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Paul Gifford, Vinod Maseedupally, Edward Lum, Helen A. Swarbrick; Sectorial Corneal Curvature Changes During Myopic Orthokeratology. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6550.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate sectorial changes in corneal curvature with myopic orthokeratology lens wear over a period of two weeks.
Nineteen eyes of 9 males and 10 females who underwent orthokeratology were analysed retrospectively. Participants with myopia less than -4.50D and astigmatism less than -1.50D were enrolled. Corneal topography from the Medmont E300 was analysed to investigate changes in the central zone and two surrounding annular zones (para-central and peripheral), with each zone sub-divided into four quadrants (nasal, superior, temporal and inferior). All participants wore BE reverse geometry lenses (Boston XO) on an overnight schedule for two weeks in one eye randomly; the other eye underwent orthokeratology treatment with different materials, and these data were not included in this analysis. A custom written Matlab program was used to extract and average all topographic data within each sector. Changes from baseline in each pre-defined sector were calculated and analysed using ANOVA and one tailed paired t tests.
Participant age ranged from 19 to 40 years (mean 30.1±6.8 years). After two weeks of treatment significant flattening was noted in all central sectors. Central superior (p<0.001) and central temporal (p<0.001) locations showed significantly more flattening than other central sectors. The para-central nasal cornea was significantly steepened compared with para-central superior (p=0.01) and para-central inferior cornea (p<0.001). The peripheral nasal cornea was significantly steepened compared with peripheral superior (p=0.02) and peripheral inferior sectors (p=0.04).
This retrospective study shows that although central flattening was achieved in all quadrants with orthokeratology, there were significant differences in various sectorial zones. As expected, the para-central and peripheral cornea became steeper; however, there was an area of flattening towards the para-central temporal and peripheral temporal locations, adjacent to the significantly flattened central temporal zone. This is consistent with the known tendency of these lenses to decenter towards the temporal cornea.
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