11.1 Amsler Grid & Confrontation Visual Field Testing
Key Takeaways
- The standard Amsler grid is 10 cm square with 5 mm squares, viewed at 30 cm, and tests the central 10 degrees.
- The patient must wear their near correction and cover one eye, keeping fixation on the central dot throughout.
- Metamorphopsia indicates retinal distortion, while a scotoma indicates an area of non-functioning retina.
- Confrontation fields compare the patient's field against the examiner's and reliably detect only gross defects.
- A hemianopic defect that respects the vertical midline localises at or behind the chiasm.
The Amsler grid
The Amsler grid tests the central 10 degrees of the visual field — the macular field — at a level of detail no automated perimeter matches in a ten-second bedside test.
The standard chart is a 10 cm square divided into 5 mm squares with a central fixation dot. Viewed at 30 cm, each small square subtends 1 degree and the whole grid subtends 20 degrees, that is 10 degrees from fixation in every direction.
The seven standard charts:
| Chart | Description | Use |
|---|---|---|
| 1 | White grid on black | Standard |
| 2 | Adds diagonal lines to the centre | Central scotoma preventing fixation |
| 3 | Red grid on black | Red desaturation in optic neuropathy and toxic maculopathy |
| 4 | Dots only, no lines | Distinguishes scotoma from metamorphopsia |
| 5 | Horizontal lines only | Detects metamorphopsia in a specific meridian |
| 6 | Black on white with fine central lines | Fine metamorphopsia near fixation |
| 7 | Fine central grid | Detailed central 4 degrees |
Technique.
- Patient wears their near correction — this is the most commonly skipped step and it invalidates the test.
- Test one eye at a time, occluding the other completely.
- Hold the grid at 30 cm under good, even illumination.
- Instruct: "Look at the dot in the centre and keep looking at it." Fixation must not wander.
- Ask four questions while fixation is maintained:
- Can you see the central dot?
- While looking at the dot, can you see all four corners and all four sides?
- Are any of the lines wavy, bent or distorted?
- Are any areas blurred, missing, dark or faded?
- Have the patient mark the abnormality on a copy of the grid, or describe its location and size.
Interpretation.
| Finding | Meaning | Common causes |
|---|---|---|
| Metamorphopsia — wavy or bent lines | Photoreceptors displaced by fluid or traction | Choroidal neovascularisation, central serous chorioretinopathy, epiretinal membrane, macular oedema |
| Central scotoma | Non-functioning central retina | Geographic atrophy, macular hole, macular scar |
| Paracentral scotoma | Focal lesion off fixation | Drusen, small haemorrhage |
| Micropsia / macropsia — squares smaller or larger in one area | Photoreceptor spreading or crowding | Retinal oedema, resolving serous detachment |
| Blurred area without distortion | Media opacity or a mild defect | Cataract, vitreous opacity |
Home monitoring is the grid's highest-value use. Patients with dry macular degeneration are given a grid and told to test one eye at a time, daily, and to report new distortion immediately, because conversion to wet macular degeneration is treatable and time-sensitive.
Confrontation visual fields
Confrontation compares the patient's peripheral field against the examiner's, assumed normal. It is quick and requires no equipment, and it detects only gross defects — but a hemianopia found in thirty seconds changes the whole visit.
Setup. Sit directly facing the patient at about 1 metre, at the same eye level. Test one eye at a time: the patient covers their left eye while you close or cover your right, so your fields overlap. The patient fixates your open eye throughout — and you watch for their fixation to wander, which invalidates the result.
Methods, from coarse to fine:
| Method | How | Detects |
|---|---|---|
| Finger counting | Present 1, 2 or 5 fingers midway between you and the patient in each of four quadrants; the patient states the number | Dense quadrantic and hemianopic defects |
| Finger wiggle | Wiggle a finger in each quadrant, asking the patient to point to the moving one | Gross field loss; more sensitive than static presentation in some patients |
| Simultaneous double presentation | Present fingers in two quadrants at once (for example both superior quadrants) and ask "left, right or both?" | Subtle hemifield loss and visual neglect, which is missed by single presentation |
| Red target comparison | Move a red pin or bottle top between hemifields and ask whether the red looks the same on both sides | Red desaturation across the vertical midline in chiasmal disease, and across the horizontal midline in optic nerve disease |
| Kinetic confrontation | Bring a target in from beyond the field edge in each of eight meridians and ask when it first appears | A rough field outline |
Documenting the result. Draw the finding rather than writing "full to confrontation" by habit. Record which method was used, note whether fixation was maintained, and state the quadrants tested.
Localising patterns
The single most valuable question is whether the defect respects the vertical midline.
| Pattern | Localisation |
|---|---|
| Monocular field loss | Anterior to the chiasm — retina or optic nerve |
| Altitudinal (respects the horizontal midline) | Optic nerve head — ischaemic optic neuropathy, or a retinal branch artery occlusion |
| Bitemporal hemianopia respecting the vertical midline | Chiasm — pituitary adenoma, craniopharyngioma, meningioma |
| Homonymous hemianopia | Retrochiasmal, contralateral to the lesion |
| Superior homonymous quadrantanopia | Temporal lobe, Meyer's loop — "pie in the sky" |
| Inferior homonymous quadrantanopia | Parietal lobe — "pie on the floor" |
| Congruous homonymous hemianopia with macular sparing | Occipital cortex |
| Generalised constriction | Advanced glaucoma, retinitis pigmentosa, panretinal photocoagulation, or non-organic |
Limitations and when to escalate
Confrontation testing misses most early glaucomatous and toxic field loss. Its sensitivity for mild defects is low, and a normal confrontation field does not exclude a field defect. Any patient with symptoms suggestive of field loss, any abnormal confrontation finding, and any patient under glaucoma or neurological surveillance needs formal automated or kinetic perimetry, which is covered in the automated perimetry and Goldmann sections of this guide.
The practical role of confrontation and Amsler testing is therefore triage and monitoring: fast, repeatable, performable at the bedside or by the patient at home, and capable of catching the large defects that must not wait.
At what distance is the standard Amsler grid held, and what field does it test?
A patient reports that the lines near the centre of the Amsler grid appear wavy. What does this indicate?
Which confrontation technique is most useful for detecting visual neglect?
Which step, if omitted, most commonly invalidates an Amsler grid result?
A confrontation field shows loss of the left half of the field in both eyes, respecting the vertical midline. Where is the lesion?