Chapter 6 Flashcards
How are anomalies of color vision classified?
Pigment affected
Nature of the defect
What are the red-green defects for dichromacy?
Proton defect- protanopia
Deutan defect- deuteranopia
What is the blue-yellow defect for dichromacy?
Tritanopia
What is the red-green defect for anomalous trichromacy?
Protan defect- protanomalous trichromacy (protanomaly)
Deutan defect- deuteranomalous trichromacy (deuteranomaly)
What is the blue-yellow defect for anomalous trichromacy?
Tritanomalous trichromacy (tritanomaly)
Define dichromacy.
Missing one of the 3 cone pigments
Define anomalous trichromacy.
Absorption spectrum of one photopigment is abnormal (less effect) (displaced from normal location)
Less effect
Define deuteranomoly.
Chlorolabe spectrum displaced to long wavelengths
Define protoanomaly.
Erythrolabe displaced to shorter wavelengths
What is the peak luminous efficiency related to brightness?
555nm
Describe luminosity in protan and Deutan defects.
Luminosity is abnormal in protan defects (L cone defect), but close-to- normal in deutan defects
Describe wavelength discrimination in dichromacy. When do dichromate’s behave as monochromats?
Good discrimination at shorter wavelengths but beyond 545nm there is no ability to discriminate between stimuli on the basis of wavelength alone
Monochromatic beyond 550nm
Describe the perception of saturation in people with anomalous in color vision.
Saturation is abnormal
Deuteranopia and Protanopia reach total white
Describe how the spectrum of color looks to patients with anomalous color vision.
Protanopia- blue to white to yellow, longer wavelengths are darker, missing erythrocyte
Deuteranopia- blue to white to yellow
Protanopia and Deuteranopia appear as monochromats beyond 550nm
Tritanopia green to white to red
Which red-green anomalies are autosomal dominant?
Tritanopia and tritanomaly (common inheritance)
What is the most prevalent color vision anomaly?
Deuteranomaly
How did hereditary red-green color vision anomalies originate?
During meiosis dichromacy can originate when crossover of M and L is incorrect resulting in one chromosome with no M pigment (offspring who inherit this will have deuteranopia)
Paired copy will have 2 copies of M pigment and 1 L offspring will have normal color vision
Intragenic- hybrid genes result, can have dichromacy, anomalous trichromacy or normal
What does the farnsworth D-15 arrangement test?
Protan, Deutan Tritan defects
Dose not distinguish dichromacy from anomalous trichromacy
How does the radius of the desaturated D-15 compare to the saturated?
desaturated has shorter radius
Describe the rabin cone contrast test.
Test function of 3 cone types
Determine stability useful for glaucoma
Describe the Nagel anomaloscope.
Allows the full diagnosis of inherited red-green anomalies
Can diagnose dichromacy and anomalous trichromacy
Does the X-chrom lens cure colorblindness?
Make monochromat a dichromat with red lens
