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In practice
Nigel Burnett Hodd, BSc, FCOptom, DCLP
Putting ChromaGen
to the test
I am fortunate to have been one of abnormality in one of the three retinal
the few contact lens practitioners to pigments (red, green and blue) or by the total
stumble across the ChromaGen man absence of one of them. Loss of the blue
at Optrafair in 1997. He was tucked pigment is very rare; less rare is the loss of
away on the Cantor & Silver stand the red and most common is a defect in the
and was selling licences to fit green. Fortunately, the green is in the centre
special coloured contact lenses. At of the spectrum and so the patient is not such
nearly £2,000 for the licence (and a liability as the loss of the red end of the
lenses 10 times more expensive spectrum causes to the protanope (failure to
than standard lenses), there were see red traffic lights on foggy nights).
not many takers. Yet those who now Table 1 shows figures on colour vision
fit ChromaGen are enthusiastic defects released by City University’s colour
about the merits of the system and vision clinic.
they are not out of pocket. Whilst
there are a lot of sceptics, there is Colour vision testing
an enormous group of patients Although colour vision assessment is a very
whose lives have been changed by complex task using many different tests, for
the system. colour vision assessment with ChromaGen,
all you need is the Isihara test for adults and
Types of defect the junior Matsubara version for children.
As there are three colour pigments in the The patients not only recognise the tests, but
retinal cones, there are three basic categories family and friends watching can appreciate
of colour defect. The rods control the amount the defects from their funny answers. This is
of light and dark and they, too, can be the most important part of the therapy and it
deficient, causing night blindness. usually takes 15 minutes to discuss with the
Essentially, the cones are concentrated in the patient all the problems that they have had
macula and foveal area of the retina and with colour during their lives, particularly at
become more and more sparse and absent the school and in their occupations. Whilst you
further away they are from the macula. should not use the Isihara test to suggest that
Optometrists know, from visual field you have cured their colour vision, it can be
screening, that the limits of the colour vision quite exhilarating for them and their
fields are quite narrow. The cones can be audience to actually read the plates correctly
severely damaged by macula disease, which with the ChromaGen lens in. (One of my
can sometimes cause total loss of colour patients was able to pass the Isihara and
vision. Such patients are unlikely to be thereby not loose his job as a printer when
helped by ChromaGen therapy. Colour they went over to computer technology. Figure 1a
defectiveness is caused by a reduction or Another was able to enter the US Air Force ChromaGen screen
Table 1
Colour vision defects - type and frequency
Type of defect Number of photopigments Frequency
Men Women
Protanopia 2 - no long-wave (red) pigment 1% 0.01%
Protanomalous 3 - long-wave (red) pigment is abnormal 1% 0.03%
trichromatism
Deuteranopia 2 - no middle-wave (green) pigment 1% 0.01%
Deuteranomalous 3 - middle-wave (green) pigment is abnormal 5% 0.35%
trichromatism
Tritanopia 2 - no short wave (blue) pigment 0.005% 0.005%
Tritanomolous 3 - short wave (blue) pigment is abnormal 0.005% 0.005%
Figure 1b
trichromatism
Author’s version
JULY 17 • 1998 OPTOMETRY TODAY 39
ChromaGen colour vision therapy
violet, purple, orange, yellow, green, amber Mechanism
and magenta. The filter which brings out the No two colour defectives are exactly the
colours on the screen the most is determined same; everybody has a different perception of
by trial and error. There may be two or three colour. However, broadly speaking, the
colours which enlarge the colour range and majority of patients are red/green deficient or
make certain colours fluoresce. red deficient in a ratio of three to one. Some
Once the optimum filter is found, an patients are almost totally monochromatic;
appropriate soft contact lens of the same they usually have a macula problem. Few
colour is inserted in the eye (Figure 2). There women are colour defective (0.4%), though
are three intensities to choose from and the when they are, their defects are usually more
tint diameter can be varied (5, 6 or 7mm). intense and complicated than the men’s (8%).
(Naturally, no contact lens should be fitted I usually explain to the patient as follows:
without a full eye examination and contact “Everybody has three colour pigments in
Figure 2 lens work up.) their retinas in an equal ratio of red, green and
ChromaGen lens on the eye The patient is then sent off on a tolerance blue. Colour defective people have a
trial for several hours to see how the lens deficiency in either red or green or perhaps
helps their general colour perception and how both. Also, like dyslexia, there may be a
after having been unsuccessful in the past, the eye reacts to the contact lens. Usually, chance of misinterpretation of the red versus
and a third was able to see the differences in about one in three patients notice an green signals in the brain.
colour of the paints he had been mixing for improvement. “ChromaGen works by changing the level
years and telling his customers not be so A final contact lens is then offered or the of each colour going to the non-dominant
fussy.) patient can have tinted spectacles. To hide the eye. For example, there might be 20% red,
spectacle tint, the lenses are usually mirrored 30% green, 50% blue in the leading eye, but
Fitting or semi-mirrored and look like sunglasses. 50% red, 40% green and only 10% blue in the
The ChromaGen therapy was first devised by These are better for outdoor use, whereas the non dominant-eye, with the ChromaGen filter
David Harris, who carried out his research contact lens can be worn all the time. In most over it. The brain is being sent two
and development at the Corneal Laser Centre cases, a plano contact lens is used and the completely different sets of signals and the
in Clatterbridge. All patients attending for the patient wears his regular spectacles over the confusion caused allows the brain to
therapy must have two eyes, because a colour top. differentiate between colours which had
filter is placed over the non-dominant eye Normal contact lens aftercare procedures previously looked the same. The result is that
whilst the patient observes a colour screen, apply, and the lens needs replacing on a six- the colour range perceived by the colour
such as shown in Figures 1a and b. monthly basis. Some patients, who are defective is increased two or three-fold.
The dominant eye sees the colours as spectacle wearers, may seize the opportunity “Before therapy, the ‘normal’ person
always seen and the non-dominant has its to switch to contact lenses for both eyes. might see 10,000 colours and the colour
colour perception changed dramatically. It Often they have avoided them before, but the defective only 2,000, but after therapy, the
does not matter if the eye is amblyopic or use of the ChromaGen lens shows them how colour defective may have 6,000 colours. The
even divergent. The filters are coloured easy and comfortable contact lenses can be. therapy does not give the colour defective
perfect colour perception, but it does give
them more colours, plus an ability to see
colour differences which they could not see
Table 2 before and more accurate colour naming.
Analysis of 33 patients attending the practice They feel more ‘normal’ and hugely excited
in six months for ChromaGen therapy by their new colour perception ability”.
Type of defect Total Success Failure
No. % No. % Study
I carried out a brief analysis of the first 33
Trichromatic 15 15 100 0 0 patients who came to my practice for colour
deutranopes vision therapy. They were attracted by the
Deutranopes 14 5 36 9 64 national press coverage generated by the
press releases issued by the Corneal Laser
Trichromatic 0 0 0 0 0 Centre.
protanopes Table 2 shows the defects divided into
Protanopes 1 0 0 1 100 four types and gives their success with a
Monochromatic 2 1 50 1 50 ChromaGen lens. There were only two
Extremely 1 1 100 0 0
females and only one protanope. Neither
anomolous trichromatic
female was straightforward. One had severe
Tritanopes 0 0 0 0 0 macular degeneration and VAs of 6/60 - she
was totally monochromatic and, therefore,
Total 33 22 67 11 33 failed to benefit from the therapy. The other
was a 15-year old with almost total loss of
Overall success rate 67% colour perception and VAs of R&L 6/18. She
40 JULY 17 • 1998 OPTOMETRY TODAY
ChromaGen colour vision therapy
benefited greatly with the use of a P3 tint. The effect of changing the lens caused
Success was defined as a patient who some changes in the colours, but also
now wears a ChromaGen contact lens or produced a shimmering sensation. A soft
spectacles on a regular basis and finds that lens was chosen and inserted in my left eye.
their colour vision is helped by its use. The I then went for a walk in Regents Park.
overall success rate was 67%. I first gained an idea of the changes
when I closed my compensated eye. When I
Discussion looked at some traffic lights, the green light
It would seem from the data that the results was now coloured rather than whiteish, but
are severely skewed as a result of the for car driving, distinguishable from red and
majority of patients being deuteranomalous. amber. My walk to Regents Park was
However, the statistics for colour defects interesting in that there was a sort of three-
suggest that I should have seen a few more dimensional, slightly scary effect - but I was
protanomolous patients. However, two thirds told that it would probably be like that to start
of the colour defectives randomly attending with. In the park, I drew two sketches of the
the practice have been helped by ChromaGen flowers. Although the pansy beds came alive,
lenses. You cannot tell what you are going to the first real difference was with the lupins.
get - patients usually just say: “I’m colour The reds of the lupins and the beds of
blind”. However, colleagues considering greenery just jumped out at me (Figures 4 Figure 3
referral should note that 100% of and 5). There were no flowers with my lens How patient I.S. saw the screen shown in
deuteranomalous trichromats (the largest covered; opened, and it was a new world - not Figure 1a
group) were thrilled with the treatment. As only 3D but fluorescent. I kept opening and
soon as the defect gets more severe, then the shutting my eye - it was very enjoyable.
success rate plummets to 36%. I have not I next looked at the sky and saw depth in
seen enough protanopes to make any the clouds, the flatness had gone, I could
conclusions, but I suspect trichromatic imagine the puffiness. Then a helicopter flew
protanopes will get greater than 50% success over and I caught the shimmering rotors,
and be far safer at traffic lights. My patient another first. It disappeared when I closed
who failed was able to see reds far more the eye with the lens in.
brightly, but he found it very disconcerting My return to 7 Devonshire Street, to have
and, after three weeks, stopped using the lens the lens removed, was full of 3D and
preferring not to see red standing out so fluorescence.
bright. Figure 4
Every patient needs to be screened and June 5, 1997 How patient I.S. saw the lupins with (right)
given a trial and even the most unlikely I had the lens fitted on June 5 and after the and without the lens
colour defects might be helped. However, full eye examination and training on how to
you can confidently recommend put the lens in and out, I set off with five
deuteranomalous trichromats, the most hours of wear, to be increased by one hour a
common defect, for ChromaGen therapy. day.
The day was overcast, but I noticed the
Patient feedback depth of colour in the clouds and sky was not
There follows reports from two patients, both there without the lens. It had almost a plain
trichromatic deutranopes. The first is backdrop without the lens, but with the lens
amblyopic in the non-dominant eye - it made a whole new world appeared. I then travelled
no difference to his success. These are back home, noticing mainly the higher
reported descriptions and we have tried to resolution of most coloured hoardings,
reproduce the illustrations provided by the papers etc, resulting from the lens. The reds Figure 5
How patient I.S. saw a bed of shrubs
first. were still fluorescent. (greenery) with (right) and without the lens
That evening I enjoyed some strawberries
Patient I.S. fitted with which came alive in their punnet. I then saw a
ChromaGen contact lens TV programme on tree blossom and the June 6, 1997
“I had seen the article in the Daily Telegraph television picture was in three dimensions; I inserted the lens at 6am and later drove
last March explaining the use of coloured the blossom was jumping out of the screen from Orpington to Farnborough on the M25.
contact lenses in the weaker eye to correct and the colours were alive. I accept that the Again, the morning sky was very different -
colour blindness. I was, therefore, very 3D effect will go as I get used to the lens. The much, much more definition. I was
interested when asked by my nephew if I other area of interest was that I was able to beginning to ignore the lens or was it
would like to try one. distinguish much more clearly the beginning to settle in the eye? The reds were
The first part of the examination was to background pictures. Watching cricket was still alive, but colours now appeared where a
find the best lens to work with. This was much more interesting - the ball was very bland background existed. I was able to read
carried out by viewing a colour VDU with a visible. and see at distances with the lens and glasses
pattern (Figure 3). I removed the lens on the second attempt. off and on.
JULY 17 • 1998 OPTOMETRY TODAY 41
ChromaGen colour vision therapy
I removed the lens on the reduces each time I wear them
second try after six hours. and is now probably down to not
more than a couple of seconds
June 13, 1997 each time I put them on. I can
I am now wearing the lenses for only assume that this is because
10 to 12 hours a day. My the process is a form of re-
morning drive along M25 is education which takes time for
beginning to stabilise in that I the brain to recognise.
am enjoying and accepting The spectacles are amazing
changes. My main enjoyment is as they change the way I see
looking at the clouds. everything. Most colours,
An immense amount of particularly reds and blues, are
detail now visible in the clouds. much brighter and stronger and,
The fluorescence is beginning to surprisingly, seem to have a
reduce, as is the 3D effect. I had greater 3D effect. I have
a long day on the June 11 and especially noticed this when
couldn’t remove the lens and so looking at traffic and warning
it was in for 13 hours, but I had signs, which now seem to jump
no major problems, or even out at me and attract my
minor for that matter. The lens is attention a lot more effectively.
now part of my way of life and I Other colours, such as
have no problems inserting or greens and browns, now have a
removing it. wider range of shades and tones
I am beginning to see ‘new’ which enables me to
colours and associate names differentiate between them a lot
with colours; previously these more easily. When I have been
were just names. out walking through country or
My most enjoyable change wooded areas, colours in the
is the early morning drive scenery are a lot more varied
around the M25 with the cloud and the overall view is not as
formations. The various, bland as before.
numerous colours really make My brother, who is also red
the journey so different and green colour blind, has borrowed
much more enjoyable - the spectacles and his thoughts
therefore, I should keep my eyes on their effects mirror my own,
on the road. with the emphasis on the
increased brightness and
August 21, 1997 variation of colours. Whereas
When I take the lens out, there before everything seemed to
appears to be a residual effect. I contain a lot more shades of
believe that I see more colours grey, the greens and browns now
than I did previously. figure where they didn’t before
The fluorescence and 3D and the other colours are more
effect have almost gone.” prominent.
I would like to thank you for
Letter from patient J.W fitted
. asking me to test your new
with ChromaGen mirrored lenses as they have made a great
spectacles improvement in the way I see
Dear Mr Burnett Hodd things and my appreciation of
I am pleased to report back that them.
my ChromaGen lenses have
been a big success and I will try
to put into words the direct and These two patient reports
indirect effects they have made show why it is wrong to
to my sight. doubt this therapy
When I first put the
- we can at last treat colour
spectacles on, the changes were
not instantaneous but after 10 to deficiency in the majority of
15 minutes, they started to sufferers.
appear. This process of change
42 JULY 17 • 1998 OPTOMETRY TODAY
