The application of a computerised videokeratography (CVK) based contact lens fitting software programme on irregularly shaped corneal surfaces

Abstract

Purpose: To explore the success of the application of a computerised videokeratography (CVK) software system for the fitting of rigid gas permeable (RGP) contact lenses (CLs) on irregular corneal surfaces and compare it to the standard diagnostic fitting procedure. Methods: This was a comparative prospective study, over a 1-year period (2004–2005). It included 41 RGP CL wearers (68 eyes) with irregular corneal surfaces. Of these, 51 (75%) had keratoconus, 7 (10%) corneal scarring (infectious or traumatic), 6 (6.82%) corneal transplants, 2 (2.9%) astigmatism, and 2 (2.9%) aphakia. Each eye was being re-fitted with a new RGP CL based on a topographical measurement in conjunction with a CL fitting software programme. The performance of the CLs was evaluated regarding visual outcome, fitting characteristics, and efficiency of the fitting procedure. Results: Of the 68 eyes, 53 (77.94%) chose the CL fitted using the CVK software system, 9 (13.24%) chose the CL fitted using the standard procedure, and 6 (8.82%) showed no preference for either CL. There was a statistically significant improvement regarding visual outcome [contrast sensitivity at the spatial frequencies of 0.66 ( p = 0.029), 3.40 ( p = 0.008), and 17 ( p = 0.032), subjective vision ( p = 0.009)], fitting characteristics [grading scale ( p = 0.00), lens comfort ( p = 0.00) and daily wearing time ( p = 0.002)], and efficiency [number of trial lenses required ( p = 0.00)] with the CL fitted using the CVK software system. Correlating factors for the likely preference for the CL fitted using the CVK software system were subjective vision ( p = 0.004), lens comfort ( p = 0.009), and convenience of the fitting procedure ( p = 0.023). Conclusion: The application of a CVK software system for the fitting procedure of RGP CLs on irregular corneal surfaces was a safe procedure and shown to be more successful and efficient than the standard diagnostic fitting method.