Eyes and aging - anisometropia 3D vision, binocular vision and increased fall risk

A new study published in the journal, Optometry & Vision Science, has confirmed what many eye doctors with elderly patients already know: changes in the eyes as we age can degrade our ability to see depth (stereopsis) and in three dimensions (3D vision). That can contribute to blurry vision, eye strain and eye fatigue, and an increased risk of falls. Falls in the elderly are troubling because they can be the cause of brain injuries, broken bones or worse.

The new study looked at the incidence of a condition called anisometropia in elderly patients. Anisometropia is a condition in which the two eyes have unequal refractive power. That means that the focusing ability of the two eyes is unequal. Each eye is in a different state of myopia (nearsightedness) and hyperopia (farsightedness). The condition is characterized by blurry vision, double visoin, eye strain, eye fatigue, loss of depth perception. When anisometropia happens in children and infants, it can impair the development of normal binocular vision, which can lead to many learning and other problems.

Anisometropia is common in elderly people and it grows exponentially with age. The study found that significant anisometropia is at least 10 times more common in those older than 75 years than it is in children.  This is an alarming statistic and must be taken seriously by eye doctors.  At our Vancouver optometry clinic, we see large number of elderly patients because of our low vision practice and so we are always on the look-out for anisometropia.

The study's authors pointed out that the prevalence of anisometropia in US children is between 2 and 4% whereas data for those near 80 years old shows that 32% have 1.00 D or more anisometropia.

Related article:

When seniors loose depth perception and need to see a developmental optometrist
Thursday, June 28, 2012

Source:

Longitudinal Increase in Anisometropia in Older Adults

Haegerstrom-Portnoy, Gunilla; Schneck, Marilyn E.; Lott, Lori A
Optometry & Vision Science:
January 2014 - Volume 91 - Issue 1 - p 60-67

When changing or replacing contact lenses part way through the day does not improve discomfort - a new study explains why

An interesting study was published in the October 2013 issue of Optometry & Vision Science.  It addresses a situation well known to many contact lens-wearers. Over the course of a day of contact lens wear, discomfort increases for some people.  And for some of these people, changing or replacing the lens to a fresh lens part way through the day does not help. Why is that?  This study may have an answer and suggests that it is not the lens, it's physical changes happening on the surface of your eyes.

The study examined the comfort reported by patients throughout and at the end of a 10-hour day of wear. Subjects were surveyed on a 0–100 scale for comfort on two separate days.

On the first day, nothing was done to the lenses they wore throughout the day, and study participants reported decreasing comfort during the day. This result was expected, as many optometrists observe this in the clinic. Doctors have long argued about the cause of this discomfort. Was it due to ill-fitting lenses?  Or was it due to changes in the surface of the eye caused by contact lens wear?

To answer that question, on the second day the lenses were removed after 5 hours of wear. After removal, either the same lens was reinserted, or it was replaced and a new lens. The assumption was that if lens comfort improved by removing and replacing the same lens, then the surface of the eye was to blame.  On the other hand, if comfort improved after switching to a new lens, then the fit of the lens may be at fault.  The control group wore lenses continuously for 10 ours with no reinsertion or switching to a new lens.

The results showed that there was no difference between the control group (that wore the lenses continuously for 10 hours) and either the group that removed and reinserted the same lens or the group that switched to a new lens.  This lead the researchers to conclude that the increasing discomfort throughout the day was not related to the lenss. They suggested that the likely cause of increasing discomfort was a "fatigue-like response in one or more ocular tissues or stimulation of ocular surface nociceptors induced by the presence of the contact lens."

Source

Consequence of Wear Interruption for Discomfort With Contact Lenses
Optom Vis Sci 2013 Oct 17;[EPub Ahead of Print], EB Papas, D Tilia, D Tomlinson, J Williams, E Chan, J Chan, B Golebiowski



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Long-Term Orthokeratology Patient Satisfaction

Yet another study supporting the use of orthokeratology (also known as corneal reshaping) appeared in the November 2013 issue of the scientific journal Contact Lens.  The new study found that long-term satisfaction rates with orthokeratology treatment were high.  We have provided orthokeratology at our Vancouver eye clinic since we opened.

Orthokeratology is a safe and effective vision correction method where patient wears a lens retainer at night that reshapes the cornea of the eye.  The result is clear vision the next day without the need to wear corrective lenses during waking hours.  A number of studies have also shown that orthokeratology is effective in slowing or stopping myopia progression and that is save and effective in children.

The researchers who conducted the new study used a questionnaire where patients rated their visual experience and satisfaction levels with orthokeratology on a scale of 0-10.

The results of the study showed that light distortion in low light conditions decreases over time and decreases more quickly in younger patients and in patients with lower amounts of myopia. Predictably, visual performance declined after a patient skipped a night of lens retainer wear but this was usually tolerated.  In addition, the majority of patients report that they skipped overnight wear at least 1 night per week, but tolerate the resulting transient decrease in vision. Overall satisfaction was high, even after skipping a night of lens wear.

Here are the results in the study's own words:

More than 50% of patients skipped lens wear at least 1 night per week. The most common wearing pattern was 6-8 hours a day for 72.7% with 54.5% of patients wearing lenses every 2-3 nights only. Subjective vision scores after lens removal was 9.1 ± 1.1 after having worn the lenses and 8.1 ± 1.4 after skipping lens wear for 1 night. Subjective vision scores before lens insertion at the end of the day was 6.9 ± 2.0 and 5.8 ± 2.4, respectively. The number of hours until noticeable blur reduced with increased level of baseline myopia (r = 0.396; P < 0.001). 

Source:

Eye & Contact Lens
Subjective Satisfaction in Long-Term Orthokeratology Patients Eye Contact Lens 2013 Nov 01;39(6)388-393, E Santolaria, A Cerviño, A Queirós, R Brautaset, JM González-Méijome

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Oral contraceptives double the risk of glaucoma, a leading cause of blindess

Research presented recently at the 2013 Meeting of the American Academy of Ophthalmology in New Orleans, shows that women who have taken oral contraceptives for three or more years are twice as likely to suffer from glaucoma.  Glaucoma is one of the leading causes of blindness and vision lost to glaucoma is lost permanently. Glaucoma slowly takes your vision, starting at the periphery and working its way to the center.  Many people with glaucoma don't know that they have it until it is too late. The only way to detect glaucoma early enough for effective treatment is through a regular eye exam.

This is normal vision:

This is vision with glaucoma in its advanced stages:

The study looked at 3,406 American women aged 40 years or older who completed a vision and reproductive health questionnaire and underwent eye exams. The researchers found that females who had used oral contraceptives, no matter which kind, for more then three years were 2.05 times more likely to also report that they had also been diagnosed with glaucoma.

The study means that women who have taken oral contraceptives for more than three years should have a regular eye exam to screen for the early onset of glaucoma.  Other risk factors for glaucoma include elevated pressure inside the eye, visual field deficits, family history, South Asian or African ancestry, a history of myopia and other risk factors.  See your eye doctor if you are concerned.

The study rings another note of caution for women when it comes to eye health. Women are at significantly higher risk than men for many eye diseases and must therefore ensure that they are vigilant about their eye health.  Read about women's eye health at the link below:

http://www.seeforlife.ca/2013/04/womens-eye-health-vancouver.html

Nutrition to prevent Macular Degeneration: The AREDS2 Study

AMD (age-related macular degeneration) is the leading cause of blindness in those over 50.  AMD breaks down cells in the layer of tissue called the retina in the back of the eye that provide
sharp central vision.  This is the type of vision that is necessary for tasks such as reading, driving, and recognizing faces.  Advanced AMD can lead to significant vision loss and is the leading cause of blindness in North America.

This is normal vision:

This is vision people with AMD:

Optimal nutrition has been shown to be effective in slowing or preventing the advanced stages of AMD, allowing patients to keep their vision for much longer than would otherwise be the case.  The most highly regard studies are known as the AREDS studies.  There are now two studies, known as AREDS and, the latest study (published in 2013), AREDS2.

The purpose of the AREDS2 study was to evaluate the efficacy and safety of particular nutrient supplementation: lutein plus zeaxanthin and/or omega-3 long-chain polyunsaturated fatty acid supplements in reducing the risk of developing AMD. The study also assessed the effect of reducing the amount of zinc and of omitting beta carotene from the original AREDS formula.

This was the original AREDS formulation:

• 500 milligrams (mg) of vitamin C
• 400 international units of vitamin E
• 15 mg beta-carotene
• 80 mg zinc as zinc oxide
• 2 mg copper as cupric oxide

These were the modifications that were tested in AREDS2?

• 10 mg lutein and 2 mg zeaxanthin
• 1000 mg of omega-3 fatty acids (350 mg DHA and 650 mg EPA)
• No beta-carotene
• 25 mg zinc

The results of AREDS2 were summarized by Stuart P Richer OD, PhD as follows:

The AREDS2 results for the average American with a suboptimal daily intake of lutein/zeaxanthin showed a statistically significant prevention of catastrophic vision loss, primarily neovascularization. That was an incredible result, favoring a new AREDS2 formulation minus beta carotene but with lutein plus zeaxanthin. 

AREDS2 showed that there was an approximate 34% reduction overall in the risk of premanent vision loss. This means that with optimal nutrition many hundreds of thousands of people could have avoided vision disability that has made them illegal to drive and that requires them to take injections that costs hundreds of dollars each time.

Not only does optimal nutrition prevent serious eye disease, nutrients such as carotenoids have been shown to improve visual performance by providing patients with better contrast sensitivity and shortened glare recovery and better visual processing.  The carotenoids lutein and zeaxanthin have also been shown to improve cognitive function in the elderly.

NEI Press Release

Below is an excerpt from the press release issued by the National Eye Institute on the results of the AREDS 2 sudy explaining that adding lutein and zeaxanthin to the original AREDS formulation had the beneficial result of a greater reduction in the risk of developing AMD when beta-carotene is removed from the formulation because beta-carotene blocks the absorption of lutein and zeaxanthin.  Therefore the optimal formulation is the include lutein and zeaxanthin but to remove beta-caroteine.  Beta-caroteine also increases the risk of lung cancer in smokers or former smokers. This is a formulation that is good for everyone, as pointed out by one of the researchers quoted below.

In the first AREDS trial, participants with AMD who took the AREDS formulation were 25 percent less likely to progress to advanced AMD over the five-year study period, compared with participants who took a placebo. In AREDS2, there was no overall additional benefit from adding omega-3 fatty acids or a 5-to-1 mixture of lutein and zeaxanthin to the formulation. However, the investigators did find some benefits when they analyzed two subgroups of participants: those not given beta-carotene, and those who had very little lutein and zeaxanthin in their diets.

“When we looked at just those participants in the study who took an AREDS formulation with lutein and zeaxanthin but no beta-carotene, their risk of developing advanced AMD over the five years of the study was reduced by about 18 percent, compared with participants who took an AREDS formulation with beta-carotene but no lutein or zeaxanthin,” said Emily Chew, M.D., deputy director of the NEI Division of Epidemiology and Clinical Applications and the NEI deputy clinical director. “Further analysis showed that participants with low dietary intake of lutein and zeaxanthin at the start of the study, but who took an AREDS formulation with lutein and zeaxanthin during the study, were about 25 percent less likely to develop advanced AMD compared with participants with similar dietary intake who did not take lutein and zeaxanthin.” 

Because carotenoids can compete with each other for absorption in the body, beta-carotene may have masked the effect of the lutein and zeaxanthin in the overall analysis, Chew said. Indeed, participants who took all three nutrients had lower levels of lutein and zeaxanthin in their blood compared to participants who took lutein and zeaxanthin without beta-carotene Removing beta-carotene from the AREDS formulation did not curb the formulation’s protective effect against developing advanced AMD, an important finding because several studies have linked taking high doses of beta-carotene with a higher risk of lung cancer in smokers. Although smokers were not given a formulation with beta-carotene in AREDS2, the study showed an
association between beta-carotene and risk of lung cancer among former smokers. About half of AREDS2 participants were former smokers. “Removing beta-carotene simplifies things,” said Wai T. Wong, M.D., Ph.D., chief of the NEI Neuron-Glia Interactions in Retinal Disease Unit and a co-author of the report. “We have identified a formulation that should be good for everyone regardless of smoking status,” he said. Adding omega-3 fatty acids or lowering zinc to the AREDS formulation also had no effect on AMD progression.

More than 4,000 people, ages 50 to 85 years, who were at risk for advanced AMD participated in AREDS2 at 82 clinical sites across the country. Eye care professionals assess risk of developing advanced AMD in part by looking for yellow deposits called drusen in the retina. The appearance of small drusen is a normal part of aging, but the presence of larger drusen indicates AMD and a risk of associated vision loss. Over time, the retina begins to break down in areas where large drusen are present during a process called geographic atrophy. AMD can also spur the growth of new blood vessels beneath the retina, which can leak blood and fluid, resulting in sudden vision loss. These two forms of AMD are often referred to as dry AMD and wet AMD respectively. 

Frequently asked quesitons

Click here for the FAQ page on AREDS2 from the National Eye Institute.

Here are two questions that we frequently get asked at our Vancouver eye clinic:

Can a daily multivitamin alone provide the same vision benefits as an AREDS formulation?

No. The vitamins and minerals tested in the AREDS and AREDS2 trials were provided in much higher doses than what is found in multivitamins. Also, it is important to remember that most of the trial participants took multivitamins. Taking an AREDS formulation clearly provided a benefit over and above multivitamins.

Can diet alone provide the same high levels of antioxidants and zinc as the AREDS formulations?

No. The high levels of vitamins and minerals are difficult to achieve from diet alone. However, previous studies have suggested that people who have diets rich in green, leafy vegetables—a good source of lutein/zeaxanthin—have a lower risk of developing AMD. In the AREDS2 trial, the people who seemed to benefit most from taking lutein/zeaxanthin were those who did not get much of these nutrients in their diet. Within this group, those who received lutein/zeaxanthin supplements had a 26 percent reduced risk of developing advanced AMD compared with those who did not receive the supplements.