Biomechanical properties in corneal refractive therapy during adaptation period and after treatment interruption: A pilot study

Purpose: To evaluate the potential influence and treatment-related changes of the corneal biomechanical properties (BMP) measured with the Ocular Response Analyzer (ORA, Reichert, Depew, NY) 15-days and 1-month after the initiation and cessation of corneal refractive therapy (CRT). Methods: Twenty-four young healthy subjects (24.04 ± 3.19 years) participated in two different experiments. In the first one (#1), twelve right eyes from 12 subjects who were fitted with CRT lenses were evaluated after 15 days and 1 month of lens wear. In the second trial (#2) 12 subjects who had been wearing CRT lenses for a period of 1 year were evaluated at 15 days and 1 month after treatment interruption. Results: There was no statistically significant correlation between baseline BMP and absolute values of structural corneal parameters at 15 and 30 days treatment, and also when these variables were normalized according to the targeted refraction. In experiment #1, Corneal hysteresis (CH) reduction was observed over the time of treatment (p = 0.019), but no significant differences were observed in the Corneal Resistance Factor (CRF) values. In addition, CRF reduction significantly correlated with spherical equivalent refraction (r = 0.597; p = 0.044), but no correlation was observed between CH or CRF reduction and the spherical component of the refraction. In experiment #2, no significant changes in CH or CRF were found initially after lens wear interruption, but a trend to increase was observed thereafter. Conclusion: CH decreases during onset of the CRT after 30 days of lens wear. Such changes seem to be reversible after cessation of contact lens wear following 1 year of treatment. Corneal biomechanics, however, do not predict the outcomes of CRT in clinical setting although with the data obtained some correlative tendencies were observed that may merit further investigation