Dr. Grossman’s Blog

Image by Sergio *Savaman* Savarese

Just because you can buy something over the counter doesn’t mean it cannot hurt you.

A review of cases published in the The New England Journal of Medicine shows that “poppers,” legal recreational drugs common in club culture, can cause light sensitivity and vision loss in some individuals.

In an article by HealthDay Reporter, researchers say, “poppers — a catch-all term for alkyl nitrites that are often inhaled by partyers for a brief ‘head rush’ and to increase sexual arousal — may compromise the normal workings of photoreceptor cells found in a key region of the eye’s retina.”  They go on to explain that “nitric oxide is known to affect the metabolism of photoreceptors and can also alter the operation of a key enzyme involved in photoreceptor function.”

Researchers did note that those who stopped taking poppers seemed to recover over a period of several months.  Experts do not yet agree fully on the correlation between the use of this drug and the damage to the eyes; some believe evidence is simply anecdotal at this stage and that more formal research is necessary.

Source: http://www.medicinenet.com/script/main/art.asp?articlekey=120899

Get further information on drugs that harm the eyes.

Image by reuben4eva

“Phantom limb pain” is something we may have heard of, but it turns out that people with vision loss are also susceptible to a similar phenomenon.

Researchers who reported at the American Academy of Ophthalmology Joint Annual Meeting With the Pan-American Association of Ophthalmology stated that patients with vision loss are much more likely to experience “vivid visual hallucinations” than previously believed.

Between 10-38% of those with vision loss from such conditions as macular degneration, experience what is called Charles Bonnet syndrome (CBS).  According to study authors, “the hallucinations that CBS patients experience are usually fully formed images such as double-decker buses driving into the patient’s living room or people sitting on a couch. To make a diagnosis of CBS, patients must have visual loss, as well as insight into the unreal nature of the hallucinations.”

The article published in Medscape Medical News says, “Scientists now hypothesize that lack of true input into the primary visual cortex allows spontaneous release of remembered images into the visual association area. ‘But these imaging studies don’t tell us why one patient experiences these hallucinations and another does not,’ says Mary Lou Jackson, MD, from the Harvard School of Medicine–affiliated Massachusetts Eye and Ear Infirmary

Doctors involved with this research do not generally proscribe any treatment for CBS and believe that patients eventually grow accustomed to the experience.

Often, patients suffering from macular degeneration will use a different part of their retinas to make up for central vision loss. According to researchers from Georgia Tech’s School of Psychology, the brains macular degeneration patients can also compensate to vision changes by reorganizing their neural connections.

Using functional MRI technology, researchers found that even though study participants were relying on their peripheral vision rather than their central vision, the brain was actually processing information as if the patients had normal, unimpeded vision.

Study leader Eric Schumacher told Science Daily: “Our results show that the patient’s behavior may be critical to get the brain to reorganize in response to disease.  It’s not enough to lose input to a brain region for that region to reorganize; the change in the patient’s behavior also matters.”  This “behavior change” is the macular degeneration patient’s ability to compensate for central vision loss by relying on other areas of the visual field.

Source: EyeWorld News Magazine

Visit our website for self help tips specifically for macular degeneration sufferers.

The Centers for Disease Control has recently turned its attention to the increasing rates of diabetic retinopathy, a complication of diabetes in which the blood vessels of the eyes are damaged resulting in potential vision loss. The study, published in Journal of the American Medical Association suggests that those with diabetes require more comprehensive eye care. 31.6% men and 25.7% of women over age 40 who have diabetes are estimated to have diabetic retinopathy.

Study authors intend their findings to guide policy makers as they oversee the country’s eye care services and rehabilitation for the estimated 8% of the U.S. population with diabetes.

Source: WebMD.com

Although individuals with age-related macular degeneration (AMD) lose central vision, their peripheral vision often remains intact.   The Macular Disease Society (based in the UK) has developed a training scheme to help people use the undamaged parts of their eyes to read and identify faces. 

According to their research, people can be taught to use their peripheral vision to compensate for damage to their central vision, using “eccentric viewing” and “steady eye techniques”.   When someone with central vision loss looks directly at an object it may disappear or appear distorted, but when they look above, below, or to one side of it, they see it more clearly.

Eccentric viewing helps people learn where to focus their gaze to make their vision better.  Once this position is identified, they can be taught how to read again using the steady eye technique:  instead of moving the eyes from left to right to read a sentence, the person can keep their eyes completely still and move the text to the left so that each word in turn moves into the area of best vision.

Learn more about macular degeneration

SOURCE:  BBC News Channel, April 10, 2009, http://news.bbc.co.uk/1/hi/health/7958838.stm

Researchers at the University of Pennsylvania School of Medicine have created the first animal model of age-related macular degeneration (AMD) caused by a mutation known to produce disease in people.

AMD is the most common cause of vision loss in elderly people, affecting more than 10 million people in the U.S. and about 50 million world-wide. Because AMD develops late in life (patients typically show symptoms of AMD after age 60), it is a difficult condition to investigate.

Although some forms of AMD are inherited, one type is thought to be caused by a mutation in the Efemp1 gene. Researchers introduced the disease-causing mutation into the Efemp1 gene of mice. These Efemp1-mutant mice develop the same basal deposits as people with AMD.

It is believed that these mice will provide a means to study how basal deposits form and what they are made of. The mice can also be used to test potential treatments to prevent basal deposit formation.

“To better develop treatments for preventing the progression of AMD, we need to understand the real biochemical details of how AMD occurs,” says lead author Eric A. Pierce, MD, PhD, Associate Professor of Ophthalmology at Penn’s K.M Kirby Center for Molecular Ophthalmology. “To do that, we need a model, and now we have one.”

Learn more about age-related macular degeneration (AMD)

Read other studies about macular degeneration

SOURCE: Model To Study Age-related Macular Degeneration Could Pave Way For Better Treatment, Pierce et al, University of Pennsylvania School of Medicine (2007, October 10).

It’s no surprise that failing eyesight leads to more accidents, but a new study shows early intervention to correct even minor visual impairment may prevent injury.

Decreased vision in older people is commonly related to an increased risk of falling, and a new study has scientifically evaluated this link. The goal of the study was to determine whether visual loss was associated with a higher incidence of injurious accidents and whether walking speed or physical activity influenced this association.

416 people aged 75 to 80 years were tested for visual acuity. Those testing at less than 20/60 in the better eye (with spectacle correction when necessary) were defined as visually impaired. Those tested with visual acuity between 20/60 and 20/40 were defined as having lowered vision. Those testing at greater than 20/40 were defined as having normal visual acuity.

Hospital records of accidents with injuries were monitored for ten years, during which 239 participants (58%) suffered at least one injurious accident. Even considering other factors (age, gender, eye-related diseases, diabetes and cardiovascular diseases), the risk of injurious accidents for participants with lowered vision was 1.45 compared with those with normal visual acuity.

Interestingly, participants with visual impairment did not have an increased risk for accidents over those with lowered vision, and neither walking speed nor physical activity had a mediating effect on the relationship between visual loss and accidents.

Researchers have therefore concluded that lowered vision is a risk factor for accidents in older people independent of mobility and physical activity.

In light of this research, early intervention strategies such as proper correction of vision or cataract extraction are truly important in preventing accidents in the elderly.

Read more about vision loss prevention

SOURCE: Kulmala J, Era P, Parssinen O, et al. Lowered vision as a risk factor for injurious accidents in older people. Aging Clin Exp Res 2008;20(1):25-30.