title: Comparison of corneal thickness of long-term contact lens wearers for different types of contact lenses.
abstract: OBJECTIVE
  To compare the central corneal thickness (CCT) values of long-term wearers of different types of contact lenses with those of each other and a normal control group.
  
  
  METHODS
  Twenty-three healthy eyes with no history of contact lens wear were used for the control group. Forty-eight eyes were evaluated in four different groups according to the type of contact lens worn; each group comprised 12 eyes. Group 1 (SofLens 38) and group 2 (Contact Day 30) had worn daily-wear frequent-replacement soft contact lenses with a 38% and 55% water content, respectively, and they had worn their lenses for an average of 4.28 +/- 1.70 years and 3.71 +/- 1.11 years, respectively. Group 3 (Wöhlk A90) and group 4 (Conflex-air) had worn daily-wear rigid gas-permeable (RGP) contact lenses with a Dk/t value of 68 and 22, respectively, and they had worn their lenses for an average of 3.00 +/- 0.63 years and 3.25 +/- 1.17 years, respectively. CCT values in micrometers were measured by optical coherence tomography.
  
  
  RESULTS
  When comparing the CCT between the control group and the contact lens groups, the CCT was significantly thinner in the group wearing Conflex-air RGP contact lenses with a low Dk/t value (P = 0.010). In comparing the CCT among the four contact lens groups, the CCT was significantly thinner in the group wearing SofLens 38 contact lenses with a water content of 38% than in the group wearing Contact Day 30 contact lenses with a water content of 55% (P = 0.004). There was also significant thinning in the group wearing Conflex-air RGP contact lenses versus the group wearing Contact Day 30 soft contact lenses (P = 0.0005).
  
  
  CONCLUSIONS
  CCT was significantly thinner in patients wearing long-term low-Dk/t RGP contact lenses compared to no contact lens wear and soft contact lenses with a water content of 55%. CCT was also decreased significantly in long-term soft contact lens wear with a water content of 38% compared to 55%.
authors.affiliation: From the Istanbul University, Cerrahpasa Faculty of Medicine, Department of Ophthalmology, Istanbul, Turkey. giskeleli@superonline.com
authors.forename: Guzin
authors.initials: G
authors.lastname: Iskeleli
authors.forename: Umut
authors.initials: U
authors.lastname: Onur
authors.forename: Can
authors.initials: C
authors.lastname: Ustundag
authors.forename: Sehirbay
authors.initials: S
authors.lastname: Ozkan
mesh_terms: D000328:Adult; D001837:Body Weights and Measures; D003262:Contact Lenses, Extended-Wear; D003315:Cornea / Q000473:pathology*; D005500:Follow-Up Studies; D006801:Humans; D007368:Interferometry; D008027:Light; D012016:Reference Values; D013997:Time Factors; D041623:Tomography, Optical Coherence