Posts Tagged ‘colour vision’
Nikolay Lamm blogs:
[These photos] hypothesize what human and cat vision looks like. Human vision is up top and cat vision is below.
- Cats have a visual field of 200 degrees compared to humans 180 degrees.
- Peripheral vision for humans is 20 degrees each side. This is represented by the blurriness.
- Peripheral vision for cats is 30 degrees each side. This is represented by the blurriness.
- Cats can see 6-8 times better in dim light than humans due the high number of rods and because of their elliptical pupil, large cornea and tapetum.
- Our retinas have many more cones than cats, especially in the area of the fovea (which is all cones and no rods). This gives us fantastic day vision with lots of vibrant colors and excellent, detailed resolution. Dogs and cats have many more rods, which enhances their ability to see in dim light and during the night. They have no fovea, but an “area centralis” that, though has more cones than other areas of the retina, still has more rods than cones. The increase in rods also enhances their “refresh rate”, so that they can pick up movements much faster (very helpful when dealing with small animals that change direction very quickly during a chase). These differences also help them to have great night vision, an excellent ability to pick up and follow quick movements, but at the cost of less vibrant color, with less detailed resolution. Interestingly, this also means that humans have the ability to see very slowly moving objects at speeds 10 times slower than cats (that is to say that we can see very slow things move that would not appear to be moving to a cat).
From Science (subscription required):
Squirrel monkeys can now see your true colors, thanks to gene therapy. Researchers have given the colorblind primates full color vision as adults by injecting their eyes with a human gene. The result raises questions about how the brain understands color, and it could eventually lead to gene-therapy treatments for colorblindness and other visual disorders in humans.
Seeking a possible treatment for the human condition, vision scientist Jay Neitz and colleagues at the University of Washington, Seattle, assembled six adult squirrel monkeys, four colorblind males and two female controls. The researchers tested them daily for a year, using a computer program that presented the primates with colorful clumps of dots on a screen of similarly varied gray dots (see video). The results established each monkey’s color vision, revealing that the female controls could see colors as a normal human would, while the male monkeys could not distinguish green and red clumps from the gray background. The team then injected the retinas of two of the colorblind monkeys with a virus that introduced the human gene for the red-detecting pigment in cone cells.
Twenty weeks after the gene therapy, however, the monkeys began to spot red and green dots in the computer color tests, and soon after they were regularly acing the trials. “That’s when we broke out the champagne,” says a still-surprised Neitz. Now, 2 years later, the monkeys remain able to distinguish all colors, almost on par with their female counterparts. Neitz attributes the monkeys’ adaptability to the fact that colorblind animals still have color-processing circuitry in their brains. The introduced gene simply gives them the ability to feed new information into the circuitry, “hijacking” a pathway previously used by blues and yellows for reds and greens as well.