Preliminary Results of Changes in Refraction and Corneal Curvature Caused By+Gz Acceleration in Patients after Orthokeratology

Abstract

Purpose: The aim of this study was to investigate the changes in visual acuity, refraction, and corneal curvature caused by sustained+Gz acceleration of patients in a human centrifuge after overnight orthokeratology. Methods: Five healthy men training to be aviation doctors, aged 25-26 years (mean=25.3 years), received overnight orthokeratology for two weeks. The human centrifuge at the Aviation Physiology Research Laboratory in Tainan, Taiwan, was used to expose the subjects to various acceleration profiles. Each subject experienced three centrifuge runs. Visual acuity, refraction, and corneal topography were measured before, and 1 min and 10 min after acceleration. We compared the study group findings with those of a control group of 13 subjects who had not undergone orthokeratology but experienced the same acceleration procedure. Results: In the orthokeratology group, nine eyes of five subjects completed the study. One eye was excluded because of keratitis. Visual acuity remained stable after human centrifugation. Refraction increased significantly at 1 min, but recovered at 10 min after centrifugation. There was a significant decrease in corneal thickness and a significant increase in anterior curvature at 1 min and 10 min after centrifugation. In the control group, best-corrected visual acuity was increased at 1 min and 10 min after centrifugation. Myopic shift was noted significantly at 1 min, but increased at 10 min after centrifugation. There was a significant decrease in corneal thickness and a significant increase in anterior curvature, at 1 min but this recovered 10 min after centrifugation. Conclusion: Visual acuity is stable, although some corneal topographic and refractive parameters change after centrifugation. Differences in the changes in refraction and anterior curvature between the orthokeratology and control groups may be due to the oblate shape of the cornea produced by the orthokeratology lens.