by Brian Zhou
“Open your eyes.”
Growing up in a small Midwestern town, I have heard many prejudiced phrases intentionally or unintentionally directed at me. However, I never expected to feel uncomfortable because of my race in the optometrist’s office.
Autorefractors are devices used to measure the refractive error of light passing through the eye when light passes through the eyeball and is reflected back to the instrument. This measurement is made to determine whether a person is near-sighted (myopic) or far-sighted (hyperopic).
An image is projected into the eye from the device, and the light passes through the cornea, pupil, and lens, and finally bounces off the retina and returns to a sensor in the autorefractor. The autorefractor then processes the reflected light beam, making a prescription for the eye from the distortions it picks up from the reflected light beam.
Originally developed by NASA to measure the vision of their pilots, autorefractors quickly became an alternative to traditional retinoscopy due to their accuracy. Due to their speed of diagnosis, ease of use, and repeatability, autorefractors became widely used.
In terms of usability, autorefractors are not suited for people with monolids. Being Asian, I have monolids with longer eyelashes. This makes it particularly difficult for the light rays to reach my eyes and then bounce back to the sensor for an accurate readout. Often, at the optometrist office, I have gotten so frustrated with myself that I tried to physically hold open each eye with my fingers. As a 7-year-old child, it was hard to keep still in the chair, push my forehead up to the bar as much as possible, and keep my eyes as wide as possible without blinking for each measurement.
For me, these measurements took up to 20 minutes to complete, and when I observed other patients from the waiting room go in and out of the room quickly with their prescriptions printed on the paper, I began to realize it was just me. I started to think that I had a problem with my eyes. Maybe they were abnormally small? It took me years to realize that monolids were natural, and honestly, the first time I even realized that other people had issues with autorefractors too was a college medical device design course, when I shared my experiences.
Autorefractors were designed based on Caucasian eyes, and this bias is factored into the measurements. Retinal vertex curvatures were shown to be different for Asians than Caucasians, which may be a reason why there is a higher prevalence of myopia in Asian countries compared to Western countries. Since the autorefractor test was designed for
Caucasian lenses, the refractive error it measures may not account for different eye shapes, which may explain errors in diagnosis.
Technicians have gotten frustrated with me because my eye shape was not cooperating with their machine, and they gave up and just used whatever result they could get. Experiences like these may contribute to a potentially high misdiagnosis rate of myopia in Asians. Ultimately, due to fundamental biases in its design, the autorefractor is not a good eye prescription test for many Asians. While genetics may also be a reason why Asians have higher rates of myopia, further research into autorefractors and how they measure the refractive error for different eyes is needed. We must question and wonder whether these machines can truly see through an unbiased lens.
More to Read:
1. Gurnani, B., & Kaur, K. (2022). Autorefractors. In StatPearls. StatPearls Publishing.
2. Kilfoil, D. (2015, October 6). What is an autorefractor? Coburn Technologies, Inc; Coburn Technologies.
3. Li, T., Zhou, X., Chen, X., Qi, H., & Gao, Q. (2019). Refractive Error in Chinese Preschool Children: The Shanghai Study. Eye & Contact Lens, 45(3), 182–187.
4. Padhy, D., Bharadwaj, S. R., Nayak, S., Rath, S., & Das, T. (2021). Does the Accuracy and Repeatability of Refractive Error Estimates Depend on the Measurement Principle of Autorefractors? Translational Vision Science & Technology, 10(1), 2.
5. Rong, S. S., Chen, L. J., & Pang, C. P. (2016). Myopia Genetics-The Asia-Pacific Perspective. Asia-Pacific Journal of Ophthalmology (Philadelphia, Pa.), 5(4), 236–244.
6. Szczotka-Flynn, L. B., & Efron, N. (2018). Aftercare. In Contact Lens Practice (pp.364–384.e2). Elsevier.
7. Verkicharla, P. K., Atchison, D. A., Suheimat, M., Schmid, K. L., Mathur, A., Mallen, E. A., Wei, X., & Brennan, N. A. (2014). Is Retinal Shape different in Asians and Caucasians? Estimation from Peripheral Refraction and Peripheral Eye Length Methods. Investigative Ophthalmology & Visual Science, 55(13), 3592–3592.