Effect of one overnight wear of orthokeratology lenses on tear composition

Purpose. To evaluate the effect of one night of orthokeratology lens wear on ocular surface health based on the changes in tear components, including ascorbate, urate, lactate dehydrogenase (LD), lactoferrin, lipocalin, lysozyme, secretory immunoglobulin A (slgA), and serum albumin. Methods. Changes in tear components in eight healthy young men before and after 7-h overnight ortho-k lens wear were studied. Subjects attended on two separate occasions during a 1-week period, on one occasion wearing lens overnight and on the other wearing no lens. Tears (yawn-induced) were collected by capillary tube before lens fitting and on awakening. Tear ascorbate and urate were measured by high-performance liquid chromatography; LD was measured by a commercial kit method; tear proteins were measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results. Ascorbate, sIgA, albumin, and LD increased significantly overnight with and without overnight lens wear (p < 0.05); however, no significant increases were found in tear urate, lactoferrin, lipocalin, or lysozyme (p > 0.05). Without lens wear, tear ascorbate, slgA, albumin, and LD increased by 21%, 34%, 9-fold, and 13-fold, respectively (p < 0.05). With ortho-k lens wear, significant flattening of the apical curvature was observed as expected, and the increases in tear ascorbate, slgA, albumin, and LD (increases were 56%, 76%, 13-fold, and 14-fold, respectively) were significantly (p < 0.05) greater than with no lens. There was significant correlation seen between changes in albumin and LD with (r = 0.762; p = 0.037) and without (r = 0.738; p = 0.046) ortho-k lens wear. Conclusions. The result of tear ascorbate suggests that corneal cell disturbance is small after one night of ortho-k lens wear. The marked increases in albumin and LD suggest that the ocular surface is under additional hypoxic stress during overnight ortho-k lens wear.