Long-Term Impacts of Orthokeratology Treatment on Sub-Basal Nerve Plexus and Corneal Sensitivity Responses and Their Reversibility

Abstract

Abstract:PURPOSE: To examine the effects of 1 year of overnight orthokeratology (OK) treatment on the sub-basal nerve plexus (SBNP) and corneal sensitivity and to assess the reversibility of these effects 1 month after treatment interruption.METHODS: 32 subjects with low-moderate myopia underwent OK treatment for one year. 15 non-contact lens wearers served as controls. At the time points baseline, 1 year of treatment, and 1 month after removing the OK lenses, two tests were conducted: corneal sensitivity (Cochet-Bonnet esthesiometer) and SBNP imaging by in vivo confocal microscopy.RESULTS: In participants wearing OK lenses, significant reductions over the year were produced in SBNP nerve density (p=0.001 and p=0.006) and number of nerves (p<0.001 and p=0.001) in the central and mid-peripheral cornea respectively. Differences over the year were also detected in central objective tortuosity (p=0.002). Following lens removal, baseline values of nerve density (p=0.024 and p=0.001) and number of nerves (p=0.021 and p<0.001) for the central and mid-peripheral cornea respectively were not recovered. At 1 month post-treatment, a difference was observed from 1 year values in central corneal sensitivity (p=0.045) and mid-peripheral Langerhans cell density (p=0.033), and from baseline in mid-peripheral objective tortuosity (p=0.049). Direct correlation was detected at 1 year between nerve density and tortuosity both in the central (p<0.01; r= 0.69) and mid-peripheral cornea (p<0.01; r= 0.76).CONCLUSIONS: Long term OK treatment led to reduced SBNP nerve density and this was directly correlated with corneal tortuosity. After 1 month of treatment interruption, nerve density was still reduced. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation

Short-Term Effects of Overnight Orthokeratology on Corneal Sensitivity in Chinese Children and Adolescents

“…In a continuation of this study, she discovered an unexpected consistency in central corneal sensitivity after one year of orthokeratology relative to that before treatment and attributed it to an undefined neuronal adaptation. Her studies showed this recovery occurred between one month and one year but she combined her data with Lum's data and concluded that the recovery occurred between three months and one year [25]. The changes in central corneal sensitivity during the first month in our study are basically the same as those in previous studies, and neuronal adaptation was thought to be the main contributor to this change [24, 26].…”

“…However, our findings show that the recovery of corneal sensitivity occurred within 3 months of OK treatment. This is not consistent with Nombela-Palomo's conclusion [25]. Neuronal adaptation is the time-dependent modulation of sensory responses following sequential stimuli and thought to be a consequence of synaptic plasticity [28].…”

“…In our study, although the means of central corneal sensitivity values of 8 subjects who already have OK lenses wearing experience seemed slightly lower than that of 22 subjects without wearing experience, we found there was no statistically significant difference between them. Moreover, previous studies have shown that central corneal sensitivity can be restored to the baseline level after stopping wearing OK lenses for 1 month (or even rebound to the higher level) [25, 34]. Therefore, we included the 8 subjects together in the analysis.…”

“…However, subsequent research conducted by the same group found that corneal sensitivity values kept amazingly stable after one year of OK treatment when compared with baseline. A possible explanation for this stabilization could be neuronal adaptation to the pressure exerted by the lens which would have occurred at sometime between three months and one year of treatment [25].…”

BCLA CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

“…Central sensitivity is reduced by approximately 50 % and recovers to pre-lens wear levels after cessation of lens wear [367][368][369]. Corneal nerve morphology is affected by ortho-k, with a reduction in nerve fibre density and re-organisation of the nerve fibre orientation [368][369][370][371][372]. The nerve fibre changes also resolve with cessation of ortho-k lens wear, in sync with the recovery in sensitivity [369,372].…”