Visual Acuity Charts

Prevention is better than cure. Designed for children older than 6, parents with young children, and general practitioners, this eyechart app displays optically precise optotypes of eye charts for you to measure distance vision accurately in order to detect myopia early, so you can take preventive measures and seek help from medical professional early to prevent pseudomyopia from progressing to myopia, or prevent nearsightedness from getting worse.

Supported Eye Charts: 
1. Snellen, with C, D, E, F, H, K, N, P, R, U V and Z, as defined in BS 4274-1:2003.
2. Tumbling E. Option to have shorter middle arm. 
3. Landolt C.
4. ETDRS, with C, D, H, K, N, O, R, S, V, and Z.
5. European-wide, with H, K, O, E, P, X, B, T, M and A.
6. HOTV.
7. Numbers.
8. Shapes.

Test Distances: 
* 6, 5, 4, 3, and 2 meters predefined.
* 20, 15, 12, 10, 6 feet predefined. 
* Custom distance 0.5 - 30 meters, or 1.6 - 98 ft. 

Scenarios: 
1. "Doctor" and "Patient". 
2. Self-diagnosis with a mirror. With one eye covered by an eye patch and holding the device near the shoulder, you stand in front of a typical bathroom mirror using the mirror mode of the app and having the device's screen facing the mirror. The actual test distance is 2 times of the distance between you and the mirror. 
3. Self-diagnosis with a Bluetooth keyboard. After putting the device standing a few meters away on a table, you use the keyboard's direction keys to indicate what your read. 


Notations： 
1. Decimal (0.50) 
2. Fraction (20/40) 
3. LogMAR (0.30) 
4. Fraction (5/10) 
5. Fraction (6/12) 
6. MAR (2) 
7. VAS or VAR (85) 

Test Modes: 
1. Manual. 
2. Auto scoring In Auto scoring, you use the swiping gestures to indicate correct readings or wrong readings, and the app calculates the score. Through enabling “Record Scores” in Settings, you can keep track of the progression of your visual acuity. Visual acuity scores of multiple testees could be recorded. 

“Visual Acuity Testing for Telehealth Using Mobile Applications” published in JAMA Ophthalmology on https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7809609/ indicates Visual Acuity Charts is the most accurate among 10 apps on iPhones being tested. 

Checking for myopia takes several procedures and the first step is often to test distant visual acuity through a visual acuity chart. And the decrement of visual acuity may indicate the development of myopia. 

Disclaimer: 
While this app may replace eye charts in print, however it CANNOT replace doctors and optometrists who carry out comprehensive eye exam for your basic eye health. The eye chart app does not test strabismus, esotropia, exotropia, hyperopia and astigmatism and which are common early vision conditions. Please visit optometrists regularly and seek help from medical professional at early signs of visual acuity problems.