title: Estimation of the hybrid lens parameters through rigid gas permeable lens fitting.
abstract: OBJECTIVE
  To estimate the fitting parameters of the hybrid contact lens in patients with corneal ectasia using the rigid gas permeable (RGP) lens.
  
  
  METHODS
  Thirty-four eyes with corneal ectasia were evaluated in this study. The patients were examined once with the RGP lens and once with the hybrid contact lens. The relationship between the base curvature of the RGP and the vault of the hybrid lens and the correlation between their powers were analyzed.
  
  
  RESULTS
  We found a linear relationship between the base curvature of the RGP lens and the vault of the hybrid lens (P < 0.001) (R(2) = 0.45). Moreover, we found a correlation between the power of the RGP and hybrid lens (P < 0.001) (R(2) = 0.4). However, a 0.5 mm decrease in the base curvature radius of the RGP lens increased the vault of the hybrid lens by 72 μ.
  
  
  CONCLUSIONS
  The results of this study could be used for better and faster selection of the first hybrid contact lens.
authors: Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran.
authors: Mohammadali
authors: M
authors: Hasani
authors: Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran; Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors: Hassan
authors: H
authors: Hashemi
authors: Department of Optometry, Iran University of Medical Sciences, Tehran, Iran.
authors: Ebrahim
authors: E
authors: Jafarzadehpur
authors: Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
authors: Abbas Ali
authors: AA
authors: Yekta
authors: Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
authors: Nooshin
authors: N
authors: Dadbin
authors: Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Mehdi
authors: M
authors: Khabazkhoob
keywords: Corneal ectasia; Hybrid lens; Keratoconus; Rigid gas permeable lens