MadSci Network: Anatomy

Re: Cones and rods (Eyes)

Area: Anatomy
Posted By: David Schneider, Faculty Health Sciences
Date: Sat Aug 24 22:53:14 1996
Message ID: 836289510.An

Dear Robert:
Thanks for the question. The eye is an amazing structure indeed. The light sensitive part of the eye is called the "retina". It is in the retina that we find the two types of cells mentioned in your question, i.e. rods and cones. Because these receptors are light sensitive, they are called "photoreceptor cells". It is the cone cells that provide us with color vision(the way I remember it is Cones for Color).

Cone cells come in three different varieties. Each is sensitive to one of the three primary colors of light: red, blue and green. Most forms of color blindness are genetic diseases that occurs more commonly in men. People who are color blind lack usually one or two of these type of cones. Most color blind individuals can see colors but are unable to detect shades of the particular cone colors they are missing. For example, a person who is missing red sensitive cones would be color blind to the color red only, not all colors.

The rod cells are responsible for contrast vision, or more acurately dim light vision.The loss of rod cells would definitely affect visual acuitiy but not greatly as most of the most sensitive parts of the retina contain only cone cells. These individuals would also have problems with seeing at night, or in dim light. This would be a very rare condition indeed. Thanks for your question.

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