Category: Eye Conditions

Scientists Learn How Humans See in Bright and Low Light

Researchers  have discovered the delicate and detailed process that controls how the eye quickly adapts to darkness and how it functions in the bright light of day, leading to an increased understanding of how the retina works.

The retina’s main light-sensing cells, or photoreceptors, consist of rods and cones.   Cones permit us to see colors and can adapt to rapid changes in light intensity – a factor in night blindness.   The molecules that make up photoreceptors sense light and develop pigments and then are destroyed when they absorb light.  The process is cyclical – the pigments are  built up or destroyed depending on how much light is present.  When they are exposed to light  key pigment components known as chromophores leave the molecule cells and migrate to the nearby layer of pigment.  There the chromophore is restored and returned to the photoreceptor cells.

Researchers discovered this by removing the pigment layer in  retinas of salamanders so that the chromophores could not be restored.  Following this change, when the photoreceptors were exposed to alternating bright light and dark the rod cells didn’t work, but the cones, that controlled adaption continued to function, even without the pigment epithelium layer.

Muller cells support the interaction with rods and cones.  Scientists treated mouse retinas with a chemical that destroyed Müller cells and then exposed the  retinas to bright light, followed by darkness. 

Without Müller cells  the photoreceptor process could not function because cones ran out of pigment and could not adapt to dark. Proper functioning of   Müller cells are required for retinas to both function in bright light and be able to adapt to darkness.

Study authors believe that in the future it may be possible to manipulate this pathway in the retina to improve vision when the other pathway, involving pigment epithelium, has been interrupted by injury or disease, such as age-related macular degeneration.

Researchers: Washington University School of Medicine, St. Louis, Missouri

Published:  Wang, et al, “An alternative pathway mediates the mouse and human cone visual cycle”, Current Biology vol. 19 (19), Oct. 13, 2009.
“Researchers discover mechanism that helps humans see in bright and low light”, https://mednews.wustl.edu/news/page/normal/14856.html

Discovery of Lymph Channels in Eye May Help Glaucoma

A Canadian research team has uncovered lymph channels in the eye, a find that could lead the way to improved treatments for glaucoma and possibly other eye diseases. Previously lymph channels were not believed to be associated with the part of the eye related to glaucoma.

A Canadian research team has uncovered lymph channels in the eye, a find that could lead the way to improved treatments for glaucoma and possibly other eye diseases. Previously lymph channels were not believed to be associated with the part of the eye related to glaucoma.

The lymphatic system consists of organs, ducts, and nodes that transport a watery clear fluid called lymph, which performs two major functions. The fluid distributes immune cells called lymphocytes and other elements throughout the body, which protect the body against infections. It also interacts with the blood to drain waste and fluids from cells and tissues. Lymphatics are found in every part of the body except the central nervous system and, until now, the eyes were excluded as well.

This discovery provides a new avenue in the potential treatment and possibly cure of glaucoma by specifically targeting the lymphatic circulation to lower eye pressure.

SOURCES:
Glaucoma Research Foundation
University of Toronto

Editor’s Note: See more information on glaucoma and related nutrients,

Lutein, black currant extract may reduce visual fatigue

Visual fatigue such as computer eye strain caused by staring at the computer for long hours, may be eased a daily supplement containing blackcurrant fruit extract (200 mg), lutein (5 mg), and zeaxanthin (1 mg), according to a randomized, double-blind, placebo-controlled cross-over trial.

Visual fatigue such as computer eye strain caused by staring at the computer for long hours, may be eased a daily supplement containing black currant fruit extract (200 mg), lutein (5 mg), and zeaxanthin (1 mg), according to a randomized, double-blind, placebo-controlled cross-over trial.

The findings, published in the journal Applied Ergonomics, adds to the ever growing body of science supporting the eye health benefits of lutein and zeaxanthin.

Editor’s Notes: See more information on how to help prevent or minimize computer eye strain.

Retinal Device Helps Some With Retinitis Pigmentosa See

More than thirty blind people can now see thanks to new technology that has restored their vision. To date, thirty-eight subjects from the United States, Mexico and Europe with retinitis pigmentosa have received retinal prostheses. While the degree of success has been variable across subjects the results are encouraging.

More than thirty blind people can now see thanks to new technology that has restored their vision. To date, thirty-eight subjects from the United States, Mexico and Europe with retinitis pigmentosa have received retinal prostheses. While the degree of success has been variable across subjects the results are encouraging.

Procedures currently help individuals with retinitis pigmentosa (RP), a disease responsible for roughly 200,000 cases of blindness in the United States.

The restoration process starts with an image captured by a small camera attached to a pair of glasses. After streaming through a video processor, the data is then transferred back through the glasses to a tiny electrode “sheet” implanted on the retina. These electrodes use electrical impulses to communicate visual information to undamaged retinal tissue (just as healthy rods and cones would have done). The result is some degree of sight.

Currently the devices have only 60 electrodes, compared to more than 2 million in HD televisions, so images are still rough. Researchers from Second Sight will follow project participants for the next three years to track progress. They hope to develop versions with 200 and 1000 electrodes in the future.

Editor’s Notes: Certain nutrients have been researched as helping to preserve vision for those with Retinitis Pigmentosa.

Poor Circulation and Age Related Macular Degeneration Study

A large study found strong evidence that older people who have age-related macular degeneration (AMD) are at increased risk for coronary heart disease (CHD), although not for stroke. This result adds to mounting evidence that AMD and cardiovascular disease may share some risk factors–smoking, High Blood Pressure, inflammatory indicators such as C-reactive protein (related to inflammation), genetic variants such as complement factor H–and disease mechanisms.

 

A large study found strong evidence that older people who have age-related macular degeneration (AMD) are at increased risk for coronary heart disease (CHD), although not for stroke. This result adds to mounting evidence that AMD and cardiovascular disease may share some risk factors–smoking, High Blood Pressure, inflammatory indicators such as C-reactive protein (related to inflammation), genetic variants such as complement factor H–and disease mechanisms.

The Cardiovascular Health Study (CHS) followed 1,786 white or African American participants, who were free of CHD or stroke at the study’s outset, for about seven years. The CHS received funding from the National Heart, Lung and Blood Institute, a division of the National Institutes of Health.

The incidence of CHD was 25.76 percent in patients with AMD, compared with 18.9 percent in those without AMD. The association between AMD and CHD was somewhat stronger in people age 69 to 78 than age 79 and up. Data were adjusted to counter potentially confounding factors like hypertension, diabetes, and smoking.

Editor’s Notes: It is estimated that the eyes/visual system requires up to 25% of the nutrients we take into our bodies to maintain healthy vision, so this is another study showing the strong correlation between circulation and macular degeneration (and resulting loss of oxygen and nutrients that reach the eyes).

See more information on nutrients for macular support.

Retinal Implants Can Restore Some Lost Vision

MIT engineers have designed a retinal implant for people who have lost their vision from retinitis pigmentosa or age-related macular degeneration, two of the leading causes of blindness.
The retinal prosthesis would help restore some vision by electrically stimulating the nerve cells that normally carry visual input from the retina to the brain.

MIT engineers have designed a retinal implant for people who have lost their vision from retinitis pigmentosa or age-related macular degeneration, two of the leading causes of blindness.

The retinal prosthesis would help restore some vision by electrically stimulating the nerve cells that normally carry visual input from the retina to the brain.

The chip would not restore normal vision but could help blind people more easily navigate a room or walk down a sidewalk. “Anything that could help them see a little better and let them identify objects and move around a room would be an enormous help,” says Shawn Kelly, a researcher in MIT’s Research Laboratory for Electronics and member of the Boston Retinal Implant Project.

Patients who received the implant would wear a pair of glasses with a camera that sends images to a microchip attached to the eyeball. The glasses also contain a coil that wirelessly transmits power to receiving coils surrounding the eyeball. When the microchip receives visual information, it activates electrodes that stimulate nerve cells in the areas of the retina corresponding to the features of the visual scene. The electrodes directly activate optical nerves that carry signals to the brain, bypassing the damaged layers of retina.

The research team, led by John Wyatt, MIT professor of electrical engineering and computer science, recently reported a new prototype that they hope to start testing in blind patients within the next three years, after some safety refinements are made. Once human trials begin and blind patients can offer feedback on what they’re seeing, the researchers will learn much more about how to configure the algorithm implemented by the chip to produce useful vision.

Source: Massachusetts Institute of Technology
See more information on the latest research on nutrition and vision.

A Step Towards a Cure for Color-Blindness

Researchers from the University of Washington and the University of Florida have used gene therapy to cure two monkeys of color blindness. 

An article published online in the journal Nature discusses the potential for this type of gene therapy to treat adult vision disorders involving cone cells, including color blindness and other retinal diseases.

Color blindness is an inherited disorder caused by a single defective or absent gene.  Jay Neitz, a professor of ophthalmology at the University of Washington (U.W.) School of Medicine and senior study author and his wife Maureen Neitz, also in the U.W. ophthalmology department, have identified this particular gene and developed a working virus vector to carry a functional copy of it.

Researchers injected the gene-carrying virus into the monkeys’ eyes. In about 20 weeks the monkeys attained full color vision and have shown no harmful side effects.

Color-blindness is a common genetic disorder, affecting more than 3.5 people in the United States, including about 8% of Caucasian men, leaving them unable to distinguish between red and green hues.

The research team hopes to be able to translate the findings into clinical trials for humans. The team used human genetic material in the monkeys in the interest of expediting future research.

SOURCE:  Colour blindness corrected by gene therapy, Nature doi:10.1038/news.2009.921

Increasing antioxidants may help Pseudoexfoliation syndrome (PES)

Study suggests that Increasing antioxidants may help Pseudoexfoliation Syndrome (PES) which can cause glaucoma.

Pseudoexfoliation syndrome (PES) is an eye condition that leads to glaucoma. This condition has been called this because deposits on the surface of the lens look like flakes of dandruff, as if the lens capsule has exfoliated (shed the flakes). This is due to parts of the eye creating these flakes. If PES results in increased intraocular pressure and/or resulting changes on the optic nerve, then treatment is typically prescribed eyedrops to lower eye pressure.

A recent study suggests that PES is a secondary result of aging, and may be due to lower availability of antioxidants to the eyes. The result may result of higher intensity of oxidative stress.Eur J Ophthalmol. 2006 Mar-Apr;16(2):268-73.

For more related information on nutrition and glaucoma, go to www.naturaleyecare.com

High-Risk Glaucoma Patients: Risk Factors

Damage to Hemifields

Scientists have determined that glaucoma patients who have damage to both hemifields (half of the visual field) of their eye will experience more rapid progression of the disease than patients who have damage to a single hemifield.

The study, published in the September 2009 journal Archives of Ophthalmology, reviews data from 205 patients.  79 were found with an initial superior defect, 61 with an initial inferior defect, and 65 with both hemifields affected.

Analysis showed significantly higher baseline intraocular pressure and thinner central corneal thickness in patients with initial damage to both hemifields.

The study authors concluded that initial damage to both hemifields increases the risk of glaucoma progression, and that doctors should consider more aggressive therapy for these patients.

Source:  Glaucoma With Early Visual Field Loss Affecting Both Hemifields and the Risk of Disease Progression, De Moraes, et al,  Arch Ophthalmol. 2009;127(9):1129-1134.

Race & Glaucoma Risk

Specific gene mutations can be the cause of glaucoma, according to Indian researchers. Almost 4% of glaucoma sufferers exhibit gene mutations.  Scientists are identifying the specific mutations found in glaucoma patients in India and across the world; they have developed a database to make the statistical and clinical information and published it in the journal Bioinformatics. Since 20% of all glaucoma cases affect Indians and people of Indian decent, this research is of specific interest to this country’s researchers.

Source: The Times of India

Glaucoma tends to affect some racial groups more than others.  In the US, African Americans are more than twice as likely to develop the disease than non-Hispanic whites.  It has also been known for some time that Latinos have an elevated risk of glaucoma as well.

A 2011 study published in the journal Ophthalmology shows that Asian Americans also run a higher risk of developing glaucoma than their white American counterparts.  Asian Americans have about a 6.5% chance of getting glaucoma.

The report also offered some specific details by ethnic group as well.  People of Japanese decent are 10 times more likely to develop normal-tension glaucoma (when the intraocular pressure is not elevated; IOP has generally been considered the telltale sign of glaucoma, but you can have the disease without having elevated eye pressure.

Source: Medical News Today

Myopia & Glaucoma Risk

A Chinese study finds that there is a relationship between the biomechanical properties of the cornea and the degree to which an individual suffers from myopia.  Amongst their findings, researchers describe how highly myopic subjects were more likely to have decreased corneal hysteresis (CH).  CH is a measure of viscous damping in the corneal tissue.  The figure indicates the “energy absorption capability” of the cornea – in other words, how it is able to scatter and diffuse light.

Scientists also notes that severe cases of myopia have been associated with an increased risk of glaucoma.

Source: Eye, (6 May 2011)

Learn more about myopia, also known as nearsightedness.

Glaucoma – Myopia Connection Studied

Researchers in Australia are working to unravel the genetic code of glaucoma and myopia.

Teams across the world have been building upon one another’s work to pinpoint the Caveolin that is thought to be responsible for glaucoma.  These same researchers are also working with the results of studies in Europe that show the genes GJD2 and RASGRF1 to be related to the development of myopia.

Both of these discoveries rely on using Twins Eye Study to corroborate the researchers findings.  Twins studies are essential to genetics twins share nearly 100% of their genetic polymorphisms and can help scientists determine whether conditions are causes by inherited or genetic factors.

Source: https://www.news.uwa.edu.au/

 

 

 

 

Lutein, Zeaxanthin and Vitamin E Reduce Risk of Cataracts

Lutein, Zeaxanthin and Vitamin E Reduce Risk of Cataracts Jan. 2008 Study

An observational 10-year study of more than 35,000 middle-aged U.S. women observed the women’s use of dietary supplements and occurrence of cataracts.*

The study found significant evidence that women who got more lutein, zeaxanthin and vitamin E were less likely to develop cataracts than women who are lacking intake of these nutrients. In fact, the women who got the most lutein, zeaxanthin and vitamin E were 18% less likely to get cataracts.

Archives of Ophthalmology (Arch. Ophthalmol. 2008;126:102-9) gathered from the Women’s Health Study.

For more related research studies, go to www.naturaleyecare.com