Abstract
Abstract: :
Purpose: To investigate the diurnal variation of anterior optic nerve (AON) capillary blood flow and its correlation with mean ocular perfusion pressure (MOPP) in untreated early primary open angle glaucoma (uPOAG). Methods: Fourteen patients with uPOAG (age 40–79, mean 56.3, SD 12, 7 men) and 11 Normals (age 53–73, mean 61.5, SD 6.7, 2 men) were examined. The IOP, systolic and diastolic blood pressure (SBP, DBP), MOPP, ONH topography and ONH capillary blood flow (Heidelberg Retina Flowmeter) were measured every two hours between 07:00 and 21:00 hours on a single day. The volunteers had two meals at 12:30 and 18:30. The mean rim flow (MRF) was calculated using the "Automatic Full–Field Perfusion Image Analyzer" software designed for the analysis of HRF images. The local flow (LF) was calculated using the mean flow values within a 10x10 pixel window, placed on the rim in the area of "maximum fluctuation topography, MFT". The diurnal change was calculated as the difference between the maximum and minimum values during the day. Repeated measures ANOVA and Pearson correlation coefficients were used for the analysis. Results: LF significantly changed during the day in the uPOAG group (p=0.04), but not in the normal group (p=0.48), but MRF did not significantly change in either group (p=0.18; p=0.53). There was no significant difference (p=0.45) between the average LF for uPOAGs (274.80, SD 111.89) and for Normals (286.28, SD 127.2), or between the average MRF(p=0.12) for uPOAGs (227.56, SD 110.52) and for Normals (243.19, SD 74.3). The uPOAGs gave the lowest LF at 07:00 and highest LF at 13:00, whereas the normal group gave the highest LF at 07:00. IOP, MOPP and SBP significantly changed during the day in the uPOAGs (p<0.02) and Normals (p<0.003). There was a significant negative correlation between the diurnal change in LF and MOPP (r=–0.64, p=0.01) in uPOAG. The diurnal change in LF and MRF was correlated with the diurnal change in rim volume in the MFT (r=0.65, p=0.01; r=0.55, p=0.04). The MFT was most frequently found in the temporal sector for both POAG (8/14) and Normals (10/11). Conclusions: The mean rim flow did not significantly change during the day. It indicates that the anterior optic nerve capillary blood flow behaves as an autoregulated capillary bed as expected, despite significant changes in IOP and MOPP. However there were sectors of the rim in uPOAG, with significant diurnal change in flow that correlated with the region of greatest diurnal change in rim topography.
Keywords: optic disc • blood supply • imaging/image analysis: clinical