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

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

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