Amsler grid: a printable check for your central vision

How to use it

Print the grid at 100%, or "actual size", and measure it. It should be 10 cm (100 mm) on each side, divided into 20 by 20 boxes of 5 mm. If your printer has shrunk it, switch off "fit to page" or "scale" and print again.

Then:

1. Sit in good, even light, with no glare or shadow on the sheet.
2. Put on the glasses you read with, if you use them. With progressives, look through the lower part of the lens.
3. Hold the grid about 30 cm (12 inches) from your eyes, or tape it to a wall at eye level and sit at that distance. A string cut to 30 cm keeps the distance the same each time.
4. Cover one eye lightly with your palm, without pressing.
5. Look at the center dot with the open eye, and keep looking at it.
6. Without moving your gaze, take in the rest of the grid. Notice whether any lines look wavy, bent or broken, whether some boxes look bigger or smaller than others, whether any area is blurred, faded, gray or missing, and if all four corners are visible.
7. Change hands and repeat with the other eye.

Step 5 is the one people get wrong. If your eye wanders along the lines, each part of the grid takes a turn in your sharpest vision, and a distorted patch can slip past.

The printed sheet has the grid and, under it, a record table with columns for the date, each eye and what you noticed. Outline anything that looked wrong on the grid in pencil, note the lighting and glasses, and keep the sheets in date order. An eye doctor can do far more with them than with a memory of "something looked off".

How often to check is something to agree with your eye doctor. People with age-related macular degeneration (AMD), or at higher risk of it, are often given a routine, and it differs from person to person. Checking again and again in one sitting does not help, because tired eyes are harder to judge.

How the numbers work

Held at the right distance, each box covers about 1 degree of your visual field, and the whole grid covers the central patch of vision served by the macula, the small part of the retina you use for reading, faces and fine detail.

The angle covered by a flat object in front of you is:

angle = 2 × arctan((width ÷ 2) ÷ distance)

With the standard grid, the width is 10 cm and the distance 30 cm. Half the width is 5 cm, and 5 ÷ 30 is 0.1667. The arctangent of that is about 9.46 degrees, and doubling it gives 18.9 degrees. So the grid spans about 19 degrees of your central field, a little over 9 degrees each side of the dot, and each 5 mm box about 0.95 degrees.

Distance changes the picture. Bring the sheet closer and each box covers more of your vision; hold it farther away and the grid shrinks to a smaller central area (at 35 cm it spans about 16 degrees). Either is fine for a quick look, but the same distance every time makes one sheet comparable with the next. The Swiss ophthalmologist Marc Amsler described the grid in the 1940s, and this layout is still the standard one.

What this tool can't tell you

The Amsler grid is a self-check that helps you notice change. It is not a diagnosis. A normal grid does not rule out AMD, since early AMD often causes no symptoms. A distorted grid does not prove AMD either: a thin membrane over the macula, a small hole in it, or swelling from diabetes can bend lines too. Telling these apart takes an eye exam, often with a scan of the retina's layers.

The grid does not test side vision, where glaucoma usually starts, or sharpness at a distance (the printable eye chart gives a rough idea of that). And with both eyes open, a good eye can cover for a weak one.

New distortion, a new dark or missing patch, or any change from your last sheet means contacting an eye doctor promptly, ideally the same day, not at your next routine visit. Wet AMD can progress quickly, and treatment started early gives the best chance of keeping the sight you have. Bring the marked sheet.

Some symptoms need care straight away:

• Sudden loss of central vision, or a dark patch that appears all at once: see an eye doctor the same day.
• New flashes of light, a sudden shower of floaters, or a curtain over part of your vision: same-day eye care, as this can mean a retinal tear or detachment.
• Sudden loss of vision in one eye, even if it returns within minutes: an emergency, as it can be a warning sign of stroke.
• Sudden severe eye pain with blurred vision, halos around lights, headache and nausea: an emergency.

For an emergency, call your local emergency number (such as 911, 999, 112, or 119 in Japan). The eye emergencies and first aid page explains what to do while you get help.

Questions people ask

A few lines have always looked slightly wavy to me. Does that matter?

If an eye doctor has seen it and called it stable, watch for change, which your record sheets will show. If you have never mentioned it, book an exam and take a marked sheet.

Is the grid worth using if I don't have AMD?

Anyone can try it, and a first sheet records your normal. It is most useful for people an eye doctor has asked to watch their central vision. AMD becomes more common with age, and smoking and a family history raise the risk. The column on AMD and the Amsler grid explains the dry and wet forms.

Can I use the grid on my phone instead?

The on-screen grid is not to scale. Screens and zoom settings vary, so the boxes will not be 5 mm and the angles above no longer hold. Print it for a standard check.

What if I can't see the center dot?

Mark it on the sheet and look toward the middle of the grid as best you can. A missing center can come from a problem in the macula, so if it is new, contact an eye doctor promptly.

Sources

• Marc Amsler's grid as used in eye care since the 1940s: 10 cm square, 20 by 20 boxes of 5 mm, read at about 30 cm.
• American Academy of Ophthalmology patient pages on age-related macular degeneration and home grid checks.
• National Eye Institute information on age-related macular degeneration.