Multipurpose solutions (MPS) are the most commonly prescribed regimen to clean, disinfect and rinse rigid lenses. The preservatives used in MPS may cause hypersensitivity and the presence of quaternary ammonium compounds (QAC) may increase development of antiseptic resistance mediated by QAC resistance genes, thus lowering the efficacy of disinfection. Povidone-iodine (PVI) has been safely used as a disinfectant for ophthalmic operations and eye drops. The cleadew GP (Ophtecs, Japan) tested in the current study is a PVI based rigid lens disinfecting solutions which does not employ QAC. If its efficacy and safety can be confirmed in this study, it will be a good alternative rigid lens care regimen for children.

Multipurpose solutions (MPS) are the most commonly prescribed regimen to clean, disinfect and rinse rigid lenses. These solutions usually contain quaternary ammonium compounds (QAC) which have been shown to be selective for carriage of organisms harbouring QAC genes in orthokeratology (ortho-k) lens wear and it raises concerns about safety with the increasing popularity of orthokeratology (ortho-k) for myopia control in children. Hydrogen peroxide system is a good alternative but this option is limited in rigid lens market. The only brand available in Hong Kong labelled as safe for rigid contact lenses has limited disinfecting power. cleadewGP (Ophtecs, Japan) is a new disinfecting solution for rigid contact lenses which does not employ QAC and instead is povidone iodine (PVI) based. PVI has been safely used as a disinfectant for ophthalmic operations and is commonly used in eye drops. PVI-based soft and rigid lens solutions have been reported to be as effective against Pseudomonas aeruginosa as other MPS and hydrogen peroxide-based solutions. However, other efficacy against other organisms need to be demonstrated to allow this solution to meet FDA requirements. The PVI-based soft lens solution was also reported to be effective against Acanthamoeba. cleadewGP is relatively new in the market and not much work has been done on the efficacy and safety of this solution. If confirmed to be effective and safe, cleadewGP may be a better alternative to ortho-k lens wearers who need to use disinfecting solutions at least for a few years while under ortho-k treatment. In the absence of QAC, there will be no concern of selection of carriage of organisms harbouring QAC genes in ortho-k lens wearers using this disinfecting solution over time.

The current study aims at investigating the effectiveness and safety of the cleadewGP for cleaning (lipid and protein removal) and disinfecting of ortho-k lenses by comparing the outcomes collected from subjects randomly assigned to one of the following study groups.

Group 1: cleadewGP without lens rubbing Group 2: cleadewGP with lens rubbing Group 3: cleadewGP with separate daily cleaner Group 4: cleadewGP with separate daily cleaner and weekly protein removal agent

Four study visits will be involved in this 6 months study: baseline, 1-month, 3-month, and 6-month after lens wear. Complimentary solutions will be provided during the study period. Solutions and accessories will be replaced at monthly interval. Effectiveness for cleaning and disinfection and safety of lens wear will be determined by comparing the changes in ocular microbiome before and after lens wear, contamination levels of lenses and accessories, biomicroscopic examination of lenses and eyes, and subjective rating of lens comfort among the four groups of subjects.

Inclusion Criteria:

• cycloplegic objective sphere between -1.00D to -4.00D
• cycloplegic objective astigmatism ≤ 2.00D
• anisometropia < 1.00D
• best-corrected logMAR visual acuity 0.10 or better in both eyes
• symmetrical corneal topography with toricity ≤ 2.00D
• normal ocular health

Exclusion Criteria:

• contraindication to ortho-k wear
• prior history of myopia control treatment
• prior history of rigid contact lens wear
• strabismus or amblyopia
• systemic or ocular conditions which might affect refractive development
• poor response or poor compliance to lens wear including poor lens handling, poor vision, and/ocular response after lens modifications