Amsler grid: how to use it at home and what changes to look for

The Amsler grid is a printed chart made of straight lines forming a grid, with a dot in the middle. You look at the dot and notice whether the lines around it look straight and complete. It is a simple check of the central part of your vision, which is the part used for reading, recognising faces and driving.

The macula is the central part of the retina at the back of the eye. In age-related macular degeneration (AMD), the macula is damaged, and the Macular Society describes it as the biggest cause of sight loss in the UK. The NHS says the first symptom is often a blurred or distorted area in the centre of your vision, and that you might see straight lines as wavy or crooked. An Amsler grid gives a structured way of looking for exactly those changes.

The Macular Society lists the Amsler grid test among the tests used when AMD is diagnosed, alongside a dilated eye examination, optical coherence tomography and fluorescein angiography. In that setting it is used to detect vision changes such as wavy or missing lines. At home, it is used for self-monitoring.

The instructions in the two UK sources we read are consistent. Cambridge University Hospitals, in its leaflet on dry AMD, says to put your usual reading glasses on and hold the grid at about 12 inches or 30 cm away from your face, in good lighting, then cover each eye in turn and look at the central dot. The Vision Matters flyer says to wear any glasses you normally use to read, hold the grid around 30 cm away, cover one eye at a time and focus on the dot in the centre.

• Find a place with good, even light and put on your reading glasses if you wear them.

• Hold the grid at about 30 cm, or 12 inches, from your face.

• Cover one eye.

• Look steadily at the central dot. Do not let your gaze drift towards the lines.

• Note whether any lines look wavy, bent, broken, blurred or missing, or whether any area is dark or missing.

• Repeat with the other eye, and compare the results with the last time you checked.

Wavy, distorted, broken or missing lines suggest that the central retina may not be working as it should. This can happen in AMD, but also in other conditions affecting the macula, so a grid on its own does not give a diagnosis. The Vision Matters flyer says that if the lines look wavy, distorted or broken, you should make an appointment with your optometrist.

For people who already have AMD, the picture is slightly different. The Cambridge leaflet explains that someone diagnosed with AMD may already see wavy, broken or blurred lines, or missing patches, on the chart. What matters is whether there is a new change or whether it is worse than before. If you notice either, the leaflet says to contact your optician or ophthalmologist immediately.

This is important because dry AMD can turn into wet AMD. Cambridge explains that regular monitoring is needed to identify early signs of dry AMD becoming wet AMD, or of wet AMD becoming more active. The Macular Society says wet AMD develops when abnormal blood vessels grow into the macula and leak blood or fluid, leading to scarring and rapid loss of central vision, which is why speed matters.

The Amsler grid is a monitoring aid. Cambridge notes that it can be hard to notice vision loss early because one eye may be affected before the other, and the good eye compensates for the affected one, so patients may not notice the problem at first. Covering each eye in turn avoids that problem, which is why the instructions stress testing eyes separately.

A normal grid does not guarantee healthy eyes. Many eye conditions have no symptoms at first, and the grid does not check peripheral vision, eye pressure or the health of other parts of the eye. The NHS notes that AMD is sometimes found during a routine eye test before you have any symptoms, and Vision Matters stresses that the home test does not replace a routine sight test.

Equally, a changed grid is not an emergency in every case, but it should not be left to your next routine appointment. Contact your optician or eye clinic promptly and explain what you have seen.

The NHS separates non-urgent and urgent advice for AMD symptoms. It says to see an optician if you are worried about your vision, because early diagnosis and treatment may help stop your vision getting worse. It says to get an urgent opticians appointment or help from NHS 111 if your vision gets suddenly worse, if you have a dark curtain or shadow moving across your vision, or if your eye is red and painful, because these can be signs of other eye problems that need to be treated straight away.

If you already attend an eye clinic, use the contact route they have given you, as they may offer a quicker pathway than waiting for a general appointment.