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The overlap of the capsulorhexis changes refractive outcome and axial IOL position determined by LENSTAR interferometry and ultrasound biomicroscopy

Poster Details

First Author: P.Fedor USA

Co Author(s):    A. Fedor   D. Fedor           

Abstract Details



Purpose:

To determine the effect of the capsulorhexis overlap over the IOL optic on the axial position of the IOL and refractive outcome.

Setting:

Private practice, Great Lakes Eye Consultants, Traverse City, Michigan, USA. MUS, Bratislava, Slovakia, EU.

Methods:

This retrospective intraindividual study comprised 38 eyes of 19 consecutive patients after cataract surgery with more than 180 degrees (50%) difference in the amount of the capsulorhexis overlap over the IOL optic in the right eyes as compared to the left eyes. We included only patients with the same platform of IOL in each eye and similar biometry in each eye. The difference between the right and left eye's axial length was within 0.25 mm, anterior corneal curvature within 1 D and anterior chamber depth within 0.25 mm. Pseudophakic anterior chamber depths were measured using Lenstar interferometry, ultrasound biomicroscopy, immersion and contact Ascan. Pseudophakic anterior chamber depths, postoperative refractions and errors of predicted refractions of IOL power calculation formulas were compared in the right and left eyes of patients with similar ocular biometry that only differed in the amount of the capsulorhexis overlap over the IOL optic.

Results:

The mean overlap of the capsulorhexis over the IOL was 81% +/- 18% in group 1 with smaller capsulorhexis and 8% +/- 14% in group 2 with the larger capsulorhexis. The difference between the overlap of the capsulorhexis over the IOL optic was 72 % +/- 19% between groups 1 and 2. Larger capsulorhexis with less overlap over the IOL optic compared to a smaller capsulorhexis with a larger overlap of the IOL optic is associated with an average anterior displacement of the IOL optic of 0.24 mm and an average myopic shift of 0.5 D. Measurements obtained using Lenstar interferometry, ultrasound biomicroscopy, immersion and contact A-scan all confirmed the different axial IOL position.

Conclusions:

Our intraindividual study of the effect of the capsulorhexis on the postoperative refraction after cataract surgery compared right to left eyes with similar ocular biometry where the only difference was the size of the capsulorhexis. The overlap of the capsulorhexis has a clinically significant effect on the postoperative axial position of the IOL. The possible causes of the shift of the IOL include capsular fibrosis, IOL geometry and the forces acting on lens membrane explained based on new model of ocular biomechanics. The introduction of femtosecond lasers to create capsulorhexis and intraocular lenses designed to correct presbyopia have changed the expected refractive outcomes to +/- 0.25 D. A recent evaluation of errors in IOL power calculations revealed a mean theoretical absolute error of 0.6 D for an eye of average dimension. The major source of error was the prediction of postoperative IOL position. We believe that the overlap of the capsulorhexis contributes significantly to the axial postoperative IOL location and refractive outcome. FINANCIAL INTEREST: NONE

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