Comparison of Retinal Nerve Fiber Layer Thickness Among Patients With Diabetic Retinopathy With and Without Panretinal Laser Photocoagulation

Abstract

Purpose: : To determine whether diabetic retinopathy and panretinal photocoagulation (PRP) alter the retinal nerve fiber layer (RNFL) thickness which in turn may account for glaucomatous appearing optic nerves in this patient population.

Methods: : Patients with diabetic retinopathy with and without panretinal photocoagulation as well as age–matched non–diabetic control subjects were enrolled in a cross–sectional study. Patients with significant ocular disease other than diabetic retinopathy were excluded. Participants underwent an ophthalmic evaluation including grading of diabetic retinopathy and optical coherence tomography (Stratus OCT). The OCT fast peripapillary RNFL thickness and macular thickness map programs were used to assess retinal thickness measurements. Three OCT scans of both peripapillary and macular areas were performed and the mean of these measurements for each eye was used for statistical analysis.

Results: : A total of 30 healthy individuals (59 eyes) and 32 diabetic patients (52 eyes) were included in this study. The diabetic patients with PRP treatment had thinner peripapillary RNFL thickness measurements than those without PRP and both these groups had thinner RNFL than control subjects, especially in the inferior region. The mean (± SD) inferior average RNFL thickness’ were 130.8 ± 14.3 µm (control subjects), 121.8 ± 23.1 µm (without PRP), 111.4 ± 21.1 µm (with PRP) and these were significantly different (P=0.002). The diabetic patients demonstrated thicker macular measurements than healthy individuals. The mean foveal thickness’ were 196.9 ± 20.6 µm (control subjects), 225.8 ± 43.7 µm (without PRP) and 216.1 ± 48.7 µm (with PRP) (P=0.007).

Conclusions: : RNFL is thinner in diabetic patients treated with PRP when compared to patients with diabetic retinopathy without PRP and to age–matched control subjects. This thinning of the RNFL may result from axonal degeneration from PRP as well as from progression of diabetic retinopathy which may cause optic nerve changes that could be confused with glaucomatous damage.

Keywords: imaging/image analysis: clinical • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials • diabetic retinopathy