THOUGHTFUL BY DESIGN. TRANSPARENT BY DEFAULT.

What a little check-in can tell you.

eyeclinic is a guided educational vision screening for adults. It offers a structured way to notice differences in clarity and visual patterns. It is not a clinically validated medical device.

A screen that is scaled to you

A standard ID-1 plastic card, 85.60 mm wide, establishes the ratio of CSS pixels to physical millimeters. The test then sizes a geometric Tumbling E to subtend five minutes of arc at the selected viewing distance, multiplied by the Snellen acuity ratio. Keep browser zoom, display scaling, screen, correction, and viewing distance consistent.

Your acuity check

Each eye sees four randomized letters per level, from 20/100 through 20/20. A level passes with at least two correct responses out of four. Three errors stop the sequence; the last passed level is reported. If the largest level is not passed, the result is “Below 20/100.” These are near-screen angular acuity equivalents, not standardized distance visual acuity measurements. Guessing and display pixel resolution can affect the result.

The red-green comparison

The duochrome check asks about the apparent sharpness of identical black letters on red and green. In clinical refraction, this comparison can help refine lens selection in a controlled setting. This screen-based check has no trial lenses and cannot isolate accommodation, measure refractive error, or replace subjective refraction. Read the clinical background on the duochrome test.

The line-pattern check

The clock dial records whether one direction appears sharper. An illustrative axis is calculated as the selected clock hour multiplied by 30 degrees, modulo 180 degrees. That observation cannot diagnose astigmatism or determine cylinder power.

About the illustrative SPH value

SPH is an unvalidated educational heuristic, not a measured prescription. Near-screen acuity and red-green preference cannot determine refractive power. Do not use these values to purchase glasses or contact lenses.

For transparency, the heuristic uses 2.5 × log10(Snellen denominator ÷ 20), rounded to a 0.25 diopter increment with a 0.25 minimum. Red preference gives a negative sign; green preference gives a positive sign. Equal preference and acuity below the largest target return “Indeterminate.” This mapping is a software illustration, not a validated optical conversion, including when usual glasses or contacts are worn.

A contrast limitation

Acuity and clock-dial optotypes use black on white for maximum contrast. The specified duochrome backgrounds (#D32F2F and #2E7D32) with black optotypes do not meet WCAG AAA contrast. The colors are retained for that comparison and are identified with text, so color is never the sole way to select an answer.

Your next step

This digital screening is for informational and educational purposes only. It is not an autorefraction or an official medical diagnosis. Please visit a certified optometrist or ophthalmologist for clinical corrective prescriptions.

Seek urgent eye care for sudden vision loss, new flashes or floaters, severe eye pain, or a curtain-like shadow. An online screening should never delay appropriate care.