Patients with diabetes have additional concerns to take into account when it comes to cataract removal. The Diabetes and Cataract Study I (DICAT I) found that 25% of diabetic subjects undergoing cataract surgery have preoperative diabetic macular edema (DME), which poses a high risk of macular worsening that may offset any visual benefits of the surgery. The process of phacoemulsification may increase inflammatory mediators in the aqueous and vitreous, leading to the development or worsening of macular edema.

A recent study examined cataract surgery’s impact on the retinas of patients with early DME—as there are few published studies on preclinical DME response compared with full-blown DME—and found that early DME is associated with poorer outcomes after cataract surgery.

To study retinal effects, researchers launched the DICAT II, a prospective, comparative, multicenter, observational study conducted at six Italian clinics. The study included patients aged ≥55 years who had type 1 or type 2 diabetes and early DME classified by spectral domain OCT. In Group 1 (78 eyes of 78 patients), patients underwent phacoemulsification-based cataract surgery. Those in Group 2 (65 eyes of 65 patients) had early DME and either had clear media or underwent uncomplicated cataract surgery ≥1 year previously. The researchers assessed central subfield thickness (CST) and BCVA in both groups.

The researchers reported that a negative impact on CST manifested after the first postoperative week. “CST peaked rapidly during the first month, then rapidly decreased,” they wrote. They noted CST worsened ≥10µm in 63 of 78 eyes in Group 1 (80.7%) and in 29 of 65 eyes in Group 2 (44.6%). CST worsening of ≥50µm was seen in 51 eyes (65.4%) in Group 1 and in 10 eyes (15.4%) in Group 2—representing a significant difference. Overall, mean CST worsening was significantly lower in Group 2 than in Group 1 (average: 38.6µm vs. 85.85µm). “Higher glycemic levels and HBA1c levels were significantly associated with the risk of >50µm CST worsening in eyes from both groups,” the researchers added.

“Cataracts develop faster and earlier in people with diabetes, compared with those with normal glycemia,” the researchers explained. “The presence of diabetes is a negative prognostic factor for cataract surgery, independently of preoperative macular impairment. Even in diabetic eyes without DME, the risk ratio of developing edema compared with non-diabetics rises from 1.8 in subjects without any sign of retinopathy to 10.3 in the presence of advanced stages.”

While intravitreal steroids or anti-VEGF administered immediately before or after cataract surgery can decrease complications of macular worsening, this is traditionally warranted only when macular edema is considered clinically relevant (i.e., when an eye shows a consistent increase in macular thickness, associated with alterations in retinal structure evident on OCT). Early or preclinical DME doesn’t meet this classification right now.

“This study not only reinforces the importance of close pre- and post-op monitoring of the maculae of patients with diabetes undergoing cataract surgery, but also focuses attention for the first time on what was previously considered an insignificant form of the disease (early DME), and highlights how even this minimal edema may be dramatically worsened by cataract surgery,” the researchers concluded.

Panozzo G, Mura GD, Franzolin E, et al. Early DMO: a predictor of poor outcomes following cataract surgery in diabetic patients. The DICAT-II study. Eye. August 3, 2021. [Epub ahead of print].