Inherited Color Vision Anomalies Quiz

Inherited Color Vision Anomalies: Overview

• Choroidal conditions are associated with B-Y anomalies, retinal conditions with R-G or B-Y anomalies, and optic nerve conditions with R-G anomalies.
• Examples of conditions with an inherited component that may present with color vision loss include cone dystrophy, cone-rod dystrophy, achromatopsia, and Leber's congenital amaurosis.
• Depending on the genetic mutation, conditions may be progressive or stationary, with progressive conditions potentially leading to legal blindness (20/200 or worse).
• Normal color vision requires three primary colors to match any color stimulus: red, green, and blue, with all spectral hues matched by a mixture of these three primary colors.
• Anomalous trichromats, categorized as protanomalous, deuteranomalous, or tritanomalous, have a decreased ability to see color or differences in color and match a given stimulus with different proportions of the three primary colors.
• Protanomalous individuals have a mutated form of the long-wavelength (red) pigment, while deuteranomalous individuals have a mutated form of the medium-wavelength (green) pigment.
• Dichromats, including protanopes and deuteranopes, lack one of the three photopigments, resulting in R-G stimuli appearing to be the same color.
• Protanopia, which is rare, leads to an inability to distinguish between colors in the G-Y-R area of the spectrum and a reduced brightness of red, orange, and yellow.
• Deuteranopia, affecting 1% of males, results in an inability to distinguish between colors in the G-Y-R area of the spectrum, with all purple colors appearing similar.
• Tritanomaly and tritanopia, affecting the S cone, result in difficulty discriminating between blue and green hues, as well as red and yellow hues, with tritanopia being known as B-Y color blindness.
• Monochromatism or achromatopsia, occurring in 1 in 1 million individuals, results in all colors appearing the same and the need for management mainly for symptom relief, such as filter glasses or contact lenses.
• Inherited color vision anomalies are mainly X-linked, with a prevalence of 8% in males and 5% deuteranomalous, as well as a prevalence of 1 in 1,000,000 for achromatopsia. Testing for these anomalies includes the use of an anomaloscope, pseudoisochromatic plates, and dichotomous tests.

Color Vision Testing and Diagnosis

• Protanomalous trichromats require more red, while deuteranomalous trichromats require more green.
• Nagel Anomaloscope is an effective and expensive test to detect R-G color anomalies and provide a differential diagnosis.
• Pseudoisochromatic plates are less expensive and provide quick screening for color vision anomalies.
• Farnsworth D15 Test determines the type of color anomaly but is more expensive.
• Pseudoisochromatic Plates are used as standard screening tests and consist of a variety of color plates with different patterns.
• Ishihara, HRR, and Color Vision Testing Made Easy are screening tools for R-G anomalies.
• The American Optical Hardy-Rand-Rittler (HRR) book differentiates between R-G and B-Y anomalies and is easily administered to children.
• Tests should be performed under daylight illumination, and if not available, the correct illumination to be used is Macbeth Illuminant C-Lamp or daylight fluorescent tube lighting.
• Farnsworth D15 Color Test is a short screening test consisting of 15 color samples, commonly used by military service, educational, and vocational centers.
• Color Vision Testing Made Easy is suitable for children, patients with disabilities, and non-communicative patients, consisting of simple objects and symbols.
• The Ishihara Procedure involves the patient wearing habitual or near correction and performing the test at 30 inches or 76cm with full room illumination.
• The Farnsworth D15 Test and HRR Test enable the diagnosis and severity scoring of color vision deficits, with specific procedures for scoring and counseling recommendations for parents of children with inherited anomalous trichromats.