Anomaloscope and Lanterns Flashcards
How does an anomaloscope work?
Evaluates the px’s ability to match a yellow target by finding the correct R-G values
What can the Nagel anomaloscope diagnose?
R-G defects
What can the anomaloscope differentiate between?
Dichromats and anomalous trichromats
On the anomaloscope, what is the normal expected range for each axis?
R-G: 37-44 (x)
Yellow brightness: 13-16 (y)
How does a deuteranope’s luminance function compare to a ‘normal’?
Very similar, slightly higher
How does a protanope’s luminance function compare to a ‘normal’?
Sensitivity shifted left (towards smaller wavelengths), so reduced sensitivity to longer wavelengths makes red appear darker
To a normal trichromat, is there any perceived difference in luminance between the R-G mixtures?
No
How does an anomaloscope determine deficiencies?
Exploits CIE diagram colour confusion lines - all colours chosen are set along colour confusion lines
What are the types of anomaloscope?
Nagel/Neitz
Besancon
Pickford-Nicolson
What is a disadvantage of the Pickford-Nicolson anomaloscope?
Uses filters to create the colours - this makes it less sensitive
On the anomaloscope, how is a deuteranope identified?
All yellow matches will have a similar brightness, but the R-G mixture will vary
On the anomaloscope, how is a protanope identified?
R-G mixture varies and yellow brightness varies (darker if more red, lighter if more green)
On the anomaloscope, how is a deuteranomalous trichromat identified?
R-G matches are more green, yellow brightness will be similar for all matches
On the anomaloscope, how is a protanomalous trichromat identified?
R-G matches are more red, yellow brightness varies
What is the main purpose of lantern testing?
Occupational testing using colour naming
