An offline app uses the blur line and the front camera to estimate diopter level, landing within a quarter diopter of the optometrist.
Checking whether your eyesight has changed usually means booking a full eye examination. The equipment is precise but heavy, and a trained optometrist has to operate it. A team at Brawijaya University asked a narrower question: could a phone estimate a myopia patient's diopter level between visits?
The method rests on a simple observation. Hold a phone close and the text stays readable. Move it away and at some point the letters blur. That threshold is the blur line distance, and it differs for each eye. The app measures that distance with the front camera and built in sensors, then converts it to a diopter value.
Ten participants measured their own eyes with the app, then had the same eyes measured by a doctor using a phoropter and a Snellen chart. Comparing the two sets of numbers turns a demo into evidence.
The small standard deviation matters as much as the average: the app was consistently close, not occasionally lucky. Participants also said the immediate result made them more willing to monitor their own condition.
Two limits are worth stating plainly. The app runs entirely offline, which is how it reaches users with poor connectivity, but that also means no clinical record leaves the phone. More importantly, it cannot measure a normal eye accurately, where the error climbed above one diopter. Anyone with a chronic condition still needs the standard test.
Brata et al. (2020). A new perspective of refractive error calculation with mobile application. International Journal of Electrical and Computer Engineering (IJECE).
As a screening aid, the case is reasonable. A quarter diopter of average error, from hardware already in a patient's pocket, is a cheap way to notice a change before the next appointment.
