Various parts of the eye work together to catch, focus and process light to make vision possible. When the eye is open, light first passes through the cornea, the eye's transparent outer windshield. The cornea takes a wide spectrum of light and bends it through the pupil, a round opening in the iris, or colored part of the eye. Directly behind the pupil is the eye's natural lens. It fine focuses the light directly onto the retina, a photosensitive membrane that lines the back of the eye. The retina then changes the light spectrum into electrical impulses and sends them through the optic nerve to the processing center of the brain where vision is interpreted.

Nearsightedness

If you can see objects nearby with no problem, but objects at a distance are more difficult, you may be near- or shortsighted. This is also commonly referred to as myopia.

Myopia most often occurs because the eyeball is too long. Another cause of myopia is when the cornea is too curved. Our ability to see begins when light enters the eye through the cornea. The shape of the cornea, lens and eyeball help bend light rays in such a manner that light is focused into a point precisely on the retina. However, if you are nearsighted, the light rays from a distant point are instead focused at a point in front of the retina. The light will only focus at that one point and will have defocused again by the time it reaches the retina.

Myopia most commonly occurs between the ages of 8 to 12 years. The degree of myopia increases as the body grows and then stabilizes in adulthood.

Farsightedness

If you can see objects at a distance clearly but have trouble focusing well on objects close up, you may be farsighted. This is also referred to as hyperopia.

Hyperopia will occur when the eyeball is too short or the cornea has too little curvature. If you are farsighted, the eyeball is too short and, therefore, light is focused at a point behind the retina. Since the light is not focused when it hits the retina, vision is blurred. To diagnose hyperopia, a comprehensive eye health exam that checks both near and far vision is necessary.

Whether you have been diagnosed with nearsightedness or farsightedness, a comprehensive eye examination at the recommended intervals will ensure that minor changes in vision are diagnosed and treated early. This will help to ensure that you have the clearest vision possible.

Astigmatism

Astigmatism is a vision condition that occurs when the surface of your eye, the cornea, is slightly irregular in shape. This irregular shape prevents light from focusing properly on the back of your eye, the retina. As a result, your vision may be blurred at distances.

People with severe astigmatism will usually have blurred or distored vision, while those with mild astigmatism may experience headaches, eye strain, fatigue or blurred vision at certain distances.

Most people have some degree of astigmatism. Almost all levels of astigmatism can be optically corrected with properly prescribed corrective lenses or laser vision correction.