[Accuracy of measurements of video-refractometry in higher ametropia]

Measurement of refraction of non-cooperative patients is a real challenge for the ophthalmologist. Retinoscopy produces exact results in experienced hands, but requires practice and time. The Videorefractor VRB 200 (manufactured by Tomey, Erlangen) was especially designed for refracting children. The aim of this study is to prove the accuracy of this tool in measuring refraction.

259 patients (age 10 month to 77 years) were measured with the VRB 200. Each patient was examined by retinoscopy in cycloplegia and refracted with the Topcon autorefraktor RM-A 6000. Ametropia was evoked at 5 emmetropic volunteers by lenses of different power, placed in a trial frame. These measurements were performed with and without use of cycloplegic drugs.

The VRB 200 showed an average error of spherical equivalent at ametropia of the range -4 to +4 Diopters (dpt) < 2 dpt. At higher ametropia the error grew increasingly. Repeated measurements of one patient showed high variation of the results. Astigmatism was measured worse by growing magnitude, especially at diagonal axis (45 degrees and 135 degrees). Anisometropia > 2 dpt has been discovered in only 72%. It was possible to examine many infants and handicapped patients, which was impossible by using the RM-A 6000. An examination by retinoscopy was possible in all cases, but needed a lot of time and patience.

The concept of good handling suffers especially by the increasing inaccuracy at ametropia beyond +/- 4 dpt. At this state of development the VRB 200 is no alternative in practical use to the conventional retinoscopy.