Related Experiment Video
Updated: Aug 11, 2026
Using an Automated Hirschberg Test App to Evaluate Ocular Alignment
Published on: March 24, 2020
Use of the HARK autorefractor in children
S J Isenberg1, M Del Signore, G Madani-Becker
1Department of Ophthalmology, Jules Stein Eye Institute, Harbor/U.C.L.A. Medical Center, U.C.L.A. School of Medicine-Los Angeles and Torrance, California 90509, USA. isenberg@ucla.edu
Insights
This study found that cycloplegic autorefraction in children improves accuracy compared to subjective refraction. Visual acuity also improved after cycloplegia, but over-refraction did not enhance results.
Area of Science:
- Ophthalmology
- Pediatric Optometry
- Refractive Error Assessment
Background:
- Accurate refractive error assessment in children is crucial for timely intervention.
- Autorefractors offer a potential tool for rapid and objective refractive measurements.
- The HARK 599 Autorefractor's utility, including its over-refraction capability, requires validation in pediatric populations.
Purpose of the Study:
- To evaluate the reliability, accuracy, and repeatability of the HARK 599 Autorefractor in children.
- To assess the impact of cycloplegia on autorefractor performance.
- To determine if subjective over-refraction improves refractive outcomes.
Main Methods:
- A prospective study involving 68 children (ages 5-16).
- Autorefraction, subjective over-refraction, and subjective refraction were performed before and after cycloplegia.
- Cycloplegic retinoscopy served as a reference standard.
Main Results:
- Autorefraction demonstrated high reproducibility (R > 0.95) for sphere and cylinder.
- Accuracy of autorefraction improved significantly after cycloplegia (R=0.97 vs. subjective refraction).
- Visual acuity of 20/30 or better was achieved in 94% of eyes after cycloplegic autorefraction, compared to 73% before.
Conclusions:
- HARK autorefraction, particularly after cycloplegia, offers improved accuracy for refractive error assessment in children.
- Cycloplegia enhances the reliability of autorefractor measurements.
- Subjective over-refraction using the autorefractor did not yield additional benefits.
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.
