Glaucoma risk factors: The cornea

Abstract

Assessment of rates of disease progression, along with considerations about life expectancy and treatment side effects, can help clinicians customize aggressiveness of therapy to increase the chances that patients will avoid functional impairment during their lifetime. Identification of baseline risk factors associated with rates of disease progression may help clinicians identify those patients at high risk for having rapid deterioration that could lead to functional impairment. High intraocular pressure (IOP) has been regarded as the main risk factor for the disease, and a positive relationship between IOP levels and glaucoma progression has been shown in numerous clinical trials. Measurement of IOP by Goldmann applanation tonometry has been found to be influenced by the central corneal thickness (CCT) of the individual. Results from studies suggest that eyes with thin corneas are at increased risk for development and progression of glaucoma. Although the relationship between CCT and risk of disease progression may be due to a tonometric artifact, there has also been speculation that CCT could be an independent risk factor for the disease. In addition to thickness, other corneal biomechanical properties have been suggested as potential risk factors for glaucoma, such as corneal hysteresis (CH). Corneal hysteresis is a measure of the viscoelastic damping of the cornea that can be estimated by analyzing corneal responses to deformation induced by an air pulse. The ability of the cornea to resist deformation might reflect the constitution of its extracellular matrix (ECM), which could be hypothesized to be related to the ECM composition of posterior ocular tissues related to glaucomatous damage, such as the lamina cribrosa and peripapillary sclera. An eye with a more deformable cornea could have an optic disc that is more susceptible to IOP damage.