Overview
IshiharaTest.com is an online color vision screening tool inspired by the classic Ishihara Color Vision Test, first introduced by Dr. Shinobu Ishihara (University of Tokyo, 1917).
Our system generates pseudoisochromatic plates algorithmically, following the visual principles of the original printed editions published by Kanehara Shuppan (Tokyo, 38-plate edition, 1972). Plates are generated on the fly rather than scanned from copyrighted originals.
Scientific Background
Color vision deficiencies (CVD) — particularly protan (L-cone deficiency) and deutan (M-cone deficiency) types — are identified by the subject's inability to distinguish patterns hidden in randomized color noise.
- Classic Ishihara plates use a pseudoisochromatic design: dots of different colors form a figure that is only clearly readable by observers with normal color vision.
- Observers with CVD perceive the figure and background as similar, so the pattern becomes invisible or indistinct to them.
- Our generator reproduces this effect through algorithmic dot placement and a curated palette of medically-informed colors inspired by traditional Ishihara color families.
Generation Algorithm
Each plate consists of approximately 1,200 circular dots varying in radius, color, and position. The figure (number) is formed by dots of one color family embedded within a background of a contrasting color family.
Plate Parameters
- Approximately 1,200 circular elements per plate
- Radius range: 2–8 px (varies with difficulty level)
- Randomized spatial placement for natural appearance
- Poisson disc sampling ensures even dot distribution
Validation and Limitations
This tool is a screening aid, not a clinically validated diagnostic. It has not undergone formal validation against certified physical Ishihara plates or controlled clinical testing. Results should be interpreted as a preliminary indication only.
References
- Ishihara, S. Tests for Colour-Blindness. Handaya, Tokyo: Hongo Harukicho (1917).
- Ishihara, S. Tests for Colour-Blindness (38-Plate Edition). Kanehara Shuppan, Tokyo (1972).
- CIE 015:2018 – Colorimetry, 4th Edition. International Commission on Illumination (CIE).
- Brettel, H., Viénot, F., & Mollon, J. D. (1997). Computerized simulation of color appearance for dichromats. JOSA A, 14(10), 2647–2655.
- Waggoner, T. L. (2002). Color Vision Testing Made Easy. Good-Lite Company.
- Pokorny, J., Smith, V. C. (1976). Evaluation of cone spectral sensitivities. Vision Research, 16(10), 1049–1055.