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

• Published in: BMJ open ophthalmology Vol. 5; no. 1; p. e000345
• Main Authors: Wan, Kin, Lau, Jason Ki-kit, Cheung, Sin Wan, Cho, Pauline
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group Ltd 04.05.2020; BMJ Publishing Group LTD; BMJ Publishing Group
• Subjects: contact lens; Cornea; Data collection; Longitudinal studies; optics and refraction; Original Research; Software; Topography; treatment other; Japan; treatment other; optics and refraction; contact lens
• ISSN: 2397-3269; 2397-3269
• DOI: 10.1136/bmjophth-2019-000345

ObjectiveTo 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 analysisThis 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.ResultsSixty-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.ConclusionICF 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.