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X. Mao, F. Lu, Y. Song, J. He; The Effect of Orthokeratological Treatment on Peripheral Refraction for Myopic Eyes With Different Degree of Myopia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1539.
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To investigate the effect of orthokeratology on peripheral refraction for myopic eyes with different myopia.
Peripheral refraction up to 30° along the horizontal visual field was assessed using an open-field autorefractor (Grand Seiko 5500) for three groups of subjects: 15 emmetropes (30 eyes, +0.13±0.37D) as a control group (G0), 15 low myopes(30 eyes,-1.57±0.28D)and 15 moderate myopes (30 eyes,-2.86±0.57D) as the experimental group G1 and G2 respectively. The myopic subjects were treated with reverse geometry orthokeratology lenses overnight, and the peripheral refraction was monitored pre- and 1 week after the treatment. Corneal curvature was measured with corneal topography.
Initial measurement showed that G0 had a relative myopic defocus in the nasal side but a relatively hyperopic refraction in the temporal side as compared to the central refraction. Both G1 and G2 had relative hyperopia in the periphery and were more relatively hyperopic than G0 while the G2 had more relative hyperopia than the G1. Peripheral J45 astigmatism (J45) was linearly related to field angle for all of the three groups (P<0.05), and the peripheral J180 astigmatism increased with the eccentricity in all three groups. After 1 week orthokeratology treatment, All myopic subjects were significantly reduced in the spherical equivalent refraction (M) in the central ±15°visual fields along with a corneal curvature flattening (P<0.05). The peripheral spherical equivalent refraction (M) had a relative myopic defocus in both G1 and G2 while G2 had more myopic defocus than G1 in nasal 30°,25°,20°and in temporal 15°,20°,25°(all p<0.05). The trend of linearity between the peripheral J45 astigmatism and the visual field was reduced. Both J180 and J45 peripheral astigmatism were increased in either G1 or G2. G2 had more peripheral J180 astigmatism beyond ±20°of the visual field than G1, but no significant difference was found for the J45 astigmatism.
Orthokeratological treatment makes central curvature of the anterior corneal surface flatten and thus effectively correct the central myopic error. The Orthokeratology also converts relative peripheral hyperopia to relative peripheral myopia, and the degree of peripheral myopic error increases with the baseline central myopic error. Peripheral astigmatism also increases with orthokeratology and depends on baseline central myopic error.
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