Effects of Contrast Sensitivity On Colour Vision Testing
Effects of Contrast Sensitivity On Colour Vision Testing
Effects of Contrast Sensitivity On Colour Vision Testing
Using caps of different hues then the patient sort them into a
particular spectrum or group.
Developed for occupational colour discrimination and can
detect CV loss across all three axes.
Numbers and shapes do not need to be discriminated less
reliant on visual acuity (VA).
More sensitive
to detect early
Time-consuming
visual
dysfunction
Contrast Sensitivity (CS)
Underwent best-corrected
logMAR VA assessment,
Farnsworth D-15 CV and Pelli-
Robson CS testing, and
computer image
discrimination testing
VA Measurement of distance VA with corrective lenses
(if worn) was using computerized logMAR VA charts
CV
Starting at the 20/30 line, testing proceeded
sequentially to the line on which greater than or
equal to half of the letters were properly read, for
Computer
each eye separately, and then both eyes together
Using the Farnsworth D-15 (D15) test, consists of 15 colour
discs comprising the entire colour spectrum.
Computer
Computer
Subjects who did not place all discs in the correct order
were ineligible for the study
Subjects were shown 212 images on a computer
monitor (Dell P2314H) at a distance of 42 inches
with luminance in the range of 0 to 4 candelas/m2
VAVA
• The discs were arranged in a clockwise manner with the pilot disc on the left side.
• Pictures were taken of the discs arranged in the proper order as well of those in
D15 test an incorrect order, i.e., some discs were switched around.
• Participants were asked to read as many letters as they could, and the faintest
triplet for which at least two of three letters were correctly identified indicated the
PR charts log contrast sensitivity score of the tested eyes.
• VA was determined by the lowest line on which at least half of the letters were
ETDRS read.
chart
Ishihara HRR D15
plates plates discs
2 points: for correctly
2 points: for correctly identifying the shape and
identifying single-digit or quadrant for both one- 1 point: if the subject was
double-digit plates. shape and two-shape successfully able to
plates. determine if the disc
order was correct or
incorrect
1 point: for correctly
1 point: if only one digit
identifying only one
was identified on a two-
shape in the two-shape
digit plate
plates.
•Mean PR scores for baseline, high, medium, and low contrast were
1.95, 1.82, 1.49, and 1.04, respectively (p = 0.004 for all).
Results
p values of comparison between contrast p values of comparison between colour
settings for each colour vision test vision tests for each contrast setting
In this study:
• CS loss had the most significant impact on HRR scores, support previous
research:
• Zhao et al (2015): positive correlation between HRR and PR CS scores in
optic neuropathy patients.
• HRR showed a larger decrease in scores (medium and low contrast settings)
• HRR scores = not accurate reflection of CV in patients with CS loss.
• D15 (gold standard) also showed a score decrease between baseline and
lowest contrast
• Contrast decrease may resemble the effects of fogging on reducing visual
acuity & affects the results of CV tests.
Discussion
Pseudoisochromatic plates require an observer to identify shapes (HRR) or
numbers (Ishihara) arranged as coloured dots of varying size, hue, and
saturation against a similarly styled background.
• Variances in spectral sensitivity differences in luminous reflectances
between figure and background colour perception altered.
What is the main result of the Hardy-Rand-Rittler (HRR) test may no be an accurate reflection
research ? of colour vision in patients with contrast sensitivity loss.
DISCUSSION
Did the result suits the theory ? Yes
Is there any comparison with another
Yes, there are some similarities and differences
research ?
CRITICAL APPRAISAL
CONCLUSION
Could it be applied in chosen
sample, reachable and target Yes, but it needs further studies
population ?
Well covered.
The execution of the index test was described in The examination procedure of Ishihara
sufficient detail to permit replication of the test. and HRR were well described with the
detail of process and equipment.
Well covered.
The execution of the gold standard was described in The examination procedure of ID15 was
sufficient detail to permit replication of the test well described with the detail of process
and equipment.
Index test results were interpreted without knowledge Not applicable.
of the results of the reference standard. (BLINDING) There was no reference standard.
What is the gold standard with which the test D15 was used as gold standard.
And each test was compared with its
being evaluated is compared?
baseline.
What is the estimated sensitivity of the test being
Not applicable
evaluated? (state 95% CI)
What is the estimated specificity of the test being
Not applicable
evaluated? (state 95% CI)
What is the positive predictive value of the test
Not applicable
being evaluated?