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.

Keywords: Videokeratography, Corneal topography, Contact lens(es), Irregular cornea, Rigid gas permeable, Fitting procedure, Keratoconus