Amsler Grid Test: Clinical Interpretation Guide for Clinicians and Patients

What the Amsler grid is, and what it actually measures

The Amsler grid is a 10 cm × 10 cm square containing a 20 × 20 grid of black lines on a white background (5 mm per cell = 1° of visual angle at 30 cm viewing distance), with a central fixation dot. Since Marc Amsler introduced it in 1947 it has been the standard at-home and in-clinic test for central 10° of the visual field.

It detects three kinds of central-visual-field abnormality:

• Metamorphopsia — straight lines appear wavy, bent, or distorted
• Central scotoma — a missing or blurry area at or near fixation
• Quadrantanopia / hemianopia — missing sectors of the grid (more often a chiasmal or post-chiasmal finding)

Standardised administration (AAO 2022 protocol)

1. Patient wears near-vision correction (reading glasses or bifocals).
2. Distance: 30 cm (about arm's length).
3. Lighting: even indoor lighting, no glare or dimness.
4. One eye at a time — cover the other eye completely.
5. Stare at the central dot for ~10 seconds.
6. Mark any abnormality by clicking / pointing / verbal description.

Repeat for the fellow eye.

Interpretation: pattern → differential diagnosis

Pattern on Amsler	Likely cause	Action
Wavy lines (metamorphopsia) — central	Wet AMD (choroidal neovascular membrane)	Urgent OCT & fluorescein angiography; anti-VEGF if confirmed
Wavy lines — paracentral, mild	Early dry AMD; epiretinal membrane (ERM); vitreomacular traction	OCT within 1–2 weeks
Central grey/dark spot	Macular oedema, central scotoma from CSR, optic neuropathy	OCT + fundus exam within 1 week
Missing quadrant (e.g. upper-right)	Macular branch retinal artery occlusion; optic nerve or chiasmal lesion	Same-day evaluation
Lines bent outward (macropsia) or inward (micropsia)	ERM, macular hole, CSR	OCT within 1–2 weeks
All lines uniformly blurred	Refractive error, media opacity, optic neuropathy	Refraction + OCT + visual field
Normal grid, blurry dot	Central scotoma (e.g. Stargardt disease)	Fundus autofluorescence + OCT

How sensitive is the Amsler grid?

Published sensitivity values for any AMD-related macular change range from 34% to 100% depending on the study, the reference standard used, and whether patients are self-testing at home or being tested in clinic (Mok 2004, Schwartz 2005, Crossland & Rubin 2007). It is more sensitive for central field defects than for peripheral, and more sensitive for metamorphopsia than for subtle scotoma. Newer microperimetry and shape-DRM hyperacuity testing can detect metamorphopsia earlier, but the Amsler grid remains the most widely available at-home screening tool.

For patients: how often and when

• Known dry AMD: weekly self-check (some clinicians say daily — evidence favours ≥ once per week for timely wet-AMD conversion detection)
• One eye already converted to wet AMD: weekly for the fellow eye
• Diabetic macular oedema (DME): monthly during active treatment, every 3 months when stable
• ERM / macular hole: pre-op and at each follow-up visit
• High myopia / pathologic myopia: monthly — macular complications can be silent otherwise

Limitations to disclose to patients

• 20% of patients with subtle macular changes may still report a normal grid. Amsler is a screening tool, not a diagnostic one.
• The grid only covers the central 10° — peripheral retinal detachment, for example, is invisible on the Amsler grid.
• Small micro-scotomas (a few cells across) can be missed if the patient fixates away from them.
• Reduced contrast sensitivity can simulate an abnormal grid even with normal anatomy — perform under good lighting and with best-corrected near vision.

Use the online tool

The EyeToolkit Amsler Grid Test renders a standard 20 × 20 grid at the correct viewing distance, lets you tap cells to mark abnormal areas, and exports a notes record for sharing with your eye-care provider. Free, no account required.

Frequently asked questions

Can the Amsler grid detect glaucoma?

Not reliably. Glaucoma preferentially affects peripheral vision, which is outside the Amsler grid's central 10° coverage. Use automated perimetry (e.g. Humphrey 24-2 or 10-2) instead.

What if my patient sees a normal grid but OCT shows fluid?

Possible explanations: the metamorphopsia is too subtle to perceive subjectively; the grid was tested at the wrong distance; or the lesion is small and outside the patient's fixation point. Treat the OCT, not the Amsler result. The Amsler grid is supplementary information, not a diagnostic test.

Is the smartphone version (on-screen) as reliable as paper?

Provided the patient views at the calibrated 30 cm with correct PPI calibration, smartphone / tablet versions have published concordance of 0.85–0.92 against paper charts. (Marmamula 2018, Han 2019.)

How often should a patient with one wet AMD eye test the fellow eye?

There is no high-quality RCT. The AAO Preferred Practice Pattern suggests ≥ weekly self-monitoring. Many retina specialists recommend twice-weekly or daily, with a 24-hour urgent visit threshold for any new distortion.

What's the difference between a red-on-black and black-on-white Amsler chart?

The red-on-black variant (originally by Amsler himself) is more sensitive to central scotoma because the red targets the red-cone pathway, which is densest at the fovea but absent at the optic disc. It is not, however, more sensitive to metamorphopsia. Use the standard black-on-white for general screening and the red-on-black as an adjunct when central scotoma is suspected.

References

1. Amsler M. Earliest symptoms of diseases of the macula. Br J Ophthalmol. 1953;37(9):521-537.
2. Crossland M, Rubin G. The Amsler chart: absence of evidence is not evidence of absence. Br J Ophthalmol. 2007;91(4):391-393.
3. Schwartz R, Loewenstein A. Early detection of age related macular degeneration: self-assessment Amsler grid. Ophthalmology. 2015;122(5):964-970.
4. AAO Preferred Practice Pattern: Age-Related Macular Degeneration. 2022.
5. Marmamula S, et al. Smartphone-based Amsler grid test for macular disease. Ophthalmology Retina. 2018;2(9):876-883.
6. Estreicher A, Biedka K, et al. The Amsler Grid in Everyday Practice: A Review of Its Role and Limitations in Primary Care. Clinical Ophthalmology. 2026;20:542357.

Educational content. Not a substitute for in-person eye examination. The Amsler grid does not replace fundus examination or OCT.