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JF Logan, SJ A Rankin, JA Jackson; Retinal Blood Flow and Neuroretinal Rim Loss in Glaucoma . Invest. Ophthalmol. Vis. Sci. 2002;43(13):315.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The vascular aetiology of glaucoma hypothesises that a compromised blood supply to the optic nerve head causes optic nerve damage. The Heidelberg Retina Flowmeter (HRF) allows non-invasive quantification of the perfusion of the retina and optic nerve head. The aim of this study was to correlate retinal blood flow against structural damage of the optic nerve head in subjects with glaucoma. Methods: Heidelberg Retina Tomograph (HRT) and HRF images were obtained in 62 subjects with normal tension glaucoma, (66.19 ± 10.11 years), 45 subjects with POAG (65.27 ± 8.74 years) and 34 controls (60.62 ± 11.14 years). Moorfields Regression Analysis software was used to classify predefined neuroretinal rim segments as 'abnormal' or 'normal', defined by the 99% prediction interval of the regression of log neuroretinal rim area against optic disc area, derived from a group of normals. HRF images were sampled using the 10X10 pixel box in the superior-temporal (ST), superior-nasal (SN), inferior-temporal (IT) and inferior-nasal (IN) retina. The HRF parameters at each measurement site were compared between the corresponding abnormal and normal rims segments in the glaucoma subjects, and between the normal rim segments in the glaucoma patients and controls. Results: The glaucomatous discs that were identified as having an abnormal IT segment have statistically lower HRF values in the IT retina than discs with a normal segment, volume (14.40 ± 4.19 and 16.16 ± 3.51 respectively, p < 0.05), and flow (218.28 ± 69.26 and 247.22 ± 60.21 respectively, p < 0.05). The HRF parameters for the other abnormal segments show a trend of lower values, although statistical significance is not achieved. The HRF parameters in the normal segments in the glaucoma patients are significantly lower in all locations measured compared to the controls. For example, in the IT retina, blood volume in the glaucoma subjects was 16.16 ± 3.51 and the controls 18.33 ± 3.64 (p < 0.05), flow 247.22 ± 60.21 and 313.22 ± 60.21 respectively (p < 0.001) and velocity 0.88 ± 0.21 and 1.11 ± 0.23 respectively (p < 0.001). Conclusion: This study shows a relationship between structural damage of the optic nerve head as measured by the HRT, and the level of retinal blood flow. The rim segments that have been identified as normal by Moorfields software in the HRT have a significantly lower blood flow than the controls. This suggests that in early glaucomatous damage local retinal blood flow may be reduced before structural damage is detected.
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