title: Effects of rigid contact lenses on optical coherence tomographic parameters in eyes with keratoconus.
abstract: BACKGROUND
  The aim was to evaluate the effect of irregular astigmatism on the retinal nerve fibre layer (RNFL), macular thickness and ganglion cell analysis obtained by spectral domain optical coherence tomography (OCT) in eyes with keratoconus.
  
  
  METHODS
  Fifty-two eyes of 31 patients (20 females) with keratoconus that required correction of irregular astigmatism with rigid gas-permeable (RGP) contact lenses were included to this study. The average, superior, nasal, inferior, temporal and 12 clock hour sector's RNFL, ganglion cell and macular thickness analyses before and 30 minutes after RGP contact lens (Rose K2 -Menicon Z material, David Thomas Contact Lenses Ltd, Northampton, United Kingdom) wear were performed to all patients with Cirrus HD spectral domain optical coherence tomography.
  
  
  RESULTS
  The average thickness of the retinal nerve fibre layer, the thickness at the nasal quadrants and 1-2-3-4 o'clock hour sectors and mean signal strength were increased significantly by RGP contact lens wearing independent of the stage of keratoconus. Central sub-field thickness increased after correction with RGP contact lens (p = 0.037). After wearing RGP contact lenses, changes on ganglion cell analysis were not significant (all p values ≥ 0.111).
  
  
  CONCLUSIONS
  OCT is a widely used device for retinal nerve fibre layer and macular thickness evaluation in patients with glaucoma and macular diseases. The study demonstrates that OCT parameters such as retinal nerve fibre layer, central sub-field thickness and mean signal strength are affected by irregular astigmatism. Correction of irregular astigmatism with RGP contact lenses should be recommended before analysing keratoconic eyes to obtain optimum results on OCT measurements.
authors.affiliation: Izmir Bozyaka Training and Research Hospital, Department of Ophthalmology, Izmir, Turkey. druzunel78@yahoo.com.
authors.forename: Umut Duygu
authors.initials: UD
authors.lastname: Uzunel
authors.affiliation: Izmir Bozyaka Training and Research Hospital, Department of Ophthalmology, Izmir, Turkey.
authors.forename: Tuncay
authors.initials: T
authors.lastname: Kusbeci
authors.affiliation: Giresun University Medical Faculty, Department of Ophthalmology, Giresun, Turkey.
authors.forename: Berna
authors.initials: B
authors.lastname: Yuce
authors.affiliation: Izmir Bozyaka Training and Research Hospital, Department of Ophthalmology, Izmir, Turkey.
authors.forename: Bora
authors.initials: B
authors.lastname: Yüksel
mesh_terms: D000293:Adolescent; D000328:Adult; D003261:Contact Lenses; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000473:pathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology; D012030:Refractive Errors; D055351:Retinal Neurons / Q000473:pathology; D041623:Tomography, Optical Coherence; D014792:Visual Acuity
keywords: irregular astigmatism; keratoconus; optic coherence tomography; retinal nerve fibre layer