Disorders of Visual Acuity
The ability of the eye to focus clearly on objects near and far involves several structures in the eye, but it all begins with the shape of the eye and the role of the cornea. The primary disorders of visual acuity are myopia, hyperopia, astigmatism, and a condition known as keratoconus.
Myopia, also known as nearsightedness, is a condition in which a person can see near objects more clearly than distant objects.
Myopia is usually the result of a larger than normal eye, causing light rays from distant objects to focus before they reach the retina. This results is blurred vision. A tendency for myopia may be inherited; frequent or prolonged near work may influence its progression. It is typically detected in school-age children, may worsen during adolescence, and generally stabilizes between the ages of 20 and 40 years of age.
Symptoms include blurred vision and an inability to see distant objects clearly.
Treatment options include eyeglasses, contact lenses, laser vision correction and INTACS.
Hyperopia, also known as farsightedness, is a condition in which a person can see distant objects more clearly than near objects.
Hyperopia usually occurs when an eyeball is smaller than normal, causing light rays from near objects to not focus properly on the retina at the back of the eye. The result is blurred vision. Babies and young children tend to be slightly hyperopic. As the eye grows and becomes longer, hyperopia generally decreases. Presbyopia, a condition with similar symptoms, is related to changes in the lens that is related to aging.
Symptoms include blurred vision and an inability to see near objects clearly.
Treatment options include eyeglasses, conductive keratoplasty (CK), laser vision correction and contact lens services.
Astigmatism often occurs in combination with myopia and hyperopia. The cornea and lens of the eye are generally spherical. When one or both are curved more steeply in one meridian (football shaped instead of basketball shaped), the person has astigmatism.
Objects, both at near and distant appear blurry, caused by the uneven curvature that prevents light rays entering the eye from focusing to a single point on the retina.
Symptoms include blurry vision at near and far distance. Eyestrain and fatigue may occur as well.
Treatment options include eyeglasses, contact lenses, or surgery including astigmatic keratotomy, laser vision correction surgery, limbal relaxing incisions, and toric intraocular lenses.