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T. Johnson, S. Fan, C.B. Toris, C.B. Camras; Uveoscleral Outflow Is Reduced in Exfoliation Syndrome . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2943.
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This study examines the effects of exfoliation syndrome (XFS) with ocular hypertension (OHT) or with ocular normotension (ONT) on aqueous humor dynamics.
Sixty–four human subjects were divided into four groups: 1) XFS with OHT (XFS+OHT, n=13); 2) OHT without XFS age–matched to Group 1 (OHT Control, n=13); 3) XFS with ONT (XFS+ONT, n=19); 4) ONT without XFS age–matched to Group 3 (ONT Control, n=19). Following washout of glaucoma medications, assessments included anterior chamber volume by pachymetry, intraocular pressure (IOP) by pneumatonometry, aqueous flow and outflow facility by fluorophotometry, and uveoscleral outflow by mathematical calculation (episcleral venous pressure was assumed to be 9 mmHg for all subjects). The four groups were compared using two–tailed t–tests and Mann–Whitney tests with Bonferroni adjustments for multiple comparisons. Additionally, the XFS subjects (Groups 1 and 3) and the Control subjects (Groups 2 and 4) were combined into two respective groups (XFS Combined and Controls Combined) and compared using two–tailed t–tests.
The table summarizes the results. Most notably, outflow facility is lower in XFS subjects with OHT when compared to XFS subjects with ONT. Uveoscleral outflow is decreased in XFS subjects (XFS Combined) compared to age–matched controls (Controls Combined).
This is the first study to demonstrate a decreased uveoscleral outflow in subjects with XFS. This reduction might be related to extracellular matrix changes in the ciliary muscle. When OHT accompanies XFS, outflow facility also is decreased. This reduction might be related to blockage of the trabecular meshwork by exfoliation material. The mechanism of IOP elevation in XFS (reduced outflow facility and uveoscleral outflow) appears to be different from that in pigment dispersion syndrome (reduced outflow facility but unaltered uveoscleral outflow).
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