For Your Information
SIGNS AND SYMPTOMS
Clinical inspection of pterygia reveals a raised, whitish, triangular wedge of fibrovascular tissue, whose base lies within the interpalpebral conjunctiva and whose apex encroaches the cornea. The leading edge of this tissue often displays a fine, reddish-brown iron deposition line (Stocker's line).
The vast majority of pterygia (about 90 percent) are located nasally. These lesions are more commonly encountered in warm, dry climates, or in patients who are chronically exposed to outdoor elements or smoky/dusty environments.
Pterygia must be distinguished
from pingueculae, which are more yellow in color and lie within the
interpalpebral space but generally do not encroach beyond the limbus.
Pingueculae also lack the wing-shaped appearance of pterygia, the
former being more oval or ameboid in appearance.
Whatever the etiology, pterygia represent a degeneration of the conjunctival stroma with replacement by thickened, tortuous elastotic fibers. Activated fibroblasts in the leading edge of the pterygium invade and fragment Bowman's layer as well as a variable amount of the superficial corneal stroma. Histologically, pterygium development resembles actinic degeneration of the skin.
Pterygia often persist after surgical
removal; these lesions appear as a fibrovascular scar arising from the
excision site. These "recurrent pterygia" probably have no
relationship to ultraviolet radiation, but rather may be likened to
keloid development in the skin.
Surgical excision of pterygia is
indicated only for unacceptable cosmesis and/or significant
encroachment of the visual axis. The treatment of choice involves
dissection and removal of the fibrous tissue down to the level of
Tenon's capsule. Free conjunctival flaps are then grafted over the
bare sclera. Postoperative adjuvant therapy with b-radiation, topical
thiotepa, mitomycin-C and other antimetabolic agents may diminish the
chance of recurrence. In cases that involve significant corneal
scarring, lamellar or penetrating keratoplasty may be indicated.
Evolution of Two-eyed VisionTwo Eyes to the Side
Nature has given animals the physical attributes necessary for survival. Lateral placement of the eyes is essential to the survival of hunted animals or herbivorous animals (e.g., horse, rabbit, cow) as it allows them to increase side or peripheral vision.
Side vision (increased by lateral placement) is a sensitive detector for motion or movement. Peripheral vision allows creatures to effectively scan for danger. The rabbit must be constantly aware of its natural enemies while it eats your garden greens. At the first sign of danger, peripheral vision, the motion detector system, alerts the rabbit that there is danger. The immediate reflexive response is for the rabbit to run.
Two Eyes in
of Two Eyes in Front
Many of you have experienced exaggerated demonstrations of stereoscopic depth by viewing I-Max 3D movies or old stereoscopes. Or, perhaps, you have seen photos of theatergoers in the 1950's wearing special Polaroid glasses in order to view 3D movies.
The fusion of these two slightly different pictures from our two "cameras" (the eyes) gives us the sensation of strong three-dimensionality or relative depth.
At near, there is a greater difference in what the two eyes view as compared to far. Thus, stereopsis is strongest and most important at near distances. At near is where man uses accurate hand-eye coordination to make tools and other items!
Animals that have lateral position of the eyes and individuals who have constant strabismus (eye turn) lack stereopsis. This does not mean that they have absolutely no depth perception. There are many one-eyed (monocular) depth perception cues that allow us to make reasonably accurate depth judgments. These monocular depth perception cues may be familiar to you and include: perspective, overlay, shadowing, aerial perspective (color of the sky), relative motion, relative size, etc.
Binocular vision cues (from two eyes), such as stereopsis and parallax, are dependent on accurate alignment of the eyes and appropriate unification of the two images by the brain. People with only monocular or one-eye depth perception skills can do fine in many situations. However, they are not allowed to fly a rocket ship, drive the trains in New York city subways, and they definitely should not be surgeons. They may have trouble catching a fly ball or becoming a NBA point guard. However, many jobs do not require stereopsis and thus the lack of stereopsis does not preclude a successful life.
Stereopsis does enhance quality of life and life choices, however! Some eye doctors might tell you that it is a luxury, but it is part and parcel of our evolution and human potential. 3D vision is a human skill we all want and deserve. Every attempt should be made to develop this visual-motor skill in a child [and it's not too late for many adults!]
What is the
What is the "critical period" and what does it mean in regards to you or your child and your treatment options. Explore this controversial topic by reading the following two articles by Dr. Jeffrey Cooper and Dr. Paul Harris, two different experts on strabismus. Dr. Harris refers to the famous 1960s Hubel and Weisel study as well as later studies by Hubel and Weisel and others. Many of the more recent studies call into question the idea of a finite "critical period." Dr. Cooper explains the Hubel and Weisel study and its implications in detail.
Myth of the Critical Period
of Vision (Critical Periods)
Why does my
eye doctor say it is "too late?"
Remember, a great deal has been learned about the human brain since the 1960s! For example, a new ground-breaking study on the brain's plasticity (its ability to change and grow) was released to broad media fanfare in the year 2000.
When is it too
late to treat strabismus or lazy eye?
Thus, every attempt should be made to improve strabismus and lazy eye, though treatment might not be as effective after the age of six, and definitely requires more work. Also, remember that if an eye turn occurs only some of the time (intermittent), the cells of the brains do not develop the changes associated with the more challenging cases of constant eye turns.
Cataracts and Cataract Surgery
A cataract is a clouding of the eye's natural lens, which lies behind the iris and the pupil. The lens works much like a camera lens, focusing light onto the retina at the back of the eye. The lens also adjusts the eye's focus, letting us see things clearly both up close and far away.
The lens is mostly made of water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it. But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract, and over time, it may grow larger and cloud more of the lens, making it harder to see.
Cataracts are classified as one of three types:
Cataract Symptoms and Signs
A cataract starts out small, and at first has little effect on your vision. You may notice that your vision is blurred a little, like looking through a cloudy piece of glass or viewing an impressionist painting. A cataract may make light from the sun or a lamp seem too bright or glaring. Or you may notice when you drive at night that the oncoming headlights cause more glare than before. Colors may not appear as bright as they once did.
The type of cataract you have will affect exactly which symptoms you experience and how soon they will occur. When a nuclear cataract first develops it can bring about a temporary improvement in your near vision, called "second sight." Unfortunately, the improved vision is short-lived and will disappear as the cataract worsens. Meanwhile, a subcapsular cataract may not produce any symptoms until it's well-developed.
If you think you have a cataract, see an eye doctor for an exam to find out for sure.
What Causes a Cataract?
No one knows for sure why the eye's lens changes as we age, forming cataracts. Researchers are gradually identifying factors that may cause cataracts — and information that may help to prevent them.
Many studies suggest that exposure to ultraviolet light is associated with cataract development, so eyecare practitioners recommend wearing sunglasses and a wide-brimmed hat to lessen your exposure. Other types of radiation may also be causes. For example, a 2005 study conducted in Iceland suggests that airline pilots have a higher risk of developing nuclear cataract than non-pilots, and that the cause may be exposure to cosmic radiation. A similar theory suggests that astronauts, too, are at risk from cosmic radiation.
Other studies suggest people with diabetes are at risk for developing a cataract. The same goes for users of steroids, diuretics and major tranquilizers, but more studies are needed to distinguish the effect of the disease from the consequences of the drugs themselves.
Some eyecare practitioners believe that a diet high in antioxidants, such as beta-carotene (vitamin A), selenium and vitamins C and E, may forestall cataract development. Meanwhile, eating a lot of salt may increase your risk.
Other risk factors include cigarette smoke, air pollution and heavy alcohol consumption. A small study published in 2002 found lead exposure to be a risk factor; another study in December 2004, of 795 men age 60 and older, came to a similar conclusion. But larger studies are needed to confirm whether lead can definitely put you at risk, and if so, whether the risk is from a one-time dose at a particular time in life or from chronic exposure over years.*
When symptoms begin to appear, you may be able to improve your vision for a while using new glasses, strong bifocals, magnification, appropriate lighting or other visual aids.
Think about surgery when your cataracts have progressed enough to seriously impair your vision and affect your daily life. Many people consider poor vision an inevitable fact of aging, but cataract surgery is a simple, relatively painless procedure to regain vision.
Cataract surgery is very successful in restoring vision. In fact, it is the most frequently performed surgery in the United States, with over 1.5 million cataract surgeries done each year. Nine out of 10 people who have cataract surgery regain very good vision, somewhere between 20/20 and 20/40.
During surgery, the surgeon will remove your clouded lens, and in most cases replace it with a clear, plastic intraocular lens (IOL). New IOLs are being developed all the time to make the surgery less complicated for surgeons and the lenses more helpful to patients. One example is a new IOL that lets patients see at all distances, not just one. Another new IOL blocks both ultraviolet and blue light rays, which research indicates may damage the retina (see illustration).
Different methods of cataract surgery are available, but they all have the same objective: the replacement of the opaque lens by an intraocular lens to achieve an adequate vision.
The surgeon will chose the most suitable method, according to the patient's need.
The facoemulsification is the most modern and effective technique. The opaque crystalline is liquefied and aspired through a vibrating end. The incision in the eye must be only of the size necessary to allow the passing of the facoemulsificator needle. This incision, performed with a small diamond seals automatically, therefore it does not require stitches, or, at the most, one or two.
Through this incision the intraocular lens is inserted, as shown step by step in these images. To the right, a model of an intraocular lens can be observed. These are made of biocompatible elements.The facoemulsification is performed under local anesthesia or with eye drops, it is therefore considered an ambulatory surgery that does not require the hospitalization of the patient.
Post operating Care
The patient can go home, and within two days
perform regular day to day activities.
The patient with cataracts, with a previous refraction vice (myopia or hyperopia), has with this surgery an additional advantage.
When having surgery, and their crystalline lens being removed, we can, in the power calculus of this lens, compensate the refraction vice.
It may happen, that after several months or even years after surgery, the capsule (bag where the intraocular lens was placed) may become opaque, being this common in a 17% of the patients.
When this happens, it is corrected performing an incision with a technique called posterior capsulotomy with Yag Laser , a simple procedure done in the doctor's office.
The decision to operate:
Both the patient and the doctor must agree, according to the need to improve the eyesight, as well as the quality of life.
What is the purpose of glaucoma surgery?
Why is surgery performed for glaucoma?
For some, glaucoma surgery is the best option. Surgery reduces intraocular pressure to lower levels than can be achieved by medicine or laser, and might also reduce or eliminate the need for long-term glaucoma medicine. The lower pressure achieved by surgery has been shown to provide a greater chance of preventing further loss of vision from glaucoma.
Is there more than one type of glaucoma
Full-thickness filtering surgery was an earlier form of glaucoma surgery. It was found to be highly effective, but tended to cause a greater number of side effects from the pressure becoming too low. Occasionally, it is performed for selected patients.
In the late 1990s, some glaucoma sub specialists advocated non-penetrating filtering surgery. This has the advantage of reducing the risk of the intraocular pressure becoming too low immediately after surgery, but seems to have a disadvantage in that there is a higher failure rate and need for repeat surgery for glaucoma.
What is a glaucoma implant?
It is generally reserved for cases of severe glaucoma due to more unusual conditions, such as abnormal vessels in the front of the eye of some people with diabetes, and glaucoma caused by ocular inflammation. Implant surgery is also used in some individuals who have previously had a trabeculectomy that was not successful.
What is the recovery period after glaucoma
Are there risks of glaucoma surgery?
However, these risks must be compared to the risks of uncontrolled glaucoma, which can lead to a total, permanent loss of vision, if the pressure cannot be controlled with eye drops, laser, or surgery.
What can be done to prevent failure of
glaucoma filtering surgery?
LASIK and other refractive surgeries: Say good-bye to eyeglasses
Considering surgery to correct your vision? Explore three procedures that can restore your eyesight.
If you wear glasses or contact lenses, you might be interested in surgery to correct your vision. Keep in mind, though, that as much as you might like to toss out your glasses or put an end to the daily ritual of inserting and removing your contact lenses, surgery to correct vision problems isn't for everyone.
Familiarize yourself with the procedures eye doctors use to correct vision problems and the risks and benefits of each. Then discuss your options with your doctor to help you decide whether refractive eye surgery is for you.
What is refractive eye surgery?
Refractive eye surgery is a surgical procedure to change the way your eye refracts light. As light rays enter your eye, your cornea and lens bend (refract) the rays to focus them on the back of your eye — your retina. If you have a refractive error, your eye is shaped in such a way that light rays aren't sharply focused on your retina.
During refractive surgery, your cornea is reshaped. Your cornea can be flattened or steepened based on your specific vision problems. Refractive surgery is usually considered an elective surgery — which means it isn't vital to your health and well-being. For this reason, Medicare and most insurance companies won't cover the cost of the surgery.
Who can have refractive eye surgery?
Refractive eye surgery is for people with certain refractive errors in their vision, such as:
Refractive surgery can't correct or prevent presbyopia — a type of refractive error that is common as you age. Most people in their 40s have some signs of presbyopia, including difficulty reading or doing up close work. If you're approaching your 40s or if you already have presbyopia, keep in mind that refractive surgery may give you clear distance vision, but it might make it even more difficult for you to see objects close up.
To avoid this, you might choose to have your vision corrected to give you monovision. With monovision, one eye is corrected to see objects far away and your other eye is corrected to see close objects. Some people can adjust to this whereas others can't. You can also choose to wear glasses solely for reading or other close up work. Ask your eye doctor about your options if you have presbyopia.
Your eye doctor will likely recommend that you try other ways of correcting your vision before you turn to surgery. Glasses or contact lenses are usually your first option. Some people might have only mild refractive errors that don't require vision correction.
What might disqualify you from having refractive surgery?
Not everyone with a refractive error is a candidate for refractive surgery. Whether surgery is right for you is also based on:
To determine whether you're a candidate for refractive surgery, your eye doctor will conduct an in-depth eye exam to determine the degree of your refractive error, the shape of your corneas and the general health of your eyes. Talk with your eye doctor about certain aspects of your eyes that might influence whether you're eligible for refractive surgery.
What types of refractive eye surgery are available?
Several surgical procedures are available if you have a refractive error in your vision. What type of surgery you choose will depend on the type and degree of refractive error that you have. Get to know the common types of refractive surgery and discuss your options with your eye doctor.
Laser-assisted in-situ keratomileusis (LASIK)
During the LASIK procedure, your eye surgeon uses a special blade or special cutting laser to cut a hinged flap about the size of a contact lens away from the front of your eye. Folding back the flap allows your doctor to access the tissue in your cornea that needs reshaping. Using a laser, your eye surgeon then targets specific parts of your cornea. The flap is then folded back into place and usually heals on its own without stitches.
Your eye doctor determines which specific areas of your cornea need to be flattened or curved during your eye exam. This allows your eye doctor to chart your eye and remove tissue from your cornea very precisely.
You will receive an anesthetic to numb your eye during the LASIK procedure, which helps ensure you'll experience little pain. You may be given medication or eyedrops after the procedure to soothe any pain you might have for several hours after your surgery. Your eye doctor might also ask you to wear a shield over your eye at night until your eye heals. You might have the option of having LASIK on both eyes on the same day.
Typically you're able to see the day of your surgery, but your vision won't necessarily be better right away. Expect your vision to improve over the next two to three months. Most people who have refractive surgery will have vision that is close to 20/20. Your chances for improved vision are based, in part, on how well your eyes saw before surgery.
Laser epithelial keratomileusis (LASEK)
If you have very thin corneas, you might choose LASEK because the procedure allows your doctor to cut out less of your cornea. People who play sports or have jobs that carry a high risk of eye injuries might also prefer LASEK because a thinner flap means less damage to your vision should the flap be torn before it can heal. As with LASIK, the LASEK procedure can be done on both eyes on the same day. Expect your vision to take time to recover — it may take several months.
Photorefractive keratectomy (PRK)
The raw surface of your cornea repairs itself, assisted by a contact lens you wear as a bandage over your eye for three or four days after surgery. You might have eye pain for a few days until your cornea heals. It generally takes up to a week for your eye to regenerate the surface tissue that was removed. During this time you'll notice changes in your vision. It may take three to six months before your vision improves completely. Most people undergoing PRK have one eye done at a time. After your first eye has healed, you might consider having surgery on your other eye.
PRK has become less common in recent years because more eye surgeons prefer the LASIK procedure. Healing after LASIK is more predictable and usually involves less discomfort and scarring.
Other types of surgery
What are the risks and benefits of refractive eye surgery?
Refractive surgery can offer you improved vision without the hassle of glasses or contact lenses. In general, you have a very high chance of achieving 20/40 vision or better after refractive surgery. About 85 percent of people who've undergone refractive surgery no longer need to depend on their glasses or contact lenses most of the time.
Your results will depend on your specific refractive error and other factors. People with a low grade of nearsightedness tend to have the most success with refractive surgery. People with a high degree of farsightedness along with astigmatism have the least predictable results.
As with any surgery, refractive surgery carries risks, including:
Talk to your doctor about your concerns. He or she can explain the risks that are most likely to affect you.
Considering refractive eye surgery
As you make your decision whether to have refractive eye surgery, consider the benefits and the risks. Also consider the cost of surgery. Most importantly, discuss your decision and your concerns with your eye doctor. He or she can help you decide if refractive surgery is right for you.
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