Corneal retardation time as an ocular hypertension disease indicator

Abstract

Objective. A detailed analysis of the corneal retardation time $τ$ as a highly related parameter to the intraocular pressure (IOP), and its plausible role as an indicator of ocular hypertension disease. Approach. A simple theoretical expression for $τ$ is derived within the corneal viscoelastic model of Kelvin-Voigt with 3 elements. This retardation time can be easily calculated from the well-known signal and pressure amplitudes of non-contact tonometers like the Ocular Response Analyzer (ORA). Then, a population-based study was performed where 100 subjects aged from 18 to 30 were analyzed (within this group, about 10% had an elevated IOP with more than 21 mmHg). Main results. A clear relationship between the corneal retardation time and the corneal-compensated intraocular pressure was found, underlying the risk for ocular hypertensive (OHT) subjects with lower $τ$ values to develop hypertension illnesses (due to the inability of poorly viscoelastic corneas to absorb IOP fluctuations, resulting in probable optic nerve damage). Significance. Our results might provide an useful tool to systematically discern which OHT patients (and even those with normal IOP values) are more likely to suffer glaucoma progression and, consequently, ensure an early diagnosis.