The healthy eye works very much like a camera. Light passes through a series of lenses in the front of the camera, focusing on the film in the back of the camera. In the eye, light passes through the cornea, lens, and vitreous gel, ultimately focusing on the retina which works like the film in a camera. Information gathered by the retina is then sent to the brain via the optic nerve.
The retina is the nerve layer that lines the inside back wall of the eye. Blood is supplied to the retina by the retinal artery which enters the eye through the optic nerve before branching into smaller blood vessels and eventually into microscopic capillaries. Blood is collected by retinal veins that exit the eye through the optic nerve. These veins are thicker and darker than retinal arteries.
Located in the center of the retina is the sensitive macula which provides central vision. When looking directly at an object, the macula allows us to see fine detail. This sharp straight-ahead vision is necessary for driving, reading, recognizing faces, and detailed work such as sewing. The majority of the retina lies outside the macula, providing peripheral or side vision.
Many serious eye conditions are caused by problems with the vitreous. Vitreous gel, a clear substance that fills the eye cavity, is attached to the retina. Jelly-like in consistency, it contains strong strands of protein. With age, vitreous gel slowly liquefies, allowing protein strands to clump together. This condition often creates liquid-filled pockets containing particles that look like specks or lines in the vision. Many patients view these particles as floaters, which often become more noticeable with age.