Tear Film Osmolarity in Response to Long-Term Orthokeratology Treatment.

PURPOSE: To compare tear film osmolarity (TFO) measurements in non-contact 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 long-term follow-up of OK treatment. These subjects were fitted with Paragon-CRT (n=16) or Seefree (n=15) 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 (281.7±5.9 mOsm/L) compared with hydrogel (291±16.5 mOsm/L) or OK lens wearers (301.7±10.8 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.

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

PURPOSE: To examine the effects of one year of overnight orthokeratology (OK) treatment on the sub-basal nerve plexus (SBNP) and corneal sensitivity and to assess the reversibility of these effects one month after treatment interruption. METHODS: Thirty-two subjects with low-moderate myopia underwent OK treatment for one year. Fifteen non-contact lens wearers served as controls. At the time points baseline, one year of treatment, and one 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). After 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 one month post-treatment, a difference was observed from one-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 one 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 one month of treatment interruption, nerve density was still reduced.

Short-Term Effects of Overnight Orthokeratology on Corneal Sub-basal Nerve Plexus Morphology and Corneal Sensitivity.

OBJECTIVE: To assess the effects of a short period of orthokeratology (OK) on corneal sub-basal 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, n=35; Group SF: Seefree; n=21) 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 (P=0.029) and SF (P=0.043) and in central corneal sensitivity in CRT (P=0.047) along with significant increases in central and midperipheral corneal Langerhans cell counts in SF (P=0.001 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.

Binocular function changes produced in response to overnight orthokeratology.

PURPOSE: To analyze the binocular function changes produced on subjects undergoing overnight orthokeratology (OK) treatment over short-term (3 months) and long-term (3 years) wear. METHODS: A prospective, longitudinal study on young adult subjects with low to moderate myopia was carried out. Binocular function was assessed by the following sequence of tests: Distance and near horizontal phoria (Von Graefe technique), distance and near horizontal vergence ranges (Risley rotary prisms), accommodative convergence/accommodation (AC/A) ratio (gradient method) and the near point of convergence (standard push-up technique). The short-term sample consisted of: 21 subjects in the control group, 26 in a corneal refractive therapy (CRT) treatment lenses group and 25 in a Seefree treatment lenses group. Those subjects were evaluated at baseline and at a 3-month follow-up visit. Twenty one subjects were old CRT wearers that attended a 3-year follow-up visit (long-term group). RESULTS: A statistically significant difference over the 3-month treatment was found for divergence at distance: the break point decreased 1.4 Δ (p = 0.0006) in the CRT group and the recovery point increased 1.2 Δ (p = 0.001) in the Seefree group. Also, the Seefree group had an exophoric trend of 2.3 Δ at near (p = 0.02) and a base-out break decrease of 2.3 Δ (p = 0.03). For the long-term group, only the base-out break point at distant vision showed a statistically significant difference of 4.9 Δ (p = 0.02). CONCLUSIONS: 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.

Accommodative changes produced in response to overnight orthokeratology.

BACKGROUND: To evaluate short-term (3 months) and long-term (3 years) accommodative changes produced by overnight orthokeratology (OK). METHODS: A prospective, longitudinal study on young adult subjects with low to moderate myopia was carried out. A total of 93 patients took part in the study. Out of these, 72 were enrolled into the short-term follow-up: 21 were on a control group, 26 on a Paragon CRT contact lenses group, and 25 on a Seefree contact lenses group. The other 21 patients were old CRT wearers on long-term follow-up. Accommodative function was assessed by means of negative and positive relative accommodation (NRA / PRA), monocular accommodative amplitude (MAA), accommodative lag, and monocular accommodative facility (MAF). These values were compared among the three short-term groups at the follow-up visit. The long- and short-term follow-up data was compared among the CRT groups. RESULTS: Subjective accommodative results did not suffer any statistically significant changes in any of the accommodative tests for any of the short-term groups when compared to baseline. There were no statistically significant differences between the three short-term groups at the follow-up visit. When comparing the short- and long-term groups, only the NRA showed a significant difference (p = 0.0006) among all the accommodation tests. CONCLUSIONS: OK does not induce changes in the ocular accommodative function for either short-term or long-term periods.