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KMID : 1011420130180040449
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Journal of Korean Ophthalmic Optics Society
2013 Volume.18 No. 4 p.449 ~ p.456
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The Effects of Corneal Eccentricity and Shape on Toric Soft Lens Rotation by Change of Postures
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Kim So-Ra
Hahn Shin-Woong
Song Ji-Soo
Park Mi-Jung
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Abstract
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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.
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KEYWORD
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Toric Soft Contact Lens , Corneal Eccentricity , Corneal Type , Rotation Direction , Speed of Lens Rotation
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