title: Effects of contact lenses on corneal thickness and corneal curvature during usage.
abstract: OBJECTIVE
  To investigate the effects of contact lenses on corneal thickness and curvature.
  
  
  METHODS
  Eighty-four eyes of 45 patients (26 female and 19 male) wearing contact lens for the first time with a median age of 23.04 +/- 7.2 years (range, 15-44 years) were included in the study. After all patients had undergone a routine ophthalmic examination, corneal thickness measurements in nine regions and corneal topography were performed before wearing contact lenses and after 1 month, 6 months, and 12 months. Patients were classified into three groups according to duration of wear. Groups were also classified into two subgroups according to the lens type (rigid gas-permeable and soft contact lenses).
  
  
  RESULTS
  Mean visual acuity was 0.82 +/- 0.26 with spectacles and 0.92 +/- 0.26 with contact lenses. At the end of 1 month, statistically significant corneal thinning and thickening were noted in different regions in group 1. In group 2, statistically significant corneal thinning was noted in all regions with soft contact lenses and rigid gas-permeable contact lenses except in the inferior temporal region at the end of 6 months. In group 3, corneal thinning was noted in all regions with soft contact lenses and rigid gas-permeable contact lenses. This corneal thinning was statistically significant in all regions with the soft contact lenses except in the inferior nasal region and with rigid gas-permeable contact lenses except in the central region. When corneal curvatures were examined, corneal flattening was seen in groups 1 and 2. In group 3, corneal steepening was noted.
  
  
  CONCLUSIONS
  Soft contact lenses and rigid gas-permeable contact lenses cause corneal thickening and corneal flattening in the first months, but they cause corneal thinning and corneal steepening with time. These alterations can be evaluated as evidence that contact lenses negatively influence corneal physiology.
authors.affiliation: Department of Ophthalmology, Istanbul Faculty of Medicine, Istanbul University, Istanbul, Turkey. byeniad@yahoo.com
authors.forename: Bariş
authors.initials: B
authors.lastname: Yeniad
authors.forename: Bülent
authors.initials: B
authors.lastname: Yiğit
authors.forename: Halim
authors.initials: H
authors.lastname: Işsever
authors.forename: Lale
authors.initials: L
authors.lastname: Közer Bilgin
mesh_terms: D000293:Adolescent; D000328:Adult; D003261:Contact Lenses / Q000009:adverse effects*; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D004108:Dilatation, Pathologic / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D017755:Prosthesis Fitting