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Y. Zhang, M. M. Garbiel, M. F. Mowrey-McKee, L. D. Hazlett; Rat Contact Lens Model: Effects of High vs. Low Dk Lens Wear. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5371.
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This study tested if high vs. low Dk contact lenses worn on an extended wear basis for 2-4 weeks caused disparate effects on either the number or location of Langerhans cells (LC) in the conjunctiva.
Female, Lewis rats (2-3 or 10 months of age) wore a specially-designed lens of either high Dk (lotrafilcon A or B, n=6 rats or low Dk (nelfilcon A, n=8 rats) for 2 (2-3 months of age) or 4 (10 months of age) weeks. Eyes were hemisected and the tissue placed in EDTA to allow epithelial removal. Epithelial sheets were processed for ADPase activity to visualize LC. Sheets were flattened, mounted onto slides, photographed at 25X and printed to 80X and LC number quantitated per field (n=10 fields/group) (Hazlett et al., 1986). Data were statistically analyzed using an unpaired Student’s t test. Contralateral non-lens wearing eyes (n=12 rats) were similarly tested.
ADPase positive LC were significantly increased in number (47 vs. 29/field) in the conjunctiva of low when compared with high Dk lens wearing rats (2-3 months of age) (p<0.0001). LC also were significantly higher in low Dk lens wearing rats vs. non-lens wearing rats (p<0.0001). In contrast, the number (27 vs. 29/field) of LC in the conjunctiva of non-lens wearing rats was not significantly different from the high Dk lens wearing animals (p=0.16). Migration of LC into the cornea was rarely seen in either high or low Dk lens wearing 2-3 month old rats and was never seen in non-lens wearing animals. In 10 month old rats, similar results were seen for conjunctival LC counts. However, in these older animals, the high Dk lens design fit extremely tightly causing corneal indentation, resulting in migration of LC into the peripheral and paracentral cornea. The low Dk lens design fit well, but still caused migration of LC into the cornea in older rats.
Low Dk lenses result in upregulation of the number of LC, powerful antigen presenting cells, in the conjunctiva when compared with high Dk lens or no lens wear. The importance of a well-fitting animal lens design was demonstrated. If the fit is very tight, LC may migrate into the cornea.
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