Ocular Changes after Simulated Ejection Following Orthokeratology

Abstract

Purposes: To determine the stability of subjects' visual acuity, refraction, corneal topography, pachymetry, anterior chamber depth, and intraocular pressure following overnight orthokeratology when subjected to vertical acceleration at six times the force of gravity (+6 Gz) in a simulated ejection system on the ground. Methods: The subjects were 10 healthy male flight surgeons, aged 25-26 years (mean 25.3), who had undergone overnight orthokeratology for two weeks before controlled rapid-sequence ejection at +6 Gz. Their visual acuity, refraction, and corneal parameters, including corneal curvature, corneal thickness, anterior chamber depth, and intraocular pressure, were recorded before, immediately after, and 20 min after the +6 Gz ejection. We compared the study group findings with those of a control group of 20 subjects who had not undergone orthokeratology but were exposed to the same ejection procedure. Results: The measurements of visual acuity, refraction, and Orbscan topographic parameters, including the anterior and posterior corneal curvatures, central corneal thickness, and intraocular pressure, made before, immediately after, and 20 min after ejection did not differ significantly between the pre- and post ejection values on paired t tests. The only significant difference in the orthokeratology group was in the anterior chamber depth, which was 2.978 mm before ejection and 3.01mm 20 min after ejection (p ＜ 0.05). Conclusion: The visual acuity, refraction, and corneal topographic changes in patients after orthokeratology are stable under rapid vertical ejection at six times the force of gravity. An increase in anterior chamber depth was the only significant change after ejection in the orthokeratology group.