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Dehydration, lens movement and dryness ratings of hydrogel contact lenses
Author(s) -
Pritchard Nicola,
Fonn Desmond
Publication year - 1995
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1046/j.1475-1313.1995.9500004w.x
Subject(s) - dryness , lens (geology) , dehydration , contact lens , chemistry , analysis of variance , in vivo , ophthalmology , optics , surgery , medicine , biochemistry , physics , biology , microbiology and biotechnology
Summary Previous studies have shown that soft lenses dehydrate during lens wear. The purpose of this study was to determine the dehydration time course of 38% water content non‐ionic Medalist TM , 58% ionic Acuvue TM and 74% non‐ionic Permaflex TM lenses, and the relationship between dehydration and in vivo diameter, movement and symptoms of dryness. Nineteen subjects randomly wore three pairs of lenses, each for 7 h. Lens movement and diameter were measured in vivo and hydration after lens removal at 1, 3 and 7 h. Dryness was rated by the subjects using a visual analogue scale. A separate experiment was conducted to measure hydration changes after 7 continuous hours of lens wear. The water content of all three lens types decreased significantly over 7 h with Acuvue decreasing more than the Permaflex and Medalist lenses in the interrupted and continuous experiments (ANOVA P < 0.05). Dehydration of Acuvue was significantly greater in the 7 h continuous experiment (9.0 ± 2.6% H 2 , ANOVA P = 0.0062) compared to the interrupted experiment. Hydration levels measured for Acuvue lenses on subjects for control purposes at 0, 1, 3 and 7 h showed no difference over time (ANOVA P = 0.0711). Movement of Permaflex lenses decreased 0.60 ± 0.57 mm (ANOVA P = 0.0005) over 7 h and the in vivo diameter of Acuvue lenses decreased by 0.12 ± 0.16 mm (ANOVA P = 0.0569). Dryness ratings increased significantly and equally for all three lenses over 7 h (ANOVA P = 0.9833). No correlation was found between lens dehydration, movement, diameter and dryness with the exception of a weak significant ( r = 0.5, P < 0.05) correlation between dehydration and dryness for Permaflex. The results of the study suggest that dehydration of soft lenses over a 7 h period does not significantly affect the clinical performance (dryness and movement) of the three lens types.