What Is Orthokeratology?

What Is Orthokeratology?

In the most basic of terms Accelerated Overnight Orthokeratology or Ortho-k is the science of changing the curvature or shape of the cornea to change how light is focused on the retina at the back of one's eye.

Think of the cornea as the eye's equivalent of a watch crystal. It is a clear, dome shaped structure that overlies the colored iris. Its tissue is most similar to clear, wet skin; and like skin it is very pliable. Because the cornea separates the eye from air and the rest of the outside world and because it has a curvature that bends light towards the back of the eye, it is responsible for most of the eye's corrective power and contributes to various conditions such as nearsightedness (myopia), farsightedness (hyperopia), and the blur of astigmatism.

When you choose Ortho-k a few key tests must be performed. Chief among these tests is the determination that your eyes are healthy. The Orthokeratologist will examine the retina and also the health of the outside of the eye. The other key procedure is the mapping of your cornea. To do this an instrument called a Topographer is used. Just like a topographical map of a camping area show hills, plains, and valleys; the topography of the eye shows your doctor exactly how your cornea is shaped. The information from your corneal mapping plus the size of your cornea and the prescription needed to correct your vision are all used to design the retainer lenses (corneal molds) needed to create the Ortho-k effect.
 

On the day you pick up your Ortho-k retainer lenses you will be instructed in how to insert, remove, and take care your vision retainers. The fit of your retainers will be evaluated and you will be scheduled to be seen after your first night of wear. On day 1, your doctor will re-evaluate your fit and newly corrected vision and another mapping of your cornea will be performed.

Throughout your initial fitting period, your Orthokeratologist will monitor your corneal health and the effectiveness of treatment. At certain times your retainer lens fit may be modified to achieve your goals.

Orthokeratology can produce results in a surprisingly short period of time. The length of treatment to achieve your goals can vary from patient to patient. Factors which can affect the speed of treatment include:

1. your initial prescription
2. corneal rigidity
3. tear quality and quantity
4. your expectations.

We advise patients that they may need to use their retainers every night to maintain their newly corrected vision although some patients are able to vary their wearing time to once every two to four nights. The reason for this is due to the flexibility of your cornea.

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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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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New Glaucoma Test Allows Earlier, More Accurate Detection

Cumbersome Glaucoma tests that require a visit to the ophthalmologist could soon be history thanks to a home test developed by a UA engineer.

Phoenix ophthalmologist Dr. Gholan Peyman demonstrates a prototype Glaucoma test instrument that's noninvasive and simpler to use than current procedures. It can also be used in situations that are difficult or impossible with current tests. (Credit: Image courtesy of University of Arizona College of Engineering)

The self-test instrument has been designed in Eniko Enikov's lab at the UA College of Engineering. Gone are the eye drops and need for a sterilized sensor. In their place is an easy-to-use probe that gently rubs the eyelid and can be used at home.
"You simply close your eye and rub the eyelid like you might casually rub your eye," said Enikov, a professor of aerospace and mechanical engineering. "The instrument detects the stiffness and, therefore, infers the intraocular pressure." Enikov also heads the Advanced Micro and Nanosystems Laboratory.
While the probe is simple to use, the technology behind it is complex, involving a system of micro-force sensors, specially designed microchips, and math-based procedures programmed into its memory.
Enikov began working on the probe four years ago in collaboration with Dr. Gholan Peyman, a Phoenix ophthalmologist. "We went through several years of refinement and modifications to arrive at the current design," Enikov noted.
The National Science Foundation has funded the work, and Enikov and Peyman now are seeking investors to help fund final development and commercialization of the product.
In addition to screening for Glaucoma, an eye disease that can lead to blindness if left untreated, the device corrects some problems with the current procedure, and can be used to measure drainage of intraocular fluid.
"Eye pressure varies over a 24-hour cycle," Enikov said. "So it could be low at the doctor's office and three hours later it might be high. With only a single test, the doctor might miss the problem. Having the ability to take more frequent tests can lead to earlier detection in some cases."
Once the diagnosis is made, several treatments are available. The question then is: How effective are they? Patients could use the probe at home to trace how much the pressure decreases after using eye drop medications, for instance.
"One of the reasons pressure builds up in the eye is because fluid doesn't drain properly," Enikov noted. "Currently, there are no methods available to test drainage."
Current tests require applying pressure directly to the cornea, but only very light pressure is safe to use, and it doesn't cause the fluid to drain.
"Our technique allows us to apply slightly greater pressure, but it's still not uncomfortable," he said. "It's equivalent to rubbing your eye for a brief period to find out if the pressure changes. If it does, we know by how much and if there is a proper outflow of intraocular fluid."
Sometimes, a surgical shunt is used to help fluid drain from the eye. "The problem with Glaucoma shunts is they can plug up over time," Enikov noted. "Or if they're not properly installed, they may drain too quickly. So you would want to know how well the shunt is working and if it is properly installed. Our device could help answer those questions."
In another scenario, certain patients cannot be tested for Glaucoma using currently available procedures. "If a patient had cataract surgery or some other surgery through the cornea, the cornea sometimes thickens," Enikov said. "The cornea's structure is different, but our test remains accurate because it's not applied to the cornea."
Instead, it presses the entire eyeball, much as you might press a balloon to determine its stiffness.
"The innovation with our device is that it's noninvasive, simpler to use and applies to a variety of situations that are either difficult to address or impossible to test using the current procedures," Enikov said. "That's why we're so excited about this probe. It has great potential to improve medical care, and significant commercial possibilities, as well."
http://www.sciencedaily.com/releases/2011/01/110104101331.htm

The above story is reprinted from materials provided by University of Arizona College of Engineering. The original article was written by Ed Stiles.
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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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