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The human eye is truly a miracle of engineering, making it possible to see objects at a wide variety of distances, and working in perfect harmony with the brain to accurately interpret the objects we view. Summary of Vision Light travels from objects to the eye. The cornea is clear and curved and allows the light to enter. Being curved, it bends the light towards a focus. The lens, behind the iris, bends it more and in a 20/20 eye it now focuses clearly on the retina. Light-sensitive cells in the retina receive the image information in the light and convert it to nerve information. A large nerve runs from the retina to the brain and carries this data to the brain’s vision center at the back of the head. The brain interprets it and finds words for it. Parts of the Eye • Cornea: The clear front part of the eye, curved and responsible for bending light as it enters. • Iris: The colored part of the eye • Pupil: The opening in the center of the iris which admits light further into the eye to the lens. • Anterior Chamber: Lies between the cornea and the iris and is filled with a clear watery substance known as the aqueous humor. It flows around the lens and iris and keeps them moist. • Lens: A clear structure behind the iris. Our eyes have a wonderful way of adjusting focus called “accommodation”. For example, when reading a book, you can see the fine print. If you look up and across the room, you can immediately see objects further away because the lens changes its curvature, automatically adjusting your focus. Its curvature is controlled by the ciliary muscles which form a circular structure around it. When they contract the lens becomes steeper and gives clear close vision. When they relax the lens flattens to give clear distance vision. • The Vitreous: A gel that fills the large posterior chamber of the eyeball, behind the lens and in front of the retina. The vitreous is clear to allow light through on its way to the retina. • Retina: If you have ever used a non-digital camera, you know that the film inside is responsible for recording pictures. The retina is like film and lines the inside back surface of the eyeball. In its center it has an area of highly concentrated cells called cones, which perceive details and color and give us our central vision – what we are focusing on directly. Towards the retina’s periphery are fewer cones and more cells called rods which give us night vision and peripheral vision. Did you know so many processes worked together automatically to enable you see? Of course, many people experience vision disorders that distort perfect vision. Sophisticated vision correction procedures such as LASIK and PRK have released millions of people from dependence on glasses or contact lenses. If your vision is less than perfect, the ophthalmology team at the Laser Eye Center of Silicon Valley offers the latest diagnostics and progressive procedures to restore your best vision.
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