Visual Acuity

MEASURE VISUAL ACUITY USING A MODERN EYE TEST! Optimized for the RETINA DISPLAY in iPhone 4 and iPod touch 4G! (IMPORTANT NOTICE: this app has been calibrated for the iPhone and iPod touch ONLY and is NOT appropriate for the iPad because of the different display resolution. For an iPad specific solution, check out "FAST ACUITY XL" or "VISUAL ACUITY XL" with its free companion app "VISUAL ACUITY REMOTE").

VISUAL ACUITY is the first eye test on the iPhone platform developed by vision scientists and dedicated to the measurement of visual acuity. It is the perfect complementary tool for the optometrists and other vision care specialists (FOR THE NON-PROFESSIONALS we recommend our less-featured apps instead: FAST ACUITY, HOTV ACUITY or SLOAN ACUITY).

Contrarily to most other acuity charts available on the iPhone, VISUAL ACUITY provides:

- eye charts that are randomly generated to prevent memory effects,

- support for viewing distance up to 8 meters (26 ft) in metric or imperial units,

- STANDARD optotypes (letters or symbols) to test literate or illiterate people, and preschool children,

- support for the most common acuity units,

- most importantly, VISUAL ACUITY follows the logMAR design recommended by the NATIONAL EYE INSTITUTE and the INTERNATIONAL COUNCIL OF OPHTHALMOLOGY.

VISUAL ACUITY uses a computerized and modern method (logMAR) which is becoming the preferred visual acuity test in many eye clinics, and is effectively replacing the imperfect Snellen chart. Why is logMAR better than Snellen? LogMAR tests:

- use special fonts for the optotypes, in which all the lines are of equal thickness for all letters,

- present the same number of letters for each size,

- can be carried out at any distance allowing testing of very poor visual acuity,

- allow each presented letter to be scored individually to provide a more precise measurement,

- provide a logMAR score as a “real number” that can be used in calculations and statistics.

Two kinds of test are available in VISUAL ACUITY: a 'single letter' test and a unique interactive 'chart' test.

The 'single letter' test follows an adaptive procedure that computes an acuity score similar to the tests performed in clinical environment (ETDRS). This test presents single letters at decreasing size until the user cannot reliably identify them.

The second test is an interactive logMAR chart. This test provides the fastest way to measure visual acuity in a precise and efficient way, and could not be easier to use:
1) set the viewing distance of the patient using the bottom slider (up to 8m),
2) adjust the vertical slider to select an acuity range so the patient can easily see the top line but cannot for the bottom line (press the + and - buttons for a finer control),
3) tap the smallest line the patient can fully read.

Several choices are available to customize both tests: optotypes (Landolt C, Tumbling E, Sloan, HOVT, Lea), acuity units (foot: 20/*, meter: 6/*, decimal, VAR, CPD or logMAR units), 4 or 8 orientations for the Tumbling E and Landolt C (8 improves the test reliability), black letter on white background or vice-versa.

Acuity scores can be saved as function of the test condition (left, right or both eyes, optotypes, corrected or uncorrected). The acuity history also keeps notes about each measurement (eg, subject’s name) which can be used to retrieve the acuity history for a given patient. Tests history can be also emailed to yourself or others.

The Tools section provides information and recommendations for the tests, a conversion tool between visual acuity units, as well as a standard Snellen chart for comparison purpose.

About KyberVision: we provide consulting, research and development services in Vision Sciences. We also develop vision-related applications for the iPhone/iPod Touch platform, that are spin-off products of Psykinematix, our Mac OS X flagship product in the field of Visual Psychophysics.

更新履歴
Major update that provides the first Acuity Testing for Apple "Retina Display" (see our comprehensible blog entry on the controversy surrounding Apple's claims - http://www.kybervision.com/Blog/files/AppleRetinaDisplay.html - and why the iPhone 4 would be the perfect device for testing "Near Visual Acuity"):
Support for iOS4
Support for the higher resolution of the iPhone 4's display
Addition of CPD (cycle per degree) units in Conversion Tool and lower acuity moved to 20/400 from 20/200
Addition of default viewing distance in Settings
Viewing distance can be precisely set by taping on the viewing distance value in all tests
Maximum measurable acuity indicated in red when changing the viewing distance (pixel size and viewing distance are the limiting factors when measuring visual acuity)
Acuity of top line indicated in red when changing the vertical acuity slider in Chart Test
Addition of auditory feedback in Single Letter Test and decrease of the delay between optotype presentation
Single Letter Test supports now all optotypes and for distance up to 8 meters
Slow or fast version of the Single Letter Test can be selected in Settings
Recommendations provided when saving the acuity score can be disabled in the Settings
Addition of a warning when running in compatibility mode on the iPad (calibration made only for iPhone and iPod touch)