Visual Acuity Charts

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To help you to detect early symptoms of nearsightedness or myopia, this mobile app reassembles Snellen Chart (traditional, Sloan, HOTV), Tumbling E ChartLandolt C Chart and LEA charts on smart phones or tablets through randomly generating optotypes at precise physical sizes according to the test distance. You may even test your own visual acuity by yourself using the mirror mode of this app in front of a mirror.

measure optotypes on iPhone and iPad using a ruler

Visual Acuity Charts on Android tablet Visual Acuity Charts on Android phone

At exactly 6 meters’ distance from the “patient”, the optotype letters on the 6/6 line (Decimal 1.0 or LogMar 0.0) shall subtend 5 minutes of arc, which means that the chart should be sized such that these optotype letters are 8.73mm tall, and the topmost (Snellen Fraction 6/60, Decimal 0.1, or LogMar 1.0) "E" should be 87.3 mm tall. An optotype letter in on a square grid.

Charts

  1. Snellen Chart, with C, D, E, F, H, K, N, P, R, U V and Z, as defined in BS 4274-1:2003
  2. Tumbling E Chart
  3. Landolt C Chart
  4. ETDRS Chart, with C, D, H, K, N, O, R, S, V, and Z
  5. HOTV Chart
  6. ETDRS European-wide Chart, with H, K, O, E, P, X, B, T, M and A
  7. LEA Symbols
  8. Numbers

Hints:

  • ETDRS stands for the Early Treatment Diabetic Retinopathy Study.
  • ETDRS Chart with the LogMAR notation is actually LogMAR Chart.

Scenarios

  1. "Doctor" and "Patient"
  2. Self-diagnosis with Mirror
  3. Self-diagnosis within Arm's Reach

Predefined Test Distances

  • 6, 5, 4, 3, and 2 meters
  • 20, 15, 12, 10, and 6 feet

And an arm's reach distance may be defined in Settings.

Remarks

  • At exactly 20 feet’ distance from the “patient”, the topmost optotypes like "E" should be 88.7 mm tall, because 20 feet equals 6.096 meters. 
  • The letters and orientations of E or C ring are randomly shuffled during startup or waking-up from sleep. This makes memorizing an eye chart and cheating a vision test impossible.

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)

All charts in any VA notation follow the LogMAR design recommended by the International Council of Ophthalmology (ICO) to address design flaws in original Snellen chart. 

Modes

  1. Autoplay
  2. Manual

In Autoplay, the app calculates the score. For LogMAR notation,  the score is (LogMAR value of the best line read) + 0.02 x (number of optotypes missed). For other noatations, the score is the notation value of the best line read and optionally minus number of optotypes missed, and the maximum missed is 2.

By default, setting "Play Interval Until Next Optotype" is none. Available intervals in second: 2, 4, 6, 8, and 10. If the "patient" could not recognize the optotype within the interval, this counts a miss.

Disclaimer

While this app may replace Snellen Chart, E-Chart, C-Chart, ETDRS Charts and HOTV Chart in print, it cannot replace doctors and optometrists who carry out comprehensive tests for your eyes. Please visit optometrists regularly and seek help from medical professional at early signs of visual acuity problems.

The app tests only shortsightedness/myopia, and does not test strabismus, amblyopia, estropia, extropia, hyperopia and astigmatismand which are common early vision conditions.

Android Devices

Requirements:

  • Minimum version: Android 4.2 
  • Install Location: Prefer Internal
  • Required Permissions: Vibration
  • Device Types: smart phone, tablet

Content rating: 3+ with IARC Rating Certificate

Get it on Google Play

iOS Devices

Requirements:

  • Minmum version: iOS 8.0
  • Entitlements: None
  • Device Types: iPhone, iPad

Device Gallery

This app has been tested on various Android devices, iPhones and iPads to ensure optotype letters are printed on screens accurately. 

Android

Google, Samsung, HTC, LG, Acer, Motorola, Sony, Huawei and Amazon Fire Tablets.

iOS

iPhoneiPad