Support
How to use
- On launch, set the distance from your eyes to the screen (10–100 cm; default 50 cm)
- Close one eye and tap the arrow that matches the direction of the gap in the Landolt ring (“C”)
- Each correct answer makes the ring smaller; a wrong answer reports the last stage you answered correctly
If you answer wrong at the very first stage (0.1), no result is shown yet: the app retests with larger rings in 0.01 steps from 0.09 down to 0.01, and the first stage you read correctly becomes your result (if every ring is answered wrong, the app reports that acuity below 0.01 could not be measured).
Distance and measurable range
| Distance from screen | Measurable acuity |
|---|---|
| 10 cm | 0.01–0.2 |
| 20 cm | 0.01–0.4 |
| 30 cm | 0.01–0.6 |
| 40 cm | 0.01–0.8 |
| 50 cm | 0.01–1.0 |
| 60 cm | 0.01–1.2 |
| 70 cm | 0.01–1.4 |
| 80 cm | 0.01–1.6 |
| 90 cm | 0.01–1.8 |
| 100 cm | 0.01–2.0 |
The upper limit follows “distance ÷ 50” (1.0 at 50 cm, 2.0 at 100 cm). For distances of 60 cm or more, we recommend two people: one holds the device, the other answers. Levels below 0.1 are measured in 0.01 steps during the retest that follows a wrong answer at the first stage (0.1).
FAQ
- Are results saved? — No. Results are shown on screen only and never recorded (the only saved setting is the distance).
- Can this replace an official eye exam? — No. It is a quick self-check for everyday eye strain. If you have any concerns, please see an optometrist.
- The ring looks different across devices — Ring sizes are computed using a fixed logical resolution of 163 points per inch rather than each device's actual pixel density, so they vary from a few percent up to about 23% between models (estimated: ~6% on iPhone Pro models, ~23% on iPad Pro 13). Day-to-day comparison on the same device is the most accurate.
- I feel unwell while using the app — Stop using it immediately.
Results from this app cannot be used as official health examination results.
Contact
Feedback and bug reports: [email protected]