Prior cataract surgery tied with higher risk of developing Diabetic Retinopathy among patients: JAMA
Cataracts and diabetic retinopathy (DR) are the leading causes of acquired blindness worldwide, which is further compounded by the fact that patients with diabetes have an increased risk of developing cataracts. Thus, many patients with diabetes concomitantly have cataracts and DR. Although extraction is the standard treatment option for cataracts, it is also reported to worsen existing cases of DR, a microvascular complication of diabetes, leading to further vision loss.
It was postulated that cataract extraction may possibly lead to a breakdown of the blood-retinal barrier and the blood-aqueous barrier and enhanced intraocular inflammatory response, all of which may result in the occurrence of DR in patients with diabetes. For this reason, current DR care guidelines also recommend measures of preoperative stabilization for patients with diabetes and existing vision threatening DR who undergo cataract extraction. These measures include optimizing glycemic control and performing panretinal photocoagulation preoperatively to better prevent post surgery complications such as neovascularization and vitreous hemorrhage among this group of patients.
Yih-Chung Tham and team aimed to assess the risk of developing DR after cataract surgery among individuals with diabetes, using 2 Asian population-based cohorts in Singapore.
A population-based prospective cohort study was conducted among participants recruited from the Singapore Epidemiology of Eye Diseases Study. The baseline visit was conducted between June 1, 2004, and March 31, 2009, and the 6-year follow-up visit was conducted between June 1, 2011, and July 31, 2016. Statistical analysis was performed from October 1 to 31, 2019. Exposure included cataract surgery performed before a follow-up visit, determined based on slit lamp evaluation of lens status at baseline and follow-up visits.
Eyes with incidence of DR were defined as those with the presence of any DR (level 15 based on the modified Airlie House classification system, graded from retinal photographs) at 6-year follow-up with no DR at baseline. The association between cataract surgery and incidence of DR was evaluated using a multivariable Poisson regression model with a generalized estimating equation to account for correlation between both eyes.
- A total of 1734 eyes from 972 participants with diabetes (392 Malay individuals and 580 Indian individuals; 495 men; mean [SD] age, 58.7 [9.1] years) were included in the analysis.
- A total of 163 study eyes had already undergone cataract surgery at baseline, and a total of 187 eyes (originally phakic at baseline) underwent cataract surgery any time during the follow-up period.
- Of these 350 eyes, 77 (22.0%) developed DR. Among the 1384 eyes that never underwent cataract surgery, 195 (14.1%) developed DR.
- After adjustments for age, sex, race/ethnicity, baseline hemoglobin A1c level, duration of diabetes, random blood glucose level, antidiabetic medication use, hypertension, body mass index, and smoking status, multivariable regression analysis showed that any prior cataract surgery was associated with incidence of DR (relative risk, 1.70; 95% CI, 1.26-2.30; P = .001).
- Subgroup analyses by race/ethnicity showed similar associations in both Malay individuals (relative risk, 1.73; 95% CI, 1.13-2.69; P = .02) and Indian individuals (relative risk, 1.93; 95% CI, 1.33-2.80; P < .001).
- After excluding eyes that were phakic at baseline but underwent cataract surgery during the 6-year follow-up period, authors observed that cataract surgery at baseline was associated with 2.07 times (95% CI, 1.34-3.20; P = .001) greater risk of developing DR.
In this 6-year follow-up cohort study, authors observed that individuals with diabetes from their Malay and Indian population-based cohorts had increased risk of developing DR after cataract surgery. This association was consistent in both racial/ethnic groups and remained significant even after accounting for relevant confounders.
These observations are supported by previous studies that reported that retinal blood flow and the blood-aqueous barrier may be disrupted during or after cataract surgery. In addition, increased levels of inflammatory biomarkers, such as interleukin 6, in the aqueous humors were also observed after cataract surgery. Taken together, it is plausible that these factors may collectively be associated with the development of DR after cataract surgery.
This study was limited by a small sample size and did not sufficiently adjust for relevant confounding risk factors that may have been associated with the outcome of interests. The study's strengths included the prospective design, large sample size, and long 6-year follow-up period between examinations.
The researchers concluded, "Our population-based study demonstrated that prior cataract surgery was associated with a higher risk of developing DR among individuals with diabetes. Nevertheless, this risk was observed mainly in incident mild and moderate DR cases. Further studies are still warranted to validate this association. On further validation, it may be conceivable for patients with diabetes to be recommended for more frequent DR screenings after cataract surgery."
Source: JAMA Network Open. 2020;3(6):e208035