The application of in vivo confocal microscopy and tear LDH measurement in assessing corneal response to contact lens and contact lens solutions

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Abstract
To evaluate differences in corneal response to daily wear (DW) of soft contact lens (CL) wear with different CL solutions and to assess the ability of in vivo confocal microscopy (CM) and tear lactate dehydrogenase (LDH) measurement to detect such differences in NZW rabbits. Daily treatment of lenses consisted of a rub and rinse cleaning, then overnight soak in one of five solutions: Sauflon All in One (ALL), Compound A (CoA), OPTI-FREE((R) )Rinsing, Disinfecting, and Storage Solution (OPT), ReNu((R)) Multipurpose Solution (REN), and UNISOL( (R)) Saline Solution (UNI). Rabbits (4/test group) wore 71% H( 2)O/type4 soft lenses approximately 7 hours daily. On days 0, 1, 3 and 7, slit lamp examination, tear LDH measurement, and in vivo CM were performed after removal of lenses. Using in vivo CM, epithelial thickness, epithelial cell area, and stromal thickness were measured, both centrally and peripherally. Epithelial thickness in ALL, CoA, and UNI-treated eyes showed a significant decrease of 15.6%, 13. 3%, and 10.6% (p < 0.05 in all groups), centrally, while CoA, OPT, and UNI showed a significant decrease of 9.3%, 7.1%, and 4.4% (p < 0. 05 in all groups), peripherally. ALL showed a significant 9.5% (p < 0.05) decrease of central cell area, while CoA showed a significant 21.5% (p < 0.01) decrease peripherally. UNI demonstrated a significant 3.2% (p < 0.05) decrease in central stromal thickness. ALL, CoA, and UNI showed a significant increase in LDH level of 152. 1%, 192.1%, and 308.2% (p < 0.05 in all groups) at day 3, respectively, but values declined at day 7. Significant changes in basal epithelial morphology were also observed with CoA on day 7 on in vivo CM. Overall, lens care solutions in combination with CL wear may interact to cause increased epithelial desquamation leading to decreased surface cell area and epithelial thickness. The clinical significance of these changes will require further investigation. In vivo CM combined with tear LDH assay is a quantitative, objective, non-invasive method of assessing CL wear and CL disinfecting solution effects on the cornea, and is able to detect differences in corneal response to different CL solutions.