Vision Problems

Lexington Eye Associates - Correcting Vision in the Boston Area with Offices in Lexington and Concord

Serving the Boston area from offices in Lexington and Concord, our refractive surgery and ophthalmology practice is dedicated to improving vision as well as educating our patients so that they can make informed decisions about their eye care. Below you will find a list of common focusing and refractive vision problems and how they affect your eyes.

How the eye functions

In a normal eye, the cornea and the lens both focus light rays precisely onto the retina. The retina converts light to electrical signals, which are carried by the optic nerve to the brain. The visual portions of the brain then interpret these nerve impulses, resulting in sight. Refractive errors are "abnormalities" in the way the light rays are focused toward the retina. These can be caused by any abnormality in the cornea or the lens, but are most commonly the result of nearsightedness (myopia), farsightedness (hyperopia), astigmatism, presbyopia, and cataracts.

Myopia or Nearsightedness

Myopia occurs when the cornea is too steep or the eye is too long. When focusing on an object in the distance, light is focused in front of the retina, resulting in blurry vision. As the object is moved closer, the vision becomes clearer since the light is focused farther back onto the retina.

Hyperopia or Farsightedness

Hyperopia occurs because the cornea is too flat or the eye is too short. Light rays are focused behind the retina, resulting in blurry vision. As the object is moved closer, the blur increases since the light is focused even farther behind the retina.

Astigmatism

Astigmatism typically results when the cornea is steeper in one direction and flatter in the opposite direction (like the side of a football) rather than spherical (like a basketball). This causes light rays to be focused at more than one point, and may cause blurry or distorted vision at all distances. Astigmatism may occur alone or in combination with myopia or hyperopia.

Presbyopia and Monovision

Presbyopia refers to the natural loss of near vision that occurs with age. It typically begins after age 40, requiring the use of reading glasses or bifocals. Although the specific cause is not known, presbyopia is thought to occur as a result of the loss of flexibility in the lens, which is required to focus on nearby objects. The lens actually loses flexibility throughout life, but this only becomes symptomatic between the ages of 40-50.

Patients over the age of 40 who have symptoms of presbyopia have a choice. If both eyes are corrected to see well in the distance, then glasses will be needed for close-up work. Vice-versa, if both eyes are corrected to see well up close, then glasses will be needed for the distance. The other alternative is "monovision." With monovision, a patient's dominant eye is corrected to see distant objects, while the non-dominant eye is corrected to see near objects. Monovision represents a compromise that allows for preservation of both distance and near vision without the use of glasses. The majority of patients have no difficulties with this procedure, although some may have trouble with this effect. Contact lenses should be used prior to surgery to mimic the monovision effect, and determine a patient's level of comfort.

Cataracts

Cataracts are a clouding of the lens in the eye. They can be the result of many factors, including medications or trauma, but are most commonly the result of aging. Cataracts obscure the focus of light and cause a degradation of one's vision that may impair aspects of one's daily activities. Other symptoms of cataracts can include glare sensitivity and difficulty seeing in brightly lit conditions. There is no medical treatment for cataracts. Only cataract surgery can be performed to restore one's vision. Fortunately, cataract surgery is the most common and most successful surgery performed in the United States.

Because the natural lens is responsible for focusing light to the retina, the removal of a cataract is performed in conjunction with the insertion of an artificial, intraocular lens. These lenses are made with a 'presciption' that is tailored for an individual patient's eye in order to optimize the focus of light to the retina and reduce a patient's need for glasses.

There are many types of intraocular lenses available. Most medical insurances will cover a "monofocal" lens. This is an intraocular lens in which light is focused for only one specific visual range. For example, if the lens is chosen to allow focus for distant objects, visual targets up close would be blurry unless reading glasses are worn. Vice-versa, if the intraocular lens is chosen to allow focus for near objects, visual targets in the distance would be blurry without the use of distance glasses. Monovision can be performed during cataract surgery as well, in which the dominant eye is corrected to see distant objects, while the non-dominant eye is corrected to see near objects.

"Premium" lenses are specialized intraocular lenses that are not covered by medical insurance. These lenses allow for the focus of light at multiple ranges and therefore can reduce, or even eliminate, one's dependency on glasses following cataract surgery. See refractive lens implants for more information on these lenses.

If you are interested in LASIK or refractive cataract surgery in the Boston area, visit Lexington Eye Associates at our Lexington and Concord offices.