title: Tear Film Osmolarity in Response to Long-Term Orthokeratology Treatment.
abstract: OBJECTIVE
  To compare tear film osmolarity (TFO) measurements in non-contact lens (CL) wearers and wearers of hydrogel or overnight orthokeratology (OK) CLs, and to assess possible effects of long-term OK on TFO.
  
  
  METHODS
  Overall, 108 subjects with moderate myopia participated in 2 experiments, and TFO was measured using the TearLab osmolarity system. In experiment 1, TFO measurements were made in 77 right eyes of 23 non-CL wearers, 26 hydrogel wearers, and 28 OK wearers. Subjects in the last 2 groups had worn their CL for at least 3 years. In experiment 2, 31 individuals (habitual soft CL wearers) were enrolled for prospective long-term follow-up of OK treatment. These subjects were fitted with Paragon-CRT (n=16) or Seefree (n=15) lenses, and TFO readings were taken at baseline and after 1 month and 1 year of lens wear and after 1 month of OK treatment interruption.
  
  
  RESULTS
  Values of TFO were within the normal limits in all 3 subject groups, although significantly lower osmolarities (P<0.01) were observed in non-CL wearers (281.7±5.9 mOsm/L) compared with hydrogel (291±16.5 mOsm/L) or OK lens wearers (301.7±10.8 mOsm/L). In experiment 2, TFO differed significantly at baseline between the Paragon-CRT and Seefree groups (P<0.05), and a significant decrease in TFO compared with baseline (P<0.01) was observed in the Paragon-CRT group after 1 month of cessation of lens wear.
  
  
  CONCLUSIONS
  Higher TFO values were observed in lens wearers (hydrogel or OK) than non-CL wearers. After interruption of OK treatment, TFO returned to similar values to those found in non-CL wearers.
authors.affiliation: Department of Optics II (Optometry and Vision), Faculty of Optics and Optometry (A.N.-B.), Contactology and Optometry Research Group (GICO), Complutense University of Madrid, Madrid, Spain; Department of Optics II (Optometry and Vision), Faculty of Optics and Optometry (M.N.-P., G.F.-M.), Complutense University of Madrid, Madrid, Spain; and Deparment of Surgery, University of Alcalá (M.A.T.), Madrid, Spain.
authors.forename: Amelia
authors.initials: A
authors.lastname: Nieto-Bona
authors.forename: María
authors.initials: M
authors.lastname: Nombela-Palomo
authors.forename: Gema
authors.initials: G
authors.lastname: Felipe-Márquez
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Teus
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000628:therapy*; D054158:Orthokeratologic Procedures / Q000379:methods; D009994:Osmolar Concentration; D011446:Prospective Studies; D013666:Tears / Q000737:chemistry*; D055815:Young Adult