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KMID : 1011420150200020141
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Journal of Korean Ophthalmic Optics Society
2015 Volume.20 No. 2 p.141 ~ p.150
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The Effects of Corneal Type and Corneal Astigmatism on Tear Volume between Rigid Gas Permeable Lens and the Cornea
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김지혜:Kim Ji-Hye
김소라:Kim So-Ra/박미정:Park Mi-Jung
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Abstract
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Purpose: In the present study, a difference in tear volume between the cornea and the rigid gas permeable (RGP) lens relative to corneal shape and corneal astigmatism was investigated by the alignment fitting status of spherical and aspherical RGP lenses.
Methods: Spherical and aspherical RGP lenses were fitted with alignment in 77 subjects (135 eyes) who were in their 20~30s. Tear volume stained with fluorescein was qualitatively analyzed by dividing cornea into center, mid-peripheral and peripheral parts.
Results: For the spherical RGP lens fitting, tear volume differences were found in each part in all corneal types. For the aspherical RGP lens fitting, tear volume differences were in each corneal part in symmetric bow tie- and asymmetric bow tie-type corneas. However, the tear was equally distributed from the center to the peripheral part in round- and oval-type corneas. In the group with corneal astigmatism lower than 1.25 D, tear volume between center and peripheral parts, and mid-peripheral and peripheral parts, was different when a spherical RGP lens was fitted. However, tear volume in each part was not different in the group with corneal astigmatism over 1.50 D. Moreover, the tear volumes of the central and mid-peripheral parts were proportionally increased with increasing corneal astigmatism in both spherical and aspherical RGP lenses. Furthermore, aspherical RGP lenses showed greater increments than spherical RGP lenses.
Conclusions: The results revealed that the difference in tear volume between aspherical RGP lens and corneawas less than spherical RGP lens, and the difference in tear volume varied according to corneal shape and astigmatism. In addition, the method of measuring relative tear volume between RGP lens and cornea that was established in the present study can be used to evaluate tear volume between contact lens and cornea.
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KEYWORD
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Corneal type, Corneal astigmatism, RGP lens fitting, RGP lens design, Tear volume
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