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Posts Tagged ‘legal blindness’

A powerful fixed lens that refracts light, your cornea can be surgically reshaped using laser eye surgery to help you see nature’s diaphanous “winged flower.” A change of one one-hundredth of an inch (fifty microns) in the thickness of this transparent curved lens (which is all that is removed using laser eye treatment surgery) can easily make the difference between legal blindness and excellent sight. Not a simple structure that merely protects your eye, your corneal lens concentrates, or bends, light inward to focus the butterfly’s image on the receptors of your “retina”. Hugging the back of the inside of your eyeball, your multi-layered retina – rather like the film in a camera – is exquisitely sensitive to light. Composed of neurological tissue, your retina, which is designed to capture and transmit images, contains the “photoreceptors” – the “rods” and the “cones” that are named for their shape. Photochemically responsive to visual stimuli, they make up an important part of the light-gathering neural circuitry of your brain.

As the dazzling reflected light touches the tears that coat the outside of your cornea, its wet surface shines with the brilliance of a smooth polished jewel. This thin tear film covers your self-cleaning eye even when you aren’t crying. Bending the light rays ever so slightly inward toward your eye’s dark entrance, known as the “pupil,” your tears – which are vital to the health of your cornea – keep it supplied with dissolved oxygen from the air. With every blink of your eyelid, the watery three-layered tear film bathes your eye’s window – which has no blood vessels – with oily lipids, dissolved salts, glucose, and mucus. Your tears act as a buffer against minor irritations such as smoke and fumes and contain an antibacterial enzyme that discourages infections. Since your cornea is richly supplied with nerves, the tiniest speck of dust will cause you to blink and tear.

With its angle of attack slightly altered by your tears, the radiant sunlight rebounding from the Monarch now darts through each of the five crystal-clear layers of your cornea. Only about five to seven cells thick, the outermost protective surface of your fixed lens, called the “epithelium” by doctors, helps guard your eye from dangerous invading microorganisms. Your epithelium possesses marvelous regenerative powers. Its cells are naturally replenished about every seven days.