Arranging pastel chips in order is the 15-hue test, also called the Farnsworth-Munsell D-15 test. The set holds 15 colored chips of similar brightness but slightly different hues. The patient puts them in a related color sequence. It gives a more precise picture of a color vision deficit than dot plates do.
The two color tests do different jobs. Pseudoisochromatic color plates are a book of plates printed with colored and gray dots. A patient with normal color vision reads the numbers or figures hidden in the dots. A patient with a deficit cannot. Plates are quick, and they answer one question: is there a deficit? The 15-hue test then shows how bad the deficit is and what kind it is. People with color deficiencies make typical errors in the chip order. Similar brightness is the trick of the test. The patient cannot sort the chips by light and dark, so only hue can guide the order. Color vision is tested one eye at a time. Most color deficits are inherited and passed from a mother to her son. Optic nerve or retinal disease can also damage color vision later in life. That is one reason the doctor may want a graded result rather than a simple pass or fail.
Keep the pair straight for the exam. Plates screen, and the 15-hue test measures. For most patients with a color deficit, red looks less bright than it does to other people. A color deficit rarely disables a patient, but it can block certain careers, which is why exact testing matters here. Set the chips out in good, even light and let the patient take his time. Choosing the right color vision test is part of the COA supplemental testing content area.
Incorrect Answers
- A. The Amsler grid is a printed square of lines with a center dot. It maps the central visual field, not color.
- B. The Worth 4-dot test checks fusion, the way the two eyes work as a pair. Its colored dots are seen through red and green glasses.
- C. These are the dot plates he already failed. They screen for a deficit but do not grade how severe it is.
Testing Pearls
- The 15-hue test uses 15 pastel chips of equal brightness, arranged in hue order.
- Its other name is the Farnsworth-Munsell D-15 test.
- Pseudoisochromatic plates screen color vision with numbers hidden in colored dots.
- Test each eye separately, since disease can affect one eye alone.
- Inherited color deficits pass from mother to son.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 8, Comprehensive Medical Eye Examination.
