Women Have Bigger Pupils Than Men

ScienceDaily (Apr. 26, 2012) - From an anatomical point of view, a normal, non-pathological eye is known as an emmetropic eye, and has been studied very little until now in comparison with myopic and hypermetropic eyes. The results show that healthy emmetropic women have a wider pupil diameter than men.

Normal, non-pathological emmetropic eyes are the most common type amongst the population (43.2%), with a percentage that swings between 60.6% in children from three to eight years and 29% in those older than 66.

Therefore, a study determines their anatomical pattern so that they serve as a model for comparison with eyes that have refractive defects (myopia, hypermetropia and stigmatism) pathological eyes (such as those that have cataracts).

"We know very little about emmetropic eyes even though they should be used for comparisons with myopic and hypermetropic eyes" Juan Alberto Sanchis-Gimeno, researcher at the University of Valencia and lead author of the study explained.

The project, published in the journal 'Surgical and Radiologic Anatomy' shows the values by gender for the central corneal thickness, minimum total corneal thickness, white to white distance and pupil diameter in a sample of 379 emmetropic subjects.

"It is the first study that analyses these anatomical indexes in a large sample of healthy emmetropic subjects" Sanchis-Gimeno states. In recent years new technologies have been developed, such as corneal elevation topography, which allows us to increase our understanding of in vivo ocular anatomy.

Although the research states that there are no big differences between most of the parameters analysed, healthy emmetropic women have a wider pupil diameter than men.

"It will be necessary to investigate as to whether there are differences in the anatomical indexes studied between emmetropic, myopic and hypermetropic eyes, and between populations of different ethnic origin" the researcher concludes.

How the human eye works

Light penetrates through the pupil, crosses the crystalline lens and is projected onto the retina, where the photoreceptor cells turn it into nerve impulses, and it is transferred through the optic nerve to the brain. Rays of light should refract so that they can penetrate the eye and can be focused on the retina. Most of the refraction occurs in the cornea, which has a fixed curvature.

The pupil is a dilatable and contractile opening that regulates the amount of light that reaches the retina. The size of the pupil is controlled by two muscles: the pupillary sphincter, which closes it, and the pupillary dilator, which opens it. Its diameter is between 3 and 4.5 millimetres in the human eye, although in the dark it could reach up to between 5 and 9 millimetres.

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Study Links Genes to Common Forms of Glaucoma

ScienceDaily (Apr. 26, 2012) - Results from the largest genetic study of Glaucoma, a leading cause of blindness and vision loss worldwide, showed that two genetic variations are associated with primary open angle Glaucoma (POAG), a common form of the disease. The identification of genes responsible for this disease is the first step toward the development of gene-based disease detection and treatment.

About 2.2 million people in the U.S. have Glaucoma. POAG is often associated with increased eye pressure but about one-third of patients have normal pressure Glaucoma (NPG). Currently, no curative treatments exist for NPG.

Researchers including lead author Janey Wiggs, M.D., Ph.D., and Lou Pasquale, M.D., Co-Directors of the Harvard Glaucoma Center of Excellence, analyzed DNA sequences of 6,633 participants, half of whom had POAG. Participants were part of two NIH-funded studies: GLAUGEN (Glaucoma Genes and Environment) and NEIGHBOR (NEI Glaucoma Human genetics collaBORation), conducted at 12 sites in the United States. Dr. Pasquale is Director of the Glaucoma Service at Mass. Eye and Ear.

The results, reported online in PLoS Genetics (April 26, 2012), found that two variations were associated with POAG, including NPG. These are the first variants commonly associated with NPG. One variant is in a gene located on chromosome 9 called CDKN2BAS whereas the other variant is in a region of chromosome 8 where it may affect the expression of genes LRP12 or ZFPM2. These genes may interact with transforming growth factor beta (TGF-beta), a molecule that regulates cell growth and survival throughout the body. Previous studies have also implicated TGF-beta in glaucoma.

"This research has provided important new insights into the disease pathogenesis and will make future studies focused on translating this information into the clinic possible. Ultimately we hope to prevent blindness caused by this very common eye disease," said lead author Dr. Wiggs.

"This study has identified an important molecular pathway in the development of POAG. Control of TGF-beta might lead to more effective therapies for this blinding disease," said Dr. Hemin Chin, associate director for Ophthalmic Genetics at the National Eye Institute.

Funding sources for this research include the National Eye Institute, National Human Genome Research Institute, Lions Eye Research Fund, Glaucoma Center of Excellence, the Margolis Fund, and Research To Prevent Blindness.

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Future Treatment for Nearsightedness - Compact Fluorescent Light Bulbs?

ScienceDaily (May 8, 2012) - Researchers at the University of Alabama at Birmingham hope to one day use fluorescent light bulbs to slow Nearsightedness, which affects 40 percent of American adults and can cause blindness.

In an early step in that direction, results of a study found that small increases in daily artificial light slowed the development of Nearsightedness by 40 percent in tree shrews, which are close relatives of primates.

The team, led by Thomas Norton, Ph.D., professor in the UAB Department of Vision Sciences, presented the study results May 8 at the 2012 Association for Research in Vision and Ophthalmology annual meeting in Ft. Lauderdale.

People can see clearly because the front part of the eye bends light and focuses it on the retina in back. Nearsightedness, also called myopia, occurs when the physical length of the eye is too long, causing light to focus in front of the retina and blurring images.

Myopia has many causes, some related to inheritance and some to the environment. Research in recent years had, for instance, suggested that children who spent more time outdoors, presumably in brighter outdoor light, had less myopia as young adults. That raised the question of whether artificial light, like sunlight, could help reduce myopia development, without the risks of prolonged sun exposure, such as skin cancer and cataracts.

"Our hope is to develop programs that reduce the rate of myopia using energy efficient, fluorescent lights for a few hours each day in homes or classrooms," said John Siegwart, Ph.D., research assistant professor in UAB Vision Sciences and co-author of the study. "Trying to prevent myopia by fixing defective genes through gene therapy or using a drug is a multi-year, multimillion-dollar effort with no guarantee of success. We hope to make a difference just with light bulbs."

Sorting through theories

Work over 25 years had shown that putting a goggle over one eye of a study animal, one that lets in light but blurs images, causes the eye to grow too long, which in turn causes myopia. Other past studies had shown that elevated light levels could reduce myopia under these conditions, whether the light was produced by halogen lamps, metal halide bulbs or daylight. The current study is the first to show that the development of myopia can be slowed by increasing daily fluorescent light levels.

One prevailing theory on myopia-related shape changes in the eye is that they are caused by the blurriness of images experienced while reading or doing other near-work chores. Another holds some people develop myopia because they have low levels of vitamin D, which goes up with exposure to sunlight and could explain the connection between outdoor light and reduced myopia. A third theory, one reinforced by the current results, is that bright light causes an increase in levels of dopamine, a signaling molecule in the retina.

To test the theories, the team used a goggle that lets in light but no images to produce myopia in one eye of each tree shrew. They found that a group exposed to elevated fluorescent light levels for eight hours per day developed 47 percent less myopia than a control group exposed to normal indoor lighting, even though the images were neither more nor less blurry. They also found that animals fed vitamin D supplements developed myopia just like ones without the supplement. Given these results, the team is now experimenting with light levels and treatment times to see if a short, bright light treatment could be effective. They have also begun studies looking at the effect of elevated light on retinal dopamine levels as it relates to the reduction of myopia.

"If we can find the best kind of light, treatment period and light level, we'll have the scientific justification to begin studies raising light levels in schools, for instance," said Norton. "Compact fluorescent bulbs use much less electricity than standard light bulbs, and future programs raising light levels will have more impact the less expensive they are."

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New Eye Imaging Techniques Are On the Horizon

ScienceDaily (May 7, 2012) - The same technology used by astronomers to obtain clear views of distant stars is now being used by optometrists to perform incredibly detailed examinations of the living Eye.

An update on new developments in ocular imaging techniques -- and how they may affect clinical vision care in the not-too-distant future -- is presented in an article titled "Adaptive Optics Scanning Laser Ophthalmoscope-based Microperimetry" published in a special May issue of Optometry and Vision Science, official journal of the American Academy of Optometry.

Cutting-edge techniques now allow researchers to visualize the fine structure of the Eye in a way that was "not conceivable 20 years ago," according to a guest editorial by Scott Read OD PhD FAAO (Candidate) and colleagues. "As these advanced imaging methods continue to develop, the potential for imaging ocular structures down to the cellular level in everyday clinical practice has become a reality -- and the potential to improve patient care is truly stunning," Dr Read and coauthors add.

New Techniques Provide Cellular-Level Images of the Living Eye The special issue presents 30 reports on the latest, most advanced techniques for imaging and measurement of various Eye structures: the retina and optic nerve, lens and ciliary body, and the anterior Eye. Written by leading researchers and clinicians, the contributions provide a fascinating look at these remarkable new technologies, with a glimpse of their likely extensions into clinical practice.

As just one example, William S. Tuten, OD, MS, and colleagues of the University of California, Berkeley, report on the development and use of an "adaptive optics scanning laser ophthalmoscope." Adaptive optics refers to the use of advanced techniques to correct for optical aberrations through any transparent media. Originally developed for use in telescopes to correct for the distorting effects of the atmosphere, adaptive optics is now being applied to evaluating the structure and function of the human eye.

Dr. Tuten and colleagues have applied adaptive optics to perimetry -- also known as visual field testing -- on the microscopic scale. Perimetry is an important part of evaluation for patients with vision disorders including macular degeneration, retinitis pigmentosa, and diabetic retinopathy. Perimetry measures vision in all parts of the visual field, including the peripheral vision.

Promising Applications to Improve Clinical Vision Care The new paper describes (and illustrates) the use of adaptive optics-guided microperimtery to assess visual fields at an unprecedented level of detail. The technique can not only show limitations in visual fields, but can trace the defect to individual retinal photoreceptor cells. High-speed tracking is used to correct for normal eye movement, or "jitter," that is practically undetectable using conventional imaging techniques.

In addition, by using microscopic blood vessels as anatomical landmarks, the adaptive optics technique permits repeated studies to be repeated over time at a high level of precision. This offers unique opportunities for studying how treatments work on the cellular level, as well as following the effects of treatment over time in individual patients.

"This technique opens new horizons for clinician-scientists, and later clinicians, to better understand, and plot out, the relationships between vision and the retinal photoreceptors at a microscopic level," comments Anthony Adams, OD, PhD, Editor-in-Chief of Optometry and Vision Science. "It enables a new understanding of vision loss in patients with retinal disorders where there are discrete photoreceptor losses -- for example, macular degeneration."

Adaptive optics-guided microperimetery and other advanced imaging technologies described in the special issue have the potential to revolutionize the management of eye diseases, Dr. Read and colleagues believe. They conclude, "With ongoing improvements in imaging speed and resolution, and with the application of innovative methods to improve the clinical usefulness of ocular imaging techniques, the future of ocular imaging is bright!"

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Contact Lenses Provide Extended Pain Relief to Laser Eye Surgery Patients

Scientists are reporting development of Contact lenses that could provide a continuous supply of anesthetic medication to the eyes of patients who undergo laser eye surgery -- an advance that could relieve patients of the burden of repeatedly placing drops of medicine into their eyes every few hours for several days.Their report appears in ACS' journal Langmuir

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Anuj Chauhan and colleagues explain that more than 1 million laser eye correction procedures are performed each year in the U.S. The surgery enables most patients to see clearly without eye glasses or Contact lenses. The procedure known as LASIK is the most common type of laser eye surgery, but complications can develop if the patient undergoes trauma or is hit very hard at any time after the procedure. Photorefractive keratectomy (PRK) doesn't have this complication, and that's why it is preferred for athletes and those in the military. A downside to PRK, however, is a longer period of pain after surgery. To ease their pain, PRK patients place drops of several medications, including anesthetics, into their eyes every few hours, which can interfere with daily life and increase the risk of drug overdose. PRK patients receive a special "bandage Contact lens" after surgery to help the outer layer of the eye heal.
The researchers tested whether anesthetics loaded onto this type of lens could release the drugs over time automatically. They found that adding vitamin E to the lenses extended the time of release of three commonly used anesthetics from just under two hours to up to an entire day -- or a few days in some instances. The vitamin E acts as a barrier, keeping the anesthetics on the eye, right where they are needed. The researchers say that, in the future, these lenses could serve as bandage Contact lenses after PRK surgery while also delivering necessary pain medications.
The authors acknowledge funding from the University of Florida.

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Glaucoma as Neurologic Disorder Rather Than Eye Disease?

 

ScienceDaily (Mar. 7, 2012) - A new paradigm to explain Glaucoma is rapidly emerging, and it is generating brain-based treatment advances that may ultimately vanquish the disease known as the "sneak thief of sight." A review now available in Ophthalmology, the journal of the American Academy of Ophthalmology, reports that some top researchers no longer think of Glaucoma solely as an eye disease. Instead, they view it as a neurologic disorder that causes nerve cells in the brain to degenerate and die, similar to what occurs in Parkinson disease and in Alzheimer's. The review, led by Jeffrey L Goldberg, M.D., Ph.D., assistant professor of ophthalmology at the Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, describes treatment advances that are either being tested in patients or are scheduled to begin clinical trials soon.

Glaucoma is the most common cause of irreversible blindness worldwide. For many years, the prevailing theory was that vision damage in Glaucoma patients was caused by abnormally high pressure inside the eye, known as intraocular pressure (IOP). As a result, lowering IOP was the only goal of those who developed surgical techniques and medications to treat Glaucoma. Creating tests and instruments to measure and track IOP was crucial to that effort. Today, a patient's IOP is no longer the only measurement an ophthalmologist uses to diagnose Glaucoma, although it is still a key part of deciding how to care for the patient. IOP-lowering medications and surgical techniques continue to be effective ways to protect glaucoma patients' eyes and vision. Tracking changes in IOP over time informs the doctor whether the treatment plan is working.

But even when surgery or medication successfully lowers IOP, vision loss continues in some glaucoma patients. Also, some patients find it difficult to use eye drop medications as prescribed by their physicians. These significant shortcomings spurred researchers to look beyond IOP as a cause of glaucoma and focus of treatment.

The new research paradigm focuses on the damage that occurs in a type of nerve cell called retinal ganglion cells (RGCs), which are vital to the ability to see. These cells connect the eye to the brain through the optic nerve.

RGC-targeted glaucoma treatments now in clinical trials include: medications injected into the eye that deliver survival and growth factors to RGCs; medications known to be useful for stroke and Alzheimer's, such as cytidine-5-diphosphocholine; and electrical stimulation of RGCs, delivered via tiny electrodes implanted in contact lenses or other external devices. Human trials of stem cell therapies are in the planning stages.

"As researchers turn their attention to the mechanisms that cause retinal ganglion cells to degenerate and die, they are discovering ways to protect, enhance and even regenerate these vital cells," said Dr. Goldberg. "Understanding how to prevent damage and improve healthy function in these neurons may ultimately lead to sight-saving treatments for glaucoma and other degenerative eye diseases."

If this neurologically-based research succeeds, future glaucoma treatments may not only prevent glaucoma from stealing patients' eyesight, but may actually restore vision. Scientists also hope that their in-depth exploration of RGCs will help them determine what factors, such as genetics, make some people more vulnerable to glaucoma.

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Vitamin B-Based Treatment for Corneal Disease May Offer Some Patients a Permanent Solution

ScienceDaily (Oct. 24, 2011) - Patients in the United States who have the Cornea-damaging disease keratoconus may soon be able to benefit from a new treatment that is already proving effective in Europe and other parts of the world. The treatment, called collagen crosslinking, improved vision in almost 70 percent of patients treated for keratoconus in a recent three-year clinical trial in Milan, Italy. The treatment is in clinical trials in the United States and is likely to receive FDA approval in 2012.

The results of the Milan study are being presented Oct. 24, 2011 at the 115th Annual Meeting of the American Academy of Ophthalmology in Orlando, Florida.

In a session titled Long-term Results of Corneal Crosslinking for Keratoconus, Paolo Vinciguerra, MD will describe the treatment and three-year follow up of more than 250 keratoconus patients who received collagen crosslinking at his clinic. Sixty-eight percent of the 500 eyes treated gained significant visual acuity, with their results remaining stable at the end of the follow-up period. Patients over age 18 were most likely to improve.

In the collagen crosslinking procedure, riboflavin (vitamin B) is applied to the Cornea, which is then exposed to a specific form of ultraviolet light. Collagen fibers regenerate with new bonds forming between them, increasing Corneal stiffness and strength. The treatment also combats the causes of keratoconus, reducing the chance that it will recur. The rest of the eye receives only minimal UV exposure during treatment. Dr. Vinciguerra's new study confirms that adverse effects are rare. Previous research by his team indicated no loss of Corneal endothelial cell, a measurement used to assess the safety of Corneal treatments, in patients who received collagen crosslinking.

"For many people with keratoconus, collagen crosslinking can provide a better and more permanent solution to their vision problems," said Dr. Vinciguerra. "Given that no current treatment in use in the U.S. offers permanent correction, this effective option represents a significant advance for Corneal medicine."

One in 2,000 people in the United States and worldwide are diagnosed with keratoconus, a disease that damages the collagen fibers that form the structure of the Cornea, which is the outer surface of the eye. The cornea's crucial task is to focus, or "refract," incoming light toward the eye's lens. To perform properly, the cornea needs to be rounded, like the surface of a ball. As keratoconus worsens and the cornea becomes thinner, it may bulge outward in a cone shape, causing nearsightedness and/or astigmatism, making clear vision impossible. As the number of fibers and links between them decline, the cornea loses up to 50 percent of its normal stiffness.

Standard treatments in the U.S., such as specialized eyeglasses, contact lenses, or implanted lenses, cannot permanently correct keratoconus, and none of these treatments address the underlying causes. Severe keratoconus often requires corneal transplant.

The 115th Annual Meeting of the American Academy of Ophthalmology is in session October 23 through 25 at the Orange County Convention Center in Orlando, Fla. It is the world's largest, most comprehensive ophthalmic education conference. Approximately 25,000 attendees and more than 500 companies gather each year to showcase the latest in ophthalmic technology, products and services. To learn more about the place Where All of Ophthalmology Meets visit www.aao.org/annual_meeting.

 

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