Magnification Effect of the Capsulorhexis by the Cornea

ABSTRACT

PURPOSE: The purpose of this study is to measure the magnification of the capsulorhexis by the cornea using open ring guided capsulorhexis (ORGC) during cataract surgery. The study also investigated the magnification changes according to anterior chamber depth and corneal power. METHODS: The subjects comprised 40 eyes from 37 patients whose astigmatism was lower than 0.25 D and who had cataract surgery using ORGC from December 2011 to April 2012. ORGC was set on the anterior capsule and photographs were obtained using a camera connected to a surgical microscope after attaching a ruler around the limbus. The pixel number of 5 mm gradations on a ruler and the inner diameter of ORGC were measured using ImageJ. The inner diameter of ORGC was known to be 5.30 mm and the size of ORGC in the snapshot was therefore calculated by proportional expression. After corneal power and anterior chamber depth were identified, the magnification effect was evaluated. RESULTS: The 37 subjects were composed of 19 males and 21 females, and their average age was 64.8 years. The average depth of the anterior chamber was 3.28 mm, and the average corneal power was 43.534 D. The measured inner diameter of ORGC was 6.14 mm (SD: +/-0.16 mm) and the average magnification of the capsulorhexis was 115.9% (SD: +/-3.1%). The results showed that in the case of shallow anterior depth and low corneal power, the magnification was low equivalent to 110%. However, when the anterior chamber was deep and the corneal power was high, the magnification was greatly increased to 120%. CONCLUSIONS: The capsulorhexis was magnified to an average of 115.9% by the cornea during cataract surgery. In particular, it is necessary to consider capsulorhexis size in cases with deep anterior chamber and high corneal power, because the magnification will be greater in those cases.