Nieto Bona, AmeliaNombela Palomo, MaríaFelipe Márquez, GemaTeus Guezala, Miguel Ángel2023-06-172023-06-172016-11-161542-232110.1097/ICL.0000000000000347https://hdl.handle.net/20.500.14352/17883Accepted September 25, 2016. Post Author Corrections: November 16, 2016.Purpose: 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. Conclusion: 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.engjournal articlehttp://dx.doi.org/10.1097/ICL.0000000000000347https://www.ncbi.nlm.nih.gov/pubmed/27861262open access617.713-089617.764Tear film osmolarityOvernight orthokeratologyContact lensesTearLab osmolarity systemOftalmologíaLentes de contactoOptometría3201.09 Oftalmología3311.11 Instrumentos ópticos2209.15 Optometría