PHAKIC IOLS

In the wake of several phakic intraocular lenses (PIOLs) pulled from European markets due to high complication rates, the few remaining designs provide good refractive outcomes with limited risk of endothelial cell loss, pupil ovalisation or induced cataracts, presenters told an ESCRS-sponsored symposium at the American Academy of Ophthalmology (AAO) annual meeting. However, problems can still occur even years after implantation, making ongoing monitoring a must for both anterior and posterior chamber IOLs.

Reviewing anterior chamber PIOLs, Francesco Carones MD, Milan, Italy, noted that both angle-supported and iris-supported lenses generate good refractive outcomes in high myopes, but also present potential safety issues, especially endothelial cell damage. Improperly sized angle-supported lenses may vault too close to the endothelium causing damage quickly, but even properly sized lenses can suddenly provoke rapid cell density loss after years of stability. Iris-supported lenses are more difficult to implant, can dislocate, potentially puncturing the iris in addition to damaging endothelium, may cause pupil ovalisation, and may cause pigment dispersion leading to glaucoma. “Safety is one of the biggest issues with this device,†Dr Carones said.

Largely because of these problems, just three anterior chamber PIOLs remain on the market in Europe; the iris-fixated Artisan/Verisyse and Artiflex/Veriflex, and the angle-supported Alcon AcrySof Cachet, Dr Carones noted. He reported extensive experience with all three, having implanted about 300 hard Artisan lenses since 2000, 111 flexible Artiflex since 2006, and 70 Cachet lenses since 2009.

Today, Dr Carones generally prefers Cachet because it is easier to implant. The Artisan requires a 6.0mm incision and the Artiflex can be challenging to attach to the iris, he said. However, he still uses Artiflex for cases with significant astigmatism and Artisan where the iris protrudes.

To confirm for himself that the Cachet is safe, Dr Carones conducted his own study. In 29 eyes in 15 patients with a mean refractive spherical equivalent of -9.88 +/-2.71 D, he measured the central and edge clearance as well as lens rotation six months after surgery. All patient had at least 3.3mm anterior chamber depth and normal anatomy, making them good candidates for PIOLs. All IOLs were inserted with a cartridge through a 2.6mm incision, and all surgeries were uneventful.

Measured by high resolution Scheimpflug imaging six months after surgery, the mean distance from the anterior IOL surface to the endothelium was 2.11mm, ranging from 1.77 to 2.37mm at the lens centre, and 1.44mm ranging from 1.20 to 1.71mm at the edges – all distances suggesting little interference with endothelium, Dr Carones said. Further, the high correlation between central and peripheral distance suggest that central measurements may be reliable for ongoing clinical assessment of lens stability.

He concluded that currently available anterior PIOLs are effective. Even so, all phakic IOLs, anterior chamber and posterior chamber, are still prone to complications. “I like to consider them as a kind of temporary solution. All phakic IOLs will need to be removed in the future.â€

Posterior PIOLs

Posterior chamber PIOLs were introduced by Fyodorov in the 1980s, said Vikentia Katsanevaki MD, PhD, Athens, Greece. In theory, the posterior PIOL is supposed to float above the crystalline lens, but in fact it often touches the lens, leading to cataracts. One design still clinically available, the Phakic Refractive Lens (Carl Zeiss Meditec), is now rarely used because it rests on the zonules, which can lead to contact with the crystalline lens, and dislocation into the vitreous as the zonules weaken, she noted (Martinez-Castillo et al. J Refractive Surg. 2004: 20:773-777).

That leaves the Visian ICL (Staar) as the only posterior PIOL in use in Europe, Dr Katsanevaki said. This collagen lens comes in several sizes to fit any size eye, and corrects both myopia and hyperopia. The latest, V4B, also offers astigmatism correction. Compared with earlier versions, this lens has a higher vault, which lowers the risk of cataract to about 0.5 per cent. That compares with reported rates of up to 20 per cent in earlier versions in the 1990s (Chen L et al. J Cataract and Refract Surg 2008; 34:7 1181-1200).

Visual outcomes are excellent. According to a three-year study reported in 2005, 94 per cent of -10 or higher myopes achieving 20/40 or better after surgery and 95 per cent within 2.0 D of intended correction. For those -7.00 or higher, 85 per cent were within 0.5 D. Contrast sensitivity improved in all categories, Dr Katsanevaki said.

The Visian ICL also has shown great promise treating keratoconic eyes.

Nonetheless, implanting posterior PIOLs is tricky, Dr Katsanevaki noted. In most cases, white-to-white measurements correlate well with sulcus size, but in about five per cent it does not. She recommends ultrasound B scans to confirm sulcus-to-sulcus measures to ensure proper lens sizing. She finds the lens safe, at least for short intervals.