Low vision requires innovative prevention and treatment strategies

Blindness and low vision have reached epidemic proportions worldwide, particularly in developing countries where there is a predominance of inadequate screening and health care.

Low vision patients, whose conditions can be caused by multiple diseases, are among the most difficult to treat because their condition is often uncorrectable. Although 80% of all vision loss is believed preventable or curable, more than 180 million people are blind or visually disabled worldwide.

The low vision problem is more severe in developing countries, where inhabitants represent nearly 90% of the world’s visually impaired population and are 10 times more likely to become blind, according to EyeCare America, a public service foundation of the American Academy of Ophthalmology.

Current research is aimed at finding better ways of diagnosing, preventing and treating potentially blinding visual problems before they lead to debilitating low vision. One of the more promising strategies involves gene and cell-based therapies, which contain engineered cells capable of preventing or slowing down vision loss. Retinal implants and electronic prosthetic chips that function like natural photoreceptors in the eye are also showing promise but are still in experimental phases.

Defining the problem

Most health organizations provide extremely broad definitions of low vision, ranging from vision as low as 20/70 in the better eye with best correction to as high as 20/400. Low vision is not discerning. It affects people of all ages and interferes with many normal daily activities most people take for granted, such as reading, cooking and navigating with ease, according to Lylas Mogk, MD.

Lylas Mogk

Depending on the cause and location of vision loss, patients’ level of functionality can vary dramatically, said Dr. Mogk, who chairs the AAO’s Vision Rehabilitation Committee and the organization’s SmartSight Task Force. Individuals with low vision can experience central or peripheral vision loss or generally blurry vision.

“When you lose central vision, you’re losing the clarity of what you’re looking right at,” Dr. Mogk said. “No other part of the retina is capable of that amount of clarity, so a very little bit of vision loss in that center is very noticeable and has a huge impact. You can lose a lot of peripheral vision and not even be aware of it and not have it interfere too much with function.”

The four primary causes of low vision in adults in developed countries are age-related macular degeneration, cataract, glaucoma and diabetic retinopathy. Low vision also happens to a lesser extent because of falls, birth defects, strokes and tumors. In developing countries, vitamin A deficiency, trachoma and inadequate health care are major contributors.

Considered curable in the United States, cataract remains the leading cause of low vision worldwide. Glaucoma, however, is ranked No. 1 in the United States and is a principal cause of blindness among African-Americans, Dr. Mogk said.

“On the list of major causes of vision loss is always cataract, but of course among those four big leading causes, cataracts are completely solvable. So we almost never see patients who have low vision because of cataracts because they have them taken out,” she said.

Mary G. Lawrence

In adults, diabetes and lifestyle factors such as smoking and poor nutrition contribute to low vision. Smoking, for example, has been associated with macular degeneration with the potential of increased oxidative damage as smoking frequency increases.

“Obviously in people who are diabetic, if they don’t follow the diabetic diet, their blood sugar is going to be out of control,” Mary G. Lawrence, MD, MPH, said. “If it’s out of control, they’re going to have earlier onset and more aggressive diabetic retinopathy. Studies have shown that blood sugar is very important for all complications of diabetes including vision loss due to diabetic retinopathy. Nutrition may also have an effect on macular degeneration.”

Patients with AMD are advised to take nutritional supplements that slow its effect, but this does not alleviate the problem, she said.

Populations at high risk

Health care disparities in diverse populations may be responsible for the prevalence of low vision in developing countries. While the reasons for blindness can vary by country, low vision can take more of a toll because of inadequate health care, Gerald J. Chader, MD, PhD, said in an e-mail interview.

“It is a huge and growing problem,” Dr. Chader said in a summary of a workshop that he organized on the topic. “The level of eye disease in the world is expected to increase greatly due to population aging. The overall percentage of elderly folks will grow from 7% now to 17% in 2050.”

Although potential treatments such as genetic and pharmaceutical therapies, stem cell transplants and artificial retinas are under development, most causes of low vision are not yet correctable or reversible.

“Right now, there are few treatments for low vision. There are many aids available, but the actual therapies are not yet available,” Dr. Chader said in the interview.

“Remember, too, that low vision has many causes — cataract, cornea problems, retinal blindness,” he said. “The one exception to my statement here is with cataract. Cataract surgery is so good that, when available, it virtually becomes a ‘cure.’”

Kevin D. Frick, PhD, an economist, said poor screening and a lack of ophthalmologists are two of the biggest problems associated with low vision in developing countries.

Kevin D. Frick

“There are not a lot of [ophthalmologists] to go around, and they tend to be located in urban areas rather than rural areas,” Dr. Frick said. “In India, the prevalence of diabetic retinopathy is becoming a concern as the population lives longer. Diabetes has become an issue. While we’re able to provide refractive correction for people with visual impairments around the world, many of them don’t have proper glasses.”

In children who are affected, common causes of low vision include amblyopia, cortical visual impairment and retinopathy of prematurity (ROP), Paul J. Rychwalski, MD, said.

Worldwide, children account for 4% of the blind. But because of differences in longevity, the societal impact is roughly equivalent to cataract, which corresponds to 48% of the world’s blind.

“In lower economically developed countries, preventable diseases such as trachoma, measles and vitamin A deficiencies are major causes of childhood blindness,” Dr. Rychwalski said. “In middle economic countries, the incidence of ROP depends on the availability and affordability of screening and treatment. There are many potential reasons for a new epidemic, including higher premature and birth rates.”

He said one of the keys to fighting low vision in children is offering pre-school screening programs that enhance early detection efforts.

Socioeconomic impact

The economic impact of low vision on the U.S. health care system is well documented. A 2004 Prevent Blindness America study determined the total U.S. cost for AMD, cataract, diabetic retinopathy, glaucoma, refractive errors, visual impairment and blindness to be $35.4 billion.

Dr. Frick, who participated in the study, estimated the annual monetary value of treatment, informal care, and quality of life decrements alone was $16.2 billion.

“Of course, there is also all the care that is spent before people become visually impaired trying to prevent it,” he said.

The Society for Neuroscience recently reported that cataract treatments account for nearly 60% of vision-related Medicare costs.

“Medicare requires that you have either visual acuity of 20/70 or less or a visual field deficit or a central scotoma” to be classified with low vision, she said. “If someone does not fall within those parameters of Medicare, chances are you can solve their problem with an office visit without having the rehabilitation,” she said.

Focus on prevention and education

Many organizations emphasize the importance of regular eye examinations. For example, EyeCare America started a blindness and low vision program that encourages the elderly to have regular checkups.

Last year, AAO launched two programs that encourage ophthalmologists to become more involved with patient education. SmartSight targets patients with visual acuity of less than 20/40, scotoma, or field or contrast loss, while EyeSmart emphasizes risk factors of eye diseases, infections and injuries and the role of the ophthalmologist in preventing, diagnosing and treating ocular conditions.

In 1999, the World Health Organization, in partnership with the International Agency for the Prevention of Blindness, launched Vision 2020: The Right to Sight, an initiative designed to eliminate avoidable blindness in cataract, trachoma, onchocerciasis, vitamin A deficiency and refractive errors.

Dr. Mogk said that early diagnosis may not help all ocular diseases, but it can make a big difference in treating glaucoma.

“Everyone needs to get their eyes checked on a regular basis because if it’s there and you catch it early, it’s treatable — successfully treatable — for the vast majority so they don’t have to lose any vision,” she said.

As the AAO Vision Rehabilitation Committee chair, Dr. Mogk’s goal is to alleviate the impact of vision loss.

“But a lot of people don’t know that there are ways of continuing living fully in spite of vision loss. They don’t understand you can keep living, but it’s a big learning curve,” she said.

Promising research

According to Dr. Mogk, retinal implants that enable individuals to regain lost visual function allow blind patients to see light, patterns and large objects but has not yet reached the stage that it can allow those with low vision to see details.

Paul J. Rychwalski

“The vast majority who have central loss already see more than large objects. They see a lot, not just the details, and we are a long way from getting an artificial retina to see details.”

Dr. Rychwalski said retina specialists around the country are working with retinal implants and stem cell transplants, but that these may not have the same eventual impact in children due to vision loss of a cortical cause, such as cortical visual impairment and amblyopia.

Dr. Lawrence said researchers are conducting stem cell work on optic nerve diseases such as glaucoma and optic atrophy.

Living with low vision

Because impaired vision can cause feelings of loss of independence and inadequacy, rehabilitation may be the most effective way to learn how to perform daily tasks and make the most of remaining vision.

Marc Jay Gannon, MD, provides specialized devices such as clip-on magnifying loupes and training techniques to help low vision patients acclimate to society. In his practice, he evaluates remaining healthy tissue and designs low vision devices for mounting on eyeglasses. An occupational therapist then teaches patients how to aim and utilize the healthy portion of their eyes through the scope, which allows them to read, watch television and even play golf.

“We’re one of the few practices that actually has a restorative program using optical devices,” he said. “And these things are actually based on devices that were used in the operating room, like the surgical loupes utilize the same kind of technology and optics that we’re utilizing in these devices.”

Dr. Lawrence encourages patients to focus on the future instead of dwelling on their poor vision.

“In patients who have had vision loss, we first and foremost make sure there is nothing medically or surgically that we can do to improve the vision,” she said. “Then we work with a patient in terms of where they are in terms of their vision. We try to do a functional approach based on the needs that the patient has.”

For more information:

• Gerald J. Chader, MD, PhD, can be reached at Doheny Retina Institute, University of Southern California, 1450 San Pablo St., Los Angeles, CA 9033; 323-442-6767; fax: 323-442-6460; e-mail: gchader@dohenyeyeinstitute.org.
• Kevin D. Frick, PhD, can be reached at Johns Hopkins Bloomberg School of Public Health, 624 N. Broadway, Room 606, Baltimore, MD 21205; 410-614-4018; fax: 410-955-0470; e-mail: kfrick@jhsph.edu.
• Marc Jay Gannon, MD, can be reached at The Low Vision Institute, 5333 N. Dixie Highway, Suite 101, Fort Lauderdale, FL 33334; 954-776-5223; fax: 954-491-0027; e-mail: gannonlvi@aol.com.
• Mary G. Lawrence, MD, MPH, can be reached at University of Minnesota, Department of Ophthalmology, 420 Delaware St. SE, Minneapolis, MN 55455; 612-625-4400; fax: 612-626-3119; e-mail: mary.lawrence@va.gov.
• Lylas Mogk, MD, can be reached at Henry Ford Visual Rehabilitation & Research Center, 29200 Schoolcraft, Livonia, MI 48150; 734-523-1070; fax: 734-523-1080; e-mail: mogk@aol.com.
• Paul J. Rychwalski, MD, can be reached at University of Louisville School of Medicine, Department of Ophthalmology & Visual Science, 301 E. Muhammad Ali Blvd., Louisville, KY 40202; 502-852-7818; fax: 502-852-2624; e-mail: paul.rychwalski@louisville.edu.

• John Misiano is an OSN Staff Writer who covers all aspects of ophthalmology.