Long-term Changes in Corneal Morphology Induced by Overnight Orthokeratology

Abstract

Purpose: To assess long-term morphological and biometric corneal changes produced by overnight orthokeratology and to examine their recovery after cessation of contact lens wear.

Methods: Prospective, single-center, longitudinal trial. Fifteen right eyes with low to moderate myopia underwent overnight orthokeratology for 1 year. The central cornea was examined using a confocal microscope and changes determined in visual acuity, refractive error and corneal topography. Cell counts were performed using both the confocal microscope’s software and the image analysis software of the USA Health Institute. All measurements were made during orthokeratology treatment and 1 month after discontinuing treatment.

Results: No significant changes in endothelial cell density were observed over time but polymegethism increased significantly and baseline values were not recovered (p < 0.01). Stromal cell density remained unchanged though numbers of activated keratocytes increased during the study and returned to baseline when lens wear ceased. Basal epithelium cell densities significantly fell (p < 0.01) and epithelial wing and superficial cells showed enhanced visibility (p < 0.05). Superficial cells increased in height and width; this width increase being significant after 1 year of orthokeratology (p < 0.01). All epithelial cell changes returned to baseline. Corneal thickness, Bowman layer thickness, subbasal plexus thickness and epithelial thickness were reduced in the central cornea but the stroma was thickened. Of these changes, the decrease in epithelium thickness reached statistical significance (p < 0.01) and baseline values were not recovered.

Conclusion: Overnight orthokeratology induces structural and optical changes particularly in the central corneal epithelium during myopia treatment. If confirmed, the irreversible changes detected indicate a need for further investigation.

KEYWORDS::

• Confocal
• Cornea
• Morphology
• Orthokeratology
• Corneal Thickness

ACKNOWLEDGMENTS

Human Subjects and Informed Consent

The authors declare that this research was performed following the tenets of the Declaration of Helsinki and that informed consent was obtained from the subjects after the nature of the study had been explained to them in detail. The study protocol was approved by the Ethics Committee of the Hospital Carlos III.

No sources of public or private financial support declared.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.