Use of the HARK autorefractor in children

PURPOSE: We investigated the reliability, accuracy, and repeatability of an autorefractor with the capability of over-refracting and measuring visual acuity for use in children in a prospective study. METHODS: Before and after cycloplegia, 68 children (mean ± SD age, 10 ± 3 years, range 5-16 years) underwent autorefraction twice with the HARK 599 Autorefractor (Humphrey Instruments Inc., San Leandro, CA), subjective over-refraction through the HARK autorefractor, and subjective refraction using a phoro-optometer. After cycloplegia, retinoscopy was performed. Results are reported for one eye (left) of each child. RESULTS: For 68 eyes of 68 children, before and after cycloplegia, correlation coefficients (R) for autorefraction reproducibility exceeded 0.95 for all comparisons of sphere and cylinder. R for spherical values for autorefraction vs. over-refraction was 0.93 and vs. subjective refraction 0.83 before cycloplegia and 0.94 and 0.97 after cycloplegia. Comparing values before and after cycloplegia, autorefraction, over-refraction, and subjective refraction, the data correlated > 0.81 for sphere and 0.75 to 0.87 for cylinder. Cycloplegic retinoscopy compared with autorefraction, over-refraction, and subjective refraction had R > 0.86 for sphere and cylinder for all comparisons except one. Cycloplegia increased the proportion of spherical equivalent values within 0.625 D of the subjective refraction from 41 of 68 eyes (61%) for auto- and over-refraction to 64 (94%) and 51 (75%) of the 68 eyes, respectively. A visual acuity of 20/30 or better was produced in 50 of 68 (73%) eyes with automated refraction before and after cycloplegia and in 62 (92%) with subjective refraction before cycloplegia and subjective refraction and retinoscopy after cycloplegia. Subjective over-refraction did not significantly improve the visual acuity. CONCLUSIONS: In children, HARK autorefraction improved in accuracy, when compared to subjective refraction, and the level of visual acuity improved after cycloplegia. Over-refraction through the instrument did not improve the results before or after cycloplegia.