Dark focus values measured by retinoscopy: a clinical chart review.

The present study investigated the utility of dark retinoscopy as a technique to measure the dark focus of accommodation during routine clinical examinations. Using data from clinical examinations collected during a period of 6 months, a clinical chart review quantified dark focus and mean spherical equivalent refractive error for 480 patients ranging in age from 6 to 55 years. Results showed significant variations in mean dark focus values over the age groups. All groups showed wide interpatient differences, with mean dark focus values that were significantly nearer than the farpoint. Individual dark focus values ranged from 2.25 to -1.00 D (hyperopic), with an overall mean of 0.53 D. Potential clinical applications of dark focus-based correction are discussed.