Retinal thickness in diabetic retinopathy - A study using optical coherence tomography (OCT)

Background and Objective: The authors conducted a controlled study to quantify macular retinal thickness in diabetic retinopathy using optical coherence tomography (OCT) as an objective and noninvasive tool. The relationship between retinal thickness and standard methods of evaluating macular edema was investigated. Patients and Methods: A total of 136 patients in different stages of diabetic retinopathy were examined with OCT. In addition, fluorescein angiograms as well as standard eye examinations were conducted. The control group consisted of 30 individuals with a normal macula. Results: In the controls, retinal thickness was 153 +/- 15 mum in the fovea, 249 +/- 19 mum in the temporal parafoveal region, and 268 +/- 20 mum in the nasal parafoveal region. In diabetic patients, retinal thickness was increased to 307 +/- 136 mum in the fovea, 337 +/- 88 Am in the temporal retina, and 353 +/- 95 mum in the nasal retina, respectively. The differences between diabetics and controls were highly significant (P < 0.001). Retinal thickening correlated with fluorescein leakage in the angiograms to some extent. There was an intermediate correlation between retinal thickness and visual acuity, particularly in patients without macular ischemia. Sensitivity of detecting clinically significant macular edema by measuring foveal retinal thickness was 89% and specificity was 96%. Conclusion: Optical coherence tomography allows us to quantify retinal thickness in diabetic retinopathy with excellent reproducibility. OCT is able to detect sight-threatening macular edema with great reliability.