The Impact of Macular Laser Photocoagulation on Contrast Sensitivity Function in Patients with Clinically Significant Macular Edema

Contrast sensitivity is an important aspect of visual function and is even more important for ordinary daily tasks than visual acuity. Contrast sensitivity function may be deteriorated to a significant level in diabetic retinopathy, especially in diabetic macular edema. The objective of this study was to determine the impact of macular laser photocoagulation—as the standard treatment of clinically significant macular edema—on contrast sensitivity function. In a prospective noncomparative interventional case series, 17 patients with clinically significant bilateral macular edema and no history of prior macular laser photocoagulation were enrolled. Baseline visual acuity, contrast sensitivity function, and fluorescein angiography were obtained and reassessed three months after macular laser photocoagulation. Clinically significant macular edema resolved in 22 (65%) of 34 eyes, three months after their first session of macular laser photocoagulation. The mean pretreatment visual acuity was 24.5/40 (0.21 logMAR) ±10.3/40. Three months after macular photocoagulation, visual acuity remained stable in 19 eyes, decreased in 12 eyes, and increased in three eyes. The mean post-treatment visual acuity was 24/40 (0.24 logMAR) ±10.8/40. There was a statistically significant (P = 0.02) decrease in visual acuity following laser therapy. In subgroup analysis, this decrease in visual acuity was only observed in those with unresolved clinically significant macular edema. The mean contrast sensitivity threshold increased in all spatial frequencies by three months after macular photo­coagulation. The maximum rise was observed in the frequency of 6.4 cycles per degree in the mid range of frequencies, with a pretreatment mean of 9.41 dB and a post-treatment mean of 11.50 dB (P<0.05). Contrast sensitivity function improved after macular laser photocoagulation in clinically significant macular edema patients.