Objective: To assess the effects of a short period of orthokeratology (OK) on corneal subbasal nerve plexus (SBNP) morphology and corneal sensitivity. Methods: Measurements were made in 56 right eyes of 56 subjects with low-to-moderate myopia who wore 2 OK lens designs (Group CRT: HDS 100 Paragon CRT, n¼35; Group SF: Seefree; n¼21) for a period of 1 month and in 15 right eyes of noncontact lens wearers as controls. The variables determined in each participant were corneal sensitivity using a Cochet-Bonnet esthesiometer and 12 SBNP variables determined on laser scanning confocal microscopy images using 3 different software packages. Correlation between SBNP architecture and corneal sensitivity was also examined. Results: Few changes were observed over the 1-month period in the variables examined in the OK treatment and control groups. However, significant reductions were detected over time in the number of nerves in the central cornea in the groups CRT (P¼0.029) and SF (P¼0.043) and in central corneal sensitivity in CRT (P¼0.047) along with significant increases in central and midperipheral corneal Langerhans cell counts in SF (P¼0.001 and 0.048, respectively). Conclusions: This study provides useful data to better understand the anatomical changes induced by OK in corneal SBNP. The different response observed to the 2 OK lens designs requires further investigation.
OK does not induce changes in the ocular accommodative function for either short-term or long-term periods.
This review has identified evidence about pseudomyopia as the result of an increase in ocular refractive power due to an overstimulation of the eye’s accommodative mechanism. It cannot be confused with the term “secondary myopia”, which includes transient myopic shifts caused by lenticular refractive index changes and myopia associated with systemic syndromes. The aim was to synthesize the literature on qualitative evidence about pseudomyopia in terms that clarify its pathophysiology, clinical presentation, assessment and diagnosis and treatment. A comprehensive literature search of PubMed and the Scopus database was carried out for articles published up to November 2021, without a data limit. This review was reported following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Following inclusion and exclusion criteria, a total of 54 studies were included in the qualitative synthesis. The terms pseudomyopia and accommodation spasm have been found in most of the studies reviewed. The review has warned that although there is agreement on the assessment and diagnosis of the condition, there is no consensus on its management, and the literature describes a range of treatment.
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
Purpose: To compare tear film osmolarity (TFO) measurements in noncontact lens (CL) wearers and wearers of hydrogel or overnight orthokeratology (OK) CLs, and to assess possible effects of long-term OK on TFO. Methods: Overall, 108 subjects with moderate myopia participated in 2 experiments, and TFO was measured using the TearLab osmolarity system. In experiment 1, TFO measurements were made in 77 right eyes of 23 non-CL wearers, 26 hydrogel wearers, and 28 OK wearers. Subjects in the last 2 groups had worn their CL for at least 3 years. In experiment 2, 31 individuals (habitual soft CL wearers) were enrolled for prospective longterm follow-up of OK treatment. These subjects were fitted with Paragon-CRT (n¼16) or Seefree (n¼15) lenses, and TFO readings were taken at baseline and after 1 month and 1 year of lens wear and after 1 month of OK treatment interruption. Results: Values of TFO were within the normal limits in all 3 subject groups, although significantly lower osmolarities (P,0.01) were observed in non-CL wearers (281.765.9 mOsm/L) compared with hydrogel (291616.5 mOsm/L) or OK lens wearers (301.7610.8 mOsm/L). In experiment 2, TFO differed significantly at baseline between the Paragon-CRT and Seefree groups (P,0.05), and a significant decrease in TFO compared with baseline (P,0.01) was observed in the Paragon-CRT group after 1 month of cessation of lens wear. Conclusion:Higher TFO values were observed in lens wearers (hydrogel or OK) than non-CL wearers. After interruption of OK treatment, TFO returned to similar values to those found in non-CL wearers. O rthokeratology (OK), also known as overnight corneal refractive therapy or corneal reshaping, is a clinical technique designed to transiently reduce or eliminate myopia. Over the years, developments in the field have made OK a feasible correction option for subjects who prefer not to wear spectacles or contact lenses (CLs) during the day. Today's fitting techniques enable predictable and safe outcomes for improving uncorrected visual acuity and contrast sensitivity, 1-4 including satisfactory subjective vision according to the National Eye Institute Refractive Error Quality of Life Instrument-42 questionnaire. 5 The success of OK has been accompanied by a need to address the corneal response to treatment. Recent research efforts have examined changes in corneal morphology and physiology by assessing the effects of treatment on cell density, 6-8 thicknesses of the corneal layers, 9-11 subbasal nerve plexus (SBNP) distribution, 7,12 and corneal biomechanics. [13][14][15] Some studies have also determined OK effects on tear film components, 16 such as inflammatory mediators. 17 These studies conducted both in animals 18-20 and humans 6,7,12 have identified corneal changes produced in stromal and epithelial cell density, SBNP thickness and distribution, 7,12 and epithelial layer thickness ans also changes in the levels and distribution of proinflammatory mediators in the tear film samples of OK wearers. 17,21 To date, however, the effects of OK treatment o...
OK induces minimal changes in the binocular function for either short-term or long-term periods, apart from a near exophoric trend over the short-term period.
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