Corneal Biomechanical Changes Caused by Acute Elevation of IOP in Eyes with and without Glaucoma

Abstract

SIGNIFICANCE Although corneal biomechanical parameters are well linked with glaucoma, their clinical utility has not yet been fully elucidated. This study was designed to provide unique evidence about the dynamic nature of corneal biomechanical parameters and their potential prognostic ability for glaucoma. PURPOSE This study aimed to evaluate the effect of acute intraocular pressure (IOP) elevation on corneal hysteresis (CH) and corneal resistance factor (CRF) and the associations of these biomechanical parameters with glaucomatous disease. METHODS Subjects participating in a prospective, longitudinal glaucoma research study had CH and CRF measured before and during ophthalmodynamometry during visits in the years 2011 to 2012. All participants were diagnosed with primary open-angle glaucoma, ocular hypertension, glaucoma suspect, or normal eyes and had a minimum of 3 years of study participation with at least five reliable visual field (VF) tests. Changes in CH, CRF, and IOP induced by ophthalmodynamometry were compared between diagnostic groups and evaluated for relationships with existing and future glaucomatous VF loss. RESULTS In 248 eyes of 248 subjects followed up for 7.7 ± 2.3 years, ophthalmodynamometry induced a mean IOP increase from 15.1 to 29.9 mmHg, causing a mean 34 ± 28% increase in CRF and 21 ± 25% decrease in CH. Magnitude of CH change did not differ between diagnostic groups or between eyes that did (n = 20) and did not (n = 95) develop new VF loss during the study period, nor was it related to rate of future VF progression. CONCLUSIONS Ophthalmodynamometry-induced IOP elevation resulted in significant acute changes in CH and CRF in this study; this suggests accounting for IOP may be important in clinical interpretation of these parameters. However, because the degree of CH change was not related to glaucoma or its progression, acute changes in CH and CRF do not seem to have a prognostic value for glaucoma.

Corneal hysteresis: ready for prime time?

“…Earlier studies have shown an inverse relationship between corneal hysteresis and IOP, i.e., as IOP decreases, corneal hysteresis increases [47,48]. Katiyar et al [49 ▪ ] induced a decrease in corneal hysteresis by 21% by doubling IOP from 15 to 30 mmHg in human eyes using a ophthalmodynamometer. Corneal hysteresis has also been shown to significantly increase after trabeculectomy and tube shunt surgeries [50], especially when IOP was reduced by more than 10 mmHg [51].…”

Glaucoma and biomechanics

“…However, the prognostic value of these corneal measurements remains an open question. Therefore, recent studies also focus on associating measurable corneal properties to supplement more conventional outcome measures and hence better quantify glaucoma risk [64], and the impact of these parameters for clinical use is a work in progress.…”