Orthokeratology Contact Lenses Work by Flattening Front of Cornea, Not the Entire Cornea.

A contact lens technique called Orthokeratology or ortho-k brings rapid improvement in vision for nearsighted patients. Now a new study shows that Orthokeratology treatment works mainly by flattening the front of the cornea, reports a recent study, "Posterior Corneal Shape Changes in Myopic Overnight Orthokeratology," appearing in the March issue of Optometry and Vision Science.

"This study appears to show that it is only, or primarily, the very front surface layers of the cornea that are altered by Orthokeratology contact lens treatment," comments Anthony Adams, OD, PhD, Editor-in-Chief of Optometry and Vision Science. The study was performed by Jeong Ho Yoon, PhD, of University of Choonhae Health Science, Ulsan, Republic of Korea, and Helen A. Swarbick, PhD, FAAO, of University of New South Wales, Sydney, Australia.


Overnight Orthokeratology Works 
-- But How?

Orthokeratology is a clinical technique to reduce nearsightedness (myopia) using specially designed rigid contact lenses to manipulate the shape of the cornea -- the transparent front part that lets light into the eye. Dr Adams likens Orthokeratology therapy to orthodontic treatment using braces to change the alignment of the teeth.

He explains "Wearing these lenses overnight for about six hours is currently the treatment approach for most clinicians who use Orthokeratology for the temporary correction of low to moderate myopia." But it has been unclear exactly how Orthokeratology works to reduce myopia: Do the contact lenses reshape just the front surface of the cornea, or do they bend and flatten the entire cornea?

To find out, Drs Yoon and Swarbick had 18 young adults with "low" (relatively mild) myopia wear Orthokeratology lenses overnight for 14 days. Using sophisticated techniques, the researchers made detailed measurements of corneal shape and thickness before, during, and after treatment.
As in previous studies, wearing Orthokeratology contact lenses led to reduced myopia, thus improving vision. The changes were significant after the first night wearing Orthokeratology lenses, By 14 days, myopia was almost completely eliminated and the participants had near-normal uncorrected (without glasses) visual acuity.

Results 'Achieved Primarily through Remodeling of Anterior Cornea'

These changes were linked to significant flattening of the anterior (front) portion of the cornea. Like the vision changes, the change in corneal shape was significant after the first night wearing Orthokeratology lenses. Although corneal flattening continued throughout the 14-day treatment period, about 80 percent of the change occurred in the first four days.

In contrast, Orthokeratology lenses caused only a small and temporary change in the shape of the posterior (rear) cornea, and only slight thinning of the central cornea. "Overall, our results support the current hypothesis that the Orthokeratology refractive effect is achieved primarily through remodeling of the anterior corneal layers, without overall corneal bending," according to Drs Yoon and Swarbick.

Overnight Orthokeratology contact lenses provide an effective treatment for relatively mild myopia. It requires custom-made rigid contact lenses designed to accommodate the shape and desired change of the patient's eye. While Orthokeratology lenses provide an alternative to LASIK surgery for correction of myopia, the patient must continue nightly contact lens wear to maintain the improvement.

The authors hope their results "will provide a more complete picture of overall corneal changes during myopic Orthokeratology." In particular, the study demonstrates that overnight Orthokeratology lenses don't change the curvature of the posterior cornea -- "at least in the first two weeks of lens wear."

This article was republished from Science Daily http://www.sciencedaily.com/releases/2013/03/130304123124.htm

Read more »

Eye Movements Reveal Reading Impairments in Schizophrenia

A study of eye movements in schizophrenia patients provides new evidence of impaired reading fluency in individuals with the mental illness.

The findings, by researchers at McGill University in Montreal, could open avenues to earlier detection and intervention for people with the illness.

While schizophrenia patients are known to have abnormalities in language and in eye movements, until recently reading ability was believed to be unaffected. That is because most previous studies examined reading in schizophrenia using single-word reading tests, the McGill researchers conclude. Such tests aren't sensitive to problems in reading fluency, which is affected by the context in which words appear and by eye movements that shift attention from one word to the next.

The McGill study, led by Ph.D. candidate Veronica Whitford and psychology professors Debra Titone and Gillian A. O'Driscoll, monitored how people move their eyes as they read simple sentences. The results, which were first published online last year, appear in the February issue of the Journal of Experimental Psychology: General.

eye movement measures provide clear and objective indicators of how hard people are working as they read. For example, when struggling with a difficult sentence, people generally make smaller eye movements, spend more time looking at each word, and spend more time re-reading words. They also have more difficulty attending to upcoming words, so they plan their eye movements less efficiently.

The McGill study, which involved 20 schizophrenia outpatients and 16 non-psychiatric participants, showed that reading patterns in people with schizophrenia differed in several important ways from healthy participants matched for gender, age, and family social status. People with schizophrenia read more slowly, generated smaller eye movements, spent more time processing individual words, and spent more time re-reading. In addition, people with schizophrenia were less efficient at processing upcoming words to facilitate reading.

The researchers evaluated factors that could contribute to the problems in reading fluency among the schizophrenia outpatients -- specifically, their ability to parse words into sound components and their ability to skillfully control eye movements in non-reading contexts. Both factors were found to contribute to the reading deficits.

"Our findings suggest that measures of reading difficulty, combined with other information such as family history, may help detect people in the early stages of schizophrenia -- and thereby enable earlier intervention," Whitford says.

Moreover, fluent reading is a crucial life skill, and in people with schizophrenia, there is a strong relationship between reading skill and the extent to which they can function independently, the researchers note. "Improving reading through intervention in people with schizophrenia may be important to improving their ability to function in society," Titone adds.


Article republished from http://www.sciencedaily.com/releases/2013/02/130219121451.htm

Read more »

Vitreous Detachment

What is vitreous detachment?

Most of the eye's interior is filled with vitreous, a gel-like substance that helps the eye maintain a round shape. There are millions of fine fibers intertwined within the vitreous that are attached to the surface of the retina, the eye's light-sensitive tissue. As we age, the vitreous slowly shrinks, and these fine fibers pull on the retinal surface. Usually the fibers break, allowing the vitreous to separate and shrink from the retina. This is avitreous detachment.
In most cases, a vitreous detachment, also known as a posterior vitreous detachment, is not sight-threatening and requires no treatment.

Risk Factors

Who is at risk for vitreous detachment?

A vitreous detachment is a common condition that usually affects people over age 50, and is very common after age 80. People who are nearsighted are also at increased risk. Those who have a vitreous detachment in one eye are likely to have one in the other, although it may not happen until years later.

Symptoms and Detection

What are the symptoms of vitreous detachment?

As the vitreous shrinks, it becomes somewhat stringy, and the strands can cast tiny shadows on the retina that you may notice as floaters, which appear as little "cobwebs" or specks that seem to float about in your field of vision. If you try to look at these shadows they appear to quickly dart out of the way.
One symptom of a vitreous detachment is a small but sudden increase in the number of new floaters. This increase in floaters may be accompanied by flashes of light (lightning streaks) in your peripheral, or side, vision. In most cases, either you will not notice a vitreous detachment, or you will find it merely annoying because of the increase in floaters.

How is vitreous detachment detected?

The only way to diagnose the cause of the problem is by a comprehensive dilated eye examination. If the vitreous detachment has led to a macular hole or detached retina, early treatment can help prevent loss of vision.

Treatment

How does vitreous detachment affect vision?

Although a vitreous detachment does not threaten sight, once in a while some of the vitreous fibers pull so hard on the retina that they create amacular hole to or lead to a retinal detachment. Both of these conditions are sight-threatening and should be treated immediately.
If left untreated, a macular hole or detached retina can lead to permanent vision loss in the affected eye. Those who experience a sudden increase in floaters or an increase in flashes of light in peripheral vision should have an eye care professional examine their eyes as soon as possible.
Article republished from http://www.nei.nih.gov/health/vitreous/vitreous.asp#a

Read more »

Who is likely to develop Dry Eye?

Who is likely to develop Dry Eye?

Elderly people frequently experience dryness of the eyes, but Dry Eye can occur at any age. Nearly five million Americans 50 years of age and older are estimated to have Dry Eye. Of these, more than three million are women and more than one and a half million are men. Tens of millions more have less severe symptoms. Dry Eye is more common after menopause. Women who experience menopause prematurely are more likely to have eye surface damage from Dry Eye.

Treatment

How is Dry Eye treated?

Depending on the causes of Dry Eye, your doctor may use various approaches to relieve the symptoms.

Dry Eye can be managed as an ongoing condition. The first priority is to determine if a disease is the underlying cause of the Dry Eye (such as Sjögren's syndrome or lacrimal and meibomian gland dysfunction). If it is, then the underlying disease needs to be treated.

Cyclosporine, an anti-inflammatory medication, is the only prescription drug available to treat Dry Eye. It decreases corneal damage, increases basic tear production, and reduces symptoms of Dry Eye. It may take three to six months of twice-a-day dosages for the medication to work. In some cases of severe Dry Eye, short term use of corticosteroid eye drops that decrease inflammation is required.

If Dry Eye results from taking a medication, your doctor may recommend switching to a medication that does not cause the Dry Eye side effect.

If contact lens wear is the problem, your eye care practitioner may recommend another type of lens or reducing the number of hours you wear your lenses. In the case of severe Dry Eye, your eye care professional may advise you not to wear contact lenses at all.

Another option is to plug the drainage holes, small circular openings at the inner corners of the eyelids where tears drain from the eye into the nose. Lacrimal plugs, also called punctal plugs, can be inserted painlessly by an eye care professional. The patient usually does not feel them. These plugs are made of silicone or collagen, are reversible, and are a temporary measure. In severe cases, permanent plugs may be considered.

In some cases, a simple surgery, called punctal cautery, is recommended to permanently close the drainage holes. The procedure helps keep the limited volume of tears on the eye for a longer period of time.

In some patients with Dry Eye, supplements or dietary sources (such as tuna fish) of omega-3 fatty acids (especially DHA and EPA) may decrease symptoms of irritation. The use and dosage of nutritional supplements and vitamins should be discussed with your primary medical doctor.

What can I do to help myself?

• Use artificial tears, gels, gel inserts, and ointments - available over the counter - as the first line of therapy. They offer temporary relief and provide an important replacement of naturally produced tears in patients with aqueous tear deficiency. Avoid artificial tears with preservatives if you need to apply them more than four times a day or preparations with chemicals that cause blood vessels to constrict.
• Wearing glasses or sunglasses that fit close to the face (wrap around shades) or that have side shields can help slow tear evaporation from the eye surfaces. Indoors, an air cleaner to filter dust and other particles helps prevent Dry Eyes. A humidifier also may help by adding moisture to the air.
• Avoid dry conditions and allow your eyes to rest when performing activities that require you to use your eyes for long periods of time. Instill lubricating eye drops while performing these tasks.

Article republished from: http://www.nei.nih.gov/health/dryeye/dryeye.asp

Read more »

Conjunctivitis: Do antibiotics help?

In more than half of all people who have conjunctivitis, the infection goes away without treatment within a week. Antibiotic eye drops or ointment can speed up recovery. Adverse effects are very rare.

Conjunctivitis makes people’s eyes red and inflamed. It often affects both eyes because the infection can easily spread from one eye to the other. Your eyes get watery and produce a yellowish-white discharge that makes your eyelids stick together. They may become very sore too. Conjunctivitis is contagious but often gets better within a week, even without any treatment. So it is often enough to simply wait.

Conjunctivitis is usually caused by bacteria or viruses.  Because conjunctivitis usually goes away so quickly, though, it is generally not worth doing tests to find out if it is a bacterial or viral infection. Doctors often prescribe antibiotics just in case, in the form of eye drops or ointments. Antibiotics only work against bacteria, though, and not against viruses, so they are not always effective.

Some people use non-antibiotic eye drops. The use of cold or warm compresses is common too. But there is not enough research on these approaches to be able to say whether they have a benefit, no effect, or are possibly even harmful. Sometimes conjunctivitis is linked to an allergy. Then it is treated with allergy medicines like antihistamines.

Research on antibiotics in the treatment of conjunctivitis

Two groups of researchers from the Cochrane Collaboration (an international network of researchers) and from various universities in England, the Netherlands and Australia analyzed the results of trials on the treatment of conjunctivitis with antibiotics. They wanted to find out whether antibiotics help in the treatment of ordinary conjunctivitis, as well as which possible disadvantages they have.

The researchers only analyzed the results of studies that compared at least two groups of people. One group of people used antibiotic eye drops or ointments. The other group used non-antibiotic eye drops or ointments, or did not have any treatment at first. The researchers were only interested in studies in which the participants were randomly assigned to one of the treatment groups. This kind of study, called a randomized controlled trial, delivers the most reliable results. Read our information "Evidence-based medicine" to find out more about how good-quality trials are carried out.

The researchers found 12 trials, involving a total of about 4,000 people with conjunctivitis. Both children and adults participated in the trials.

Antibiotics can speed up recovery

Overall, the analysis of the trial results showed that conjunctivitis goes away somewhat faster if antibiotics are used. This is what was found for people who went to see their family doctor because they had conjunctivitis:

• The infection cleared up within one week in 71 out of 100 people who did not use antibiotics.

• The infection cleared up within that same amount of time in 80 out of 100 people who used antibiotics.

In other words, antibiotics were found to speed up recovery in 9 out of 100 people.

In studies that were carried out in a specialist practice, it took a little longer for the infection to clear up – both in the people who used antibiotics and in those who did not use antibiotics. One possible explanation for this is that people who go to see a specialist doctor probably have more severe cases of conjunctivitis. But the antibiotics had a similar beneficial effect to that found in the family doctor trials.

None of the trials reported that antibiotics had adverse effects. The trials did not look into whether antibiotics helped lower the risk of the infection spreading.

Recognizing signs of complications and avoiding the spread of infection

As already mentioned, conjunctivitis usually goes away without treatment. But some symptoms could be signs of more serious problems. These symptoms include worsening vision, increased sensitivity to light, the feeling that you have something in your eye, and a severe headache together with nausea. It is important to see a doctor if you have any of these symptoms.

In people who wear contact lenses, the infection can spread to the cornea (the clear surface of the eye itself). Inflammation of the cornea, also known as keratitis, is not common though: it is estimated that conjunctivitis leads to keratitis in about 3 out of every 10,000 contact lens wearers. In the trials that the researchers included in their analysis, none of the participants developed keratitis.

If conjunctivitis is caused by viruses it can be highly contagious and hard to get rid of. But there are several things that can be done to try to stop viral infections from spreading. Because the virus is easily spread through finger contact, it is important to avoid touching your eyes with your hands, and to wash your hands if you do accidentally touch your eyes. It is also a good idea to have your own towels and washcloths, and not to share them with other people. Another important way to protect others from infection is by not shaking hands with them and not touching their face.

 

Original Article found at http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0005040/

Published by the Institute for Quality and Efficiency in Health Care (IQWiG)Next planned update:
October 2015. You can find out more about how our health information is updated in our text "Informed Health Online: How our information is produced".

References

• IQWiG health information is based on research in the international literature. We identify the most scientifically reliable knowledge currently available, particularly what are known as “systematic reviews”. These summarize and analyze the results of scientific research on the benefits and harms of treatments and other health care interventions. This helps medical professionals and people who are affected by the medical condition to weigh up the pros and cons. You can read more about systematic reviews and why these can provide the most trustworthy evidence about the state of knowledge in our information "Evidence-based medicine". We also have our health information reviewed to ensure medical and scientific accuracy.
• Jefferis J, Perera R, Everitt H, van Weert H, Rietveld R, Glasziou P et al. Acute infective conjunctivitis in primary care: who needs antibiotics? An individual patient data meta-analysis. Br J Gen Pract 2011; 61(590): e542-548. [Full text]
• Sheikh A, Hurwitz B, van Schayck CP, McLean S, Nurmatov U. Antibiotics versus placebo for acute bacterial conjunctivitis. Cochrane Database Syst Rev 2012; (9): CD001211. [Summary]

 

Read more »

Elusive Gene That Causes a Form of Blindness from Birth Dlscovered

Researchers from the Massachusetts Eye and Ear Infirmary, The Children's Hospital of Philadelphia, Loyola University Chicago Health Sciences Division and their collaborators have isolated an elusive human gene that causes a common form of Leber congenital amaurosis (LCA), a relatively rare but devastating form of early-onset blindness. The new LCA gene is called NMNAT1. Finding the specific gene mutated in patients with LCA is the first step towards developing sight-saving gene therapy.

Share This: LCA is an inherited retinal degenerative disease characterized by reduced vision in infancy. Within the first few months of life, parents usually notice a lack of visual responsiveness and unusual roving eye movements known as nystagmus. LCA typically involves only vision problems, but can be accompanied by disease in other organ systems in a minority of patients. LCA is a common reason children are enrolled in schools for the blind. "The immediate benefit of this discovery is that affected patients with mutations in this new LCA gene now know the cause of their condition," said Eric Pierce, M.D., Ph.D., co-senior author and director of the Ocular Genomics Institute at Mass. Eye and Ear. "Scientists now have another piece to the puzzle as to why some children are born with LCA and decreased vision. The long-term goal of our research is to develop therapies to limit or prevent vision loss from these disorders." NMNAT1 is the 18th identified LCA gene.

The gene resides in a region that was known to harbor an LCA gene since 2003, but the specific disease gene has been undiscovered until now. These findings will be published on July 29 in the online edition of Nature Genetics. To identify NMNAT1, scientists performed whole exome sequencing of the family of two siblings who initially presented for evaluation of LCA but who had no mutations in any of the known LCA genes. Being seen by a multi-disciplinary team that took the case from careful clinical characterization to genetic testing to the research laboratory was an essential ingredient for success. "By using whole exome sequencing, we found a mutation in a gene that no one could have predicted would be associated with LCA," said Dr. Pierce. "Whereas most of the known LCA genes involve dysfunction of retinal ciliary proteins necessary for light detection in the eye, NMNAT1 is uniquely distinguished by being the first metabolic enzyme linked to LCA," said Marni J. Falk, M.D., co-first author and Clinical Geneticist at The Children's Hospital of Philadelphia and University of Pennsylvania Perelman School of Medicine. Having found a mutation in NMNAT1 in this one family, the investigators next asked if mutations in NMNAT1 also cause disease in other patients with LCA.

Screening of 284 unrelated patients with LCA from the United States, England, France and India allowed them to identify 13 other patients with mutations in NMNAT1 as the cause of their disease. Drs. Falk, Pierce and colleagues also studied how the identified mutations in NMNAT1 affect the function of the NMNAT1 protein, and thus may cause dysfunction and death of the light sensitive photoreceptor cells in the retina. Working together with Eiko Nakamaru-Ogiso, Ph.D., in the Department of Biochemistry and Biophysics at The University of Pennsylvania, they found that mutations in NMNAT1 appear to decrease the ability of the NMNAT1 protein to produce NAD+, a key mediator of cellular signaling and energetics. Early treatment for patients with NMNAT1-related LCA could be especially beneficial. Researchers found that all but the youngest patient with NMNAT1 mutations had damage to the macula, the center of the retina that is needed for central vision. "This 4-year-old girl who doesn't have central vision loss yet can possibly benefit substantially if we can devise a therapy for her NMNAT1-mediated LCA that prevents her from developing severe central vision loss," Dr. Pierce said.

Reprinted from: http://www.sciencedaily.com/releases/2012/07/120729142135.htm

Story Source:

The above story is reprinted from materials provided byMassachusetts Eye and Ear Infirmary.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Read more »

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."
Other social bookmarking and sharing tools:
http://www.sciencedaily.com/releases/2012/05/120508163228.htm
Story Source:

The above story is reprinted from materials provided by University of Alabama at Birmingham, via Newswise. The original article was written by Greg Williams.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Read more »