Evaluation of Changes in Corneal Biomechanics in Patients with Systemic Sclerosis

Abstract

Our study compares the biomechanical properties of the cornea in patients with long-term pre-existing (for at least 10 years) systemic sclerosis (SSc) with those of healthy suspects. The examination was performed in 14systemic SSc patients and 38 healthy volunteers. Non-invasive assessment of corneal biomechanical parameters, including central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF), was performed in one randomised study eye in accordance with a standardised protocol. Intraocular pressure (IOP) values were analysed using different measuring techniques, including Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT) and Ocular Response Analyzer® (ORA)-based non-contact tonometry (NCT), GAT-correlated IOP (IOPgat) and CCT-compensated-IOP (IOPcc). When measured with DCT and ORA-based NCT, IOP levels were significantly lower in SSc patients than in the control group (DCT IOP: p = 0.048, NCT IOPgat: p = 0.002, NCT IOPcc: p < 0.001). CCT was also significantly reduced in the SSc (p = 0.001). There were no statistically significant differences between the groups in CH and CRF. The difference between the corrected values (CHcorr - CRFcorr) was negative in the two groups. This was slightly lower for the SSc patients (delta = - 0.83) than for the control group (delta = - 0.66). For SSc patients, there were highly significant negative correlations between CH and CRF and between CHcorr and CRFcorr. In contrast, in the control group there was a non-significant positive correlation between age and biomechanical properties. In the course of the disease SSc leads to various alterations in connective tissue, which can also involve corneal tissue. CCT becomes significantly thinner and simultaneously partially loses elastic properties and gains viscosity. This accounts for reduced IOP values with dynamic contour tonometry as well as with ORA-tonometry (Goldmann-correlated IOP, CCT-compensated IOP). This distinct pre-existing significant negative correlation between age and CH and CRF values in patients with SSc could be due to slight regression of the viscous components and diminution of corneal damping capacity.