Smartphone-Based Visual Acuity Measurement for Screening and Clinical Assessment

摘要: Visual acuity is perhaps the most well-known and important measure of visual function. The concepts “20/20” “the big E” are familiar to patients physicians in all fields medicine. can be measured rapidly inexpensively, with low-cost charts available commercially, online for printing, increasingly mobile devices. Clinically, considered one vital signs eye at a predetermined distance, often using Snellen chart. Developed 1860s, this chart has several design flaws, such as nongeometric progression letter size variable number letters used per line (eg, “E” top ≥5 on 20/20 line). When measuring epidemiologic surveys or an outcome clinical research, insufficiently standardized, other have been developed address these deficiencies.1 well known retroilluminated logMAR (logarithm minimum angle resolution) that was Early Treatment Diabetic Retinopathy Study (ETDRS) since become standard method prospective research.2 Each ETDRS 5 (“optotypes”) fixed proportion larger (1.2589× 0.1 log) than below. Despite any viewer’s starting acuity, worsening 3 lines corresponds doubling angle, making more amenable rigorous analyses.1 Because EDTRS requires 4-m examination room large retro-illumination system cost upwards $1000,3 yet adopted widely use. In August 2015 issue JAMA Ophthalmology, Bastawrous et al4 described novel smartphone-based technique distance acuity. ETDRS-based app (the Peek Acuity app) validated against clinic measurement part survey among adults central Kenya. uses smartphone platform, conferring advantage over traditional measurement. grading done within app, tester blinded regarding correct response. new only 4 orientations. examinee points direction arms E, records answer by swiping across screen same direction. This helps prevent subtle subconscious clues “Are you sure?” raised eyebrow incorrect response), examiner not responsible determining when testing completed how scoring done. senses ambient light automatically adjusts brightness. If surroundings too bright accurate measurements, alert generated. When comparing study participants’ homes centralized 272 participants, found mean difference between measurements less 1 vision. clinic, letters. authors were unable perform second scenario, which might revealed degree test-retest variability (TRV) their reference helped put relatively low TRV context. In studies, up 2 reported testing.2 investigators use took no longer concluded repeatable consistent. also highlighted value added platform beyond including connectivity ability associate global positioning coordinates data. A clinician investigator interested replace must account practical considerations. First, individual handsets vary resolution, requiring users calculate adapt appropriate patient, although it possible could automated feature app. Second, smartphones may costly, particularly models highest-quality screens. Indeed, currently sold $100 despite its having replaced subsequent iterations model. Moreover, tumbling E version nor initial validation Indeed 10 optotypes chart. The phone technology delivery health care expanding. There 100 vision test apps Google Play Store, but few, if any, robustly validated.5,6 medical community should allow convenience affinity trump responsibility collect data. adverse consequences poor performance, generating unreliable data displaying inappropriate information patients.7 gaps regulatory framework, agencies circumvented disclaimers developers stating “entertainment only.” Yet clear designers target sophisticated users. principles governing protecting guide development innovations.8 Principles Digital Development set guidelines organize best practices,9many appear followed team. However, robust still scant. demonstrate, through tool cross-cultural capabilities, possibility applying tools meaningful way deliver wherever they reside.