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D. A. Ghate, V. Gulati, C. B. Toris, C. B. Camras; The Correlation Between Anterior Chamber Biometric Parameters and Aqueous Humor Dynamics. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4893.
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Previous studies have shown that central corneal thickness (CCT) is an independent risk factor for the development of glaucoma. Parameters of aqueous humor dynamics have been previously shown to be different in subjects with ocular normotension (ONT) and ocular hypertension (OHT). This study evaluates the correlation between the parameters of aqueous humor dynamics and anterior chamber biometry, including CCT and anterior chamber volume (ACvol), in subjects with ONT and OHT.
This retrospective study included 157 patients (94 with ONT, 63 with OHT). Any eye medications used were discontinued for 3 weeks before the study. The study included measurements of intraocular pressure (IOP) by pneumatonometry, aqueous flow (Fa) and outflow facility (Cfl) by fluorophotometry, anterior chamber depth and CCT by pachymetry, and episcleral venous pressure by venomanometry. Uveoscleral outflow (Fu) and ACvol were calculated mathematically. One eye of each patient was used in the analysis. Pearsons correlation was used to compare CCT or ACvol with IOP, Fa, Cfl, or Fu.
CCT was found to be significantly negatively correlated with Fu in the ONT (R2=0.10, p=0.002) or the OHT (R2=0.08, p=0.03) groups, and significantly negatively correlated with Fa in the ONT group (R2=0.21, p=0.000003). ACvol was significantly positively correlated with Fa in the ONT (R2=0.06, p=0.02) or OHT (R2=0.08, p=0.03) groups and significantly positively correlated with Cfl in the OHT group (R2=0.07, p=0.03). No other significant correlations were found.
In our study, using fluorophotometry to determine Fa and Fu, a thicker CCT is associated with reduced Fu in the ONT and OHT groups and reduced Fa in the ONT group, suggesting that changes in corneal thickness may be associated with changes in the components of the uveoscleral pathway and the ciliary processes in some subjects. In our study, a larger ACvol is associated with increased Fa in both the ONT and OHT groups and increased Cfl in the OHT group. Previous studies have shown that when comparing different species, a larger ACvol is associated with a greater Fa with cats> humans>monkeys>mice. Our study demonstrates that this correlation also holds true within the human species.
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