About the tool

A careful screen, not a diagnosis

Vision Checker makes a traditional directional E screening practical on an ordinary calibrated screen at a measured distance of 1 meter.

How it works

A standard 20/20 optotype subtends five arcminutes of visual angle. Vision Checker calculates the corresponding physical size at 1 meter, then converts it to screen pixels using the 50 mm ruler calibration you set. Larger denominator values produce proportionally larger E symbols.

At each level, the E appears in five random orientations. Identifying at least four correctly advances to the next smaller level. The last passed level is shown as an approximate Snellen result.

What it is useful for

The tool can support consistent at-home comparisons, such as checking each eye separately or comparing the same glasses in two positions. It can also help you notice a repeatable change worth discussing with an eye-care professional.

Important limitations

This is not a validated clinical chart in a controlled examination room. Display density, calibration error, viewing distance, contrast, lighting, browser zoom, accommodation, dry eyes, fatigue, and guessing can change the result. It does not assess eye health, peripheral vision, color vision, depth perception, visual fields, or the cause of reduced vision.

Privacy by design

The screening runs in your browser. Your choices, answers, and result are not sent to Vision Checker. Only the calibration width is kept locally so it can be reused on the same browser.

Editorial and advertising independence

Advertising helps keep the tool free. Ads are separated from test controls and do not influence the screening calculation, result, or health guidance. Advertisements do not represent endorsements.

Contact

Corrections, accessibility feedback, and general questions are welcome at the address listed on the live site.