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P. Kang, H. A. Swarbrick; Peripheral Refraction in Myopic Children Wearing OK and GP Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3934.
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To investigate the influence of orthokeratology (OK) and conventional gas-permeable (GP) contact lenses on peripheral refraction in children with progressive myopia.
10 subjects (aged 11-16 years) were enrolled in a study in which one eye was fitted with a BE OK lens and the fellow eye with a J-Contour GP lens (Capricornia Contact Lens). Lenses were worn over a 3-month period and peripheral refraction (Shin-Nippon NVision K-5001 autorefractor) was measured at 10º, 20º, 30º and 35º in the nasal and temporal visual field. Corneal topography (Medmont E300) was also measured at baseline and after 3 months of lens wear. Repeated-measures ANOVA and post-hoc paired Student t-tests with a critical p-value of 0.05 were employed for statistical analysis.
Mean spherical equivalent refraction M became significantly less hyperopic in the periphery (F= 25.172, p<0.001) with OK lenses while GP lenses caused no significant change over the 3-month period (F=0.006, p=0.937). J180 increased with OK lenses (F=22.782, p<0.001) while no significant change in astigmatism was found with GP lenses (F=1.548, p=0.229). There was no significant change with either OK or GP lenses in J45 (FOK=0.000, pOK=0.996; FGP=0.020, pGP=0.889). A significant difference in axial corneal power between OK and GP lenses was apparent after the 3-month period (F=24.230, p<0.001). OK lenses caused significant flattening centrally (F=4.935, p=0.039) while GP lenses induced no change in corneal topography (F=0.573, p=0.569).
At baseline, myopic children were found to have a relatively hyperopic peripheral refraction indicating a more prolate ocular shape. OK lenses in children induced a myopic shift in M in the periphery and an increase in astigmatism after 3 months of lens wear; this is similar to changes previously documented in adults. In comparison, conventional rigid GP lenses caused no significant changes in peripheral refraction. Further investigation is required to determine if the effect of OK lenses is similar in adults and progressing myopic children over a longer lens-wearing period.
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