Preservation of retinal sensitivity in central visual field after panretinal photocoagulation in diabetics

Changes in retinal sensitivity within central 30 degrees following panretinal photocoagulation (PRP) for more severe diabetic retinopathy were investigated. Twenty-five eyes with visual acuity of 0.4 or better and minimal maculopathy were studied prospectively. All underwent PRP in two sittings, and Humphrey field analyzer 30-2 threshold test was done before and 1 week, 1 and 3 months after the treatment. The mean retinal sensitivity threshold was obtained from each hemifield between 15 and 30 degrees and from the central 15 degree area, and the changes in the values were analyzed. Mean sensitivity threshold in the upper visual field at pre-PRP, post-PRP 1 week, 1, 3 months were 15.62, 13.81, 14.31, 14.85, respectively. Values in the lower field were 18.71, 17.25, 17.10, 18.17. Difference between pre-PRP and post-PRP was statistically significant at 1 week but no longer thereafter. Retinal sensitivity within the central 15 degrees remained stable. The data show that retinal sensitivity decreases significantly 1 week after PRP but recovers upto 95% of pre-PRP level over the following 3 months.