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N. Tahhan, F. Sarfraz, N. Raad, C. Raad, T. Weber, R. Du Toit, E. Papas; Orthokeratology and the Eyelid . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3714.
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Purpose: Our aim was to determine the relation between eyelid tension and refractive effects in orthokeratology (orthok) and the effect of lid position (open vs closed) on lens centration. Methods: Thirteen Caucasian and 13 Asian subjects were randomly fitted with BE and ABE (Capricornia Australia) reverse geometry contact lenses in one random eye. Subjects wore the lens for one hour with the eyes open. After one week of no lens wear, they wore the lens again for one hour with their eyes closed. Upper eyelid tension was measured objectively using a custom designed eyelid tensiometer. Refraction and Eyesys (version 4.2) corneal topography measurements were taken at baseline and after each period of lens wear. Lens centration on the open eye and topography treatment zone centration after both open and closed eye lens wear was evaluated. Data were analysed using Student’s t-tests and Pearson correlation. Results: There were no significant differences between either lens centration and treatment zone centration in the open eye nor in treatment zone centration in open vs closed eye for either Asian or Caucasian groups. There were no significant differences in eyelid tension between the groups (Asian 22.1 + 4.6mN vs Caucasian 20.9 + 5.7mN). No correlation was found between lid tension measurement and refractive change (r=0.15, p=0.45). There was no significant difference between Asian and Caucasian eyes in the amount of myopic reduction with either closed or open eye lens wear. Refractive changes in Asian eyes were significantly lower with closed eye wear compared to open eye wear (0.52 + 0.49D vs 0.87+ 0.36D respectively, p<0.05), but refractive change with open and closed eye mode did not differ significantly in the Caucasian group (1.04 + 0.71D open eye vs 0.88 + 0.49D closed eye, p=0.41). Conclusions: The results suggest that practitioners can assume that lens centration during eye closure will be similar to that in the open eye. There was no demonstrable relationship between lid tension and myopic reduction with orthok. This suggests lid forces play a less significant role than those of the tear film with orthok therapy.
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