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M. C. Shammas, J. Pae, J. R. Ehrlich, N. M. Radcliffe; Corneal Hysteresis and Its Relationship With Parapapillary Atrophy. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5552.
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Parapapillary atrophy (PPA) and corneal hysteresis (CH) have recently been identified as risk factors for glaucoma damage and progression1,2. PPA is a manifestation of retinal pigment epithelium absence while CH is a marker of corneal viscoelasticity. In this study, we sought to determine whether PPA and CH are related.
We retrospectively analyzed 293 consecutive patients (538 eyes) seen at Weill Cornell Eye Associates who underwent both CH measurement using the Ocular Response Analyzer (Reichert) and optic disc stereophotography. Each patient had a full ophthalmologic exam and reliable 24-2 SITA-standard automatic perimetry (HVF) with the Humphrey Field Analyzer II completed within one year of the CH measurement. Patients with non-glaucomatous visual field loss were excluded. Data collected included age, CH, and the Glaucoma Hemifield Test (GHT) and mean deviation (MD) from the most recent reliable HVF. A single masked observer evaluated stereophotographs for PPA parameters, including: total PPA clock hours, ß-PPA clock hours, ß-PPA percent width of optic disc, 0-3 ordinal rating of total PPA, and presence/absence of ß-PPA in each disc quadrant. Relationships between PPA and CH and other variables of interest were explored using logistic and linear regression analysis.
For each unit increase in CH there was a 14% decrease in likelihood of abnormal GHT (OR 0.84, 95% CI 0.77, 0.96; p < 0.01). Increasing ß-PPA clock hours was associated with abnormal GHT, with 10-12 clock hours (compared to 0-3 clock hours) conferring an odds ratio of 4.19 (95% CI: 2.15, 8.13; p <0.001), however, this affect was attenuated when controlling for age (OR 2.48, 95% CI: 1.27, 4.84, p< 0.01). There was a weak negative linear relationship between CH and ß-PPA clock hours (r=-0.11; p<0.05). This association was not affected by the location of the PPA. Age was shown to be highly associated with both CH and PPA (p <0.001), and the relationship between CH and PPA was non-significant when controlling for age (p =0.88).
CH and PPA are both related to glaucoma, however their weak relationship to each other is confounded by age. CH and PPA may relate to glaucoma risk through distinct pathophysiologic processes.1. Jonas JB. Curr Opin Ophthalmol. 2005;16:84-8.2. Congdon NG, et al. Am J Ophthalmol. 2006;141:868-75.
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