Empirical Versus Trial Set Fitting Systems for Accelerated Orthokeratology Carole Maldonado-Codina, PH.D., M.C.OPTOM., F.A.A.O., Suzanne Efron, B.SC.(HONS.), M.C.OPTOM., Philip Morgan, PH.D., M.C.OPTOM., F.A.A.O., Tony Hough, B.A., M.B.A., and Nathan Efron, D.SC., PH.D., M.C.OPTOM. Purpose. To compare the short-term clinical performance of two reverse-geometry rigid contact lens systems for accelerated ortho- keratology with different fitting approaches and designs: an experi- mental lens that was fitted empirically (No. 7 Contact Lens Labora- tory, Ltd.) and a more established lens using a trial set system, the BE lens (NKL). Methods. 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. Results. 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 stain- ing, and subjective reaction. Discussion. Both lens types investi- gated 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. Key Words: Corneal topography—Empirical—Orthokeratol- ogy—Reverse-geometry—Rigid gas permeable contact lenses. Orthokeratology has been defined as the temporary reduction, modification, or elimination of myopia by the programmed appli- cation of rigid contact lenses. 1 The developmental history of orthokeratology from the original Orthofocus technique of Jessen 2 to present-day accelerated orthokeratology has been well docu- mented elsewhere. 3–5 The renewed interest in orthokeratology in recent years has been facilitated mainly by advances in lens materials, manufacturing technology, and corneal topography measurement systems. The improved oxygen transmissibility of current-generation reverse-geometry 6,7 lenses, in which the first back peripheral radius is steeper than the back central optic radius, allows safe overnight wear and gives patients freedom from lenses during waking hours. Improvements in manufacturing technology have allowed more complex lens designs to be fabricated and have ensured credible and consistent lens parameters. Current video- keratoscopes allow enhanced measurement of corneal shape versus standard keratometry, thereby aiding more accurate lens fitting and improved patient treatment after the fit. Currently, more than 20 different reverse-geometry lenses have been purposefully designed for accelerated orthokeratology. These lenses incorporate different fitting methods, including fitting the lenses empirically and using trial lenses and accompanying spe- cialized computer software. This situation makes it potentially difficult for a practitioner new to orthokeratology to choose which design will be most successful or suitable. A practitioner may prefer the design that appears the simplest and easiest to use, but it is not obvious if this is achieved by empirical fitting, using diagnostic lenses, or following the guidelines from computer programs. It may be preferable to select a fitting system that gives a higher first-fit success rate, even if this system is more compli- cated. Additionally, the amount of myopic correction obtainable and how quickly it is achieved are important factors to consider when choosing a lens. These questions were addressed in a recent investigation that showed similar efficacy with each of four lens designs incorporating different fitting philosophies. 8 Although results such as these are positive for orthokeratology in general, they make it difficult for a manufacturer wishing to compete in the orthokeratology market to design a fitting system. The aim of this investigation was to compare the clinical performance of two reverse-geometry lens systems consisting of mutually exclusive integrated fitting approaches and lens designs, whereby one system was based on an empirically fitted system and the other system used a system with a trial set. Additionally, it was This work was sponsored by No. 7 Contact Lens Laboratory, Ltd. From Eurolens Research (C.M-C., S.E., P.M., N.E.), Department of Optometry, University of Manchester, Manchester, United Kingdom; and CLS Software, Ltd. (T.H.), St. Neots, Cambridgeshire, United Kingdom. Address correspondence and reprint requests to Dr. C. Maldonado-Codina, Department of Optometry, University of Manchester, PO Box 88, Manchester, M60 1QD, United Kingdom; e-mail: c.m-codina@manchester.ac.uk Accepted August 9, 2004. DOI: 10.1097/01.ICL.0000146170.27288.A3 Eye & Contact Lens 31(4): 137–147, 2005 © 2005 Contact Lens Association of Ophthalmologists, Inc. 137