Portable, low-cost refraction device shows promise for first-level assessments

ClickCheck, a portable and low-cost refractive error measurement device, demonstrates a high level of agreement with the standard-practice subjective refraction (SR) in terms of spherical power, according to a recent study. Nevertheless, improvements are needed to yield better cylindrical power evaluations.

“Being a portable, low-cost, and easy-to-use refraction device, ClickCheck can be used for first-level assessment of refractive errors, thereby enhancing the efficiency of refractive services, especially in low- and-middle-income countries,” the researchers said.

The study included 1,079 participants (mean age 39.02 years, 56 percent women) who underwent SR and auto-refraction (AR), followed by refractive measurement using the ClickCheck device (CR). All assessments were conducted by a trained professional or researcher assistant. The device then generated eyeglass prescriptions and the resulting visual acuity parameters were compared against SR to assess ClickCheck’s accuracy.

Spherical power measurements in the right eye using all three refraction methods were available for 958 participants. Average spherical correction was –0.66 D for both SR and AR, while CR yielded a corrective value of –0.89 D. The difference in means was statistically significant (p=0.026). [PLoS One 2022;doi:10.1371/journal.pone.0272451]

Intraclass coefficients (ICC) showed that CR had a high level of agreement with both SR (ICC, 0.940, 95 percent confidence interval [CI], 0.933–0.947) and AR (ICC, 0.965, 95 percent CI, 0.960–0.969).

Moreover, ClickCheck yielded a repeatability coefficient of 0.68 D, indicating that repeated measurements using the portable device are unlikely to differ from each other by more than 0.68 D. An ICC of 0.995 (95 percent CI, 0.989–0.997) further suggested that repeated measurements of ClickCheck would highly correlate with each other.

Meanwhile, Bland-Altman analysis revealed that SR and CR measurements differed from each other at an average value of 0.224 D, suggesting that the portable device measures higher myopic spherical values as opposed to the clinical standard. However, since AR differed from CR in a similar manner, with a difference of 0.222 D, there appeared to be no evidence of systematic measurement bias as regards ClickCheck.

“Our results indicate a high level of accuracy for spherical refractive error measurements using CR with reference to gold standard SR among participants aged 7 to 70 years. The visual acuity achieved by the participants using corrections based on CR also was found to have moderate level of agreement with SR,” the researchers said.

“This lends support to the use of the ClickCheck device for first level screening before performing complete subjective refraction,” they added.

In contrast, the portable refractive device appeared to underperform when it came to cylindrical correction. ClickCheck detected a mean cylindrical correction of –1.21 D, while SR found an average value of –1.34 D. ICC showed only moderate-to-low agreement between CR and SR (0.493, 95 percent CI, 0.100–0.715). Agreement was even worse with AR (ICC, 0.306, 95 percent CI, –0.233 to 0.610).

Moreover, whereas ClickCheck found only 48 eyes needing cylindrical correction, SR detected such an outcome in 513 eyes.

“With refinement in the cylindrical power measurement, we believe that this device can play an important role in providing a first-level assessment of refractive errors prior to performing subjective refraction by trained personnel,” the researchers said.