Investigation of the Effect of Short-term Orthokeratology With Increased Compression Factor on Ocular Parameters

Subjects were fitted with ortho-k lenses of conventional (0.75 D) and increased (1.75 D) compression factor. The laterality of the compression factor for each subject was randomised.

Subjects were instructed and trained with proper lens handling and disinfection procedures. Lenses were given to the subjects only when they demonstrated proper techniques.

All subjects were required to attend regular follow-ups (baseline, first overnight, and weekly over one-month period). The follow-ups were scheduled (except for the first overnight which was scheduled in the early morning) at a similar time to the baseline visit (+/- 2 hours) to minimise any potential influence of diurnal variation on ocular biometrics.

Additional unscheduled visits were provided when necessary to ensure good ocular health and vision throughout the study period.

Inclusion criteria

• 6 to 10 years old
• Myopia: between 0.50 D and 4.00 D in both eyes
• Astigmatism: <1.50 D; ≤ 1.25 D for with-the-rule astigmatism (axes 180 ± 30); ≤ 0.50 D for astigmatism of other axes in both eyes
• Anisometropia: ≤ 1.50 D
• Symmetrical corneal topography with corneal toricity <2.00 D in both eyes
• Agree for randomization

Exclusion criteria

• Contraindications for orthokeratology wear (e.g. limbus-to-limbus corneal cylinder and dislocated corneal apex)
• Any type of strabismus or amblyopia
• Myopic treatment (e.g. refractive surgery and progressive lens wear for myopic control) before and during the study period
• Rigid contact lenses (including orthokeratology lenses) experience
• Systemic condition which might affect refractive development (for example, Down syndrome, Marfan's syndrome)
• Ocular conditions which might affect the refractive error (for example, cataract, ptosis)
• Poor compliance for lens wear or follow-up