Posters

Defining the true corneal power for IOL calculations in a post-RK patient

Poster Details

First Author: E. Imenova BULGARIA

Co Author(s):    D. Mitova                    

Abstract Details

Purpose:

To define the main problems in calculating the IOL power in patients with preceding radial keratotomy(RK) . To analize the refractive outcomes after Phaco+IOL in post-RK patients and to identify the true corneal power for IOL calculation in these patients- average keratometry or the flat meridian on Orbscan videokeratometry

Setting:

A retrospective analysis of 6 patients with preceded RK (7 eyes), 5 women and 1 men(age 60 to 67) post phaco emulsification and implantation of mono focal IOL. None of them had any other ocular pathology

Methods:

The IOL calculation and average keratometry (Av.K) was done by the Lenstar optical biometer. The average keratometry was replaced by the central flat zone of the cornea (F.m. K.) calculated by the Orbscan II videokeratography system (Bausch & Lomb) and IOL power were recalculated . The IOL power of the two calculations were compared. Distance VA was measured using the Snellen Chart one month post IOL implantation.

Results:

We devided the patients in two groups-those with no significant differnce in both keratometries and those with significant difference. In all of the cases the highest result of the IOL calculation was taken which corresponds to the Orbscan keratometry readings. In all cases we achieved emmetropic or near ememetropic condition. Because of the limited number of patients it is hard to estimate the statistical significance of the data.

Conclusions:

The avarege keratometry tends to overestimate the true corneal power due to the smaller effective optical zone in post-RK patients. With Orbscan we can choose the diameter of the zone which we want to measure. The central flat 3 mm zone of the Orbscan tends to be more reliable and should be taken as the true corneal power for exactness of IOL power calculation in this group of patients. This is mostly important for the cases with significant difference between F.m.K and A.K.

Financial Disclosure:

NONE