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E. J. Cohen, J. S. Myers, K. M. Hammersmith, E. Yildiz, P. R. Laibson, C. J. Rapuano; Keratoconus and Normal Tension Glaucoma: A Study of a Possible Association With Abnormal Biomechanical Properties as Measured by Corneal Hysteresis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3543.
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To test the hypothesis that keratoconus and pellucid patients who have glaucoma or are glaucoma suspects have lower corneal hysteresis (CH) and/or corneal resistance factor (CRF) measurements) compared to controls.
A prospective study at a tertiary eye center of keratoconus and pellucid patients with glaucoma or suspect glaucoma and age matched controls, was performed. After informed consent was obtained, corneal topography, Ocular Response Analyzer (ORA, Reicher, Buffalo, NY), pachymetry, intraocular pressure (IOP), A scan measurements, Humphrey visual fields (VF), and disc photos were done. Analyses compared cases to controls on primary (CH and CRF) and secondary variables. Disc photos and visual fields were rated in a masked fashion.
The mean CH (8.2 (SD=1.6), 8.3 (SD=1.5)) and CRF (7.3 (SD=2.0), 6.9 (SD=2.1)) were low and did not differ significantly between 20 study (29 eyes) and 40 control patients (61 eyes), respectively. CH had a negative, significant correlation with maximum corneal curvature by topography (p< 0.002) and positive, significant correlation with central corneal thickness (p<0.003). The mean cup to disc (C/D) ratio was larger (0.54, SD=0.20) among cases than controls (0.38, SD=0.20), p=0.003. Visual fields (VF) were suspicious for glaucoma more often among the study eyes (11/29, 33.9%) than controls (8/60, 13.3%), p=0.019.
CH was low in study and control patients and was correlated with severity of keratoconus/pellucid, but not with glaucoma/glaucoma suspect or control status. Evidence of glaucoma was more common in study eyes than controls, but was present in both.
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