Association of Various Optical Coherence Tomographic Patterns of Diabetic Macular Edema With Central Subfield Thickness and Visual Acuity: A Cross-Sectional Observational Study

Introduction Diabetic macular edema (DME) is the most common and vision-threatening complication in diabetic patients with diabetic retinopathy (DR), especially in those with Type 2 diabetes mellitus. Optical coherence tomography (OCT) is a reliable tool most commonly used for assessing macular morphology and provides quantitative information on the macula. OCT also examines the outer retinal layers, which can predict visual outcomes. Thus, our study aims to identify the association of various OCT-detected DME morphological patterns with central subfield thickness (CST) and visual acuity. Materials and methods This is a cross-sectional observational study of 50 patients with DME detected on OCT who visited the Ophthalmology Department of Saveetha Medical College and Hospitals for a period of six months, from November 2023 to April 2024. A complete ocular examination, including best corrected visual acuity, scored with the logMAR scale, anterior segment examination, and fundus biomicroscopy using 90D and 78D lenses, was performed. Early Treatment of Diabetic Retinopathy Study (ETDRS) grading of DR into mild to very severe non-proliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) was noted. Spectral-domain OCT was used to diagnose DME. The CST was measured, and DME was classified into four patterns: sponge-like retinal swelling (SLRS), cystoid macular edema (CME), subretinal fluid (SRF), and posterior hyaloid traction (PHT). Results In the present study, males represented 60%, and females represented 40%. The mean age of the patients was 58.07 ± 6.80 years, with a mean duration of diabetes of 11.91 ± 5.14 years. Of the 50 patients with 100 eyes, only 60 eyes showed DME on OCT. CME was the most common morphological pattern (37%), while the least common pattern was PHT (10%). No significant association was found between a specific morphological pattern and control of diabetes. The most common pattern observed was SLRS in moderate NPDR, CME in severe NPDR, SRF in very severe NPDR, and PHT in PDR. Very severe NPDR patients showed all patterns of DME, and the PHT pattern was observed only in very severe NPDR and PDR. The highest mean CST was observed in the very severe NPDR stage, and the least was in the moderate NPDR stage. The mean CST was highest in SRF patterns and lowest in SLRS patterns. The best mean visual acuity was observed in the SLRS pattern, while the worst mean visual acuity was observed in the SRF pattern, followed by the PHT pattern. Conclusion Our study highlights the importance of OCT in patients with diabetes, as OCT patterns of DME are critical for predicting visual outcomes in DR. Severe grades of DR are usually associated with SRF and PHT patterns. Since patients with SRF and PHT patterns have the worst visual outcomes, these patients, upon identification, need to be counseled about their poor visual prognosis. Those with less severe DR should be closely monitored and advised on effective diabetes control to prevent progression and protect their vision.