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Pauline Kang, Kathleen Watt, Tina Chau, Jenny Zhu, Helen A Swarbrick; Binocular vision changes after short-term orthokeratology. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1482.
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© ARVO (1962-2015); The Authors (2016-present)
Following recent anecdotal reports of improvements in binocular vision with orthokeratology (OK), this study aimed to characterize the effects of short-term OK on accommodative vergence functions and stereopsis.
18 young adult myopes (23 ± 4 years of age) were fitted with Paragon CRT lenses (Paragon Vision Sciences) in both eyes and lenses were worn overnight for 28 days. Central refraction (Shin-Nippon autorefractor), stereopsis (Randot test), distance and near horizontal phorias (Howell card), fixation disparity (Saladin near point card and Sheedy disparometer), accommodative facility and AC/A ratios (Howell card with ±1 D and ±2 D flippers) were measured at baseline before any lens wear, and after 7, 14 and 28 days of OK. Depending on normality of data, RM-ANOVA or Friedman test were used to analyze changes in binocular vision over the course of OK treatment.
OK lens wear caused a significant hyperopic shift in central M in both eyes (both p<0.001). There was no significant change in stereopsis (p=0.095) or distance phoria (p=0.070) during 28 days of OK. There was a significant change in near phoria in the exo-direction which reached statistical significance after 14 days of OK lens wear (p=0.011). However, neither horizontal nor vertical fixation disparities at near showed significant change. Interestingly, distance (p=0.019) and near (p=0.018) accommodative facility improved with OK. However, AC/A ratio gradient with -2 D (p=0.076), -1 D (p=0.730), +1 D (p=0.826) or +2 D (p=0.920) lens stimuli did not significantly change during the 28 days of OK treatment.
Myopes with near esophoria may benefit most with OK lens wear, in terms of binocular vision posture. Improvements in accommodative facility at both distance and near may reflect overall improved accommodative function. As reduced accommodative facility has been linked to myopia progression in children, this may be another mechanism involved in myopia control with OK.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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