Phakic intraocular lens has minimal effect on corneal endothelial health

January 1, 2010

An angle-supported phakic lens had a minimal effect on corneal endothelial cell health in patients followed up to 4 years after implantation.

Improvements in the safety outcomes of phakic IOLs have been observed recently, primarily due to advances in lens design and materials. However, long-term evaluation of their safety remains important, said Dr. Knorz, a member of the Medical Faculty Mannheim of the University of Heidelberg, Mannheim, Germany.

One of the key features to observe is corneal endothelial health, which is essential to maintaining corneal transparency. The endothelium has limited regenerative capacity and is vulnerable to cell loss from increasing age.

A combined analysis of first and second eyes was performed since both eyes had been included at one study site, while only one eye per patient was assessed at the others. Patients were excluded if their endothelial cell density was too low based on their age, and they were required to have an anterior chamber depth of 3.2 mm or more.

Images from all study sites were examined at a central reading center. The analysts looked for acute loss (the change from the preoperative measurement to 6 months postoperatively) and annualized chronic loss (from 6 months to every year of follow-up). They also evaluated the percent of hexagonality and coefficient of variation.

The rate of acute loss was 3% at both the center of the cornea and in the periphery, according to Dr. Knorz. The chronic loss rate was about 1% in the center of the cornea and 0.5% in the periphery, which is below the standard of 2% per year. The rate was annualized at 4 years, at which time 65 subjects were included in the analysis. Values for hexagonality (about 57%) and coefficient of variation (30%) were within normal ranges.

"Over the long term, the corneal endothelial health seems to be maintained after implantation of [this] anterior chamber phakic IOL," Dr. Knorz said, adding that the mean cell loss was very low and the cell morphology was stable.

Investigations of the IOL are ongoing, he said, and patients will continue to be monitored.