Choroidal thickness measured using swept-source optical coherence tomography is reduced in patients with type 2 diabetes

OBJECTIVE To compare choroidal thickness between patients with type 2 diabetes (T2D) and healthy controls measured using swept-source optical coherence tomography (SS-OCT). METHODS The sample comprised 157 eyes of 94 T2D patients, 48 eyes of which had diabetic macular edema (DME), and 71 normal eyes of 38 healthy patients. Subfoveal (SF) choroidal thickness, and choroidal thickness at 500-μm intervals up to 2500 μm nasal and temporal from the fovea were measured using the SS-OCT. Choroidal thicknesses were compared between groups using Student's t-test. Additionally, Pearson correlations were calculated between diabetes duration, glycosylated hemoglobin (HbA1c) levels, and choroidal thickness. RESULTS Mean diabetes duration was 16.6±9.5 years, while mean glycosylated hemoglobin was 7.7±1.3%. Overall, the choroid was significantly thinner in T2D patients. Individuals with DME had reduced choroidal thickness in all measurements, except at 2000 and 2500-μm nasal positions, compared to healthy controls. There was a moderate correlation between choroidal thickness and HbA1c levels in DME patients (SF: r = 0.342; p = 0.017). Diabetes duration did not correlate significantly with choroidal thickness. CONCLUSION SS-OCT measurements revealed that the choroid was significantly thinner in T2D patients, moderate non-proliferative diabetic retinopathy patients, and DME patients than in healthy individuals. Further studies are needed to clarify the effect of diabetes on this layer and the relationship between choroidal thickness and DME.