Empirical versus trial set fitting systems for accelerated orthokeratology

To compare the short-term clinical performance of two reverse-geometry rigid contact lens systems for accelerated orthokeratology with different fitting approaches and designs: an experimental lens that was fitted empirically (No. 7 Contact Lens Laboratory, Ltd.) and a more established lens using a trial set system, the BE lens (NKL).

Twenty-four subjects were enrolled in a clinical study in which the two reverse-geometry lenses were worn contralaterally for seven nights. The No. 7 lens was manufactured based on subject keratometric readings, refraction, and horizontal visible iris diameter. The BE lens was fitted in accordance with fitting guidelines provided by the manufacturer and included the use of proprietary computer software in addition to an overnight trial before lens ordering. Data were collected at baseline, day 1, and day 7 (morning and afternoon). Unaided visual acuity, best-corrected visual acuity, subjective refraction, corneal topography, biomicroscopy (corneal staining), and subjective reaction were recorded at each visit.

Nine subjects (18 eyes) completed the study. All eyes fitted with the No. 7 lens and 67% of the eyes fitted with the BE lens were within +/-1.00 diopter of the attempted correction after seven nights of lens wear. There was more myopic reduction (F = 16.2, P=0.0002), better unaided high-contrast visual acuity (F = 8.7, P=0.005) and low-contrast visual acuity (F = 9.5, P=0.003), and more change in corneal numerical eccentricity (F = 8.6, P=0.005) with the BE lens than with the No. 7 lens. There were no significant differences between the lenses for best-corrected visual acuity, change in apical radius, corneal staining, and subjective reaction.

Both lens types investigated in this study were effective in temporarily reducing myopia and in providing good unaided visual acuity during the day (without lenses) in subjects with low levels of myopia. Subjective reaction showed that the lenses were perceived as being equally effective, but clinical data showed that the BE lens effected more myopic reduction and better unaided visual acuity than did the No. 7 lens during the 7-day period investigated.