The mechanism of glaucoma in medulloepithelioma is varied and can be due to i) direct infiltration of the the trabecular meshwork by the tumour ii) by free tumour cells which can get dislodged from the main mass and obstruct the aqueous outflow channels iii) secondary angle closure from neovascularisation of the angle iv)hyphema resulting from bleeding of the new vessels and v) displacement of the lens iris diaphragm forwards with secondary angle closure. In our case, there was evidence of invasion of the trabecular meshwork by tumour cells along with peripheral anterior synechiae. Trabeculectomy done in the first case allowed the tumour cell entry into the superficial part of sclera and conjunctiva.

The diagnosis of medulloepithelioma is often established after enucleation. In a series of by Broughton and Zimmerman 56 cases only 2 cases were diagnosed from iridocyclectomy specimens. In our case, ultrasonography revealed a large mass arising from ciliary body region. The possibility of retinoblastoma was also considered. Medulloepithelioma can be differentiated from retinoblastoma by the relative higher age at presentation(median age, 3.8 years). However it can present as early as six months to as late as 79 years. Other differences are the unilaterality of medulloepithelioma and lack of any family history. The initial presentation is generally as an iris or ciliary body mass lesion. Ultrasonography helps to detect it’s site of origin and internal characteristics like calcification, necrosis etc. Our case illustrates that in children with unilateral glaucoma, medulloepithelioma should be considered in the differential diagnosis.

Medulloepithelioma, though a slow growing tumour, can perforate the eye and spread to the orbit. The common site of

  

metastasis is the lymph node. Other sites of metastatis are parotid gland and lungs. In the series of Broughton and Zimmerman of 56 cases, 8 had orbital extension, four of these patients died of metastasis from the tumour, and for four other patients, followup information was not available.1 Medulloepithelioma can be benign and malignant. Criterion for malignant transformation is defined by presence of poorly differentiated neuroblastic cells which may resemble retinoblastoma, extensive pleomorphism with or without mitotic activity, presence of sarcomatous areas and invasiveness to other structures with or without extraocular extension.1

The role of ancillary studies in medulloepithelioma has not been fully established. Ultrasonography of medullo-epithelioma can be variable. Two cases described by Byrne and Green, had dome-shaped, highly reflective, and moderately vascular mass lesion. In one case multiple cystic spaces were seen. High reflective echoes can be seen in this tumour due to presence of teratoid elements like cartilage.6 Orellana et al have described a method of scleral depression simultaeneously with tilting of the globe during ultrasonography to allow access to the region of the ciliary body which increases the diagnostic capabilties7. In a case of unilateral congenital glaucoma with no view of the posterior segment in the first decade, an ultrasound examination with special attention to the ciliary body is indicated to rule out such tumour.

Excisional biopsy such as irido-cyclectomy can provide the diagnosis if tumour is suspected early. Orellana and associates7 reported a case of medulloepithelioma in a 8 year old boy where the diagnosis of medulloepithelioma was made by cytologic examination and ultrastructural studies of vitreous aspirate and subsequently confirmed by histopathologic study.

Local resection has been suggested as the primary modality of treatment. However, recurrence of the tumour following local resection has been reported with subsequent enucleation.8 In case of glaucoma associated with medullo-epithelioma, enucleation is usually necessary because of the pain and the advanced stage of the tumour for local resection.9

Our case illustrates that in children with unilateral glaucoma, medullo-epithelioma should be considered in the differential diagnosis.

ACKNOWLEDGEMENT :

The authors thank Prof. Narsing A. Rao, Director, A. Ray Irvine Opthalmic laboratory, Doheny Eye Institute, Los Angeles for reviewing the pathology slides.

REFERENCES

1. Broughton WL, and Zimmerman LE: A clinicopathologic study of 56 cases of intraocular medulloepitheliomas. Am J Ophthalmol 85:407-418, 1978.

2. Shields CL, Shields JA, Sheilds MB and Augsburger JJ: Prevalence and mechanisms of secondary intraocular pressure elevation in eyes with intraocular tumours. Ophthalmology 94:839-846, 1987.

3. Gallie BL, Musarella MA, Chan HSL. Ocular oncology. In: Crawford JS, Morin JD, eds. The Eye in Childhood. New York: Grune & Strattton, 1983; 307-29.

4. Biswas J, Parameswaran A, Badrinath SS: Medulloepithelioma (Diktyoma) - a case report. Nethralaya Insight. Vol. 2, Jan 1985.

5. Panda A, Dayal Y and Mohan M L: Medulloepithelioma of ciliary body. Ind. J Ophthalmol 33:183-186, 1985.           6.Byrne SF and Green RL: Intraocular tumors. Ultrasound of the Eye and Orbit’, St. Louis, Mosby Year Book, 1992, pp 133-213.

 7. Orellana J, Moura RA, Font RL, Boniuk M, Murphy D: Medulloepithelioma diagnosed by ultrasound and vitreous aspirate. Electron microscopic observations. Ophthalmology 90:1531-1539, 1983.

8. Kirela T and Tarkuanen A: Recurrent medulloepithelioma of the ciliary body immunohistochemical characteristics. Ophthalmology 95:1565-1575, 1988.

9. Shields JA, Shields CL & Shields MB: Glaucoma associated with intraocular tumors. ‘The Glaucomas’. Clinical Science Vol. 2. 2nd Edition St. Louis, Mosby 1996. pp: 1131-1139

 AN APPEAL

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Day after day, year after year, Nethralaya treats hundreds of patients absolutely free of cost and gives them back their sight. Treatment is provided free of cost to all patients with a monthly income below Rs.1,750/-.

Yet there is no discrimination between the free patient and the one who pays. Apart from the treatment, food, medicines and travel expenses are absolutely free.

Those free patients depend on Nethralaya, and Nethralaya depends on you.

So, come and join the Ophthalmic Mission Trust.

For questions about tax exempt status and contributions, please contact:

Mr S V Acharya,
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  COME, GIVE THE GIFT OF SIGHT

Model Eye for
Nd YAG Laser Capsulotomy

Dr Rajesh Fogla and Dr Srinivas K Rao
Neodymium YAG laser is an important therapeutic tool in the armamentarium of the ophthalmologist. It has various applications but is most commonly used for performing YAG laser capsulotomy for posterior capsular opacification following cataract surgery.

The incidence of posterior capsular opacification following cataract surgery ranges from 30 - 50 %, being higher in the younger age group1. It is one of the main reasons for decreased vision following cataract surgery. Yag laser capsulotomy is a non invasive procedure compared to the surgical discission of posterior capsule, and it as effectively creates an opening in the opacified posterior capsule with minimal complications. The complications which have been reported are related to the excessive use of laser energy during this procedure.

For a beginner it is important to learn how to focus the aiming beam accurately so as to achieve optimal effect with minimal use of laser energy. Proper technique helps

to prevent damage to the intraocular lens ie pitting, during the procedure. It is therefore necessary to practice on inanimate targets like a model eye. Autopsy eyes have been used for anterior segment laser surgery but the availability of such tissue is limited.2 The corneal clarity is also reduced in such eyes due to post-mortem changes, which hampers the laser procedure and makes it rather more difficult.

We present a model eye that we have devised, to facilitate learning the use of Yag laser in performing capsulotomy.

Materials and methods :

The model eye devised is intended to simulate natural conditions both with and without intraocular lens.

A circular opening of 8 mm diameter is made in a plastic table tennis ball. A hard contact lens of +20 Diopters is then placed over this opening using adhesive. (Fig1) A crescent shaped opening about 18mm long and 3 mm wide is made, 8mm away from the edge of the contact lens

 

Fig 1: Photograph of the Model Eye with i) +20 diopters contact lens(arrow), ii) crescent shaped opening above and iii) triangular opening below.

 

Fig 2: Photograph of the cardboard sheet with central opening covered with cellophane sheet and Intraocular lens placed anteriorly (arrow).

concentric to it. (Fig1) A 2 mm triangular opening is created 8mm away from the edge of the contact lens, 1800 opposite to the centre of crescent shaped opening. A cardboard or plastic sheet of 0.5 to 1mm thickness, 30mm ´ 17mm in dimensions is taken and 10mm ´ 10mm opening is created 5mm from the lower margin. (Fig2 ) The lower margin is then trimmed at the edges to give it a rounded appearance. At the centre of the lower margin a 1mm area is spared during the trimming process. When the cardboard sheet is introduced into the plastic ball this 1mm ´ 1mm protrusion comes out of the triangular opening inferiorly which facilitates stabilisation within the plastic ball . Cellophane is then pasted over the opening in the cardboard sheet. An intraocular lens can be placed in front of the cellophane sheet prior to pasting, to simulate pseudophakic conditions. (Fig2 ) Now the cardboard sheet is inserted into the plastic ball and the eye is ready for use.

The plastic ball is held in one hand and the other hand is used to operate the joystick of the slit lamp to focus the aiming beam. For accurate focussing i) the two
He-Neon aiming beams should coincide and ii) speckling of the laser beam should be visible. A puncture in the cellophane sheet (the model posterior capsule) is made with correct focussing only ,using energy in the range of 2.0 to 3.2 mJ.

         

Fig 3: View of model posterior capsule after exposure to Nd YAG laser.  Arrows indicate opening created by laser

 

The retraction of the edges of the opening seen clinically with the posterior capsule , however does not occur with the cellophane sheet .Typical results are shown in Fig 3 where disruptions in the cellophane sheets can be seen.

We feel that by using this model eye one can master the technique of Yag laser applications in the human eye. Zeimer and Mori have described a similar commercial model eye (Eyetech Ltd., Skokie, Illinois) to practice laser applications.3 Comparatively this model eye that we have described is very easy and simple to make and really inexpensive. We feel that this model eye shall provide an adequate simulation of the most commonly used laser procedure and alleviate the need for experimental subjects.

References :

1. Mc Donell PJ, Zarbin MA, Green WR : Posterior capsule opacification in pseudophakic eyes; Ophthalmology, 90:1548-1553 ; 1983

2. Shammas AV, Minckler DS: Autopsy eye model for laser trabeculoplasty and iridectomy ; Am J Ophthalmol , 102 : 664 - 665 ; 1986

3. Zeimer RC, Mori MT : An Interactive Model Eye for use with Ophthalmic
Instruments : Arch Ophthalmol , 106 : 126 - 127 ; 1988

 

 

  
 

               APEX PLUS LASER

 

Cassette is placed in the optical rail just behind the laser

rail in the delivery head which accomodates the mask carrier - the Emphasis cassette. The mask is placed in the cassette using a suction holder and the cassette is loaded into the rail

As the laser is fired, successive pulses ablate the thin central portion of the mask - the quartz substrate is transparent to the laser beam. As the mask is eroded, the laser beam passes through to the underlying cornea and when the mask is completely eroded, the greatest amount of tissue would have been ablated centrally, with progressively less tissue removed toward the periphery of the ablation zone.

 

   

 Principle of the erodible mask technique.  The laser beam ablates the acrylic mask before reaching the underlying cornea, and therefore transfers the shape of the mask onto the corneal surface in a smooth fashion.

   

Emphasis cassette in which the erodible mask is fixed

 

Simple astigmatic masks allow the treatment of astigmatism while both myopia and astigmatism can be simultaneously corrected using a toric mask. The major advantage of the erodible mask is the lack of diaphragm-induced steps on the corneal surface. All of the above approaches deal with the correction of regular astigmatism.

While an approach to the management of irregular astigmatism has been suggested by Gibralter and Trokel using customised treatment plans based on corneal topographic maps, the treatment of this condition is still unsatisfactory. Future directions in the management of irregular astigmatism include a computer-controlled small-diameter laser beam that scans the corneal surface according to a software program, which incorporates the data from preoperative and possibly intraoperative corneal topographic analysis and depicts true corneal tissue elevation and depressions rather than a Placido disc-based image reflection.

 

 Last Page:

Correction of Astigmatism using the Excimer Laser

Dr Srinivas K Rao

Astigmatism, the second most common refractive error and a frequent accompaniment to myopia and hyperopia, occurs when incoming rays of light do not reach a point focus on the retina. Uncorrected astigmatism is an important cause of poor visual acuity, and if greater than one diopter can reduce uncorrected visual acuity to less than 6/12. Astigmatism can broadly be classified as regular and irregular, and can be due to congenital, posttraumatic, postsurgical or corneal causes. Early attempts at correcting astigmatism soon realised the inadequacy of spectacles especially in higher errors, in which instance a contact lens appeared to be superior. However, even with the advent of toric contact lenses, visual and maintenance requirements prompted a continuing search for a satisfactory surgical solution. Initial surgical treatment consisted of corneal incisions and steepening sutures. While such an approach works quite well and is still the only modality possible in the intraoperative milieu of cataract surgery, it still has all the disadvantages of invasive surgery. The use of the excimer laser offers the possibility of submicroscopic precision in the removal of corneal tissue. At present, two types of lasers are in vogue:

1. Lasers using a wide beam approach eg., Summit, VISX, Chiron-Technolas

2. Lasers using a scanning approach

- Scanning slit eg., Nidek, Meditec

- Flying spot eg., Laser-sight, Novatec

These systems use widely varying methodologies to reprofile the cornea for the correction of astigmatism. With the VISX system,

astigmatism can be treated either simultaneously or sequentially. In a simultaneous correction an elliptical ablation is performed with the long axis of the ellipse placed along the flatter corneal meridian. The ablation pattern is created using a rectangular aperture that shortens in width and an iris diaphragm that simultaneously expands. For a sequential ablation, the cylindrical error is first corrected using rectangular apertures that progressively widen and have their long axis oriented along the flatter meridian.

Following this, the spherical error is corrected by superimposing a 6 mm spherical cut over the existing cylindrical ablation. Scanning slit systems like the Nidek laser use an expanding iris and slit with a scanning and rotating slit. The Meditec laser however, uses a variably rotating hourglass aperture placed over the patient’s eye, in conjunction with a scanning slit. Flying spot lasers use a computer-controlled delivery system that rapidly scans the small circular spot over the corneal surface in a predetermined fashion. All of these techniques do involve an etching of the corneal surface by the successive laser pulses though the scanning systems do reduce this step formation to some extent.

A radically different approach has been adopted by Summit Technology, Inc., in their new APEX PLUS laser.

They make use of proprietary mask technology to achieve astigmatic and hyperopic ablations, in addition to the correction of myopia which was possible with the earlier Omnimed laser. The erodible or ablatable mask consists of a polymer that adheres to a quartz substrate and is placed in the beam path. To facilitate centration of treatment, the engineers at Summit have devised

This issue of Insight is sponsored by:

Rampion Eyetech Pvt. Ltd., Kalash, New Sharda Mandir Road, Paldi, Ahmedabad - 380 007

Apex Laboratories Pvt. Ltd., 44, Gandhi Mandapam Road, Kotturpuram, Madras - 600 085

Medical & Vision Research Foundations thank the above sponsors for their generosity.

Editor : Dr. Mahesh P Shanmugam  

End of Insight