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KMID : 1011420200250030257
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Journal of Korean Ophthalmic Optics Society
2020 Volume.25 No. 3 p.257 ~ p.263
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The Effect of pH on the Thickness of Soft Contact Lenses
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Park Ji-Yeon
Hwang So-Dam
Kim So-Ra
Park Mi-Jung
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Abstract
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Purpose: This study aimed to investigate the effect of pH change on the central and peripheral thickness of soft contact lenses, and the effects of the characteristics of lens material and pigmentation of soft contact lenses on thickness variation.
Methods: The central and peripheral thickness of clear and circular lenses made of nelfilcon A, hilafilcon B, etafilcon A were respectively measured after an incubation in phosphate buffer adjusted with pH 6.6, 7.4 and 7.8 for 24 h.
Results: Compared with an incubation in pH 7.4, the same pH as tears, the thickness was larger in pH 6.6 and pH 7.8 depending on lens material; however, this difference was insignificant. There was no difference in the central and peripheral thickness between clear and circular lenses made of nelfilcon A. The central thickness of the hilafilcon B circle lens was not different from that of clear lens; however, its peripheral thickness was thicker than that of clear lenses. Etafilcon A material, on the other hand, had a thinner central thickness in circular lenses; however, its peripheral thickness was thicker. The difference between the thickness of the center and periphery depending on the pigmentation in hilafilcon B and etafilcon A lenses became larger as the pH increased.
Conclusions: In this study, it was revealed that there may be thickness changes of the center and periphery of soft contact lenses depending on the pH change of tear because of eye diseases or the difference of pH in lens care solutions. In addition, from this study, it is proposed that the difference in thickness changes depending on the characteristics of the material and pigmentation may cause difference of comfort in clinical practice.
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KEYWORD
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Soft Contact Lenses, pH, Central Thickness, Peripheral Thickness, Pigmentation
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