|
Ophthalmology and Optometry
|
|
Friday, 17 May 2013 |
|
Myopia Progression Control (MPC) developed by Visioneering Technologies, Inc. (VTI) shows significant potential for decreasing myopic progression based on animal study results, according to a paper published in Investigative Ophthalmology and Visual Science (IOVS). A breakthrough contact lens design for myopia progression control.
Conducted by the Centre for Contact Lens Research at the University of Waterloo’s School of Optometry & Vision Science in Canada, the purpose of the randomized, masked animal study was to determine the effect of wearing VTI’s unique MPC optical design on the development and progression of defocus-induced myopia in newly hatched chickens.
According to the published study, the patented VTI MPC lens designs caused a significant reduction in the development of defocus-induced myopia over a 14-day wearing period as compared to a control contact lens that was identical in every aspect except for the inclusion of the VTI MPC optical design. It further reported that there was also a significant axial length difference with the Control group showing increased ocular axial growth as compared to the Test VTI MPC design groups.
Dr. Jill Woods, who was the lead author on the publication, commented: “This study using VTI MPC lens designs (-10D) is the first to report nearly complete inhibition of defocus-induced myopia in chickens compared to control lenses (also -10D). The lack of significant axial length increase seen with the VTI MPC test groups indicates that these lens designs reduced defocused-induced myopia progression through the inhibition of axial elongation.” Dr. Woods added: “Further work is still needed to determine the exact mechanisms by which the lens designs decreased the development of myopia, but the potential shown to decrease the development of myopia was significant.”
Myopia, the inability to see objects clearly at a distance, has a prevalence rate of 40% to 50% in the U.S. and Europe, with prevalence rates as high as 80% in some Asian countries. Myopia is the main cause of distance visual impairment worldwide, and is also associated with an increased risk of certain potentially sight-threatening conditions including glaucoma and retinal detachments.
The chicken model has been used to test the ocular development of myopia and other ocular conditions for over 50 years, according to Dr. Elizabeth Irving, professor and University Research Chair at the University of Waterloo’s School of Optometry and Vision Science and also an author on the publication. Dr. Irving, who has spent most of her career studying the development of refractive conditions in animals and humans, noted: “The chicken model of myopia development is not always directly applicable to humans, but most of the significant findings found in chicks have been subsequently replicated in monkeys and a wide variety of other species, indicating that the chicken model is robust and therefore an indicator of the possibility of similar results with the lens design in humans.”
“To date, various strategies to prevent or slow the progression of myopia in humans, such as bifocals, undercorrection and cycloplegia, have generally either been unsuccessful in the long-term, or given rise to unacceptable side-effects,” according to Dr. Sally Dillehay, vice president of clinical and regulatory affairs for VTI.
Dr. Dillehay added, “If the VTI MPC lens designs can be as effective in humans as they were in this chicken study, the potential for controlling myopia progression is significant. We have already conducted several short-term trials in humans and the vision with the VTI MPC lenses has been excellent.” VTI is now in the planning stages for the longer-term trials to demonstrate that the lens is effective in humans for decreasing the progression of myopia, according to the company.
Visioneering’s new contact lens technology has multiple applications including control of myopic progression as well as multifocal vision correction for presbyopia. The company expects to introduce a contact lens for presbyopia incorporating its unique technology in early 2014, according to Joe DeLapp, president and CEO of VTI. An intraocular lens using VTI’s technology for presbyopia is also under development.
|
|
Ophthalmology and Optometry
|
|
Thursday, 16 May 2013 |
|
Relief from dry eye and other symptoms of discomfort experienced by contact lens wearers may come through simply switching contact lens products a new study has found. Advanced contact lens products are extremely safe and provide comfortable wear for more than a hundred million people worldwide yet discomfort remains one of the main reasons people stop wearing contact lenses. As many as 12 million people drop out of lens wear annually but researchers have found relief for some may be as simple as selecting a different combination of their contact lens and disinfecting solution.
According to scientific journal Optometry and Vision Science, which published the research in its May edition, the study conducted by the Brien Holden Vision Institute in Sydney provides scientific support for a clinical approach commonly recommended by eye care professionals. The new study was designed to evaluate the amount of improvement that might reasonably be expected by switching contact lenses and lens care products. The results indicate that "roughly half" of patients with contact lens-related symptoms have improved comfort by switching to a different lens/solution combination.
However, the authors note that, even with the improvement, discomfort still increases toward the end of the day. They call for continued efforts by eye care professionals and researchers to eliminate this persistent problem and provide "a maximally comfortable result," for patients who wear contact lenses.
|
|
Ophthalmology and Optometry
|
|
Monday, 06 May 2013 |
|
People have long taken for granted that glasses and contact lenses improve vision for nearsightedness, but the genetic factors behind the common condition have remained blurry. Now researchers at Duke Medicine are closer to clearing this up.
Mutations in a gene that helps regulate copper and oxygen levels in eye tissue are associated with a severe form of nearsightedness, according to a study published in the American Journal of Human Genetics on May 2, 2013.
Nearsightedness – also known as myopia – is the most common human eye disease in the world. It occurs if the eye is too long or the cornea has too much curvature, which keeps light entering the eye from focusing correctly.
High-grade myopia, a more severe form of nearsightedness, affects up to two percent of Americans and is especially common in Asian populations. Individuals with high-grade myopia are at an increased risk for other serious eye problems, including retinal detachment, cataracts and glaucoma.
Studies suggest that myopia is caused by a combination of environmental factors, such as large amounts of reading, and genetics. Nearsightedness runs in families, but little is understood about genetic factors that cause it.
In recent years, researchers have reported several genes or locations of genes associated with myopia, and have continued to search for additional clues.
“This is the first time a gene mutation for autosomal dominant nonsyndromic high-grade myopia in Caucasians has been discovered,” said senior author Terri Young, M.D., MBA, professor of ophthalmology, pediatrics and medicine at the Duke Eye Center, Duke Center for Human Genetics and the Duke-National University of Singapore Graduate Medical School (Duke-NUS). “Our findings reflect the hard work and collaboration of our international research team.”
In this study, Young and her colleagues sought to identify these genetic factors by studying families with high-grade myopia. They performed next-generation deep sequencing on four relatives from an 11-member American family of European descent.
Analyzing DNA extracted from blood and saliva, the researchers identified mutations in the SCO2 gene in common among family members with high-grade myopia, but absent in those family members with no myopia. They confirmed four mutations in the SCO2 gene in an additional 140 people with high-grade myopia.
Once the researchers identified the mutations in DNA samples, they turned to human eye tissue and verified that the SCO2 gene was expressed in areas of the eye connected to nearsightedness.
To further support their findings, they performed an experiment in which mice were made nearsighted in one eye by wearing a strong lens. Collaborators at Duke-NUS, the Singapore Eye Research Institute and Yong Loo Lin School of Medicine at the National University of Singapore found that SCO2 gene expression decreased in the nearsighted eye, suggesting that SCO2 may play a role in the development of nearsightedness.
In the body, the SCO2 gene helps metabolize copper, an element important for regulating oxygen levels in eye tissue. Increased stress brought on by too much oxygen may alter the eye’s development and function.
Dennis J. Thiele, PhD, George Barth Geller Professor in the Department of Pharmacology and Cancer Biology at Duke, said the finding suggests that different kinds of mutations in the SCO2 gene result in different diseases. Thiele, an expert in copper metabolism who was not involved in the research, noted that another SCO2 gene mutation is responsible for a lethal form of cardiomyopathy.
“This is a fascinating finding, and it points to the relevance of copper metabolism to a spectrum of different human diseases,” Thiele said.
Since normal copper metabolism is important for eye health, future research may focus on whether copper deficiency could place someone at higher risk for nearsightedness.
“Our findings, plus information from the literature, suggest that copper deficiency could predispose people to develop myopia,” Young said. “While this wasn’t directly tested in this study, it’s possible that our diets – which are deficient in a number of minerals and vitamins – play a role, and it may be something as easy as taking a supplement with copper that helps thwart the development of myopia.”
Young noted that multiple factors are likely responsible for developing nearsightedness, and this warrants additional research. She hopes to continue by studying animal models with SCO2 mutations to better understand the gene’s connection with nearsightedness.
|
|
|
Ophthalmology and Optometry
|
|
Wednesday, 24 April 2013 |
|
 A research team led by Dr. Robert Hess from Canada's McGill University and the Research Institute of the McGill University Health Centre (RI-MUHC) has used the popular puzzle video game Tetris in an innovative approach to treat adult amblyopia, commonly known as "lazy eye". By distributing information between the two eyes in a complementary fashion, the video game trains both eyes to work together, which is counter to previous treatments for the disorder (e.g. patching).
This medical breakthrough provides direct evidence that alleviating suppression of the weaker eye, by forcing both eyes to cooperate, increases the level of plasticity in the brain and allows the amblyopic brain to relearn. The research is published in the journal Current Biology.
Amblyopia is the most common cause of visual impairment in childhood, affecting up to 3 per cent of the population. It is caused by poor processing in the brain, which results in suppression of the weaker eye by the stronger eye. Previous treatments for the disorder, which have focused largely on covering the stronger eye in order to force the weaker eye to work, have proven only partially successful in children and have been ineffective in adults.
"The key to improving vision for adults, who currently have no other treatment options, was to set up conditions that would enable the two eyes to cooperate for the first time in a given task," says Dr. Robert Hess, senior author of the paper and Director of Research Department of Ophthalmology at the RI-MUHC and at McGill University.
According to Dr. Hess and his colleagues, the adult human brain has a significant degree of plasticity and this provides the basis for treating a range of conditions where vision has been lost as a result of a disrupted period of early visual development in childhood. The researchers examined the potential of treating amblyopic adults using the video game Tetris, which involves connecting different shaped blocks as they fall to the ground.
"Using head-mounted video goggles we were able to display the game dichoptically, where one eye was allowed to see only the falling objects, and the other eye was allowed to see only the ground plane objects," explains Dr. Hess, who also serves as director of McGill Vision Research. "Forcing the eyes to work together, we believed, would improve vision in the lazy eye."
The researchers tested a sample of 18 adults with amblyopia. Nine participants played the game monocularly with the weaker eye, while the stronger eye was patched; the other nine played the same game dichoptically, where each eye was allowed to view a separate part of the game. After two weeks, the group playing the dichoptic game showed a dramatic improvement in the vision of the weaker eye as well as in 3-D depth perception. When the monocular patching group, who had showed only a moderate improvement, was switched to the new dichoptic training, the vision of this group also improved dramatically.
The suitability of this treatment in children will be assessed later this year in a clinical trial across North America.
|
|
Ophthalmology and Optometry
|
|
Monday, 15 April 2013 |
|
U.K.'s National Institute for Health and Care Excellence (NICE), the independent body responsible for driving quality improvement and excellence in the health and social care system, has issued final draft guidance recommending ranibizumab (Lucentis, Novartis) as a treatment for sight problems caused by macular oedema, which affects someone's ability to see detail and colour. The draft guidance relates to macular oedema caused when the vein to the retina or one of its branches is blocked (central or branch retinal vein occlusion). NICE recommends the treatment should only be prescribed if the manufacturer makes it available to the NHS under terms agreed with the Department of Health as part of a patient access scheme. The draft guidance has been issued to consultees, including the manufacturer, Novartis, national patient and carer groups and bodies representing health professionals, for appeal and factual changes, and is published on the NICE website for information.
The macular is the central part of the retina responsible for seeing colour and fine detail. Macular oedema occurs when fluid collects in the retina at the macular area, which can lead to severe visual impairment in the affected eye. Straight lines may appear wavy, and people can have blurred central vision or sensitivity to light. A reduction in the number of connective tissues around the capillaries and an increased amount of a protein called vascular endothelial growth factor (VEGF) causes the blood retinal barrier to become porous. This leads to plasma in the surrounding retina, causing a build-up of excess fluid (oedema) which disrupts the fovea, the area of the eye responsible for sharp vision.
The draft guidance recommends ranibizumab as an option for treating macular oedema following central retinal vein occlusion (CRVO). It also recommends the drug as a treatment option following branch retinal vein occlusion (BRVO) when standard treatment with laser photocoagulation (where a laser is used to seal ocular blood vessels) has not worked, or when it is not suitable because of the extent of macular haemorrhage.
The incidence of RVO increases with age. Other risk factors for RVO include high blood pressure, hyperlipidaemiaiii, glaucomaiv, thrombophiliav and diabetes. Macular oedema secondary to RVO is further divided into either branch retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO).
Ranibizumab, which is given by injection into the eye, works by preventing the production of VEGF. By inhibiting VEGF, ranibizumab can decrease the oedema and limit visual loss and/or improve vision.
Sir Andrew Dillon, Chief Executive at NICE, said: "The loss of vision associated with macular oedema can have a significant effect on the patient's quality of life and independence. We are recommending this treatment for NHS use in people with CRVO and some people with BRVO only if the manufacturer provides it to the NHS under terms agreed in a patient access scheme, which makes the treatment more cost effective."
The draft guidance follows consideration of further evidence and a patient access scheme submitted by the manufacturer, as well as the results of further work carried out by the NICE Decision Support Unit. The independent Appraisal Committee concluded that ranibizumab is a clinically and cost-effective treatment option for non-ischaemic macular oedema secondary to CRVO and secondary to BRVO only if treatment with laser photocoagulation has not been beneficial, or when laser photocoagulation is not suitable because of the extent of macular haemorrhage.
|
|
Ophthalmology and Optometry
|
|
Friday, 12 April 2013 |
|
Researchers have discovered that using two kinds of therapy in tandem may be a knockout combo against inherited disorders that cause blindness. While their study focused on man’s best friend, the treatment could help restore vision in people, too.
Published in the journal Molecular Therapy, the study builds on earlier work by Michigan State University veterinary ophthalmologist András Komáromy and colleagues. In 2010, they restored day vision in dogs suffering from achromatopsia, an inherited form of total color blindness, by replacing the mutant gene associated with the condition.
While that treatment was effective for most younger dogs, it didn’t work for canines older than 1 year. Komáromy began to wonder if the older dogs’ cones – the photoreceptor cells in the retina that process daylight and color – might be too worn out.
“Gene therapy only works if the nonfunctional cell that is primarily affected by the disease is not too degenerated,” he said. “That’s how we came up with the idea for this new study. How about if we selectively destroy the light-sensitive part of the cones and let it grow back before performing gene therapy? Then you’d have a younger, less degenerated cell that may be more responsive to therapy.”
So, Komáromy and colleagues recruited more dogs with achromatopsia between 1 and 3 years old. To test their theory, they again performed gene therapy but first gave some of the dogs a dose of a protein called CNTF, which the central nervous system produces to keep cells healthy. At a high enough dose, its effect on photoreceptors is a bit like pruning flowers: It partially destroys them, but allows for new growth.
“It was a long shot,” said Komáromy, associate professor in MSU’s Department of Small Animal Clinical Sciences.
But it worked.
“We were just amazed at what we found,” he said. “All seven dogs that got the combination treatment responded, regardless of age.”
While achromatopsia is quite rare, Komáromy said it’s a good model disease for other disorders affecting the photoreceptors, conditions that constitute a major cause of incurable blindness in dogs and humans. Those disorders affect individuals of both species in much the same way, so the combination treatment’s promise isn’t just for Fido.
“Based on our results we are proposing a new concept of retinal therapy,” he said. “One treatment option alone might not be enough to reverse vision loss, but a combination therapy can maximize therapeutic success.”
|
|
