The role of light scatter in the degradation of visual performance before and after Nd:YAG capsulotomy.

The aim of this study was to determine whether capsulotomy size influences visual performance. Snellen visual acuity and forward light scatter (light scattered towards the patient's retina, but out of the focussed retinal image) measurements using simple computer graphics based on van den Berg's technique were used to measure visual performance. Twelve patients were studied: 4 had small central capsulotomies through undilated pupils and 8 had wide capsulotomies through dilated pupils. The two groups were matched for age and pre-laser Snellen acuity. Following treatment, both groups had equal improvements in Snellen acuity. There was only a significant (p < 0.001) improvement in forward light scatter readings in the group who received wide capsulotomies. Measurements of forward light scatter are more sensitive than Snellen acuity testing in demonstrating loss of visual performance in patients with media opacities. It is recommended that pupils are dilated prior to Nd:YAG capsulotomy if forward light scatter from capsule remnants and the consequent glare disability are to be minimised.