Many eye conditions that result in low vision also result in color vision deficiencies. While the most common congenital color defects produce little in the way of performance limitations in and of themselves, the additional loss of sensory information that arises from a color defect for an already compromised visual system could have greater consequences. Conversely, the residual color discrimination that some low vision observers show could provide a viable avenue along which information could be presented to enhance performance on certain tasks dependent upon visual input. This line of reasoning suggested that a useful approach would be: a) to evaluate what residual color discrimination low vision observers display and b) to evaluate what influence the introduction of chromatic contrast might have on specific tasks for normal and low vision observers.
In the evaluation of residual color discrimination, the answers to two complementary questions are sought: 1) What color contrasts does an individual discriminate most poorly, and 2) what color contrasts does an individual discriminate best. To assess the color discrimination of low vision observers, former Lighthouse research investigator Dr. Kenneth Knoblauch and his colleagues at the Institute, modified standard color tests by increasing the size of test elements to make them easier to see by low vision observers. In addition, they developed specialized computer-controlled testing equipment for measuring the color discrimination of low vision observers for stimuli of a variety of sizes. Results to date from ongoing studies using these approaches indicate that many low vision observers do show improvements in color discrimination when tested with larger objects. In addition, results indicate that standard approaches to testing color vision would not have been adequate to indicate the degree of color vision actually present in low vision observers. Future studies will concentrate on modeling the color vision losses experienced by individuals with low vision to provide tools for predicting what color contrasts will be most visible to such individuals. More recently, Drs. Knoblauch and Arditi have produced practical guidelines making color choices that are likely to have good effective contrast for those with low vision (Knoblauch and Arditi, 1993; Arditi and Knoblauch, 1994).
With knowledge of the color contrasts that an individual discriminates best, the degree to which color cues influence performance on specific tasks can be evaluated. An initial study performed by Dr. Knoblauch and his colleagues concentrated on the effect of color contrast on reading performance in normal and low vision observers. Under most practical situations, color contrast was found not to enhance reading performance and in some low vision observers, color, as opposed to luminance or brightness, contrast interfered with reading performance. The reasons why some low vision observers perform more poorly with reading material defined by color contrast are not well understood and will be the subject of future investigations. Other tasks under study for which color might provide a useful cue are visual search and object recognition. Some of these studies were funded by a grant from the National Eye Institute.
A major goal of our color contrast work is the dissemination of simple, comprehensible guidelines for choosing colors that work effectively for all, including those with the acquired color deficiencies that almost always accompany low vision, and those with congenital color deficiencies. We have developed a brochure (Arditi, 1999/2002), that is now in its third edition, that we hope accomplishes this goal. The most recent version of these guidelines is accessible on the internet Effective Color Contrase.
Arditi, A. (1999/2002). Effective color contrast: Designing for people with partial sight and congenital color deficiencies. New York: Lighthouse International.
Arditi, A., & Knoblauch, K. (1994). Choosing effective display colors for the partially sighted. Society for Information Display International Symposium Digest of Technical Papers, 25, 32-35.
Arditi, A., & Knoblauch, K. (1996). Effective color contrast and low vision. In R. Cole & B. Rosenthal (Eds.), Functional assessment of low vision (pp. 129-135). St. Louis, MO: Mosby.
Knoblauch, K. (1993). A note on the theory of wavelength discrimination in tritanopia. Journal of the Optical Society of America A, 10, 378-381.
Knoblauch, K. (1995). Dual bases of dichromatic color space. In B. Drum (Ed.), Color vision deficiencies XII (pp. 165-176). The Dordrecht, Netherlands: Kluwer Academic Publishers.
Knoblauch, K., & Arditi, A. (1993). Designing effective color contrasts for the partially sighted. Lighthouse Research Institute Technical Report VR02. New York: Arlene R. Gordon Research Institute of The Lighthouse Inc.
Knoblauch, K., & Arditi, A. (1994). Choosing color contrasts in low vision: Practical recommendations. In A. C. Kooijman, P. L. Looijestijn, J. A. Welling, & G. J. van der Wildt (Eds.), Low vision: Research and new developments in rehabilitation (pp. 199-203). Amsterdam, The Netherlands: IOS Press.
Knoblauch, K., Arditi, A., & Szlyk, J. (1991). Effects of chromatic and luminance contrast on reading. Journal of the Optical Society of America A, 8, 428-439.
Knoblauch, K., Bieber, M., & Werner, J. S. (1996). Assessing dimensionality in infant color vision. In F. Vital-Durand (Ed.), Infant vision, Oxford, England: Oxford University Press.
Knoblauch, K., & Fischer, M. (1993). Low vision issues in color vision. In B. P. Rosenthal, & R.G. Cole (Eds.), Problems in optometry: A structured approach to low vision care: Vol. 3., (No. 3), (pp. 449- 461). Philadelphia, PA: J. B. Lippincott.
Knoblauch, K., Fischer, M., Robillard, N., Grunwald, I., & Faye, E. (1991). The effect of test element size on performance of the D-15 in age-related maculopathy and congenital color deficiency. In B. Drum, J.D. Moreland, & A. Serra (Eds.), Color Vision Deficiencies X. Proceedings of the International Symposium, Cagliari, 1989, Documenta Ophthalmologica Proceedings Series 54 (pp. 37-45). Dordrecht, The Netherlands: Kluwer Academic Publishers.
Knoblauch, K., & Maloney, L. T. (1996). Tests of the indeterminacy of linear chromatic mechanisms from chromatic discrimination data. Vision Research 36 (2), 295-306.
Knoblauch, K., & McMahon, M. J. (1995). Discrimination of binocular color mixtures in dichromacy: Evaluation of the Maxwell-Cornsweet conjecture. Journal of the Optical Society of America A, 12 (10), 2219-2229.