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Erin Tomiyama, Kathryn Richdale; Efficacy of Euclid Spherical and Toric Orthokeratology Lenses in Decreasing Corneal Astigmatism. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6359. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies showed a lack of agreement between corneal toricity and subjective refraction with orthokeratology, possibly due to higher order aberrations. To date there is limited data on patients with moderate astigmatism (>1.25 DC). The purpose of this study was to objectively compare changes in corneal astigmatism after successful Euclid spherical (Emerald) or toric (Sapphire) orthokeratology lens wear in patients with astigmatism.
This retrospective study evaluated 12 eyes of 6 subjects; half fit with sphere and half with toric lenses. All subjects had reliable baseline topography, pre-treatment refractive data, and post-treatment data after finalization of a successful fit (1-2 months of nightly wear). Medmont and Pentacam topographers were both used but within each subject remained consistent. Data were collected from the University of Houston College of Optometry. Pre- and post-treatment data were analyzed using paired t-tests.
The mean sphere and cylinder refractive error was -4.54±2.22 DS and -2.13±0.89 DC for toric and -1.71±0.40 DS and -0.38±0.34 DC for sphere lens wearers. The range of corneal astigmatism at baseline varied from 1.70-3.38 D in toric and 0.4-0.63 D in sphere lens wearers. The mean baseline elevation difference between the steep and flat corneal meridian at a 7-8 mm chord for subjects fit in toric lenses was 62.3±13.1µm and 3.5±3.2µm for those fit in sphere lenses.The change in corneal astigmatism for all subjects was 1.49±1.16 to 1.15±0.98 DC (p=0.08). For toric wearers, corneal astigmatism decreased from 2.49±0.74 to 1.93±0.79 DC (p=0.16); for sphere wearers, corneal astigmatism decreased from 0.49±0.09 to 0.37±0.24 DC (p=0.20). In this sample, the amount of corneal astigmatism corrected was not significantly different between lens designs. In toric wearers, the mean change was 0.56±0.84 DC and for sphere wearers it was 0.12±0.20 DC (p=0.24). This equated to 21% decrease in corneal astigmatism after lens wear compared to baseline with toric and 27% decrease in corneal astigmatism with sphere lenses.
Overall, the decrease in corneal astigmatism after lens wear in either group was not significantly different. Previous studies have suggested a ~50% decrease in astigmatism for patients with fitted with spherical orthokeratology. Research is ongoing to examine changes in corneal astigmatism with spherical and toric orthokeratology.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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