CCT a risk factor for glaucoma damage

Central corneal thickness (CCT) and corneal hysteresis could present a pressure-independent risk factor for glaucoma damage, according to a report in the May issue of the American Journal of Ophthalmology.

N.G. Congdon and colleagues from the John Hopkins University School of Medicine conducted an observational study of 230 patients undergoing measurements for hysteresis, on the Reichert Ocular Response Analyser, and CCT by ultrasonic pachymetry. Charts were reviewed to determine highest known intraocular pressure (IOP), target IOP, diagnosis, number of years with glaucoma, cup-to-disk ratio (CDR), mean defect, pattern standard deviation, glaucoma hemifield test and the presence or absence of visual field progression. Of the 230 patients (127 female, 103 male) 85% had a diagnosis of primary open-angle glaucoma (POAG) or suspected POAG.

The researchers found that lower corneal hysteresis values (p=0.03) were associated with visual field progression, but CCT was not. When axial length was included in the model, hysteresis was not a significant risk factor (p=0.09). Thinner CCT measurements were associated with a higher CDR but neither CCT nor hysteresis were linked with mean defect, pattern standard deviation or glaucoma hemifield test. Thinner CCT was associated with the state of glaucoma damage, as indicated by CDR, and axial length and corneal hysteresis were linked to progressive field worsening.

It was concluded that CCT and hysteresis may constitute a risk factor for glaucoma damage, related to the composition of the eye wall itself.