This project aims to investigate/examine high myopic subjects on full correction ortho-k (using Topaz ortho-k lenses for high myopia) compared to subjects undergoing partial reduction ortho-k and their relationship with myopia and myopic progression.
For many years, commercially-available ortho-k lenses aim to reduce low - moderate myopia. Attempts to use these lenses for reduction of high myopia have been shown to give rise to complications such as corneal staining and lens decentration. Thus, practitioners may choose a more conservative way for high myopic children, that is, offering partial reduction ortho-k. Partial reduction ortho-k is target for 4.00-5.00D reduction and the residual refractive errors will be corrected with single vision spectacles to allow good visual acuity in the daytime. Partial reduction ortho-k has been shown to slow axial elongation in high myopic children, however, the main disadvantage is that the children have to wear spectacles in the daytime to correct residual refraction. Euclid has recently designed a new lens, Euclid's Topaz, for high myopic children. It is currently commercially available to correct myopia for up to 10 D. However, evidence of its effectiveness for visual correction and slowing AL growth is lacking. While numerous studies have shown that orthokeratology is an effective clinical treatment to slow axial eye growth in children, the exact mechanism underlying this reduction in myopia progression associated with orthokeratology remains unclear.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
66
Conventinally designed (Emerald) ortho-k lenses (target for -4.00D) and thinner specs during day time
Newly designed (Topaz) ortho-k lenses for high myopia (target for full correction)
School of Optometry, The Hong Kong Polytechnic University
Kowloon, Hong Kong
RECRUITINGChange in axial length elongation over 24 months.
To determine the change in axial length measured at baseline and two years after lens wear using IOLMaster
Time frame: 2 years
First fit success rate of a newly designed ortho-k lens for high myopic children
The success rate in using the first pair of lenses to achieve target refractive correction will be determined
Time frame: 1 month
Quality of life (questionnaire)
Quality of life will be determined by questionnaires (using revised Pediatric Refractive Error Profile (PREP) 1 in traditional Chinese version) before and after ortho-k in the two groups of subjects
Time frame: 3 months
Ocular aberration
Ocular aberration will be measured by Complete Ophthalmic Analysis System (COAS) aberrometer
Time frame: 2 years
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