What Is Low Vision? A Brief Guide for Healthcare Professionals

The American Foundation for the Blind (AFB) designates February as Age-Related Macular Degeneration (AMD) and Low Vision Month. Each February, AFB joins with communities, organizations, patients, and caregivers across the country to raise awareness about low vision, its prevention, and ways to treat it.

Sensory deprivation, especially low vision, is not uncommon among older adults. Early detection is important, both to prevent and treat vision impairment and to recognize possible signs of an underlying health issue.

By understanding the causes and consequences of low vision, healthcare professionals who work with seniors can use this month as an opportunity to stress the importance of early detection throughout the year.

What Is Low Vision?

The National Eye Institute (NEI) reports that more than four million American adults over age 40 are visually impaired. However, since the American Optometric Association (AOA) says that "anyone with noncorrectable reduced vision is visually impaired," the number of people with low vision is likely much higher. According to Lighthouse International, functional visual impairment is characterized by reduced peak contrast sensitivity, inadequate field of vision, or insufficient resolution. Any combination of these problems can occur in one or both eyes. Vision impairment can become problematic if it interferes with a senior's ability to perform essential daily tasks. It can also increase her risk for a fall-related injury.

As reported by the AOA, the World Health Organization categorizes vision loss at six levels. The first, from 20/30 to 20/60, is called near-normal vision and only minimally affects daily living. Next is moderate low vision, from 20/70 to 20/160, which may only slightly impact a person's life. However, severe low vision, from 20/200 to 20/400, can significantly impact a person's life, especially increasing the risk for falls. In fact, the threshold for considering a person legally blind is 20/200. Those with vision level numbers more severe than 20/400 are considered to have profound low vision, near total blindness, or total blindness. Low to moderate vision loss can be generally managed by an optometrist, but seniors living with severe to profound low vision should be cared for by a low vision specialist.

Causes of Low Vision

A senior's eyesight can become impaired for a variety of reasons, though disease is the most likely cause, either to the eye itself or as a result of a disorder elsewhere in the body. Four specific eye diseases cause the majority of vision loss.

Age-Related Macular Degeneration

As its name implies, AMD is specific to older adults. It is the leading cause of vision loss among older adults in the United States, and more than two million adults were living with it in 2010, according to NEI.

Beyond age, other risk factors for AMD include:

  • A family history of the disease
  • Smoking
  • High cholesterol levels
  • Hypertension and cardiovascular disease

Characterized by a loss of central vision, the disease process slowly disintegrates the macula part of the retina. Nearly 90 percent of macular degeneration cases are nonexudative (dry), while exudative (wet) macular degeneration is responsible for the most severe cases of AMD. Although AMD is usually bilateral, some people have it in only one eye. Seniors are often unaware that they may have AMD until it's detected in an eye exam. Older adults should therefore have their eyes routinely examined at least once a year.

Seniors can monitor the possible onset of AMD themselves using the Amsler Grid, although this should not replace a professional eye exam. An individual who sees any distortions while staring at a dot centered within the grid of 400 small squares should be examined for AMD.

The impact of treatment depends on the stage of the disease and the patient's ability and motivation to participate. Diets rich in carotenoids, specifically lutein and zeaxanthin, appear to slow the progress of dry AMD from advancing to the wet stage, which occurs in approximately 10 percent of cases. These antioxidants can be found in such fruits and vegetables as squash, spinach, honeydew melon, apples, green beans, grapes, corn, and broccoli. Exercising and wearing sunglasses to guard against harmful UV radiation from the sun may also help.

Treatments range from drugs designed for specific functions to such high-tech solutions as laser surgery, which can either slow the disease's advance or help seniors learn to live with a loss of central vision.

Diabetic Retinopathy

Approximately 7.6 million American adults have diabetic retinopathy, an eye disease resulting from poorly controlled diabetes that damages blood vessels in the retina. Although diabetes can affect the eyes in several ways, diabetic retinopathy is the most common.

Diabetic retinopathy typically develops in both eyes, and it can occur in four stages. The first, mild nonproliferative retinopathy, is characterized by microanerurysms in the blood vessels of the retina. If the disease advances into the moderate nonproliferative retinopathy stage, some of the vessels supplying the retina become blocked. Blood supply to the retina may continue to decline during the severe nonproliferative retinopathy stage, causing the body to prepare to grow new blood vessels around the retina. These new vessels grow during the final stage, proliferative retinopathy. If they begin to leak, vision loss or even blindness could result.

If fluid leaks into the macula, where forward vision occurs, it could cause a condition called macular endema, in which the macula swells and vision becomes blurred. This is one of the few symptoms of diabetic retinopathy. The leaking vessels may also cause visible specks of blood. It's common to experience no symptoms during the early stages of this disease, however. If your patient is experiencing symptoms, this could indicate an advanced stage of the disease, and the patient should immediately see an eye care professional.

Early detection of proliferative retinopathy is important because the most effective method for combating it, scatter laser treatment, works best before the vessels around the laser begin to leak. Blood can also be surgically removed in a procedure called a vitrectomy. Macular edema is treated with focal laser surgery, which is similar to scatter treatment but is a much more precise procedure. With proper diabetes management and more frequent eye exams, the risk of blindness due to proliferative edema can be reduced by up to 95 percent, according to the NEI.

Glaucoma

Glaucoma occurs in about 2.7 million American adults and is more common among older adults. In the eye, continually cycling fluid passes through a mesh-like filter. If this filter becomes clogged, fluid can build up and increase pressure on the eye, and this pressure can damage the optic nerve. Glaucoma can affect one or, more commonly, both eyes. If left uncontrolled, it can lead to peripheral vision loss or even blindness.

Primary open-angle glaucoma is the most common type of this disease. There are no immediate symptoms, and an individual may not be aware that it could be gradually causing damage to her sight. While there is no cure, its progression can be slowed with drug therapy in the form of eye drops and pills. Laser or other surgical techniques may be used if medications are not effective.

The exact cause of glaucoma is not known. It can result from medical conditions such as diabetes, other eye conditions, elevated eye pressure, or long-term use of corticosteroid medications. It is more likely to occur among African Americans, and there is likely a hereditary factor.

Cataracts

Cataracts are the leading cause of blindness worldwide, but not in the United States. This is because cataract surgery is relatively safe and widely available in the US. However, 24 million American adults had cataracts in 2010, according to NEI. The prevalence of cataracts grows with age, increasing from 5 percent among those in their early 50s to 15 percent in those in their early 60s and 36 percent in their early 70s. NEI reports that approximately half of adults in their late 70s have cataracts, and they are more prevalent among white women.

A cataract is a slow and gradual opacity of the eye's lens (though there are fast-developing types). Exposure to ultraviolet light may contribute to its progression. Over time, a senior with cataracts may experience blurred vision and a greater difficulty with glare. Because of its slow onset, your senior patient may be oblivious to the disease until it has advanced. Surgery is the only solution, and early detection increases this treatment's effectiveness.

Low Vision Rehabilitation

Low vision specialists are optometrists or ophthalmologists who go far beyond routine eye exams. They are trained to explore the impact that vision loss can have on someone's life and often head up rehabilitation centers. The mission of these services is to restore an individual's ability to perform important functions.

Working alongside these doctors are professionals trained specifically in areas of vision rehabilitation, including vision rehabilitation specialists, orientation and mobility specialists, and certified low vision therapists. An important component of their work is to train people in the use of optical devices. Rehabilitation is a team effort that may also include social workers, nurses, dietitians, and occupational therapists.

Resources

Healthcare providers are in a position to refer their visually impaired patients to the help they need. Many resources are available for you, your patients, and their family caregivers. Some of these include:

One individual may define low vision differently from another. For instance, a senior with a profound loss of vision could be far more functional, active, and healthy than someone with minimal visual impairment. Healthcare providers who understand this reality are in a better position to make life easier and safer for their individual patients.

Healthcare professionals across the spectrum may be able to help those with low vision. Contacting the American Foundation for the Blind is an excellent first step toward making AMD and Low Vision Awareness Month successful.

If you know a senior patient with vision impairment who would benefit from information about medical alert system, refer your patients to Philips Lifeline.

 

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February is Age-Related Macular Degeneration (AMD) and Low Vision Awareness Month. Here are the four most common causes of vision impairment in seniors that healthcare professionals should be aware of.