What is the Amsler grid? Amsler grid: (AM-slur) test card, graph paper-like grid used in detecting central visual field distortion or defects

What is the Amsler grid? The Amsler grid is a small book of six charts, although many offices use a tablet style amsler grid that contains tear off sheets that the patient can draw on and be placed in their chart. The Amsler grid is a simple screening test used to assess the macula (the center of the retina).

The Amsler grid consists of evenly spaced horizontal and vertical lines printed on black or white paper. A small dot is located in the center of the grid for fixation. While staring at the dot, the patient looks for wavy lines and missing areas of the grid.

The test may be used diagnostically to discover the presence and or location of defects in the central field of vision. The test is also frequently given to patients to use at home to monitor macular degeneration. The patient should see all the lines straight and parallel with no broken, wavy, distorted, or missing areas.

EXAMPLES: (NOT ACTUAL SIZE) normal amsler abnormal amsler

the amsler grid is used for qualitative vision evaluation of the central 20˚of vision (10˚ on each side of fixation). the amsler grid is a type of visual field testing.

how is the amsler grid used? The Amsler grid should be held by the patient at normal reading distance. This test should be performed prior to the instillation of any eyedrops. The patient should be using their best correction for near. The test is performed one eye at a time.

The patient is asked to look at the dot in the center of the grid. The purpose is to see if the patient notes any abnormalities in the grid while focusing on the center dot

Some questions you may want to ask the patient are… “While looking at the dot in the center, can you see the whole grid? “Is any part missing or distorted?” “Are any of the lines wavy, bent or bowed?”

You should have the patient draw any abnormalities found. Make a note on the grid paper of the patient’s name, date and which eye. Grid should be placed in patient’s chart. Use a separate sheet of grid paper for each eye. If there are no abnormalities found in one or both eye– you may note in chart WNL(within normal limits) for the appropriate eye(s).

WHEN SHOULD THE AMSLER GRID BE PERFORMED? The Amsler grid should be performed when a patient presents with a decreased visual acuity that is not. improved with pinhole. Many times the patient will have a chief complaint of distorted or strange visual symptoms

WHAT EYE PROBLEMS DOES THE AMSLER GRID DETECT? The Amsler grid is used to detect central vision defects or distortions. The cause of this type of defect or distortion is usually a result of macular dysfunctions such as macular degeneration, or other retinal problems. Defects may also be attributed to advanced glaucoma or neurological problems

HISTORY OF THE AMSLER GRID Dr. Marc Amsler, a Swiss ophthalmologist invented the Amsler grid. It appears that he got the idea from patterns on a small card with a grid pattern that Landolt designed to place in the center of his perimeter to test the macula. Some problems with the perimeter cards were difficulty of use, and not being able to test for metamorphopsia.

THE GRID Each square measures 5 mm and when the grids are held at 30 cm from the patient each square subtends 1 degree on the retina. The amsler grid is very simple. The Amsler grid is available in a chart of 6 grids, as well as individual grids or tablets.

Commonly used grid

The most common Amsler grid today is white on black or black on white. In some cases the black and white Amsler does not detect early and subtle defects. Colored grids can be used for various purposes. Red lines on a black background are useful for: Optic nerve problems Chiasmal disorders Toxic amblyopia

Also available are blue-on-yellow, blue-on- red and white-on-red background. Red Amsler grid screening may allow practitioners to identify patients who are more likely to have hydroxychloroquine( 羟 氯喹 [ 抗疟药, 红斑狼疮抑制药 ] ) ocular toxicity.

The appearance is due to a combination of spreading and squeezing of the cones. This condition is termed “Metamorphopsia” ( 视物变形症 ) Patients with this defect may describe objects as distorted.

THE IMAGE BELOW IS AN EXAMPLE OF “MICROPSIA”( 视物显小症 )- DISTORTED VISION IN WHICH OBJECTS APPEAR SMALLER THAN THEIR TRUE SIZE.

COMMON DEFECTS The grids below are examples of what a person with macular degeneration might see.

This is an example of what a patient with macular edema might see. This appearance is attributed to the cones being spread apart. The retinal image will stimulate fewer cones and the lines of the Amsler grid will appear smaller and seem to bend away from the patient.

LESS COMMON DEFECTS. the image on the left is an example of “macropsia”( 视物显大症 )- distorted vision in which objects appear larger than normal. This is caused from the cones being forced closer together, making the retinal image fall on more cones than normal. This type of defect can be created by a tumor.

the image on the left is an example of a central scotoma. This may be caused by Central Choroidal Dystrophy, or CongenitalToxoplasmosis( 弓形体病 ). A scotoma may be “positive” or “absolute”

positive scotoma – non seeing area that the patient is aware of as being dark or black absolute scotoma – non seeing area despite the size, color, or brightness of the target

the image on the left may be reported by an advanced glaucoma patient. this type of defect is an arcuate scotoma.

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