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Questions and Answers
What type of color vision deficiency is most commonly inherited?
How many faulty gene copies do females need to express color vision deficiency?
Which of the following can cause acquired color vision deficiencies?
What is the primary way males inherit color vision deficiencies?
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What percentage of male offspring will have color vision deficiency if their mother is a carrier?
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In a family with a male color deficient parent, what is the likelihood that a daughter will be a carrier?
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What condition could cause different color vision deficiencies in each eye?
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Which statement is true regarding blue cone monochromacy?
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What fraction of patients has a colour vision defect?
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Which of the following is NOT a characteristic of rod photoreceptors?
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Which type of cone is found in the largest number in the human retina?
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What is the primary function of cones in the retina?
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What percentage of blue-S cones are typically present in the human retina?
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How many types of cone photoreceptors do humans have?
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What is the primary determinant of colour vision defects in humans?
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Which statement about trichromats is accurate?
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What is the main reason that patients seek advice regarding their colour vision?
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What is the approximate number of rods in the human retina?
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What is the primary purpose of screening plates in color vision testing?
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What do the patterns of surrounding dots in diagnostic plates indicate?
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Which of the following tests is specifically designed to confirm the type of color deficiency?
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According to the normal result of the D15 test, how should the lines appear when a patient has normal vision?
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What does a higher total numerical score in the Farnsworth-Munsell 100 hue test indicate?
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What is the male prevalence of protanopia in the population?
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Which type of color vision deficiency has individuals with three cones but incorrect spectral sensitivity in one?
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In which type of occupations are color vision tests particularly stringent?
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Daltonism is commonly referred to as what type of deficiency?
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What is the primary function of lantern tests in color vision assessment?
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What is the significance of the Nagal anomaloscope in color vision testing?
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What is the prefix used for red wavelength defects?
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Which color deficiency is most prevalent among males?
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How does lighting affect color vision tests?
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What adaptation strategies might patients with color vision deficiencies use?
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What type of test can quantify the extent of a color vision defect?
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What type of color deficiency do dichromats have?
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What does the duochrome test evaluate?
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How are individuals categorized with only two different cones?
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Which specific color deficiency can the City test detect?
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Which term refers to a deficiency in blue sensitivity?
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What color vision test is designed for identifying signal colors specifically in occupations?
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Which statement about trichromats is true?
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The Ishihara test primarily identifies which type of color vision deficiencies?
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What does deuteranopia refer to?
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Why was the need for color vision tests identified in the 19th century?
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In terms of visual acuity, what is expected from the sequence arrangement in the D15 test?
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What is the recommended viewing distance for the Ishihara test plates?
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Study Notes
Colour Vision Deficiency
- Around 1 in 20 patients will have a colour vision defect.
- Optometrists are often the first to identify these defects in children.
- Patients often seek advice about colour vision for occupational reasons.
Retinal Anatomy
- Humans are trichromats, having three types of cones.
- Rod photoreceptors are found across the retina and have a high sensitivity to contrast.
- Rod and cone photoreceptors connect to a ganglion cell, except for blue cones which directly connect to multiple ganglion cells.
- Most animals are dichromats, with the exception of primates.
Colour Vision Deficiency: Congenital and Acquired
- Congenital colour vision defects are stable throughout life.
- Acquired colour vision defects can progressively worsen or improve.
- Congenital deficiencies are inherited and are typically X-linked recessive, impacting mostly males.
- Acquired deficiencies can be caused by pathologies affecting the macula, optic nerve, lenticular discolouration, and some drugs.
Colour Vision Deficiency: Red-Green Defects
- The gene responsible for red-green colour blindness is carried on the X chromosome.
- Males inherit the gene from their mothers and have a 50% chance of being affected.
- Females have a 50% chance of being carriers, passing on the defective gene to their children.
- Protanopia and protanomaly are red-deficient conditions, while deuteranopia and deuteranomaly are green deficient conditions.
Colour Vision Deficiency: Other Types
- Blue cone monochromacy: Individuals have only one type of cone (blue); this is a rare X-linked condition affecting males.
- Rod monochromacy: Individuals lack functional cones; this rare condition affects both males and females.
Colour Vision Testing
- Ishihara Test: Identifies red-green congenital deficiencies.
- City University Test: Based on Farnsworth Munsell 100 hue test; can pick up tritan defects and assess acquired deficiencies.
- D15 Test: A reduced version of the 100 hue test; can confirm red, green, or blue defects.
- Farnsworth Munsell 100 Hue Test: Scores indicate the severity and type of the deficiency.
- Lantern Tests: Used for occupations requiring specific colour identification, such as pilots, maritime and railway personnel.
- Nagal Anomaloscope: The definitive test differentiating between dichromats and anomalous trichromats.
Considerations When Conducting Colour Vision Tests
- Lighting: Tests should be conducted in natural daylight or under CIE approved illuminants.
- Patient Adaptation: Patients with colour vision deficiencies have developed strategies for adapting to their condition.
- Occupational Requirements: The level of colour vision deficiency excluded depends on the occupation.
- Treatments: Tinted spectacles, contact lenses, and ‘Chromagen’ lenses may be used to improve colour perception.
The Impact of Colour Vision Deficiency
- Education: Can have a significant impact on a child’s education and future career choices.
- Sports & Hobbies: Can impact a patient’s ability to participate in certain activities, although adaptations can be made.
- Driving: Driving is possible with a colour vision deficiency, but drivers may experience difficulties distinguishing traffic light colours.
- Duochrome Test: Can still be used, as it relies on the lens’s ability to refract light (longitudinal chromatic aberration) rather than the retina.
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Description
Explore the fascinating world of colour vision deficiency and retinal anatomy. This quiz delves into both congenital and acquired defects in colour vision, understanding the role of trichromacy and the functioning of rod and cone photoreceptors. Test your knowledge on how these factors impact individuals and their daily lives.
