Cataract surgery may not cause progression of diabetic retinopathy

The authors report visual acuity outcomes of small-incision phacoemulsification cataract surgery in patients with diabetic retinopathy using prospectively collected data from the Danish National Patient Registry. CDVA increased significantly after surgery, regardless of the degree of diabetic retinopathy. These results are encouraging and dispute the hypothesis that cataract surgery causes progression of retinopathy.

Of 7,323 patients with diabetic retinopathy, 285 underwent surgery. The postoperative CDVA outcome was positively correlated with preoperative CDVA and negatively correlated with the degree of diabetic retinopathy and age (P < 0.001). A history of focal laser treatment for clinically significant macular edema (CSME) increased the risk for not gaining visual acuity. In post hoc analysis, the proportion of patients in the cohort without diabetic retinopathy appeared to increase the year before cataract surgery (P = 0.03) and decrease the year after cataract surgery (P < 0.001).

The incidence of CSME the year after cataract surgery was 4 percent, which is low compared with the incidence in previous studies. However, this result should be interpreted with caution. Cataract surgery was not performed in patients with untreated CSME, and fluorescein angiograms were not used to evaluate postoperative CSME because the patients were followed at a screening clinic.

Whether or not diabetic retinopathy progresses after phacoemulsification compared with the natural history of the disease remains controversial. The increasing proportion of patients with no diabetic retinopathy up until cataract surgery in part reflects increasing lens density, making retinal examination difficult. This phenomenon has its greatest impact in eyes with a low degree of retinopathy, where the signs may be subtle and combined with a pronounced cataract. The apparent progression after cataract surgery may only be due to removal of the dense lens making the optics clear enough for retinopathy to be sufficiently visualized.