Glare Sensitivity Test

What it measures

This check gives a rough, relative sense of your disability glare susceptibility — how much a bright glare source placed next to a faint, low-contrast target hurts your ability to read it. It compares the faintest contrast you can read in glare-free conditions against the faintest you can read with a bright light beside the target.

How it works

First you read a descending ladder of low-contrast digits with no glare, noting the faintest step you can identify. Then you read the same ladder again, but this time a bright, glowing white patch sits right beside each target — mimicking a headlight or low sun in your field of view. Bright light scatters inside the eye (intraocular straylight), forming a veil of light over the retina that washes out faint contrast. The bigger the drop between your no-glare and with-glare results, the more that scattered light is disabling your vision. Because this runs on an ordinary screen, it is a relative, experimental comparison rather than a calibrated measurement.

Tips for an accurate result

• 1Keep both rounds identical except for the glare — Same distance, same brightness, same room lighting. The number that matters is the difference the bright light makes, so everything else should stay the same between rounds.
• 2Notice glare in real life too — If oncoming headlights at night, wet roads, or low sun strongly wash out your vision or throw halos and starbursts around lights, that real-world experience is far more telling than any screen test.
• 3Re-test if a result surprises you — Screen reflections, a bright window behind you, or tired eyes can all skew a round. If the drop seems unexpectedly large, control your lighting and run it again before reading anything into it.