Objective: To assess the incidence or progression of macular edema (ME) after cataract surgery in diabetic patients using optical coherence tomography (OCT) and correlating this with degree of diabetic retinopathy or other risk factors.
Design: Prospective cohort study.
Participants: Fifty diabetic eyes undergoing cataract surgery.
Methods: Each eye underwent 7-field fundus photography no more than 3 months before surgery. Optical coherence tomography testing was performed within 4 weeks before surgery and at 1- and 3-month postoperative visits. Best-corrected visual acuity (BCVA) was recorded at each visit. Macular edema was defined as an increase of center point thickness on OCT > 30% from preoperative baseline.
Main outcome measures: Changes in foveal thickness and BCVA.
Results: The incidence of ME on OCT was 22% (95% confidence interval, 13%-35%). The average increase in center point thickness at 1 month for eyes with ME was 202 microm, which resulted in a nearly 1-line loss of vision (0.07 logarithm of the minimum angle of resolution [logMAR] units) compared with eyes without ME gaining >2 lines of vision (0.24 logMAR units) (P>0.001). Eyes with no diabetic retinopathy developed minimal thickening of 18 mum and 14 mum at 1 and 3 months, respectively, associated with approximately 2 and 3 lines of improved vision, respectively (0.22 and 0.26 logMAR units). Eyes with moderate or severe nonproliferative diabetic retinopathy or proliferative diabetic retinopathy developed thickening of 145 mum and 131 mum at 1 and 3 months, respectively, associated with <1 and 2 lines of improved visual acuity, respectively (0.08 and 0.17 logMAR units). This difference (P = 0.05) in thickening (127 microm and 117 mum at 1 and 3 months, respectively) was correlated inversely with visual improvement (r = -0.662). Both duration of diabetes > or = 10 years (P = 0.04) and insulin dependence (P = 0.007) were associated with reduced visual improvement.
Conclusions: Diabetic eyes have a high incidence of increased center point thickness on OCT after cataract surgery, associated with a loss of vision at 1 month, with limited visual recovery at 3 months. Treatment to prevent this might improve outcomes in similar individuals after surgery.