Farnsworth–Munsell 100-Hue Test

Overview About This Test

The Farnsworth–Munsell 100-Hue Test (FM100) is a sensitive assessment of colour discrimination ability and colour deficiency classification. Despite its name, it uses 85 movable caps across four racks, arranged to represent a complete hue circle. Each of the three forms of dichromatism (protan, deutan, tritan) produces a characteristic failure axis on the polar plot.

Setup Pre-Test Conditions

1. Test under standard illuminant D65 daylight (6500 K), ideally a colour-matching booth. Avoid incandescent or fluorescent sources.
2. Corrected vision must be adequate — the test is primarily chromatic, not acuity-dependent. Ensure spectacles/contacts are worn.
3. Allow 2–3 minutes light adaptation before commencing.
4. Present one rack at a time with the lid closed on remaining racks to prevent memorisation.
5. The two anchor caps at each rack end are fixed and labelled — do NOT move them. Only the intermediate caps are rearranged by the patient.

Procedure How to Administer

1. Remove the intermediate caps from Rack I and scramble them in front of the patient.
2. Ask the patient: "Please arrange these coloured caps in order, so that the colours form a smooth gradual sequence between the two end caps."
3. Time each rack — normal completion is 2–4 minutes per rack; excessive time may indicate colour confusion.
4. Repeat for Racks II, III, and IV.
5. Record the cap sequence exactly as placed. Enter the position numbers into this tool.
6. Test each eye separately (right eye first by convention).

Scoring Error Score Calculation

For each cap, the error score is: |Position_left − Correct| + |Position_right − Correct|. Scores range from 0 (perfect) to 4 (maximum error). Total Error Score (TES) is the sum of all individual scores.

• TES < 16: Superior colour discrimination
• TES 16–100: Normal range (age-dependent)
• TES > 100: Colour deficiency likely
• TES > 200: Severe deficiency or acquired pathology