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Chromagen Lenses and Abnormal Colour Perception

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Chromagen Lenses and Abnormal Colour Perception S Afr Optom 2011 70(2) 69-74 Chromagen lenses and abnormal colour perception O Matthew Oriowo* and Abdullah Z Alotaibi† *Department of Optometry, Faculty of Health Sciences, University of Limpopo, Turfloop Campus, Private Bag X1106 Sovenga, 0727 South Africa †Department of Optometry, College of Applied Medical Sciences, King Saud University, PO Box 10219, Riyadh, 11433 Saudi Arabia < [email protected]> Received 26 October 2010; revised version accepted 16 May 2011 Abstract pants comprised two subjects with protanomaly, two with protanopia, five with deuteranomaly, and Background: The Chromagen lens system compris- two with deuteranopia. Amongst the two female es of tinted spectacle or contact lenses, each with a participants, one subject showed deuteranomaly, specific colour wavelength filter which controls the and one showed protanomaly. Different types of spectra of the light entering the eye. This study in- Chromagen spectacle lenses displayed some lev- vestigated whether spectacle-mounted Chromagen els of colour vision enhancement depending on lenses would enhance colour perception in individ- type of CVD. uals with abnormal colour vision. Conclusion: The findings support the notion that Methods: The Ishihara colour test was used to chromagen lenses could enhance colour vision test for colour vision deficiency (CVD) and also perception in some cases of red-green colour vi- to evaluate the effect of the Chromagen spectacle sion defects. Clients with CVD should be man- lens on colour perception in 13 subjects. An Oculus aged on an individual case basis. (S Afr Optom Anomaloscope was used to confirm and sub-classi- 2011 70(2) 69-74) fy the types of CVD. Subjects comprised of school age children from the Riyadh area in Saudi Arabia. Key words: Chromagen lenses, colour vision de- Results: The distribution amongst the male partici- ficiency, Ishihara colour test, anomaloscope Introduction of the problem until it is detected during a routine or screening eye examination. This can sometimes be Individuals with abnormal colour vision may sim- a considerable shock, especially if the subject is en- ply have a reduced sensitivity to certain colours, which gaged in a career making decision where the desired appear rather muted and lack natural colour vibrance. career involves making colour based judgements1. For However, this reduced sensitivity can be very sig- example, traffic lights would generally look different nificant, with the affected person having considerable to people with red-green CVD. However, most driv- difficulty discriminating amongst even quite marked ers with CVD would judge traffic lights based on the differences in shades (hues) of a given colour1. Con- position of the lights and rarely present with problems versely a patient may have such a minor colour vision in identifying the traffic light indicators. The several deficiency that he or she may be completely unaware daily challenges faced by individuals with CVD un- * BSc(Hons)Optom MSc PhD FAAO †BSc(Hons)Optom MSc PhD 69 The South African Optometrist ISSN 0378-9411 S Afr Optom 2011 70(2) 69-74 O Matthew Oriowo and Abdullah Z Alotaibi -Chromagen lenses and abnormal colour perception derscore the significance of colour vision enhance- the system will not work if the same coloured lenses ment ophthalmic aids to individuals requiring such are used in both eyes11. aids. One type of colour vision enhancing aid is the However, despite the widespread promotion and Chromagen lens system. prescribing of the Chromagen lens system, there still The most common forms of inherited CVDs are the exists a dearth of information in peer-reviewed sci- red/green types with the blue defects occurring very entific literature regarding the lens5. The Chromagen rarely in inherited form. Complete achromatopsia - a lens system in both contact lens and spectacle lens complete lack of colour vision in which an individu- forms, uses filters to make comparative changes in the al can only see shades of grey, is also very rare. The brightness of coloured objects, thus enhancing colour prevalence of both congenital blue defects and achro- perception. It should be noted that the concept of as- matopsia is estimated1-3 at a frequency of 1:30300, sisting colour perception in individuals with CVD, affecting males and females equally4. In humans, col- utilizing tinted lenses was first proposed in 1837 by a our vision sensations are produced by different com- German scientist, namely August Seebeck who wrote binations of the primary colours: red, green and blue. about the possibility to correct colour vision defi- In terms of terminology, deficiencies in colour vision ciency with some sort of coloured lenses6. Historical may result from a partial (-anomaly) or complete (- reviews regarding the development of coloured oph- anopia) inability to perceive any of the primary col- thalmic lens aids for CVD are available in the litera- ours. According to the deficient or abnormal cone pig- ture7-11. ments, colour blindness may be classified into protan Every colour defective individual has a different (red), deutan (green) and tritan (blue) types. colour perception level. The results of Swarbrick et Normal colour perception has a significant impact al5 suggest that deutan subjects are likely to show on optimal educational, professional, and social ac- greater improvement with Chromagen lenses, than tivities/performance. Any assistive device that can protan subjects using a colour test such as the Ishi- help those with abnormal colour perception would be hara colour plates. Also, Richer and Adam9 were of beneficial. A currently available assistive device that the opinion that deutan subjects are likely to derive has been promoted commercially for colour percep- more useful luminance information from the use of a tion enhancement in clients with abnormal colour vi- red filter, while protans may be more reliant on chro- sion is the series of Chromagen spectacle or contact maticity cues9. The objective of the present study was lenses. A survey of the ophthalmic literature shows to investigate the effect of the Chromagen lens on the that experimental investigation regarding the use of colour vision of Saudi Arabian school children with the Chromagen lens in improving the colour percep- abnormal colour vision perception. tion has not been fully explored5-11. The Chromagen lens system was developed by David Harris in Eng- Methods land, and has been widely promoted particularly in the Participants ranged between 8 and 19 years of age United Kingdom5. The Chromagen lens system com- and were randomly selected from schools in Riyadh prises of lenses, each with a wavelength filter which city. Children were screened for colour vision defects controls the spectra of the light entering the eye. The and the results are reported elsewhere by the same Chromagen lens tints are available in seven hues (ma- authors12. Colour vision deficient subjects and their genta, pink, violet, yellow, aqua, orange and green), parents were questioned about any history of previous and most tints are available at light, medium and dark medical or ocular disease or long-term use of medica- densities. The question is ‘how does the Chromagen tion to rule out acquired colour defects. Near visual lens system work?’. The CVD patient uses an appro- acuity for all subjects was normal. Subjects with any priate tinted lens in one of the eyes, usually the non evidence or history of ocular pathology were exclud- dominant eye. In this case both eyes actually see dif- ed. Informed consent was obtained from all subjects. ferent colours and because of that the brain can ex- The study received the appropriate approval from the tract some other information out of certain colours. King Saud University College of Applied Medical Patients can also use two different tints in each of Science Research Committee, and the protocol for their eyes. This depends very much on patient’s per- the research project followed the tenets of the Hel- sonal impression and choice. It should be noted that sinki declaration. Colour vision was tested using the 70 The South African Optometrist ISSN 0378-9411 SS Afr Optom 2011 70(2) 69-74 O Matthew Oriowo and Abdullah Z Alotaibi -Chromagen lenses and abnormal colour perception Ishihara 24 plate colour test (at a reading distance of instrument program; and was required to evaluate approximately 60 - 70 cm from subject’s face), under them as being identical or different by pressing the stable non-flickering fluorescent light with a mini- equal button (on the right of instrument) or unequal mum illumination of 280 lux. The minimum illumi- button (on the left of instrument). For the screening nation of 280 lux has been described to be adequate mode, it is not necessary that the subject undertakes for valid colour vision testing13, 14. The Ishihara is a a colour adjustment in the upper mixed colour field, generally accepted method for clinical colour screen- therefore the subject was instructed to use only the ing and gross detection of congenital red/green col- lower knob. The results obtained with the anomalo- our defects by investigators15-19. The Ishihara colour scope enable the researchers to classify the subjects plates were held 60 - 70 cm from the subject and tilted as being normal or having a protan or deutan defect. so that the plane of the page was at right angles to the Subjects were then further sub-classified into pro- subject’s line of vision. tanopes (dichromats), protanomalous trichromats, All the tests were conducted under binocular view- deutanopes and deutanomalous trichromats with the ing conditions. Each subject was asked to read the anomaloscope. numbers on the first 13 plates, and describe what he The numbers of correct responses with the Ishihara or she could see on pages 14 and 15 with five sec- colour plates without and with Chromagen lens type onds per plate allowed. The test was performed twice employed were determined, and the percentage level for all subjects.
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