Macular edema and visual outcome following cataract surgery in patients with diabetic retinopathy and controls.

Background: Cystoid macular edema (CME) is a well-known complication after cataract surgery, and diabetic retinopathy is reported to be an important risk factor for impaired visual recovery. In this prospective study, we compared visual outcome 6 months after surgery in eyes with moderate retinopathy and no previous ME with a control group, and observed the incidence of ME seen on fluorescein angiography (FA) and optical coherence tomography (OCT).
Methods: Thirty-four patients with type-2 diabetes and 35 controls were enrolled. Best-corrected visual acuity (VA) letters ETDRS was measured pre-op, at day 7, week 6 and month 6. FA performed pre-op and at week 6 was divided into three leakage patterns. OCT performed pre-op, at week 6 and month 6 was qualitatively divided into three types. Macular thickness was measured in three circular fields (central subfield, inner and outer circle) from the macular maps.
Results: There was no statistically significant difference in VA before surgery, at day 7 or at 6 months, but at 6 weeks there was a significant difference with lower VA in the diabetic group. Six percent of control and 12% of diabetic eyes developed a clinical CME defined as a loss of >5 letters between day 7 and week 6. Incidence of FA leakage was 23% in control and 76% in diabetic eyes. At 6 weeks, 20% of control and 44% of the diabetic eyes had qualitative changes on OCT. A statistically significant increase in thickness was observed for all three macular areas in both groups, part of it remaining at 6 months. There were, however, no differences in central macular thickness between the groups at any visit. Retinal thickening had poor correlation with VA.
Conclusion: The final visual outcome in eyes with mild to moderate retinopathy, without previous ME, is as good as in normal eyes, but an increased frequency of macular changes may protract recovery of full vision. Changes on OCT or FA are often seen without any obvious effect on VA. OCT is as good as FA at detecting a clinical CME, and is the technique recommended for follow-up before FA is considered.