Visual Loss, Blindness to Double by 2050

But the numbers will be lower if Americans get more eye exams and refractions. 
By Bill Kekevian, Senior Editor

The number of Americans with visual impairment or blindness will climb to more than eight million by the year 2050—approximately twice the current number—and an additional 16.4 million Americans are expected to have vision impairment due to uncorrected refractive error, based on a National Institutes of Health analysis of six large studies. 

Several factors explain the increases, including the aging of the baby boom generation and a rise in systemic diseases (such as diabetes) that can impact patients’ vision. This study also shows that refractive error is the leading cause of visual impairment in the United States, as well as worldwide.

But these predictions aren’t inevitable. Optometrists and ophthalmologists can help lessen these estimated numbers by encouraging patients to get vision screenings and eye exams, according to the investigators. Vision screening and proper refractive correction could produce clinical improvements in up to 72% of Americans with vision impairment and 22% of those with blindness, they say.

“Early detection and intervention—possibly as simple as prescribing corrective lenses—could go a long way toward preventing a significant proportion of avoidable vision loss,” said Paul A. Sieving, MD, PhD, director of the National Eye Institute, which funded the study.

Among all demographic groups, non-Hispanic white women will represent the largest proportion of people affected by visual impairment and blindness, with their numbers rising to 2.15 million visually impaired and 610,000 blind. However, the highest prevalence of visual impairment among non-whites will shift from African Americans (15.2% in 2015 to 16.3% in 2050) to Hispanics (9.9% in 2015 to 20.3% in 2050).

The study even localized its predictions by state, speculating that blindness will most affect Mississippi (up to 1.25% by 2050) and Louisiana (1.2% by 2050). For visual impairment, Florida will have the highest per capita prevalence (3.98% by 2050) and Hawaii (3.93% by 2050) will closely follow. 

Scientists Reverse Diabetic Retinopathy in Lab Study

Researchers from Indiana are investigating a potential new intraocular treatment, based on manipulating the renin angiotensin system (RAS), that may prevent or even reverse diabetic retinopathy. In studies using mice, it seems to be working, according to The American Journal of Pathology. 

Long believed to be irreversible, retinal damage from diabetes could one day be ameliorated by therapy to reduce proinflammatory cells.

The research is based on the hypothesis that an imbalance between two axes of the RAS leads to development of diseases like diabetic retinopathy. The team injected a therapeutic agent known as AAV-ACE2 directly into the vitreous cavity of the eye of diabetic mice to increase angiotensin converting enzyme-2 (ACE-2) expression.

The researchers’ conclusion was reached after two experiments. The first saw the agent administered two weeks prior to a streptozotocin injection, which induced diabetes in the mice. The second saw it administered six months after a streptozotocin injection, after diabetic retinopathy developed.

The investigators found both strategies effectively decreased the numbers of proinflammatory cells present in the diabetic retina. 

In addition, the intravitreal approach is designed to deliver the agent without interference from the blood-retinal barrier. Hypothetically, this therapy could be modified to address vascular diseases in other systems, such as the heart or kidneys.

Exercise Tires the Eyes as Well as the Body

But caffeine perks eyes up again, research shows. 

Strenuous exercise can dampen the central nervous system (CNS)—an effect known as central fatigue. Research published in Nature now shows that this fatigue also weakens the oculomotor muscles and reduces saccadic speed. But, as one might expect, a shot of caffeine appears to be the remedy. 

In this study, researchers at the University of Auckland, New Zealand, assigned 12 cyclists to three hours of stationary cycling. Immediately after the workout, the researchers tested saccadic eye movements and found that the subjects’ saccade velocity decreased by 8%.

“It’s remarkable that tiring the legs also slows the eyes,” says co-lead investigator Nicolas Gant, PhD, MSc. “This might well be the reason the tired cyclist never saw that bus coming!”

This effect was reversed in individuals given caffeine, who experienced an increase in their saccadic velocities by up to 11% after exercise. “The amount of caffeine we gave during exercise was the equivalent of two cups of coffee. We saw no effect [in control subjects] with a decaffeinated placebo drink,” Dr. Gant says. 

The researchers concluded that strenuous exercise of the locomotor system impairs the human oculomotor system, but caffeine exerts a protective effect on oculomotor control. 

But exercise had no effect on non-oculomotor perceptual tasks, such as visual attention and visual processing.

“Interestingly, the areas of the brain that process visual information are robust to fatigue,” Dr. Gant says. “It’s the pathways that control eye movements that seem to be our weakest link.”

However, Dr. Gant adds, “there’s hope for coffee drinkers because this visual impairment can be prevented by consuming caffeine.”

Infants with Zika Virus Show Retinal Findings 

Presence of the Zika virus at birth may lead to certain ophthalmologic findings in infants, reports a study in the May 2016 issue of JAMA Ophthalmology. 

Previous research has found the virus can transmit from an infected mother to the fetus in utero and lead to microcephaly, with resultant optic nerve and macular abnormalities.

For this study, researchers conducted a cross-sectional analysis of 40 infants born with microcephaly and presumed Zika virus infection in Brazil between May and December 2015. The researchers grouped the infants into those with fundus abnormalities and those without. 

The researchers found that 37 eyes in 22 infants had fundus alterations. They observed optic nerve abnormalities in 25 eyes of 15 infants, and found macular abnormalities in 24 eyes of 17 infants. 

These fundus findings were associated with infants with smaller cephalic (head) diameter at birth, and in infants whose mothers reported symptoms during the first trimester, the researchers write. 

The latter finding mirrors the history of other congenital infections, the researchers note. 

However, “no mothers reported conjunctivitis or ocular symptoms during pregnancy, which differs from the findings encountered during the Micronesia outbreak,” they state in the JAMA Ophthalmology article. “Furthermore, the last country before Brazil to have a [Zika virus] outbreak was French Polynesia, and it did not report ocular abnormalities in infants.”