[Effect of the different diameter of posterior capsulotomy on visual field]

The purpose of this study is to determine the influence of two different diameter of posterior capsulotomy on visual field.

Forty patients with posterior capsule opacification (PCO) of grade II after phacoemulsification and intraocular lens implantation were randomly divided into two groups. 20 cases received laser capsulotomy with 2 mm diameter. Other 20 cases received laser capsulotomy with 4 mm diameter. One and half months after laser capsulotomy, vision field of every patient was examined using the automated perimetry for central 30 degrees and peripheral 60 degrees. Visual field in 21 patients with a transparent posterior capsule after cataract surgery was also evaluated by the same automated perimetry.

There were significant reductions in the total visual field sensitivity, the mean deviation (MD) and the pattern standard deviation (PSD) in 2 mm diameter capsulotomy group compared with 4 mm diameter capsulotomy group (P < 0.001). There were no significant difference in visual field between 4 mm capsulotomy group and the transparent posterior capsule group (P > 0.05).

Better visual acuity could be obtained after laser capsulotomy with 2 mm capsulotomy, however the generalized sensitivity reduction and irregular localized depression of visual island might occurred. 4 mm diameter capsulotomy may be a better choice in laser capsulotomy in patients with PCO.