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http://dx.doi.org/10.14479/jkoos.2013.18.4.449

The Effects of Corneal Eccentricity and Shape on Toric Soft Lens Rotation by Change of Postures  

Kim, So Ra (Dept. of Optometry, Seoul National University of Science and Technology)
Hahn, Shin Woong (Dept. of Optometry, Seoul National University of Science and Technology)
Song, Ji Soo (Dept. of Optometry, Seoul National University of Science and Technology)
Park, Mijung (Dept. of Optometry, Seoul National University of Science and Technology)
Publication Information
Journal of Korean Ophthalmic Optics Society / v.18, no.4, 2013 , pp. 449-456 More about this Journal
Abstract
Purpose: The present study aimed to investigate the effects of corneal eccentricity and shape on the rotational pattern of toric soft lens by the postural change of lens wearers. Methods: The corneal eccentricity of 41 eyes (aged 20s) having -1.0 D with-the-rule corneal astigmatism (WRCA) was measured, and then toric soft lenses were fitted with the amount of total astigmatism. In lying and straight postures, the rotation of toric soft lenses was recorded by a camera attached to slitlamp and analyzed. Results: Most toric soft lens designed with accelerated stabilization rotated to the temporal direction, which was the lying position direction, regardless of corneal eccentricity, and some lenses rotated to the nasal direction for high corneal eccentricity and corneal type of asymmetric bowtie. There was no correlation between the amount of rotation and corneal eccentricity right after of contact lens wearing in straight and lying posture, however, the amount of rotation was the greater for the cornea with the higher eccentricity after the subjects laying down for some period. The speed of lens rotation started to decrease after the subjects laying down, but the speed was not different according to corneal eccentricity difference. The amount of lens rotation for symmetric and asymmetric bowtie-typed corneas increased more than it for oval-typed cornea, and it was same even with time elapsing. The speed of lens rotation in lying posture was the slowest in asymmetric bowtie-typed cornea compared with other corneal types. Conclusions: From the present study, it was revealed that the rotational pattern of toric soft lens was affected by corneal eccentricity and corneal shape when the wearer's posture changed. Thus, it should be considered for the development of the fitting guideline and the design of toric soft lens.
Keywords
Toric Soft Contact Lens; Corneal Eccentricity; Corneal Type; Rotation Direction; Speed of Lens Rotation;
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