Evaluation of colour-correcting lenses

Vien Cheung Research Fellow in Colour and Imaging Science [email protected]

CREATE 2010

Human Visual System

S Rod M L wavelength nm

Colour blindness (deficiency) Anomalous trichromats have three cone classes but one of the cones is normally shifted to a different peak wavelength sensitivity.

Dichromats possess only two cone classes.

Anomalous Trichromacy

Protanomally (L cone) Deuteranomally (M cone) Tritanomally (S cone)

males (%) 6.30

1.30

5.00

<0.0001

females (%) 0.40

0.02

0.35

<0.0001

Dichromacy

Protanopia (L-cone missing) Deuteranopia (M-cone missing) Tritanopia (S-cone missing)

Rod Monochromacy (no cones) 2.40

1.30

1.20

<0.001

0.03

0.02

0.01

0.03

<0.00001

<0.00001

What is it like to be a dichromat?

tritanope (blue-yellow) deuteranope (red-green) protanope (red-green)

Testing colour blindness Farnsworth-Munsell 100 hue test Ishihara test

Solution for colour-defective vision?

ColorView lenses, tinted with active coating, have specific spectral permeation characteristics.

ColorView A1 lenses ChromaGen coloured lenses have specific density and hue that (it is claimed) improve colour discrimination in 97% of people with colour blindness problems ChromaGen lenses

Evaluation of colour-correcting lenses Hypothesis – the lenses improve colour vision in some areas of colour space but at the expense of making colour discrimination worse in other areas of colour space.

Deuteranomalous (M cone) Color View A5 Ishihara Test Farnsworth-Munsell 100-hue Test

Results before after Ishihara Test



12 out of 25



25 out of 25

Results Farnsworth-Munsell 100-hue Test Error scores are noted when transpositions are made: 4 marks = each 2-cap transposition 8 marks = each 3-cap transposition 0-16 = superior discrimination 20-100 = average discrimination

150 180 210 120 90 60 240 270 300 30 330 0

Results Farnsworth-Munsell 100-hue Test

Discussions Ishihara Test - results were significantly improved when the colour correcting lenses were applied. The observer responded correctly for all 25 plates with very little hesitation. Farnsworth-Munsell 100-hue Test - errors lie predominantly on yellow/green and blue/purple region supports the optician’s diagnosis of the observer being deuteranomalous. The correction lenses did not improve the observer’s colour discrimination but rather induced greater deficiency. The results suggest that wearing colour-correcting lenses of the type used in this study could enable an observer to pass a screening test for colour deficiency.