Online Eye Testing

Special eye charts are used for different screening purposes beyond a standard Snellen chart. One example is the Early Treatment Diabetic Retinopathy Study, or ETDRS, visual acuity chart.

This chart is used in clinical and research settings to measure vision in a structured way. Online viewing can give only a rough idea, so it should not replace a complete eye examination.

Hold your screen at about 1 foot distance in good light and check whether you can read the sample sentences comfortably.

Have your eyes checked if you cannot read the first two sentences or if near work feels blurred, strained, or uncomfortable.

The astigmatic mirror is a screening chart used to notice possible astigmatism. Look at the lines near the center from a comfortable distance.

If some lines look darker, clearer, or more widely spaced than others, or if the inner circle does not look round, schedule an eye check for a proper refraction and corneal evaluation.

The Amsler grid is a square mesh of horizontal and vertical lines used to screen central vision changes. Test one eye at a time while wearing your reading glasses if you use them.

• Focus one eye on the dot in the center.
• Check whether you can see the dot and all four corners.
• Notice if all small squares are visible.
• Look for any missing, blurred, bent, or wavy lines.

This example shows how an Amsler grid may appear when central vision is distorted. Wavy lines, missing patches, or a blurred central area should be evaluated by an eye doctor.

Sudden central distortion, a new dark spot, or rapid change in reading vision can be urgent, especially in patients with known macular disease.

Look at the pattern of dots and note which number you can see. A person with typical color vision may see a 5, while a person with red-green color vision deficiency may see a 2.

Screen color and device brightness can affect this test, so it is only a basic guide. A formal color vision test is needed for diagnosis.