1. Evaluation of colour-correcting lenses Vien Cheung Research Fellow in Colour and Imaging Science t.l.v.cheung@leeds.ac.uk CREATE 2010

3. Human Visual System wavelength nm relative sensitivity SMLRod

4. Colour blindness (deficiency) males (%)females (%) Anomalous Trichromacy6.300.40 Protanomally (L cone)1.300.02 Deuteranomally (M cone)5.000.35 Tritanomally (S cone)<0.0001 Dichromacy2.400.03 Protanopia (L-cone missing)1.300.02 Deuteranopia (M-cone missing)1.200.01 Tritanopia (S-cone missing)<0.0010.03 Rod Monochromacy (no cones)<0.00001 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.

5. What is it like to be a dichromat? tritanope (blue-yellow) deuteranope (red-green)protanope (red-green)

6. Testing colour blindness Farnsworth-Munsell 100 hue test Ishihara test

7. Solution for colour-defective vision? ColorView A1 lenses ColorView lenses, tinted with active coating, have specific spectral permeation characteristics. 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

8. Evaluation of colour-correcting lenses Deuteranomalous (M cone) Color View A5 Ishihara Test Farnsworth-Munsell 100-hue Test 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.

9. Results before after 12 out of 25 25 out of 25 Ishihara Test

10. 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

11. Results Farnsworth-Munsell 100-hue Test

12. 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.