Contributions of the capsulorrhexis to straylight

OBJECTIVES: To quantify the effect of the capsulorrhexis on straylight and to determine optimal capsulorrhexis size.

METHODS: Fifty-six pseudophakic eyes with intact capsulorrhexis were included in the study. Straylight was measured with a straylight meter before and after pupil dilation. Capsulorrhexis and pupil diameter were measured and opacity of the anterior capsule was graded (on a scale of 0-5) with the slitlamp. Capsulorrhexis size and opacity were compared with the difference in straylight values between natural and dilated pupils.

RESULTS: The mean capsulorrhexis diameter was 4.5 mm (range, 2.9-6.2 mm). Most anterior capsular rims were opaque in the area of contact with the intraocular lens (62.5% higher than grade 1). Mean straylight before pupil dilation was log(s)=1.25 (range, 0.68-2.13), which increased to 1.46 (range, 0.88-2.22) after pupil dilation, which corresponds to a 62% increase (P <.001). The effect of capsulorrhexis size and opacity on the increase in straylight in scotopic conditions can be quantified by the following formula: Deltas = 19 x (grading of anterior capsular rim) x (fraction of pupil area covered by rhexis).

CONCLUSIONS: The influence of size and opacity of the capsulorrhexis via straylight is described in a quantitative model. Capsulorrhexis size must be greater than 4 mm to prevent functional problems at night.