title: Effect of one overnight wear of orthokeratology lenses on tear composition.
abstract: OBJECTIVE
  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 (sIgA), 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, sIgA, 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, sIgA, 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.
authors.affiliation: Department of Optometry and Radiography and School of Nursing, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China. orrsch3@inet.polyu.edu.hk
authors.forename: Camus Kar Man
authors.initials: CK
authors.lastname: Choy
authors.forename: Pauline
authors.initials: P
authors.lastname: Cho
authors.forename: Iris Frances Forster
authors.initials: IF
authors.lastname: Benzie
authors.forename: Vincent
authors.initials: V
authors.lastname: Ng
mesh_terms: D000328:Adult; D000418:Albumins / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003262:Contact Lenses, Extended-Wear / Q000706:statistics & numerical data*; D003315:Cornea / Q000502:physiology*; D018592:Cross-Over Studies; D005136:Eye Proteins / Q000378:metabolism*; D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007781:Lactoferrin / Q000378:metabolism; D054835:Lipocalin 1; D008297:Male; D009113:Muramidase / Q000378:metabolism; D013666:Tears / Q000378:metabolism*
chemical_list: D000418:Albumins; D002352:Carrier Proteins; D005136:Eye Proteins; D007071:Immunoglobulin A, Secretory; C518443:LCN1 protein, human; D054835:Lipocalin 1; C042434:tear proteins; D007770:L-Lactate Dehydrogenase; D009113:Muramidase; D007781:Lactoferrin; D001205:Ascorbic Acid