Choroidal thinning measured by swept-source optical coherence tomography (SS-OCT) appears to be an early imaging biomarker for the development of referable diabetic retinopathy (DR), according to research published in Investigative Ophthalmology & Visual Science.

Researchers conducted a prospective cohort study to evaluate the association between choroidal thickness and the 2-year incidence of referable DR in patients with type 2 diabetes mellitus (DM).

All patients underwent comprehensive ocular examinations, including standard 7-field fundus photography. The researchers measured the macular choroidal thickness using a commercial SS-OCT device and quantified the association between choroidal thickness and new-onset referable DR. They evaluated the prognostic value of choroidal thickness using the area under the receiver-operating characteristic curve (AUC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI).


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A total of 1345 patients with type 2 DM (mean age, 64 years; range 30-80; 59% women and 41% men) were included in the study. The average duration of type 2 DM was 8 years.

At the 2-year follow up visit, 9% of patients had newly developed referable DR. In a stepwise multivariate model adjusting for other factors, increased referable DR risk was associated with greater hemoglobin A1C value (RR, 1.35; 95% confidence interval [CI], 1.17-1.55; P <.001), higher systolic blood pressure (RR, 1.02; 95% CI, 1.01-1.03; P =.005), lower triglyceride level (RR, 0.81; 95% CI, 0.69-0.96; P =.015), presence of DR (RR, 8.16; 95% CI, 4.47-14.89; P <.001), and thinner average choroid (RR, 0.903; 95% CI, 0.871-0.935; P <.001). The addition of average choroidal thickness to the model improved NRI (0.464±0.096; P <.001) and IDI (0.0321±0.0068; P <.001) for risk of referable DR and improved the AUC from 0.70 (95% CI, 0.66-0.76) to 0.76 (95% CI, 0.72-0.80).

“This study is the first longitudinal study of diabetes based on SS-OCT in a large sample to find that [choroidal] thinning is independently associated with [referable DR] occurrence and is an essential imaging marker for DR progression,” researchers explain. “Automated quantitative assessment of [choroidal thickness] using SS-OCT can provide prognostic information about [referable DR] risk in patients with type 2 DM.”

The primary limitations of the study included lack of ancestral diversity in the study population (all Chinese patients with type 2 DM), a limited follow up duration, and variation in the time of day for the SS-OCT imaging.

Reference

Wang W, Li L, Wang J, et al. Macular choroidal thickness and the risk of referable diabetic retinopathy in type 2 diabetes: a 2-year longitudinal study. Invest Ophthalmol Vis Sci. 2022;63(4):9. doi:10.1167/iovs.63.4.9