Treating high myopia

July 1, 2013

An angle-supported pIOL improves quality of vision, even in mesopic conditions

"We know that young highly myopic patients suffer from poor distance vision, particularly in mesopic conditions," said Dr Antionio Toso (San Bassiano Hospital, Bassano del Grappa, Italy) when discussing the reasoning behind his study looking at the visual and aberrometric outcomes in eyes implanted with an angle-supported phakic intraocular lens (pIOL).1 "What I aimed to do was to try to understand whether visual acuity could improve in myopic eyes implanted with the AcrySof Cachet pIOL (Alcon Laboratories, Fort Worth, Texas, USA) and if these improvements were also seen in mesopic conditions."

Move towards refractive surgery

"My daily work in cataract and vitreoretinal surgery made me move towards refractive surgery with pIOLs implantation for the treatment of high myopia to improve the quality of myopic patients' lives," explained Dr Toso. "I used to think I had to provide the best distance visual acuity to the patients, however, this parameter can no longer be considered a good one to evaluate visual outcomes after any ophthalmic surgery. I realized that more recent attention has been focused on the effects of residual higher-order aberrations (HOAs), as happened in cataract surgery with aspheric IOLs."

Studying SA: The dominant HOA

Drs Toso and Morselli included 35 eyes of 18 patients in the statistical analysis. All eyes had high myopia and were implanted with an AcrySof Cachet angle-supported pIOL. Measurements of the pre- and post-op total SA and PSF were taken using a Luneau 80 Wave+ wavefront aberrometer at a fixed pupil diameter under pharmacologic mydriasis.

"My chief and I decided to study SA because this is the main aberration modified by this pIOL in the optical system of the eye implanted. It is well known that the impact of SA increases with pupil dilation. As a consequence, SA is the dominant HOA in degrading optical quality of vision," continued Dr Toso. "Therefore, we decided to get all aberrometric data, in pre- and postoperative examinations, by measuring HOAs and PSF value even in mydriasis (with tropicamide 1% eyedrops). We used a wavefront aberrometer with high resolution Hartmann-Shack technology at a fixed entrance pupil scan size of 5.0 mm."