Effects of contact lenses on corneal endothelium - A morphological and functional study

Purpose: To study the corneal endothelial morphological changes and endothe lial barrier function in contact lens wearers. Methods: Specular microscopy and anterior segment fluorophotometry were performed on 116 controls (grou p 1) and 76 daily wear soft contact lens wearers. Group 2 patients (n = 34) had been wearing contact lenses for less than 5 years and group 3 (n = 42) for more than 5 years. The relationship of corneal thickness, endothelial cell density, hexagonal cell percentage, coefficient of variation in cell a rea, corneal autofluorescence and corneal endothelial permeability to the c ontact lens wear duration was studied. Results: The average corneal thickne ss of contact lens wearers did not differ significantly from controls (0.53 3 +/- 0.031, 0.538 +/- 0.044, 0.532 +/- 0.031 mm for groups 1, 2 and 3, res pectively; p = 0.89). However, there was a significant tendency toward corn eal thinning with a longer history of contact lens wear (r = -0.31, p = 0.0 02 in groups 2 and 3). The percentage of hexagonal cells decreased with bot h increasing hours of contact lens wear per day (r = -0.36, p < 0.001) and the duration of contact lens wear in years (r = -0.33, p < 0.001), but ther e was no significant change in endothelial cell density in contact lens wea rers. The coefficient of variation in cell size correlated more closely wit h increased hours of contact lens wear per day (r = 0.35, p = 0.002) than w ith the duration of contact lens wear in years (r = 0.12; p = 0.31). In the functional study, corneal autofluorescence increased in contact lens weare rs (5.13 +/- 0.71 ng/ml in group 1, 6.45 +/- 2.03 ng/ml in group 2 and 7.21 +/- 1.51 ng/ml in group 3, respectively, p < 0.001) and the mean endotheli al permeability decreased in contact lens wearers (3.89 +/- 0.95 x 10(-4)/c m in group 1, 2.71 +/- 0.73 x 10(-4)/cm in group 2 and 2.95 +/- 0.91 x 10(- 4)/cm in group 3, respectively, p = 0.003). Conclusions: Daily wear soft co ntact lenses caused morphological changes in the corneal endothelium. With an increasing span of contact lens wear, there was a significantly increase d variation in cell size, a decreased hexagonal cell percent age, an eviden t intercellular dark area and rosette formation. The corneal autofluorescen ce increased and the overall endothelial permeability decreased as a conseq uence of contact lens wear. Contact lens wear also caused corneal thinning, and the cornea became thinner with increasing duration of contact lens wea r. Copyright (C) 2001 S.Kaiger AG, Basel.