The Dr. Bill Takeshita Foundation

Last Modified: Sat, 18 Aug 2007

View other Common Causes of Vision Impairment

Cataracts are one of the leading causes of vision impairment among adults and children. A cataract is the term used when the internal lens of the eye becomes clouded or opaque. Cataracts may be present at birth or may develop at any age as a result of trauma, diabetes, or normal aging. Cataracts cause blurred sight, problems with glare, reduced peripheral vision, and color vision disturbances. Cataracts generally do not cause total blindness because they are typically removed before they cause severe vision loss. Cataract surgery is the most common eye surgery performed in the United States and the prognosis of improving vision is excellent.

Inside the eye is a normally clear lens called the crystalline lens. The lens focuses light on the retina, protects the retina from the ultra-violet rays of the sun, and also changes shape to allow the eye to focus at various distances. The crystalline lens accumulates a new layer of cells each year. As the lens becomes thicker, it loses some of its flexibility and transparency. By the age of 40 years, many adults are no longer able to shift the focus of the eye from far to near and require reading glasses. This normal age related condition is called presbyopia. As time proceeds, the lens develops opacities and becomes clouded and is called a cataract.

In the early stages of cataracts, blurred vision and problems with glare can often be corrected with specialized glasses, filters, and low vision aids. However, in the more advanced stages, cataracts require surgical removal of the clouded lens to allow more light to enter the eye. When the cataract has been removed from the eye, the eye is called “aphakic,” meaning that it does not have a lens in the eye. Patients with aphakia require the use of contact lenses or powerful glasses to focus the light on the retina. Today, most adults who have undergone cataract surgery have an artificial lens called an intra-ocular lens (IOL) implanted in the eye to focus light on the retina. This eliminates the need for contact lenses and thick glasses. Eyes with an artificial intra-ocular lens are called “pseudophakic.”

Cataracts that are present at birth are called congenital cataracts. Congenital cataracts are sometimes an inherited trait or they may be a consequence of birth trauma, rubella, or metabolic abnormalities. Cataracts can be mild and may not affect vision or they may be severe and cause severe vision impairment. In cases of severe cataracts, surgery is recommended and contact lenses and bifocals are generally prescribed rather than implanting intra-ocular lenses because the eyes of children will change in size and they may require different power lenses. Cataract intra-ocular lens implants are considered after the eyes are fully developed and their prescription has stabilized.

Age related cataracts are the most common types of cataract that causes vision impairment among adults. These cataracts are described based on the location of the region of the lens that is clouded. Opacities or clouded regions in the peripheral are called cortical cataracts while those in the central area are called nuclear sclerotic or posterior sub capsular cataracts. Adults with cataracts frequently complain of difficulty reading traffic signs, recognizing faces, and glare around headlights when driving at night. They may also complain that they do not see colors as well as they used to. Adults with centrally located cataracts have more problems during the day when their pupils constrict due to the bright sunlight. This forces light to pass through the clouded lens. In contrast, patients with cataracts located peripherally see better during the day when their pupils are small and worse at night when their pupils are dilated.

Diabetics are more likely to develop cataracts at a younger age. Elevated blood sugar levels can affect the internal crystalline lens, causing swelling of the lens after eating which can cause nearsightedness. As blood sugar levels decrease, the crystalline lens changes shape and patients may then become farsighted. Frequent changes in spectacle prescriptions are one indication of diabetes. Continued shifts of blood glucose levels may contribute to the early formation of cataracts. ''' Recommendations'''

• Newborn babies should be evaluated for cataracts shortly after birth. Any discoloration of the pupils of the eyes should be noted and a referral to a pediatric ophthalmologist should be made. For more information, see Eye Care Professionals.
• Some children with cataracts do not require surgery while others do. When surgery is recommended, it is critical that children are fit with glasses or contact lenses and that they wear them all day. This will allow maximal stimulation to the brain.
• Vision stimulation is recommended for all infants with cataracts.
• Infants will benefit from vision stimulation to maximally develop the visual cortex of the brain. For specific details, please see Developing Your Child’s Vision.
• Adults and children who have undergone cataract surgery should wear glasses to increase their range of focus and to protect the eyes from the harmful rays of the sun. Without glasses, patients will only be able to focus at one distance.
• Tinted contact lenses, specialized melanin filters, and the use of a hat with a dark brim can reduce problems of glare for *Students will benefit from being positioned in the front portion of the class with their backs facing windows, doors, and glare sources. The use of a black chalkboard and bold architecture chalk are generally easier to see than dry erase boards due to the glare created by the white board. In the event that a dry erase board must be used, it is very helpful to only use bold black dry erase markers rather than colored markers.
• Students with cataracts will benefit from using tinted paper, bold line paper and bold pencils or black felt pens or 1.0 mm gel pens to improve readability. Students who are bothered by glare will also benefit from placing their paper on a dark blotter or dark piece of construction paper to help them to see the edges of their paper.
• Students will benefit from having copies of material normally written on the board or presented on overhead transparencies. If PowerPoint presentations are used, a dark background with white letters written in Arial or Tahoma will improve readability for students with low vision.
• At home, the use of an incandescent light bulbs hidden behind a dark torchierre floor lamp can provide excellent general lighting while reducing glare. A small desk lamp such as an OTT full spectrum lamp may provide a soft light for reading and writing.
• Computer users will benefit from changing the background of the display to a black or blue background with white letters. Enlargement of the font size will also increase readability. For information on how to modify the computer screen, see “Solutions To Help You User Your Computer.
• Students with congenital cataracts will benefit from a consultation with a low vision specialist to prescribe low vision aids, specialized computer software and technology such as Zoom Text magnification software, scanning programs such as Open Book and *Teenagers with cataracts who are interested in learning whether they have sufficient vision for driving should have a low vision examination by an optometrist who specializes in fitting bioptic-driving glasses.
• Specific low vision aids that are often helpful to patients with cataracts include:
  • Aspheric reading glasses
  • Prescription CPF, Transitions, Melanin, and NoIR filters.
• For more information, please see Low Vision Rehabilitation