Novel iPhone app can measure near functional visual acuity

A new smartphone-based application, dubbed the Smart Vision Check (SVC), demonstrates its use in self-monitoring near functional visual acuity (NFVA) in a relatively healthy population, reports a study. The SVC has high reproducibility and can assess NFVA-related parameters similar to conventional tests.

“Harnessing the benefits of telemedicine, we believe that the SVC may improve our understanding of the daily changes in NFVA and related at-risk individuals, thereby potentially screening presbyopia at an early stage,” said the researchers.

In total, 115 healthy volunteers aged ≥20 years with bilateral best-corrected visual acuity of ≥20/25 participated in this study. The SVC was designed for use on an Apple iPhone SE2 to measure NFVA. Users could simply tap on the orientation icon manually to avail of its function.

Another device, AS-28, was used to measure conventional FVA, with ‒2.50 D added to the best distance correction at baseline.

No significant difference was observed between the AS-28 and SVC in NFVA-related measurements (p>0.05). The Spearman correlation coefficient of NFVA measurement between the two devices was >0.60 (p<0.001). [Sci Rep 2022;12:2234]

On the Bland‒Altman plot, minimal bias was seen, with limits of agreements of 0.34 logMAR for NFVA with habitual correction when comparing the AS-28 and SVC. In addition, the repeated SVC-measured NFVA had an intraclass correlation coefficient of 0.915 (95 percent confidence interval, 0.800‒0.969).

“This application is the first validated smartphone-based NFVA test, which enabled us to detect the dynamic change of VA that is closely linked to the ocular surface condition and quality of life,” the researchers said. “All tests were fully automated and did not require clinician input unless taking care of the right viewing distance of 40 cm.”

Moreover, the SVC could identify asymptomatic early presbyopia, which may reduce health disparities and increase patient outcomes associated with difficulty in near vision work.

“If the SVC is applied in practice, this application may be used by a diverse population in a large sample size at a relatively low-cost,” the researchers said.

Multifunctional, flexible

Mobile health technologies are being used more and more in medical practices because of their flexibility and multifunctionality. [Acta Inform Med 2014;22:206-209; J Diabetes Sci Technol 2018;12:577-586; JMIR mHealth uHealth 2020;8:e14897]

“Due to the proximity and complexity of ophthalmic examinations, patients with nonemergent diseases encounter severely limited access to healthcare services during the COVID-19 pandemic,” the researchers said. “Therefore, a method for at-home assessment of visual function is urgently required.”

However, presbyopia detection remains a challenge due to the following reasons: measuring visual acuity at a specific moment may not reflect the daily visual performance, and the majority of patients are not aware of their symptoms. [Cornea 2007;26:S29-S35; J Clin Med 2021;10:3942]

“Monitoring a dynamic change in vision-related indices in a portable device, the SVC is useful for raising awareness and preventing the exacerbation of presbyopia, regardless of the participants’ recognition,” the researchers said.