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Pauline Kang, Helen A. Swarbrick; Time Course Of The Effects Of Orthokeratology On Peripheral Refraction And Corneal Topography. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4713.
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To investigate the time course of the effects of overnight orthokeratology (OK) lens wear on peripheral refraction and corneal topography.
Nineteen adult subjects (age range 18-38 years; 12M, 7F) were enrolled. Central refraction was between -1.00DS and -4.00DS with ≤-1.50DC. Both eyes were fitted with BE OK lenses (Capricornia Contact Lens) and lenses were worn overnight only for a minimum of two weeks. Peripheral refraction (Shin-Nippon NVision K-5001 autorefractor) was measured at 10º, 20º, 30º and 35º in the nasal and temporal visual field (VF) after 1, 4, 7 and 14 nights of OK lens wear. Corneal topography (Medmont E300) was also measured at the same time points, and corneal refractive power was calculated at points along a horizontal corneal chord extending out to 2.8mm on the nasal cornea and 1.5mm on the temporal cornea. Repeated-measures ANOVA was used to analyze both refraction and corneal refractive power across the horizontal meridian and doubly MANOVA was performed to assess for changes in peripheral refraction and corneal refractive power profile over time.
There was a significant change in spherical equivalent M over the 14 days of OK treatment at all positions (p<0.05) except at 35° in the temporal VF and 20° and 30° in the nasal VF. At all other positions, the general trend was a hyperopic shift in M except at 35° in the nasal VF where there was instead a myopic shift in M. The most significant change in M occurred between baseline and Day 1 and the effect showed less dramatic progression between subsequent days. OK caused significant change in corneal refractive power at all positions along the horizontal corneal chord (p<0.001). The general trend was a reduction in corneal power or flattening of the cornea at all positions except at 2.4mm and 2.8mm on the nasal cornea where there was an increase in corneal refractive power or steepening of the cornea.
OK caused significant changes in both peripheral refraction and corneal topography. The greatest change in M and corneal refractive power across the horizontal corneal chord occurred during the first night of OK lens wear. Subsequent changes in both peripheral refraction and corneal topography were less dramatic across subsequent days.
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