| Author: | Tan, Qi |
| Title: | Combined atropine with orthokeratology in childhood myopia control (AOK) – a randomized controlled trial |
| Advisors: | Cho, Pauline (SO) |
| Degree: | Ph.D. |
| Year: | 2021 |
| Subject: | Myopia -- Treatment Orthokeratology Contact lenses Hong Kong Polytechnic University -- Dissertations |
| Department: | School of Optometry |
| Pages: | xiv, 153 pages : color illustrations |
| Language: | English |
| Abstract: | The mechanism underlying the control effect of atropine or orthokeratology (ortho-k) in retarding myopia progression in children is unclear. The former treatment is believed to act via muscarinic receptors in the eye (e.g. retina, choroid, and sclera) and the latter via an optical mechanism. There may be an additive effect in controlling myopia progression if atropine is combined with ortho-k. A 2-year randomized controlled trial was performed to explore whether combining 0.01% atropine with ortho-k (AOK) would result in less axial elongation than ortho-k alone (OK). As it has been well-documented in previous randomized studies that 0.01% atropine has negligible side-effects compared to those at higher concentrations, this concentration of atropine was used in the current study. To gain a better understanding of the mechanism underlying a possible additive effect if 0.01% atropine was used together with ortho-k, measurements of mesopic and photopic pupil sizes, the amplitude of accommodation, choroidal thickness, and ocular aberrations, which include lower-order (LOA) and higher-order aberrations (HOA) were performed. After two years, significantly less axial elongation was observed in AOK than in OK subjects (mean ± SD, 0.17 ± 0.20 mm vs 0.31 ± 0.19 mm), indicating that an additive effect exists when 0.01% atropine is used in conjunction with ortho-k for myopia control. Also, the combined treatment was well tolerated by subjects, with no difference in the percentages of occurrence of adverse events, although more symptoms of photophobia (12% vs zero) and haloes (12% vs 6%) were reported by AOK subjects. However, these symptoms were transient and/or well-tolerated, and no inconvenience was reported by subjects. Comparison of choroidal thickness changes over two years between subjects undergoing AOK and those receiving OK revealed greater choroidal thickening in the former group at all visits (e.g. 24-month visit, 20.9 ± 21.5 μm vs -4.9 ± 15.6 μm). Furthermore, choroidal thickening was associated with slower axial elongation in both treatment groups over two years, suggesting that the magnitude of choroidal thickening, seemingly a treatment response, may play a role in the treatment effect of either combined 0.01% atropine and ortho-k or ortho-k alone. After commencement of the treatments, no difference in retinal image quality was observed between the two groups, despite a significant reduction in LOA and an increase in HOA for a 3-mm pupil in both groups. The key findings were that slower axial eye growth was associated with a greater increase in the RMS values of total HOA and Coma, a greater decrease in the RMS value of LOA, a higher level of some HOA terms (e.g. vertical coma) for a photopic pupil in the AOK group, whereas no associations were observed between axial eye growth and any of the aberration metrics in the OK group. This suggests that an optical mechanism involving the changes in the profile of ocular aberrations may underly an additive effect of the combined treatment of 0.01% atropine and ortho-k when compared with ortho-k alone. |
| Rights: | All rights reserved |
| Access: | open access |
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