Orthokeratology with increased compression factor (OKIC): study design and preliminary results.

OBJECTIVE: To present the study design and the baseline data of a prospective cohort study investigating the safety, refractive correction and effectiveness of myopia control in subjects fitted with orthokeratology (ortho-k) lenses of different compression factors. METHODS AND ANALYSIS: This study is a 2-year longitudinal, double-masked, partially randomised study. Myopic children aged between 6 and 10 years are recruited and they may choose to participate in either the ortho-k or spectacle-wearing group. Subjects in the ortho-k group are randomly assigned to wear ortho-k lenses of either conventional compression factor (CCF, 0.75 D) or increased compression factor (ICF, 1.75 D). For the ortho-k subjects, the time and between-group effects within the first month of lens wear were analysed. RESULTS: Sixty-nine ortho-k subjects (CCF: 34; ICF: 35) and 30 control subjects were recruited. There were no significant differences in baseline demographic data among the three groups of subjects (p>0.19). At the 1-month visit, the first fit success rates were 97% and 100% in the CCF and ICF ortho-k group, respectively. A higher percentage of ICF subjects could achieve full correction (CCF: 88.2%; ICF: 94.3%). The change in axial length was significantly higher in the ICF group (CCF, 0.003 mm; ICF, -0.031 mm) (p<0.05). No significant between-group differences in daytime vision or in the coverage and depth of corneal staining between the two ortho-k groups (p>0.05) were observed at any visit. CONCLUSION: ICF did not compromise the corneal integrity and the lens centration within the first month of lens wear. The preliminary performance of ortho-k lenses with ICF of 1.00D shows that it was safe to be used in the longer term for the investigation of myopia control. TRIAL REGISTRATION NUMBER: NCT02643342.

Refractive and corneal responses of young myopic children to short-term orthokeratology treatment with different compression factors.

PURPOSE: To evaluate changes in refractive and corneal responses in myopic children wearing orthokeratology (ortho-k) lenses with conventional compression factor (CCF, 0.75 D) and increased compression factor (ICF, 1.75 D). METHODS: This was a double-blind self-controlled study. Subjects were randomly fitted with CCF in one eye and ICF in the fellow eye. Weekly monitoring of refraction, visual acuity (VA), external ocular health, and corneal responses were performed over one month of lens wear and after discontinuation of lens wear until stabilization was achieved. RESULTS: Twenty-five subjects, aged 9.4 ±â€¯1.0 years, completed one-month lens wear, of whom 23 completed the washout period. The first fit success rates for CCF and ICF were 93% and 96%, respectively. Myopia, unaided VA, central corneal thickness, anterior corneal curvatures (K), apical power (AP), and corneal resistance factor (CRF) all changed significantly during the study period (P <  0.003). Between-eye difference was significant only for myopia reduction (P =  0.001). About 4% and 8% of ICF and CCF eyes were under-corrected. The attempted target was achieved in about 80% of CCF and 60% of ICF eyes at week 4. At the end of the washout period (3 weeks), myopia, K, and AP were significantly different compared to baseline (P <  0.001). CONCLUSION: Increasing the compression factor did not affect the first fit success rate and external ocular health, but did allow faster correction of refractive error within one month of lens wear. Further investigation is warranted to investigate the long-term effects of ICF on myopia control compared to CCF.

Effect of multipurpose solutions on in vivo surface wettability of a silicone hydrogel lens.

PURPOSE: To compare the in vivo surface wettability of silicone hydrogel (SiHy) contact lenses pre-soaked overnight in different multipurpose solutions (MPS) and normal saline. METHODS: In this double-blinded, randomized and self-controlled study, 36 subjects were fitted with three pairs of contact lenses (senofilcon A) pre-soaked overnight in five different MPS and saline in a randomized order. Each pair of lenses (pre-soaked in two different solutions the night before) were worn for 15min before assessment of pre-lens non-invasive tear break-up time (PL-NITBUT) using the Medmont corneal topographer (video recording). Corneal integrity was assessed using a slit lamp and a resting interval of 20min was allowed between each pair of lenses to ensure post-lens wear corneal integrity. RESULTS: Thirty subjects completed the study. The median PL-NITBUT ranged from 2.84s to 3.08s with lenses pre-soaked in different MPS, compared to 2.78s with lenses pre-soaked in saline. No significant differences in PL-NITBUT were found among lenses pre-soaked in different solutions (p=0.647). CONCLUSION: In vivo surface wettability, in terms of PL-NITBUT after 15min of lens wear, of senofilcon A contact lenses pre-soaked overnight in different MPS were not significantly different from those pre-soaked in saline.