Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1996-10-15
1998-09-01
Dang, Hung X.
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351246, A61B 310, A61B 300
Patent
active
058018085
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method and an apparatus for determining spectral sensitivity parameters of colour-sensitive receptors in the eye.
BACKGROUND ART
The human eye is able to detect electromagnetic radiation in the wavelength range of visible light, which extends from approx. 380 nm to 780 nm. The light efficiency of human vision as a function of wavelength is defined by the so-called visibility curve. In the human eye there are three colour-sensitive receptors (pigments) assuring colour vision, called protos which is sensitive to red, deuteros which is sensitive to green, and tritos which is sensitive to violet. Sensation of the yellow colour is aroused by simultaneous stimuli of the protos and the deuteros. Simultaneous stimuli of the tritos and the deuteros causes the vision of the colour turquoise, while simultaneous stimuli of the tritos and the protos leads to the sensation of the colour purple. Other transitional shades of colours are produced by simultaneous stimuli of the three receptors with different intensities.
Diagrams of spectral sensitivity of the protos, the deuteros and the tritos for people having normal (average) colour vision are well known (FIG. 1). It is known furthermore that the sensitivity of colour-sensitive receptors grows substantially if the intensity of lighting decreases and it drops significantly if the lighting intensity is higher. This kind of phenomenon is called adaptation, which takes place in each receptor independently of each other to a different extent, if the intensity of lighting does not change in the total spectrum range, but has a lower influence on certain receptors and higher influence on others. This is called chromatic adaptation (Leo M. Hurvich: Color Vision, Sinauer Associates Inc., Sunderland, Mass., USA, 1981, pp. 196-200).
It is well known that people do not have exactly the same colour vision. According to the current state of medical art, there are so-called colour blind people who only see two basic colours instead of three. If there is a lack of protos receptors, the colour blind person is called protanop, in lack of deuteros receptors, we speak about a deuteranop person, and if tritos receptors are missing, the person is called tritanop. Additionally, there are people with anomalous colour vision suffering in parachromatism. Although they have all the three receptors, they have a sensation of colours which deviates from that of a normal person. The most frequent form of anomalous colour vision appears as red-green parachromatism. People suffering in red-green parachromatism do not recognize pseudo-isochromatic tables (known in practice as dotted figures) and they are not able to distinguish between red, yellow and green signals used in traffic control. Different types of parachromatism are described on pages 222-269 of the textbook of Leo M. Hurvich mentioned above.
Since people suffering in parachromatism are handicapped in numerous walks of life vis-a-vis individuals of normal colour vision, various approaches have already been recommended for correcting the error of colour vision. In the international application No. PCT/HU93/00045 filed on 18 Aug. 1993, the difference between an eye with colour vision to be corrected and the eye with normal colour vision is compensated by a colour filter of a transmission characteristic appropriately selected on the basis of the abnormal spectral sensitivity of the protos, deuteros and tritos receptors of the eye with a colour vision to be corrected. Consequently, to select the colour filter, the spectral sensitivity curves of the person suffering in parachromatism must be measured and the displacement of the curves along the wavelength must be determined.
It is known that the spectral sensitivities of receptors in the eye can be determined by individual measurements (W. B. Marks, W. H. Dobbelle, E. F. Mac Nichol: Visual Pigments of Single Primate Cones, Science, Vol. 143, March 1964). Rushton performed microspectrographic measurements on eyes of living human beings and monkeys (W. A
Abraham Gyorgy
Wenzel Gottfriedne
LandOfFree
Method and apparatus for determining spectral sensitivity parame does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for determining spectral sensitivity parame, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for determining spectral sensitivity parame will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-275474