Recent developments in automatic refraction

A detailed description of the Ophthalmetron is given. This is an automatic refractometer using the principle of infra-red retinoscopy and having a sensitivity range from -18.00 D to +17.00 D with a resolution of 0.25 D. By means of a rapid light scan across the patient's pupil the instrument determines the direction of motion of the retinal reflex in all meridians and a movement null-point is determined electronically. Results are then plotted automatically on a chart drum. Some early validation studies have shown the Ophthalmetron to provide a refraction end-point in good agreement with conventional retinoscopic findings. The paper concludes with an appendix in which the features of three commercially available automatic refractometers are compared.