Evaluation of choroidal thickness in different stages of diabetic retinopathy

Abstract

Purpose: to assess changes of choroidal thickness (CT) in diabetic patients in different stages of diabetic retinopathy and diabetic macular edema using spectral domain optical coherence tomography. Patients and methods: One hundred and sixty three subjects were enrolled: 113 diabetic patients (186 eyes) and 50 normal individuals as controls. Eyes were divided into two groups according to age; group A from 35 to 50 years and group B from 51 to 65 years. Both groups classified according to retinopathy grade: DR1 (no DR), DR2 (mild- moderate nonproliferative diabetic retinopathy (NPDR)), DR3 (severe NPDR), DR4 (untreated proliferative diabetic retinopathy (PDR)) and DR5 (previously treated PDR). All participants underwent full ophthalmic examination, stereoscopic color fundus photography, and spectral domain optical coherence tomography (RS-3000; Nidek). Spectral domain optical coherence tomography examination consisted of linear scans, 6 mm in length, centered onto the fovea, and macula multi scans. Choroidal thickness was measured manually at the fovea and at 500, 1000, and 1500 um distance along all scans in the macula. Results: Mean age was not significantly different between patients with diabetes and controls. In the macular area, CT was significantly lower in the nasal quadrant versus all other quadrants (P, 0.0001), in both groups. No significant CT difference was found between controls and diabetic eyes without detectable DR. Diabetic macular edema did not influence CT. In early NPDR (mild and moderate) and treated PDR the mean choroidal thickness was significantly decreased than control. In severe NPDR and treated PDR, the mean subfoveal choroidal thickness was not different than control. There was a statistically significant increase in choroidal thickness in PDR when compared with the mild NPDR group (P=0.027). DME was associated with a non-statistically significant increase in choroidal thickness compared with eyes without DME (P=0.13). Conclusion: Choroidal thickness is reduced in diabetic eyes. Subfoveal choroidal thickness increased with the severity of diabetic retinopathy but showed no statistically significant association with the presence of DME. Spectral domain optical coherence tomography clearly confirms in vivo previously reported histopathologic observations. The role of choroid in the pathophysiology of DR needs to be adequately investigated.