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Radwan Ajlan, Denise Descovich, Ali S. Hafez; Risk Factors Affecting Optic Nerve Head Blood Flow after therapeutic IOP Reduction in Patients with Open Angle Glaucoma and Ocular Hypertension. Invest. Ophthalmol. Vis. Sci. 2012;53(14):251.
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To detect possible risk factors affecting changes in Optic Disc Rim Blood Flow (ODRmF) following therapeutic IOP reduction in patients with open angle glaucoma (OAG) and ocular hypertension (OHT).
40 patients (20 subjects with OAG and 20 subjects with OHT) with clinical indications for therapeutic IOP reduction were included in this study. IOP reduction was achieved by medical, laser, or surgical therapy. All subjects had IOP reductions more than 20% and a minimum of 4 weeks follow-up. Blood flow measurements were originally performed using SLDF analysis of Heidelberg Retina Flowmeter images. Subjects were divided into 2 main groups based on the percentage change of optic disc rim blood flow following therapeutic IOP reduction: Group A with ≥ 20% change in ODRmF (N=20), Group B with < 20% change in ODRmF (N=20). Possible demographic and clinical risk factors that could affect changes in ODRmF were compared in both study groups. These factors include age, sex, co-morbidities, baseline IOP, cup to disc ratio, % IOP reduction and baseline rim blood flow. Statistical evaluations were performed using two tailed paired t-test and analysis of variance.
Both groups had similar % IOP reduction (33% in Group A versus 32% in Group B). Group A showed 108% increase in ODRmF (from 122±48 to 230±69au) whereas Group B showed 3% decrease (from 306±95 to 290±93au). Mean baseline rim blood flow was significantly lower in Group A patients compared to Group B patients (P=0.000008). Such difference remained significant in both OAG patients (P<0.0001) and OHT patients (P=0.001). ANOVA correlation between the baseline ODRmF and the amount of the change in the flow after IOP reduction was statistically significant in both subgroups (P<0.0001). No difference between the two groups was found in other risk factors studied.
Greater improvements in optic disc rim blood flow was associated with lower baseline rim flow values. This finding was apparent in both OAG patients and OHT patients. In addition to indicating a vascular response to therapy, the reported changes suggest that autoregulation of the optic nerve head blood flow may be defective in patients with impaired baseline rim perfusion.
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