What is the funcrion of the retina and the iris?

Retina"s function is image formation.The iris regulates Amt.

of light that enters the eye.

What is the funcrion of the retina and the iris?
the iris is like an aperture on a camera and is used to control the amount of light that enters the eye. The retina captures the light and sends it to the brain for processing, kind of like film in a camera
Reply:The iris, visible through the clear cornea as the coloured disc inside the eye, is a thin diaphragm composed mostly of connective tissue and smooth muscle fibres. Unlike the common belief, the iris does not change colours in an adult (except in the case of certain pathologies, such as pigment dispersion syndrome), although it may appear to do so depending upon the colour of clothing a person is wearing. Moreover, the colour(s), texture, and patterns of each person’s iris are as unique as a fingerprint. The iris acts like the shutter of a camera. The pupil—the (normally) circular hole in the middle of the iris, comparable to the aperture of a camera—regulates the amount of light passing through to the retina at the back of the eye. As the amount of light entering the eye diminishes (such as in the dark or at night), the iris dilator muscle (which runs radially through the iris like spokes on a wheel) pulls away from the centre, causing the pupil to “dilate” and allowing more light to reach the retina. When too much light is entering the eye, the iris sphincter muscle (which encircles the pupil) pulls toward the centre, causing the pupil to “constrict” and allowing less light to reach the retina.

When light enters the eye, it first passes through the transparent cornea. Its spherical shape focuses the light through the pupil to the lens. The lens and vitreous humour then focus the light to converge and cross at a point on the retina. This crossing causes the image produced on the retina to be an inverted (upside down) version of the image actually being viewed. The signal is sent through the optic nerve to the visual cortex of the brain where the image is then flipped again and perceived in the upright position. If either the cornea or the lens are misshapen or damaged, the image will be focused in front of or behind the retina, and vision will be blurred.

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