Color vision
Last reviewed: 23.04.2024
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The study of color vision can be informative in the clinical evaluation of hereditary dystrophies of the retina, when its disturbances occur before the visual acuity decreases and scotomas appear.
[Basic principles of color vision research
Color vision is provided by the functioning of 3 types of cones, each of which has its maximum spectral sensitivity: blue (tritane) - 414-442 nm, green (deuteron) - 522-539 nm and red (prota) - 549-570 nm. For the normal perception of the visible spectrum, all three types are required. Color anomaly can touch every cone pigment: color weakness (for example, protanomalia - weakness of perception of red color) or lack of color perception (for example, protanopia - lack of perception of red). With trichromasia, all 3 types are functionally active (but not necessarily functionally complete), whereas the absence of perception in the spectrum by one of the types of cones is called dichromasia, and two - monochromasia. Most people with congenital disorders of color perception are abnormal trichromates with a violation of the proportion of the contribution of this or that part of the spectrum to their color syringe. Violation of the perception of red color due to the functional inferiority of red cones is called protomanomaly, green cones are deuteranomalie, blue cones are tritanomalie.
Acquired diseases of the macular area are characterized by more pronounced defects, detected by blue-yellow perimetry, and optic nerve diseases - red-green.
Methods of studying color vision
- The Ishihara tables are used to study individuals with congenital defects in the perception of red and green colors. 16 tables show the balls forming the forms or figures that the researcher must recognize. The sufferer of color anomalies is not able to distinguish all the figures, and the inability to name the test object (with sufficient visual acuity) indicates a simulation.
- The City University test includes 10 tables, each consisting of one central color and four peripheral colors. The examinee needs to choose a peripheral color that is most comparable to the central one.
- The Hardy-Rand-Rittler test is similar to the Ishihara tables, but is sensitive to all three types of birth defects.
- The 100-tonne Farnsworth-Munsell test is informative for congenital and acquired chromatic abnormalities, but is rarely used in practice. Contrary to the name consists of chips 85 shades in 4 compartments. The extreme chips are fixed, the rest can be mixed by the researcher.
- the subject is offered to lay out the mixed chips in the correct order;
- The box is closed, turned over and evaluated numbers inside the chips;
- data are marked in a simple cumulative way on a circular map;
- Each form of dichromasia is characterized by insufficient color perception in its meridian.
- The 15-tone test of Farnsworth is similar to the Farnsworth-Munsell test, but consists of 15 chips.
For more information on checking color sensitivity, see this article, and the Rubkin tables in this.