Posts Tagged ‘Astigmatism’

How does LASIK work?

Thursday, February 18th, 2010

LASIK is the most commonly performed refractive surgery procedure. You may hear people calling it “LASIX,” but the correct name is LASIK, which is short for “laser-assisted in situ keratomileusis.”

Why is it so popular? LASIK has advantages over other vision correction procedures, including a relative lack of pain afterward and the fact that good vision usually is achieved by the very next day.

An instrument called a microkeratome is used in LASIK eye surgery to create a thin, circular flap in the cornea. Another, newer way of making the flap is with a laser.

The surgeon folds the hinged flap back out of the way, then removes some corneal tissue underneath using an excimer laser. The excimer laser uses a cool ultraviolet light beam to precisely remove (”ablate”) very tiny bits of tissue from the cornea to reshape it.

When the cornea is reshaped in the right way, it works better to focus light into the eye and onto the retina, providing clearer vision than before. The flap is then laid back in place, covering the area where the corneal tissue was removed.

Both nearsighted and farsighted people can benefit from the LASIK procedure. With nearsighted people, the goal is to flatten the too-steep cornea; with farsighted people, a steeper cornea is desired. Excimer lasers also can correct astigmatism by smoothing an irregular cornea into a more normal shape.

ArrivaCostaRica.com is the primary web site for information about plastic surgery and dentistry in Costa Rica. See www.arrivacostarica.com

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Posted in Astigmatism surgery, Excimer, Excimer Laser, Eye Surgery, Lasik Surgery, Refractive Laser Surgery, Vision Surgery | No Comments »

Astigmatism

Monday, November 23rd, 2009

“What is a stigmatism?” is a question that eye doctors hear every day, but actually it’s spelled “astigmatism.” Although astigmatism is the most common vision problem, most people don’t know what it is.

Astigmatism may accompany farsightedness or nearsightedness. Usually it is caused by an irregularly shaped cornea (called corneal astigmatism). But sometimes lenticular astigmatism results from an irregularly shaped lens, which is located behind the cornea.

Either kind of astigmatism can usually be corrected with eyeglasses, contact lenses, or refractive surgery.

What Causes Astigmatism?

Astigmatism occurs when the cornea is shaped more like an oblong football than a spherical baseball, which is the normal shape. In most astigmatic eyes, the oblong or oval shape causes light rays to focus on two points in the back of your eye, rather than on just one. This is because, like a football, an astigmatic cornea has a steeper curve and a flatter one.

In regular astigmatism, the meridians in which the two different curves lie are located 90 degrees apart. In irregular astigmatism, the two meridians may be located at something other than 90 degrees apart; or there are more than two meridians.

Regular astigmatism is usually easy to correct (see treatments below), but irregular astigmatism can be complicated and more difficult to correct, depending on the extent of the irregularity and its cause.

Usually astigmatism is hereditary: many people are born with an oblong cornea, and the resulting vision problem may get worse over time.

But astigmatism may also result from an eye injury that has caused scarring on the cornea, from certain types of eye surgery or from keratoconus, a disease that causes a gradual thinning of the cornea.

Astigmatism Treatment

Unless it is extreme, astigmatism can be compensated for satisfactorily with eyeglasses or contact lenses.

If your eyeglass or contact lens prescription contains three parts rather than one, your eyecare practitioner has found some astigmatism in one or both of your eyes. A prescription with three parts looks like this: -2.75 -1.25 x 90.

  • The first part indicates your main spherical correction, meaning the amount of power (in diopters) required in a lens to sharpen your visual acuity to an acceptable level, usually 20/20. In this example, the person has myopia and requires a negative (concave) lens to correct it.
  • Part two shows the extent of the astigmatism in diopters. Again, the minus sign means a concave lens is needed.
  • Part three is the axis (in degrees) of the cylinder required to bend certain light rays to compensate for the cornea’s oval shape.

Many people with astigmatism believe that they can’t wear contact lenses or that only rigid contact lenses (RGPs, also called GP lenses) can correct astigmatism.

This was true many years ago, but now soft toric contact lenses can correct astigmatism. Toric lenses have a special correction built into them and may also contain a prescription for nearsightedness or farsightedness if you need it.

While soft torics work well for many people, if you have severe astigmatism, you’ll likely do better with RGP contact lenses or eyeglasses. Your eyecare practitioner will advise you.

ArrivaCostaRica.com is the primary web site for information about plastic surgery and dentistry in Costa Rica. See www.arrivacostarica.com

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Posted in Astigmatism surgery, Refractive Laser Surgery | No Comments »

Living with LASIK

Tuesday, July 14th, 2009

Learn about how LASIK vision correction can free you of your dependency on vision correction devices such as glasses and contacts.

If you need glasses or contact lenses to get through your daily activities, you know the downside of that. Whether it’s glasses or lenses:

• They get lost at times
• They can be damaged or broken
• They need to be cared for and cleaned
• You have to have them updated periodically

There have been many advances in vision correction, so you can choose from many types of glasses or contact lenses, but that doesn’t change the fact that you still depend on them every day.

If your vision limitations are caused by a refractive error, you could consider the alternative of LASIK surgery. Refraction refers to the bending of light rays as they enter your eyes.

Refractory error
In a perfectly shaped cornea (the front surface of the eye) light rays bend at just the right angle to focus on your retina (the back inside surface where images are formed, as on a camera film). From the retina, the optic nerve picks up the image information and takes it to the brain, which interprets it, finds the right name for it, and tells you, “That’s a daffodil.”

Many of us have imperfectly shaped corneas. Maybe they’re too short, too long, too flat, too steep, or have tiny irregularities on them.

This causes the light rays to bend at the wrong angle.

• They might bend too sharply and focus in front of the retina. This creates nearsightedness (myopia)
• They might bend too little, and come to a focus behind the retina. This creates farsightedness (hyperopia)
• They might bend inconsistently because of small irregularities on the cornea, and focus inconsistently, creating blurry patches in your vision (astigmatism)

What LASIK does
LASIK vision correction surgery corrects the shape of your corneas, so that the light rays will bend at the correct angle and focus sharply on the retina. It’s a short, safe, and painless procedure and gives permanent vision improvement.

There’s something you can do to enhance your LASIK results:

• Choose a quality eye surgeon
• In turn, the surgeon will choose you if you’re a good candidate for LASIK. Good outcomes are not possible on poor candidates.

You might see advertisements for LASIK at “$399.99 per eye!” or some such amount. Those facilities may indeed offer a lower price, although you’ll probably incur extra expenses in the end (“hidden costs”). But they make up for the lower fees by cutting corners:
• Minimal pre-screening
• Cheaper equipment
• Older lasers
• Less staff
• Less surgeon time for you
• Little or no follow-up
• Pre-screening

There’s more to being a good candidate for LASIK surgery than having:
• Myopia
• Hyperopia, or
• Astigmatism

Some other conditions can disqualify you. If you’re:

• Diabetic
• Under 18
• Pregnant
• Are taking certain medications
• Have any of a variety of diseases

A quality eye surgeon will carefully select his LASIK patients and give them as much time as necessary to ensure the best possible results. If you qualify, your outcome will be astonishing. You’ll notice the difference immediately! You’ll wonder why you didn’t get around to freeing yourself up sooner from those glasses or contact lenses.

ArrivaCostaRica.com is the primary web site for information about plastic surgery and dentistry in Costa Rica. See www.arrivacostarica.com

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Posted in Hyperopia surgery, Lasik Surgery, Myopia Surgery, Presbyopia Surgery | No Comments »

Living More Freely with LASIK

Friday, April 24th, 2009

Learn about how LASIK vision correction can free you of your dependency on vision correction devices such as glasses and contacts.

If you need glasses or contact lenses to get through your daily activities, you know the downside of that. Whether it’s glasses or lenses:

• They get lost at times
• They can be damaged or broken
• They need to be cared for and cleaned
• You have to have them updated periodically

There have been many advances in vision correction, so you can choose from many types of glasses or contact lenses, but that doesn’t change the fact that you still depend on them every day.

If your vision limitations are caused by a refractive error, you could consider the alternative of LASIK surgery. Refraction refers to the bending of light rays as they enter your eyes.

Refractory error
In a perfectly shaped cornea (the front surface of the eye) light rays bend at just the right angle to focus on your retina (the back inside surface where images are formed, as on a camera film). From the retina, the optic nerve picks up the image information and takes it to the brain, which interprets it, finds the right name for it, and tells you, “That’s a daffodil.”

Many of us have imperfectly shaped corneas. Maybe they’re too short, too long, too flat, too steep, or have tiny irregularities on them.

This causes the light rays to bend at the wrong angle.

• They might bend too sharply and focus in front of the retina. This creates nearsightedness (myopia)
• They might bend too little, and come to a focus behind the retina. This creates farsightedness (hyperopia)
• They might bend inconsistently because of small irregularities on the cornea, and focus inconsistently, creating blurry patches in your vision (astigmatism)

What LASIK does
LASIK vision correction surgery corrects the shape of your corneas, so that the light rays will bend at the correct angle and focus sharply on the retina. It’s a short, safe, and painless procedure and gives permanent vision improvement.

There’s something you can do to enhance your LASIK results:

• Choose a quality eye surgeon
• In turn, the surgeon will choose you if you’re a good candidate for LASIK. Good outcomes are not possible on poor candidates.

You might see advertisements for LASIK at “$399.99 per eye!” or some such amount. Those facilities may indeed offer a lower price, although you’ll probably incur extra expenses in the end (“hidden costs”). But they make up for the lower fees by cutting corners:
• Minimal pre-screening
• Cheaper equipment
• Older lasers
• Less staff
• Less surgeon time for you
• Little or no follow-up
• Pre-screening

There’s more to being a good candidate for LASIK surgery than having:
• Myopia
• Hyperopia, or
• Astigmatism

Some other conditions can disqualify you. If you’re:

• Diabetic
• Under 18
• Pregnant
• Are taking certain medications
• Have any of a variety of diseases

A quality eye surgeon will carefully select his LASIK patients and give them as much time as necessary to ensure the best possible results. If you qualify, your outcome will be astonishing. You’ll notice the difference immediately! You’ll wonder why you didn’t get around to freeing yourself up sooner from those glasses or contact lenses.

ArrivaCostaRica.com is the primary web site for information about plastic surgery and dentistry in Costa Rica. See www.arrivacostarica.com

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Posted in Eye Surgery, Hyperopia surgery, Lasik Surgery, Myopia Surgery | No Comments »

Tear Today, Gone Tomorrow…

Tuesday, March 10th, 2009

Many people live with a condition called “dry eye” on a daily basis. Dry eye occurs when a person’s eyes do not generate the proper amount of tears to keep the eyes adequately lubricated. People with dry eye may have symptoms such as:
• A feeling of scratchiness in the eyes
• A burning sensation
• Large amounts of mucous
• Sensitivity to wind and smoke
• Increased light sensitivity

Oddly enough, people with dry eye may also experience excessive tears as the lacrimal glands, which produce tears, try to compensate for the lack of lubrication.

Laser-Assisted in Situ Keratomileusis, also known as LASIK eye surgery, is a procedure to correct vision in patients who live with:
• Myopia or nearsightedness
• Hyperopia or farsightedness
• Astigmatism

While most people who undergo this surgery by qualified, experienced surgeons end up with 20/20 vision or better without complications, LASIK can leave some patients with the dry eye condition. This is especially true if the patient had dry eye prior to the surgery. In those cases, candidate screening was inadequate and the surgery should not have been done.
How Does LASIK Cause Dry Eyes?
During LASIK eye surgery, the surgeon cuts a thin corneal flap so the cornea can be reshaped underneath the flap using a laser. Creation of the flap inevitably cuts some of the corneal nerve fibers related to tear production.

The lacrimal glands are beneath the upper eyelids and just below the eyebrows. They produce tears which flow through a drainage system and flush debris from the eyes. When these nerves are disrupted by flap creation, tear production is reduced and this happens in all LASIK procedures. In most cases the nerves regenerate within a few months and tear production becomes normal. In the meantime, moisturizing eyedrops are prescribed.

Special lubricating drops may also be prescribed for people with mild dryness prior to LASIK surgery to minimize potential complications. Usually dry eyes are a disqualifying condition for LASIK. But an eye surgeon will assess each individual and make a judgment call.

Dry Eye Syndrome
In a few cases, the nerves do not regenerate well and that person suffers from Dry Eye Syndrome. This is a chronic condition rather than a temporary side effect of LASIK. It can also exist quite unrelated to LASIK.

It can be treated or managed. Prescription eyedrops can help. Your eye surgeon may insert plugs into the tear duct openings (the puncta; singular is punctum). These openings are in the inner corners of the eyes and allow tears to drain from the eyes into the nasal passages. Punctal plugs reduce tear drainage to keep the eyes better lubricated.

If you are considering LASIK eye surgery, be sure to inform your LASIK surgeon of your medical history, including any previous diagnosis of dry eye, as well as medications you are currently taking. This will help the surgeon provide you with the most effective, comfortable post-op experience possible.

ArrivaCostaRica.com is the primary web site for information about plastic surgery and dentistry in Costa Rica. See www.arrivacostarica.com.

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Posted in Astigmatism surgery, Eye Surgery, Hyperopia surgery, Lasik Surgery, Myopia Surgery | No Comments »

Can LASIK Correct Your Astigmatism?

Tuesday, March 3rd, 2009

If your vision is blurred by astigmatism, you may be afraid that you don’t have any options to correct your vision. LASIK technology has allowed thousands with astigmatism regain their 20/20 sight with a simple procedure.

The short answer is Yes, LASIK can correct it along with nearsightedness and farsightedness.

What is astigmatism?

It’s a blurriness of vision caused by the cornea (the transparent part at the front of the eye), not being perfectly round. It’s one of the 4 types of common refractive vision problems.

With normal vision, when we focus on an object, let’s say it’s our mother:

· Light rays enter the eye, pass through the cornea and travel to the retina, the back inside surface of the eye

· They land in a single focal point, are transmitted by the optic nerve to the brain, and we go, “Hi, Mom”.

When the cornea or the lens is slightly distorted in shape:

· The rays are slightly deflected, arriving at the retina in two places, so that the optic nerve sends confusing information to our brain, and we walk on, seeing only a blurry female shape.

Astigmatism is a lower order aberration

Astigmatism, nearsightedness, and farsightedness are known as lower order aberrations, as opposed to the higher order aberrations, such as glare and halos.

At first, LASIK could only correct the lower order aberrations, but now it can correct both higher and lower orders.

LASIK

In 1997, the FDA approved LASIK for treatment of astigmatism, and in 2002 it approved Wavefront LASIK Surgery.

Traditional LASIK

· The eye surgeon cuts a thin round flap from the cornea, leaving part of it still connected like a hinge

· The flap is folded back to give access to the lower level of tissue, the stroma

· The laser is directed on to the stroma and vaporizes little areas, removing irregularities

· The flap is replaced and healing takes only a couple of days

Wavefront LASIK surgery

· This is also called Custom LASIK.

· The surgeon’s computerized device shines a light at each of your eyes

· It lands on the retina, then rebounds to a sensor

· The sensor tracks any irregularities in the front of this light wave as it emerges from your eye

· With this information, the computer program creates a 3-D map of the exact shape of your cornea

· From this map, the LASIK surgeon creates a mathematical formula on the computer which then uses it to guide the laser

· The laser vaporizes only those tiny pieces of tissue from the cornea that are causing blurry vision

All this may sound complicated, but it works very efficiently and precisely. Studies to date have shown that:

· Over 90% of people who have Wavefront LASIK surgery gain 20/20 vision

· Less than 80% of people who have traditional LASIK gain 20/20 vision

Photo-Refractive Keratectomy (PRK)

This procedure was the first laser treatment for astigmatism. It uses an excimer laser, as does LASIK, and is a procedure that gently removes tissue from the cornea’s surface and then uses a laser to make it more round. It’s still used sometimes, for people with specific corneal conditions, but currently, more than 95% of cases are treated with LASIK.

What is 20/20 vision?

It’s normal acuity of vision, meaning clarity of vision from a distance.

When you look at the eye chart, with its big E at the top and lines of letters, each line smaller than the one above it, your visual acuity is being measured.

In this context, “normal” really means “a convenient standard”. Over the years, by looking at lots of people’s eyesight, eye doctors decided what a “normal” person should see when standing 20 feet away. If you have “normal” visual acuity, it’s by definition the same acuity that most people have at 20 feet.

Visual acuity is described by two numbers: 20 plus some other number, like 20/20 or 20/200 or 20/40. These pairs of numbers refer to:

· The distance of 20 feet, that for this purpose we postulate a “normal” person as standing at, and

· The distance someone must stand away from the chart, in order to see what the “normal” person can see at 20 feet

In countries that use metric measurements, the standard distance is 6 meters, so normal vision is referred to as 6/6 vision.

· If you have 20/80 vision, that means you must stand 20 feet away to see what our “normal” person can see at 80 feet. In other words, you’re shortsighted.

· If you have 20/200 vision, the legal definition of blindness in the US, you have to be only 20 feet away to see what a “normal” person can see from 200 feet.

· If your vision is 20/10, you’re better than “normal”. You can see from 20 feet what someone else can’t see till they’re 10 feet away

The “normal” line is second to bottom, so if you can see it clearly standing 20 feet away, you have normal vision.

· If you can see that big E at the top from 200 feet away, you also have normal vision.

· If you can see the very bottom tiny line of letters, standing 20 feet away, you have 20/10 vision. Someone with normal vision would have to stand 10 feet away.

Of course, our eye doctors don’t have rooms 200 feet long. The eye chart is scaled down to fit the room it’s in.

ArrivaCostaRica.com is the primary web site for information about plastic surgery and dentistry in Costa Rica. See www.arrivacostarica.com.

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Posted in Astigmatism surgery, Eye Surgery, Lasik Surgery | No Comments »