The ciliary body secretes a fluid called aqueous humor other than the shape of the lens. This fluid flows through the anterior chamber and posterior chamber of the eye. The fluid remains constant and that is produced and leaves the eye through a canal which carries it into the bloodstream. Vitreous chamber is the other cavity of the eye, which is a major region behind the lens which is filled with soft, jelly-like material. This vitreous humor regulates the shape of the eyeball and is not perfectly formed again. Blindness can be caused due to escape from the eye. To further refract light rays, both these humors (aqueous and vitreous) function.
The thin, delicate and sensitive nerve layer of the eye is retina. This retina is a layered structure with many layers of neurons interconnected by the synapses. Light energy, which is in the form of waves travels through the eye, it is refracted by the cornea, lens and fluids. Cone-rod dystrophy explains a number of diseases where the loss of vision is caused by the deterioration of cones or rods in the retina. The light focuses on sensitive receptor cells of the retina which are called the rods and cones. There are nearly 6.5 million cones and 120 million rods in the retina. These cones are mainly found in the central area of the retina. Rods are super-sensitive; cones are most useful in normal and bright light. These cones are responsible for color and central vision. The cones are of three types and each type is stimulated by one of the primary colors in red light, green light or violet light. Generally in most of the cases of color blindness affect either the green receptors or red receptors, so that the two colors cannot be distinguished from each other. These rods function at reduced levels of light and are merely responsible for peripheral vision. Sensitivity of the rod is shifted towards shorter wavelengths when compared to day wavelength.
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