Abstract
Abstract: :
Purpose: To correlate flow values of the neuroretinal rim of the optic nerve head (ONH), nasal peripapillary retina and temporal peripapillary retina with the clinical parameter of cup to disc (C/D) ratio in patients with ocular hypertension (OHT). Methods: Twenty uncontrolled OHT patients were prospectively enrolled in the study. Mean neuroretinal rim and peripapillary retinal blood flow measurements were performed using scanning laser Doppler flowmetry (SLDF) and full-field perfusion analysis of five Heidelberg Retina Flowmeter (Heidelberg Engineering, Heidelberg, Germany) images. Statistical evaluations were performed using Student's T-test and Pearson's correlation test. Results: Ocular hypertensives had mean C/D ratio of 0.4 ± 0.2 (range from 0.15 to 0.70) at the time of imaging. Their mean neuroretinal rim blood flow was 277 ± 158 whereas peripapillary nasal flow was 287 ± 104 and peripapillary temporal flow was 309 ± 78. Ocular hypertensives were divided into two equal subgroups. Ten subjects had C/D ratio ≥ 0.4 (mean 0.54 ± 0.13) and 10 subjects had C/D ratio < 0.4 (mean 0.27 ± 0.07). OHT eyes with C/D ratio ≥ 0.4 showed significantly lower mean neuroretinal rim flow compared to OHT eyes with C/D ratio < 0.4 (203 ± 79 versus 350 ± 185, P = 0.039). Peripapillary retinal blood flow showed no significant difference between the two subgroups (P ≥ 0.39). For the entire OHT group (N = 20), mean neuroretinal rim blood flow values showed an inverse though statistically non-significant correlation with clinical C/D ratio (r = -0.36, P = 0.11). Conclusions: Mean neuroretinal rim blood flow was significantly higher in OHT patients with C/D ratios less than 0.4 when compared to OHT patients with larger C/D ratios. This suggests that reduced neuroretinal rim blood flow in higher risk ocular hypertensives may be an early event in the development of glaucomatous optic neuropathy, appearing prior to the manifestation of visual field defects.
Keywords: optic flow • imaging/image analysis: clinical • optic disc