Analysis of Nerve Fiber Layers After Photocoagulation in Diabetic Retinopathy

Abstract

Purpose: : To determine if there is changes in the nerve fiber layers by Optic Coherence Tomography (OCT) in Diabetic Retinopathy after photocoagulation.

Methods: : This is a prospective, longitudinal, comparative, and observational study. All patients with diabetic retinopathy were included from May to October 2005. We divided patients into 2 groups: Group 1 included patients with proliferative diabetic retinopathy without treatment and Group 2 included patients with diabetic retinopathy who have been photocoagulated all ready and required new treatment. All patients with history of glaucoma, intraocular surgery or vascular occlusion were not included. Both groups underwent photocoagulation and nerve fiber layer thickness analysis (OCT 3, Zeiss,) was done before and 4 to 6 weeks after treatment.

Results: : We included 33 eyes from 24 patients. Mean age was 56 years old (range from 38 to 72). Fifty percent of cases in Group 1 peripapilar nerve fiber layer thickness was decreased in the temporal and inferior areas and 56.25% in Group 2. More changes were seen in Group 1: a decrease of 40µ in the superior area, 46µ nasal, 40µ inferior, 32µ temporal (mean 39.5µ) compared with Group 2 with a decrease of 31µ in the superior area, 53µ nasal, 12µ inferior 17µ temporal ( mean 28.25µ) (p>0.05). Minimal changes were observed in mean macular nerve fiber layer thickness: 57.37µ pretreatment and 58.12µ pos–treatment for Group 1 and 67.17µ pretreatment and 58.22µ pos–treatment for Group 2.

Conclusions: : Nerve fiber layer thickness may change after photocoagulation, producing damage in the internal layers of the retina and not only in the outer ones.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • laser • nerve fiber layer