Abstract
Purpose: :
To assess if inhibition of VEGF with intravitreal bevacizumab (1.25 mg/0.1ml) causes any change in the RNFL thickness as measured by optical coherence tomography.
Methods: :
Peripapillary RNFL thickness was measured using the Fast scan protocols of Stratus OCT prior to bevacizumab injections and at each subsequent follow-up visits (4-6 week intervals). Fellow untreated eyes were imaged as the control group. If the fellow eye required treatment of any kind the patient was excluded. Only treatment naïve eyes were included. Scans with signal strength < 6 were excluded. Patients with a history of glaucoma were excluded. A change of 8 microns in thickness was accepted to be within normal limits of the test-retest variability.Statistical Methods: A mixed model repeated measures analysis of variance (RM ANOVA) with the dependent variable of the average peripapillary RNFL thickness, as measured by OCT, was performed.
Results: :
Ten eyes of ten patients were included the study and their fellow eyes acted as controls. Indication for injection included exudative age related macular degeneration (n=8) and diffuse macular edema secondary to diabetic retinopathy (n=2). Treated eyes averaged 2.25 injections (range 1-4) and average follow-up was 72 days (range 39-125 days). Average pre-injection RNFL thickness in the treated eyes was 90.04 +/- 3.27 microns and final RNFL thickness in this group was 92.67+/- 3.27. In the control eyes baseline RNFL thickness was 91.05 +/- 2.40 and at last follow up the RNFL thickness was 90.89 +/- 2.40. The eye x time interaction was not significant; this implies that any changes from baseline to follow-up were not different between the injected and non-injected eyes. There was no significant main effect of eye (p<0.8443), implying that irrespective of time, there was no difference in RNFL between the injected and non-injected eye. There was no main effect of time (p<0.6898), implying that irrespective of eye, there was no change of RNFL from baseline to follow-up.
Keywords: age-related macular degeneration • nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)