What is the Amsler grid used for?

It is a self-monitoring aid for the central twenty degrees of vision. People with age-related macular degeneration, or at risk of it, use it to notice a change between appointments. It is a way of catching a change early, not a way of finding out whether you have a condition.

Why does this one ask me to hold up a bank card?

Because a grid drawn in pixels is a different physical size on every screen, and a grid of unknown size tests an unknown part of your vision. Every bank and ID card is 85.6 mm wide worldwide, which makes it a ruler almost everyone has. Matching the outline to a card tells the page how big its own pixels are.

How far away should I sit?

The page works it out and tells you, because the right distance depends on how big the grid ended up on your screen. The standard printed chart is 10 cm across viewed at 30 cm. On a narrow phone the grid draws smaller, and the distance shortens by the same proportion so that it still covers the same twenty degrees.

Should I wear my glasses?

Wear the glasses you read with, not your distance glasses. If the whole grid looks blurry rather than one part of it, that is usually the wrong correction rather than a retinal problem, and it is worth sorting out before reading anything into the result.

Why one eye at a time?

Because with both eyes open the other eye fills in the gap so completely that you will not notice it happening. Almost every scotoma a person eventually discovers was there for a while, invisible, because the fellow eye covered it. Checking one eye at a time is the entire point of the exercise.

Can the Amsler grid diagnose macular degeneration?

No. It cannot diagnose anything, and no home test can. It can tell you that something looks different from how it looked last time, which is worth an appointment. Diagnosis needs an examination of the retina, which usually means dilating drops and a scan.

My grid looked completely normal. Does that mean my eyes are fine?

No, and this is the most important limitation to understand. The grid is known to miss real changes, partly because the brain quietly fills in small gaps in a way you cannot feel. It also looks at only the central twenty degrees, and a great deal of eye disease is silent until it is advanced. A normal grid is not a substitute for a dilated eye examination.

I saw wavy lines. What happens now?

If it came on within the last day or two, telephone an eye-care professional today and use the words new distortion in my central vision. New distortion can indicate a condition where treatment works considerably better started early than late. If it is long-standing and has already been examined, it is a matter for your next appointment, and for watching whether it changes.

How often should I check?

Follow whatever schedule your eye-care professional gave you. If nobody has given you one and you are monitoring a known risk, many people check weekly. Checking on a regular rhythm matters more than checking often, because the value is entirely in comparing today against last time.

Is it better to print it?

A printed chart is the traditional way and it removes any question about screen size and brightness, so if you have a printer, print it and stick it on the fridge at eye level. The advantage of the screen version is that it walks through the procedure and produces a dated record, which a chart on the fridge does not.

Free tool

An Amsler grid that is actually the right size.

The Amsler grid is a square of fine lines with a dot in the middle. You look at the dot, one eye at a time, and notice whether any of the lines are wavy, broken, blurred or missing. It is a way of catching a change in your central vision early. It is not a test that can diagnose anything, and a clean result does not mean your eyes have been examined.

Nearly every version of this online is drawn in pixels, which makes it a different physical size on every screen, at a distance nobody specifies. This one measures itself against a bank card before it draws anything, then tells you how far away to sit.

Start the check Just diagnosed with AMD?

Set up
/Right eye
/Left eye
/Your record

Before you start

Stop and get seen today if any of these apply

A sudden shower of new floaters, or flashes of light
A curtain or shadow coming across your vision from any direction
A sudden loss of vision in one eye, painless or otherwise
Sudden distortion that came on over hours
Eye pain with redness, or vision that is misty with haloes around lights

None of those are questions a grid can answer, and all of them are time-sensitive. Telephone an eye-care professional or an urgent eye service rather than working through this page.

Set the size of the grid

A grid drawn in pixels is a different physical size on every screen, and a grid of unknown size tests an unknown part of your vision. One minute of setup fixes that, and this browser will remember it.

Hold any bank or ID card flat against the screen, on top of the outline below, and drag the slider until the outline is exactly the width of the card. Every card of this type is the same size worldwide, which is what makes it a ruler.

Outline width

CALIBRATED: 1 MM = 3.78 PX · A 10 CM GRID WILL DRAW AT 378 PX

No card to hand? Leave it as it is. The check still tells you something useful, but the size of the grid will be a guess and the result is worth less than a properly measured one.

Get the conditions right

Put on the glasses you read with. Not your distance glasses, and not none at all if you normally need them.
Sit somewhere evenly lit, with no reflection or glare on the screen.
Turn the screen brightness up to something comfortable but bright.
You will check one eye at a time, right first. Cover the other one with your palm rather than pressing on it.

On this screen

The grid will draw 100 mm across, so hold your head about 30 cm (12 in) away. That is the standard chart size at the standard distance.

What this grid cannot do

Worth saying plainly, because a home test that oversells itself is worse than no home test. The Amsler grid misses real disease. Part of that is the brain: presented with a small gap in the visual field, it fills the gap in with whatever surrounds it, smoothly and without telling you. People with a documented scotoma frequently look at a grid and see an unbroken one.

The other part is coverage. The grid looks at the central twenty degrees. Glaucoma characteristically begins outside that area, and by the time it reaches the middle a great deal has already been lost. Diabetic changes, retinal tears and most of what an examination looks for are similarly invisible here.

So the grid earns its place as a way of noticing change between appointments, in someone who is already having appointments. It is a poor substitute for one, and it was never designed to be a replacement. Keep the eye examinations.

About this tool

What is the Amsler grid used for?: It is a self-monitoring aid for the central twenty degrees of vision. People with age-related macular degeneration, or at risk of it, use it to notice a change between appointments. It is a way of catching a change early, not a way of finding out whether you have a condition.
Why does this one ask me to hold up a bank card?: Because a grid drawn in pixels is a different physical size on every screen, and a grid of unknown size tests an unknown part of your vision. Every bank and ID card is 85.6 mm wide worldwide, which makes it a ruler almost everyone has. Matching the outline to a card tells the page how big its own pixels are.
How far away should I sit?: The page works it out and tells you, because the right distance depends on how big the grid ended up on your screen. The standard printed chart is 10 cm across viewed at 30 cm. On a narrow phone the grid draws smaller, and the distance shortens by the same proportion so that it still covers the same twenty degrees.
Should I wear my glasses?: Wear the glasses you read with, not your distance glasses. If the whole grid looks blurry rather than one part of it, that is usually the wrong correction rather than a retinal problem, and it is worth sorting out before reading anything into the result.
Why one eye at a time?: Because with both eyes open the other eye fills in the gap so completely that you will not notice it happening. Almost every scotoma a person eventually discovers was there for a while, invisible, because the fellow eye covered it. Checking one eye at a time is the entire point of the exercise.
Can the Amsler grid diagnose macular degeneration?: No. It cannot diagnose anything, and no home test can. It can tell you that something looks different from how it looked last time, which is worth an appointment. Diagnosis needs an examination of the retina, which usually means dilating drops and a scan.
My grid looked completely normal. Does that mean my eyes are fine?: No, and this is the most important limitation to understand. The grid is known to miss real changes, partly because the brain quietly fills in small gaps in a way you cannot feel. It also looks at only the central twenty degrees, and a great deal of eye disease is silent until it is advanced. A normal grid is not a substitute for a dilated eye examination.
I saw wavy lines. What happens now?: If it came on within the last day or two, telephone an eye-care professional today and use the words new distortion in my central vision. New distortion can indicate a condition where treatment works considerably better started early than late. If it is long-standing and has already been examined, it is a matter for your next appointment, and for watching whether it changes.
How often should I check?: Follow whatever schedule your eye-care professional gave you. If nobody has given you one and you are monitoring a known risk, many people check weekly. Checking on a regular rhythm matters more than checking often, because the value is entirely in comparing today against last time.
Is it better to print it?: A printed chart is the traditional way and it removes any question about screen size and brightness, so if you have a printer, print it and stick it on the fridge at eye level. The advantage of the screen version is that it walks through the procedure and produces a dated record, which a chart on the fridge does not.

If the grid showed you something

These two cover what usually comes next: what the appointment involves, and the difference between the two forms of macular degeneration, which is what decides how quickly anyone needs to move.

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You Have Just Been Told You Have AMD. What Now?

The first thing to find out is which stage you have, because everything else depends on it. What to ask, what to watch for, and what not to buy yet.

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Dry AMD and Wet AMD: What the Difference Actually Changes

One is gradual and monitored, the other is urgent and treated. Which you have decides what happens next, what to watch for, and whether supplements apply.

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Sources

01American Academy of Ophthalmology, patient guidance: what is an Amsler grid and how is it used. Link
02National Eye Institute, age-related macular degeneration: symptoms, risk factors and detection. Link
03American Academy of Ophthalmology, patient guidance on comprehensive dilated eye examinations and how often to have them. Link
04ISO/IEC 7810, identification cards — physical characteristics, ID-1 format (85.60 mm x 53.98 mm), the basis of the on-screen calibration. Link