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
What are some limitations of lanterns?
Doesn’t specify or quantify defect (due to colour naming)
Different standard for every occupation
Only undertaken at specialist centres
On the Giles-Archer lantern, how long is a colour presented for?
5 secs
On the Giles-Archer lantern, how many errors count as a failure?
1 error
On the Giles-Archer lantern, what counts as an error?
Any R or G misname
Inability to distinguish dark red
Naming Y as R or G
On the Giles-Archer lantern, what doesn’t count as an error?
Confusing white and yellow
Which occupations is the Holmes-Wright lantern used for?
Aviation
Marine
Which occupations is the Beyne lantern used for?
Marine
Rail
Aviation
Are any errors allowed on the Beyne lantern?
No
What settings is the Fletcher CAM lantern used for?
Clinical
Aviation
Marine
