How the Eye Works

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=82 BGCOLOR="#003333" TEXT="#F7F7FF"> <div> <FONT SIZE="5" COLOR="#FFFFFF" FACE="Arial" ><B>Hermitage Eye Care</B></FONT><B>     |   </B><B>  </B><A HREF="index.htm" TARGET="_top" TITLE="Hermitage Eye Care"><U><B>home</B></U></A></div> <div> <A HREF="id28.htm" TARGET="_top" TITLE="Glaucoma"><U>Glaucoma</U></A>   |   <A HREF="id29.htm" TARGET="_top" TITLE="Macular Degeneration"><U>Macular Degeneration</U></A>   |   <A HREF="id30.htm" TARGET="_top" TITLE="Cataracts"><U>Cataracts</U></A>   |   <B>How the Eye Works</B></div> <div> </div> </td> </tr><tr> <td valign="top" width=210 BGCOLOR="#003333" TEXT="#F7F7FF"> <div> <IMG SRC="070c68f0.png" border=0 width="198" height="143" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </td> <td valign="top" height=398 BGCOLOR="#006633" TEXT="#F7F7FF"> <div> <I>How the Eye Works</I></div> <div>    Vision begins when light rays are reflected off an object and enter the eyes through the cornea, the transparent outer covering of the eye. The  <A NAME="cornea_1"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>cornea bends, or "refracts" the rays that pass through a round hole called the pupil.</div> <div>    The colored part of the eye that surrounds the pupil is called the iris. The iris opens and closes to regulate the amount of light passing through. In dim light, the iris dilates to open the pupil and allow more light to enter the eye. In bright light, the iris constricts to close the pupil.</div> <bR> <div>    The light rays then pass through the lens of the eye, which flexes to further focus the light rays on the retina in the back of the eye. The retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones. Cones are concentrated in the center of the retina in an area called the macula. In bright light conditions, cones provide clear, sharp central vision and detect colors and fine details.</div> <bR> <div>    Rods are located outside the macula and extend all the way to the outer edge of the retina. They provide peripheral, or side vision. Rods also allow the eyes to detect motion and help us see in dim light and at night.</div> <bR> <div>    Rods and cones convert light into electrical impulses that the optic nerve sends to the brain. The brain then interprets these impulses into an image.</div> <bR> <div>    The eye system is a delicate and complicated part of the human anatomy. All parts of the eye and many parts of the overall body affect your ability to see.</div> <bR> <div>    In a comprehensive eye health and vision examination, the health of your eye is evaluated from cornea to retina.</div> <bR> <div>    The health of the  <A NAME="cornea"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A>cornea can suffer from dehydration, ulcers, infections, age-related degeneration, and injuries. Contact lens wearers need to be especially aware of damage to the cornea that can be caused by poor wearing and cleaning habits.</div> <bR> <div>    Irrigation of the eye by the tear duct system is critical to good external eye health and comfort. Blocked drainage ducts can result in frequent eye infections from stagnant pools of tears. Tears low in protein content can result in excessive watery eyes and dehydration of the eye.</div> <bR> <div>    Cataracts can cloud the lens of the eye, reducing the amount of light that gets through to the retina. The lens also becomes less flexible with age, resulting in the vision condition called presbyopia.</div> <bR> <div>    The retina of the eye is a delicate structure that can be damaged by trauma to the eye and damage to the delicate blood vessels of the eye caused by systemic diseases such as high blood pressure and diabetes. Age-related macular degeneration (ARMD) is an irreversible disease of the eye caused by thinning of the retina. ARMD affects the cones of the eyes and is one of the leading causes of blindness in people over age 60.</div> <bR> <div>    The nerves that transmit electrical impulses from the retina can become damaged by glaucoma. Glaucoma results from increased pressure in the eye from poor drainage of the fluid of the eye. This pressure bears down on the delicate nerves of the eye, causing permanent nerve damage. The onset of glaucoma is subtle and requires early intervention for successful treatment.</div> <bR> <div>    Systemic diseases such as diabetes can have a devastating affect on eye health. In fact, diabetes is the leading cause of blindness among working-age Americans. All diabetes and medical organizations recognize and promote the importance of frequent eye health examinations for diabetic patients.</div> <bR> <div>    In a comprehensive eye health and vision examination from Dr. Hammond, the health of your eye is evaluated including test for glaucoma, cataracts, and retinal diseases.  Vision is tested up close and in the distance.   At Hermitage Eye Care, you can rest assured that the exams are thorough and comfortable.</div> </td> </tr></table></body>