An asymmetry of corneal properties between eyes with binocular primary open angle glaucoma (POAG) may correlate to asymmetric rates of visual ﬁeld loss, new research shows. A study published in the Journal of Glaucoma suggests that the viscoelastic properties of the cornea may be correlated with the viscoelastic properties of the lamina cribrosa and peripapillary sclera. While central corneal thickness (CCT) has already been identified as a potential risk factor for glaucoma development and progression, this study provides more evidence that corneal hysteresis (CH) may be useful in predicting glaucomatous visual field loss.
The study followed primary open angle glaucoma (POAG) patients at various stages of the disease who also had inter-ocular asymmetries in CH. After controlling for variables in baseline severity, race, gender, intraocular pressures (IOP), and CCT, CH asymmetry between eyes within the same patient was the only factor that had a statistically significant (P =.032) value in asymmetric visual field loss progression. The results suggest that clinicians may need to adopt a unique approach for each eye when treating glaucoma in patients with CH asymmetry.
The study included a total of 126 subjects with a mean age of 67 (± 11) years who had been diagnosed with POAG in both eyes. Subjects were followed for an average of 4.3 (± 0.8) years, with an average of 11 visits per patient. Baseline corneal pachymetry readings and CH readings were obtained for each patient. A comprehensive ophthalmologic biomicroscopy, IOP measurement, gonioscopy, ophthalmoscopy examination, and standard automated perimetry (SAP) were conducted at baseline and every six months thereafter.
All SAP measurements were based on the SITA Standard 24-2 strategy of the Humphrey Field Analyzer II-i. A simple SAP mean deviation curve was built using SAP mean deviation values and eyes were labeled as “better” or “worse” based on the slopes of the curve. The asymmetry between the “better” and “worse” eye in mean and peak IOP values, CCT, CH, baseline mean deviation, and standard automated perimetry mean deviation were analyzed at the conclusion of the study.
The pathophysiology of glaucoma continues to be a topic that requires research and each new study seems to bring us just a little bit closer to understanding the risk factors, moderators, and mechanisms of glaucoma progression.
One of the authors of this study has a financial relationship with relevant manufacturers.
Estrela T, Jammal AA, Mariottoni EB, et al. The relationship between asymmetries of corneal properties and rates of visual field progression in glaucoma patients. J Glaucoma. 2020;29(10):872-877. doi:10.1097/IJG.0000000000001625