Anterior Chamber PIOL
     
 

The anterior chamber phakic intraocular lenses (ACPIOLs) include “angle supported” lenses (Vivarte [Novartis], NuVita [Bausch and Lomb, Rochester, NY]) and “iris clip” lenses (Verisyse [Worst-Fechner/Artisan Lens] AMO, Santa Ana, CA.). Inherently, the anterior chamber lens runs the risks of damaging the patient’s endothelium and/or iris, and of inducing glaucoma and/or diplopia.14 At the same time, the lens design avoids any contact with the patient’s crystalline lens, and allows for visibility of the placement the lens.

Bausch and Lomb took the Baikoff angle-supported lens design and created the NuVita lens (Fig 6) . This lens can be used for highly myopic patients, who have refractive errors in the range of –7.00 D to –20.00 D. The single-piece design and large inflexible 5-mm optic section need a large (6-mm) corneal incision for insertion. These characteristics have led to increased astigmatism, discomfort, and problems with sutures when using this lens.16 Of greater concern, this lens has been reported to induce endothelial decompensation with possible long-term consequences.16 Other studies showed pupil ovalization, reports of glare and haloes, and reports of angle-closure glaucoma (Fig. 7) .14 Bausch and Lomb has opted to not continue testing this lens in the US; however, it is still available in Europe. The company has also started working on a new lens design — a hydrogel angle-fixed foldable ACPIOL that is almost ready for US clinical trials. Hopefully, this new lens will address the problems associated with the NuVita lens.

Novartis’ Vivarte, a single-piece acrylic lens, is also angle-supported (with 3 points of contact in the angle), but has a flexible haptic and a foldable, hydrophilic optic section (in contrast to the rigid haptics of the NuVita lens) (Fig 8) . The ability to fold the lens allows the surgeon to insert the lens through a self-sealing 3.5-mm corneal incision, thus avoiding both induced patient astigmatism and the use of sutures. This lens also boasts multiple diameters (12, 12.5, and 13.0 mm), an optic diameter of 5.5 mm, and refractive ranges of –6.5 D to –31.00 D in 0.5 D steps. Although it is fairly early in the clinical trials of this lens, the 3-point touch seems to have reduced the endothelial changes previously seen with other designs. With its foldable insertion and its ability to correct a healthy range of myopic refractive errors, this lens may prove to be a valuable tool.

Currently, the ACPIOL with the most clinical data is the Artisan lens from AMO (marketed as the Verisyse), distributed in the US and Japan by AMO (Irvine, CA). The lens was originally named the “Worst” lens, after its developer Jan Worst. It was renamed for obvious marketing reasons. Using an iris clip on either side of the lens, the Verisyse lens is carefully threaded through the peripheral iris fibers (Fig. 9) . Moreover, the peripheral placement allows for dilation of the pupil without any iris damage, unlike the older iris-clip designs for pseudophakia. Fabricated with a UV-absorbing Perspex-C.Q. polymethylmethacrylate (PMMA) material and an overall diameter of 8.5 mm, the lens width is 5 or 6 mm. Since the PMMA material is non-flexible, this lens necessitates a 6-mm incision .This larger incision may lead to induced astigmatism and decreased uncorrected acuity, such as seen with the NuVita lens,16 which would prevent a successful refractive outcome. However, with its one-size-fits-all sizing, variable optic-zone diameters, visible insertion, and reversibility the Verisyse lens has proven to be an effective tool. The myopic lens is available in refractive ranges from –5.00 D to –15.00 D (6 mm OZD) and from –15.00 D to –20.00 D (5 mm OZD), and the available hyperopic lens range is from +3.00 D to +12.00 D. In recent US FDA clinical trials, the lens has resulted in impressive uncorrected visual acuities, with high predictability and stability. Some early complications (at 2 to 4 weeks) that were noted included glare and haloes, irregular pupils, corneal edema, and cells and flare (Fig. 10) . The only complications that appeared to persist longer than a few weeks (4 to 6 months) were glare and haloes. Currently, the lens is under investigation for astigmatism correction. The Verisyse has received a letter of pre-market approval (with restrictions) from the FDA and is awaiting full approval.

Another ACPIOL that is available outside the US is Ophthalmic Innovations International Phakic 6 H 125 IOL. The lens is very similar to the NuVita with more flexible haptics to decrease the chance of pupil ovalization. The 6-mm anterior chamber lens can correct –25 D to +10 D refractive errors, and has a patented heparin surface modification (HMS). Heparin is a carbohydrate molecule that is not recognized as a foreign substance by the body and thus does not elicit any immunologic response. As well as, a 2-piece ACPIOL, by Charles Kelman, MD, is in early clinical trials in the US.

To summarize, the anterior chamber may pose some hidden complications for refractive surgeons. There needs to be enough room to comfortably place the lens without causing any endothelial cell loss. It appears that any significant damage to the cornea mainly depends on the surgeon’s skill. Also, as these lenses are noticeable in the eye, and they may cause some reflection. Historically, cataract surgeons rarely place a lens in the anterior chamber, with the exception of secondary implants or to correct surgical complications.

 
      

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