What causes amblyopia?
The visual system of the child is not fully developed at birth. The visual brain cells of a child are developing during their first decade of life. Any insult to the child's vision during this time period can lead to amblyopia.

Following are the common causes of amblyopia:
Squint: This is the commonest cause of amblyopia. The brain to avoid double vision ignores the image from the deviating eye. This leads to poor visual development of the deviating eye and hence amblyopia.
Unequal refractive error (anisometropia): In this condition, the two eyes have different refractive errors. Because the brain can not "balance" this difference, it picks the eye that is "easier" to use and develops a preference for this eye only. The eye with greater refractive error is suppressed and thus gets amblyopic. An early treatment by giving the right glasses for correction can prevent and correct this problem.
Stimulus deprivation: Any form of stimulus derivation to either one or both eyes in early childhood may lead to a severe form of amblyopia. These causes for stimulus deprivation may be ptosis, cataract, glaucoma, patching or any other obstacle that blocks the vision in the eye.

How can we detect if the child has amblyopia?
Detecting amblyopia in child is difficult, as the child may not be aware of having one strong eye and one weak eye. If the child has a squint or some other abnormality, the parents may notice that something is wrong. The vision of the child can be tested by the ophthalmologist by special tests. Poor vision in an eye may point towards a possibility of amblyopia. Remember, poor vision in an eye does not always mean amblyopia. It is important to rule out other causes of poor vision in child.

Is it treatable?
Yes. In most of the cases the amblyopia is treatable. The treatment involves 'forcing' the brain to use the weaker eye and thus stimulating its visual development. This is done by patching the better eye. The schedule of patching is decided by the ophthalmologist depending upon the degree of amblyopia and the age of child.

When should it be treated?
As soon as possible. The earlier the amblyopia is detected and the treatment started, the better are the results. The aim is to stimulate the brain to use the suppressed eye before permanent change has occurred, so that it gets a chance of normal development. Generally speaking, an amblyopia that is not treated by 10 years of age has a poor chance of recovering the vision.

Why is it important to treat amblyopia?
If an amblyopic eye is not treated by 10 years of age, the amblyopic eye may permanently stay weak. This has many disadvantages like:
Both eyes can not be used simultaneously and hence depth perception (three-dimensional vision) is not present. Many occupations are not open for people who have good vision in one eye only.
It is important to give best possible vision to the amblyopic eye even if the other eye is seeing well. The importance of this becomes obvious, in case the person loses the other (better) eye, sometime later due to some injury or disease.

What are the factors that determine the success of treatment?
The success of amblyopia treatment largely depends upon the motivation of parents and the cooperation of the child. Patching of the better eye, especially when the amblyopic eye has very poor vision is not tolerated well by the child. The parents have to understand the importance of this treatment and should explain the same to the child to ensure better cooperation.

The other factors that determine the success of treatment are:
The severity (depth) of amblyopia
The age at which the treatment is started: The earlier the treatment is started, the better are the results
Any other complicating factor in the eye preventing sufficient gain of vision, e.g., glaucoma, cataract, retinal or optic nerve disorders

My child has squint and amblyopia. Which should be treated first?
Amblyopia has to be treated first in all these cases. Once the amblyopia has been taken care of, the surgery may be done for squint correction.

What is diabetic retinopathy?
Retina is the layer at the back of the eye that is sensitive to light. Diabetes affects the small vessels of the retina in the eye. There are various stages of diabetic retinopathy:

Non-proliferative or background diabetic retinopathy: When blood vessels in the retina are damaged, they can leak fluid or bleed. This causes the retina to swell and form deposits called exudates. This is an early form of diabetic retinopathy and may not lead to any decrease in vision, but it can lead to other more serious forms of retinopathy that affect the vision.

Macular edema: The fluid and exudates collects in the macula (the part of the retina that allows us to see fine details), thus decreasing the vision. Sometimes there may be a macular edema without any loss of vision. Therefore it is important to have periodic checkup to detect and treat these conditions at an early stage.

Proliferative diabetic retinopathy: This is an advanced stage of diabetic retinopathy, where the blood supply of retina is compromised. In response to this, new fragile blood vessels grow on the surface of the retina (neovascularization). These new vessels are very fragile and bleed easily. These may lead to serious vision problems if they bleed into the vitreous (the clear, jelly-like substance that fills the center of the eye) which is known as vitreous hemorrhage. This prevents the light from reaching the retina and thus can blur the vision.

The new blood vessels and the bleed into the vitreous can also cause scar tissue to develop, which can pull the retina away from the back of the eye. This is known as retinal detachment, and can lead to blindness if untreated.

In addition, abnormal blood vessels can grow on the iris (the colored part in the front of your eye, which can lead to glaucoma).

What are the risk factors for diabetic retinopathy?
The longer the person has diabetes, the greater are his/her chances to develop diabetic retinopathy. Almost 80% of people, who have diabetes for 15 years or more, have some damage to the blood vessels in their retina. The other risk factors are high blood pressure, anemia, kidney diseases, and pregnancy.

Can something be done to prevent diabetic retinopathy?
There is no treatment that can prevent diabetic retinopathy altogether. Persons with any form of diabetes may develop diabetic retinopathy. But it has been proven that a good control of diabetes can delay and slow down the rate of progress of diabetic retinopathy and its complications. Besides a good control of blood sugar, one must exercise regularly, keep the blood pressure under control, avoid smoking, and avoid obesity.

How do I know if I have diabetic retinopathy?
You might not know that you are having diabetic retinopathy, as there are no symptoms in the earlier stages of the disease. Therefore it is essential to have periodic evaluation of your eye by an ophthalmologist to detect the condition early. Early diagnosis and timely treatment is very essential in preventing the complications of this disease and thus maintaining vision.

How frequently should I get my eye examined?
If you have diabetes, you should get a yearly examination with your ophthalmologist. Your pupils may be dilated with eyedrops, so that your ophthalmologist may have a good look at the back of your eye. Once you develop diabetic retinopathy, then your ophthalmologist will advise you if you need some investigations, treatment or just need to follow up. In these cases the frequency of follow up visits is decided on basis of the severity of the disease.

What are the tests done for diabetic retinopathy?
Your vision is assessed by the usual charts. The back of your eye is examined after dilating your pupils, using an instrument called ophthalmoscope. Sometimes your ophthalmologist may advise a special test called Fluorescein angiography.

What is fluorescein angiography?
It is test in which a series of photographs of the retina are taken with the help of a special camera. These photographs are taken after giving the patient an injection of a yellow dye. This dye reaches the retina through the blood stream and helps in seeing the blood vessels of retina more clearly. This test helps the doctor to determine which areas to be treated with laser.

So a regular retinal checkup is very essential in these patients to look for the holes and to treat them with laser or else they might lead to a retinal detachment, which needs surgery. Also, whenever the patient with high number develops symptoms like flashes or floaters, he/she must immediately get the eyes examined to look for retinal hole, tear or retinal detachment.

High myopes are also predisposed to develop abnormal new vessels in the central area (macula) called Choroidal Neovascular Membrane (CNVM), which leads to sudden marked fall in vision due to hemorrhage or fluid leakage. The treatment modalities being tried out for myopic CNVM are photodynamic therapy (PDT) with verteporfin, Transpupillary Thermo Therapy (TTT) laser and surgical options like macular translocation.

What are the ways of changing the curvature of cornea?
The commonly used methods for refractive surgery are:
PhotoRefractive Keratotomy (PRK) : It is being used less commonly nowadays.
Laser-Assisted In-Situ Keratomileusis (LASIK) :This is the most popular form of Laser treatment.
LASEK (or Epi-LASIK) :This newer form of treatment may be suitable in some selected patients with very high power.

What is Excimer laser?
Excimer laser is a far Ultra Violet (UV) light energy of wavelength 193 microns. It is invisible to human eye. This laser breaks the chemical bonds within the molecules (photoablation) with minimal thermal damage to the surrounding tissues. Thus it is very precise and can remodel the cornea with an accuracy of more than a thousandth of a millimeter.

How does Excimer laser correct the refractive error?
The effect of excimer laser on the cornea is very similar to grinding of a glass lens to change its refractive power. In eyes with refractive errors, excimer laser because of its high level of precision, can change the shape of the cornea to change its refractive power to the desired state and thus correcting the refractive error.

In myopia, the central part of the cornea is made flatter, and thus decreasing the refractive power of the cornea and of the eye, and thus correcting the refractive error.

Similarly in hypermetropia, the laser removes a ring of tissue from the peripheral part of the cornea and thus makes the central part steeper and corrects the refractive error.

As we know, in astigmatism, the cornea is more curved in one direction. Excimer laser can correct astigmatism also by selectively ablating the cornea in the required direction.

What is LASIK?
LASIK involves putting the PRK treatment not on the surface of the cornea, but under a protective corneal flap. A very thin (about 0.16 mm) and precise flap is raised by a special instrument known as microkeratome. The result is a corneal flap attached at one edge, the hinge. The surgeon folds the flap to expose the inner stromal layer of the cornea. The excimer laser treatment is applied on this stromal bed to remodel it. After this the flap is repositioned to its original position and it does not require any suture. Since the corneal epithelium has only been minimally disturbed, there is only mild discomfort after the procedure.

What is Customised LASIK?
This is a special form of LASIK in which the treatment parameters are customised for the particular patient, based not only on the refractive error, but also on the corneal map of the eye and other findings detected by special tests. This procedure tries to correct aberrations, maintains normal shape of the cornea and gives better night vision.

Who is a suitable candidate for LASIK laser surgery?
The person must be 18 years or older with a stable power. A contact lens user must discontinue the use of contact lenses at least 2 weeks before the procedure. A detailed eye checkup is done to look for suitability for the procedure. Before the Laser is done the eyes are checked with special machines to determine the exact power, the corneal mapping is done and corneal thickness is measured. In patients with high minus power, a special retinal checkup is done for detecting any possible weak areas in the retina, which may need to be treated before the LASIK is performed. The LASIK laser is performed only after ruling out any contraindication and confirming the suitability of the procedure.

What happens during the Laser surgery?
The LASIK surgery is done as an outpatient procedure and does not require any admission. It is painless and is done after putting the anesthetic drops and does not require any injections. The laser procedure takes approximately 15-20 minutes for both eyes. After the procedure, the patient can go back home after 20-30 minutes.

What are the complications of LASIK?
LASIK is a very safe procedure with a majority of patients achieving very good results. However, since it is a surgical procedure, it does carry some chances of complications as well, which would be discussed with you before the surgery. The overall rate of significant complications in LASIK is only of the order of 1-2%. Some of these complications may be:
Undercorrection or Overcorrection
Glare and difficulty in night driving
Flap complications, perforation
Infection
Scarring of the cornea

What are the precautions to be followed after LASIK, and when can one resume work?
After LASIK surgery one needs to avoid using cosmetics in and around the eye for a week or two. One should also avoid wetting or rubbing the eyes for some period. Use the medications regularly and report immediately in case of any discomfort, redness, injury or any other problem. There is no restriction in reading, watching TV, going for walks etc. In majority of cases, routine office or simple household work may be resumed in a day or two.

How are the results of refractive surgery?
Before undergoing any refractive surgery procedure, one must realize that none of these procedures can guarantee you perfect vision without glasses in all the cases. These surgeries are based on the average calculations from a large population, but as different individuals may respond differently to surgery, there might be some variation in the outcome results obtained. The aim is to decrease your dependence on glasses/contact lenses. The reliability of the procedure is quite good in mild to moderate levels of refractive errors, with most of people being able to carry out their daily activities without glasses. But for high degrees of refractive errors, the variation is more and some people may still need glasses, though of much lesser power than before, to see clearly.

If the child has poor vision in only one eye then it may be difficult to notice it. The eye with poor vision may not be aligned properly with the other eye, thus causing squint (strabismus). The child may also have rhythmic jiggling movements of the eyes (nystagmus).

Sometimes the cause of poor vision may be visible as a whiteness of the cornea or whiteness behind the pupil. In some cases the eyes of child with glaucoma may be watering and very sensitive to light.

The poor vision may also be noticed incidentally when the child is being examined by a doctor or during vision screening in the school.

What are the causes of poor vision in a child?
These causes are:
Refractive error
Cataract
Glaucoma
Squint (strabismus)
Injury to the eye (sometimes the child may not tell about the injury to parents)
Diseases of cornea
Diseases of retina and optic nerve
Inherited disorders
Tumor (Retinoblastoma)
Other eye abnormalities

What to do if I suspect that my child does not see properly?
As we see, there can be many causes for poor vision in a child. Some of these are very simple and treated easily, while others may be very difficult to manage and sometimes may even be life threatening. Therefore it is prudent to contact an ophthalmologist at the earliest if you suspect poor vision in your child. He or she will confirm poor vision and then look for the cause of the same. A timely treatment is very crucial in saving the sight and sometimes the life of the child.

How can one determine the vision in a small child who will not cooperate for vision testing?
There are many special tests available which help the doctor in determining the visual acuity of children in all age groups. The ophthalmologist will decide which tests to use and will get an idea of the visual loss and the chances of getting good vision after treatment.

Why is it important to detect poor vision in child?
If the poor vision in child is not treated early enough, the eye may not develop properly and develop a condition called amblyopia (lazy eye). Therefore, if the eye is treated at a later stage, the eye may not get good vision. It is very important to treat the cause of poor vision, e.g., refractive error, cataract, glaucoma, diseases of cornea etc. as early as possible to prevent amblyopia.

Early detection is also very important in case of tumor (retinoblastoma), which if detected early, may be treated easily without having to remove the eye. If it is not detected, then it may even lead to loss of life.

I have a child with poor vision. Can my other children also have some eye problem?
The chances of other children getting affected depend upon the cause of poor vision. Many of these conditions may be hereditary and may require examination of other siblings of the child. Also in hereditary diseases, a genetic counseling may be done to the parents if they plan to have another baby in future.

ROP needs to be treated as soon as it reaches a critical stage called Threshold ROP. The simple treatment is with laser or cryotherapy (freezing) helps in preventing sight threatening complication in most of these children. Untreated ROP may lead to marked visual loss. All premature babies need regular eye examination till they start going to school, for delayed complications like myopia.

What is Macular Degeneration?

The retina is a layer within the eye made up of nerve cells that perceive light which is then transmitted to the brain so that we have vision. Thus, the retina acts very much like the film in a camera. Vision is distorted or decreased with significant AMD.

The retina has blood vessels that run within it just like the pattern in a wallpaper, but it also depends on support for proper nourishment from an underlying layer of blood vessels called the choroid. In between the choroid and the retina is a barrier filter called Bruch’s membrane that prevents unwanted fluid from accumulating under the retina. Although we talk of the macula as the central part of the retina the critical area within the macula is called the fovea. This is only 1/15 of an inch in diameter, about the size of a pinhead. Thus, our central vision which allows us to read and see fine detail depends on the health of this small, but very highly specialized area.

What Causes Macular Degeneration?

While we do not understand completely how the changes occur, dry macular degeneration is due to atrophy (wasting away of retinal tissue). In the wet form vision loss is usually caused by the growth of abnormal blood vessels that leak fluid and blood under the foveal area of the macula. The dry type of macular degeneration affects 90% of patients and the wet type the remaining 10%. Most macular degenerations start out as the dry type. The rate of visual loss in the dry stage is highly variable and many people maintain reading vision and good distance vision for years. At any time in the course of the disease, however, the condition can convert to the wet type and, at that point, significant visual symptoms usually suddenly occur.

In the wet type of AMD abnormal blood vessels from the choroid grow through cracks in the barrier filter (Bruch’s membrane) like grass through cracks in the sidewalk. They then leak fluid or blood and it is this leakage that initially distorts or decreases the vision. Ultimately, a large scar may form secondary to the leakage and bleeding which has occurred under the retina.

Although there is no way to halt or reverse damage from dry age-related macular degeneration, certain lifestyle and dietary measures can be taken that can help to decrease the risk of disease progression to the more advanced stages.

If you smoke cigarettes, you should try to stop. Smoking increases your risk of disease progression. Studies also suggest that a diet rich in leafy green vegetables may be beneficial. (If you are taking certain types of blood thinners, ask your medical doctor first before making significant dietary changes since they could negate to some degree the affect of some blood thinners.)

Lastly, published results from the Age-Related Eye Disease Study (AREDS) showed that a certain formulation of anti-oxidant vitamins and minerals can reduce the risk of dry age-related macular degeneration progressing to more advanced stages and associated vision loss. The daily dose of vitamins used in the study is listed here:
500 mg. vitamin C
400 I.U. vitamin E
15 mg. of beta carotene
80 mg. of zinc oxide
2 mg. copper oxide

Please check with your doctor before starting this vitamin/mineral combination. In general, Vitamin E supplementation should not exceed 400 I.U. and smokers should not be on any beta carotene supplementation.

Risk Factors for AMD include:

• Family history of AMD (parents, brothers and sisters with the disease). Patients with a family history may show large drusen (yellow spots under the retina).
• Smoking
• High blood pressure and high cholesterol levels
• Obesity

Things You Can Do to Help Preserve Your Vision

• Do not smoke.
• Focus on healthy eating with a diet rich in green leafy vegetables, fruits, and fish once or twice a week.
• Cook with virgin olive oil, and avoid trans fats found in processed baked goods.
• Maintain normal blood pressure and cholesterol levels.
• Watch your weight.
• Exercise

If you have been diagnosed with intermediate level dry AMD or advanced dry AMD in one eye, take the vitamin and mineral combination of vitamin C, vitamin E, beta-carotene and zinc, as stated earlier, after checking with your personal physician (once again smokers should not take beta-carotene).
Screening of those with a family history of AMD and those who smoke should be encouraged so that if large drusen are noted, the appropriate nutritional supplements mentioned earlier can be recommended. Because macular degeneration is more common as one gets older we encourage those in the Medicare population to be screened as well.

Laser photocoagulation

A series of studies sponsored by the National Institute of Health ( USA) have proven that selected patients with wet macular degeneration have a lower risk of severe visual loss if they are treated by laser photocoagulation than if no treatment is instituted. It is estimated that about 10-15% of patients with the wet type of macular degeneration may be candidates for standard laser therapy. While the treatment may successfully eliminate the abnormal vessels, in approximately 50% of patients the abnormal vessels cannot be permanently obliterated.

Photodynamic therapy (PDT) with verteporfin (Visudyne)

PDT utilizes both an injection of a photosensitizing drug called verteporfin (Visudyne) and a non-thermal laser light exposure to treat certain types of choroidal neovascularization. Clinical trials have shown PDT to be effective in slowing down or limiting the amount of vision loss in patients who have choroidal neovascularization located directly under the center of the retina. The treatment does not, however, lead to recovery of vision already lost from the disease process and it may not prevent additional loss in all patients. Currently, steroid solutions injected directly into the eye before or after PDT are being explored to see if they reduce swelling in the retina, thereby enhancing the effect of PDT.

Anti-Blood Vessel Medical Therapy

Many new drugs are being developed that block blood vessel growth factors in the eye which have been shown to be involved in the development of choroidal neovascularization. In wet AMD these drugs may inhibit or slow the growth of the neovascularization and also possibly reduce its leakiness. Recent clinical trials have shown that treatment for wet AMD with centrally located choroidal neovascularization significantly reduced vision loss associated with wet AMD, but only rarely did the treatment result in any vision improvement.

The two most common types of cataracts are: the cortical cataract and a posterior subcapsular cataract. Depending on the type of cataract, a patient will experience different vision problems, but the most common cataract symptoms include:

• Blurring vision.
• Sensitivity to light or glare.
• Double vision in one eye.
• Poor night vision.
• Needing brighter light to read.
• Experiencing fading or yellowing of colors.

If the cloudiness is not near the center of the lens, you may not be aware that you have a cataract.

Many cataracts take years to develop to the point where vision is seriously affected. Most occur as a result of the normal aging process. The types of age-related cataract are usually described by their location in the lens. They are: nuclear cataracts, cortical cataracts and subcapsular cataracts.

Nuclear cataracts occur in the center of the lens and may induce other eye problems, such as myopia. A cortical cataract, which tends to occur more in persons with diabetes, begins at the outer portion of the lens, then slowly moves inward. Subcapsular cataracts develop under the capsule, often at the back of the lens. This type of cataract also occurs more in persons with diabetes, but it is also found in persons with high myopia, adults with retinitis pigmentosa and in people who take steroids.

There are other kinds of cataracts not related to the aging process. Traumatic cataracts develop as a result of an eye injury. Others can develop from metabolic blood disorders, eye infections and inflammations and certain types of medications.

Another type, called congenital cataract, occurs at birth, particularly if the mother has had rubella (German measles) during pregnancy. A nuclear cataract occurs in the center of the lens.

Research continues to look for ways to prevent cataracts. Until then, useful vision can be restored in 98 percent of all patients who have normal, healthy eyes.

Treatment for Cataracts

Cataracts can be removed at any age. You no longer have to wait until the cataract "ripens" or until you lose your sight before surgery can be performed. In fact, the placement of an intraocular lens (IOL) implant to restore vision is best done in an eye when the cataract interferes with your daily activities or causes a decrease in vision.

In removing cataracts, the clouded lens (cataract) must be removed surgically. Till now cataracts cannot be removed via laser.

A common surgical procedure used today is extracapsular cataract extraction. The surgeon makes an incision in the eye and the front (anterior) capsule of the lens to remove the clouded lens. The lens tissue within the capsule is emulsified and removed. The sac-like capsule that surrounds the lens remains in place. This capsule is left intact for two reasons: to avoid disturbing the gel, or vitreous, that fills most of the eye, and to support an intraocular lens.

After the cataract has been removed, the incision is closed. Often the sutures, which are finer than human hair, do not need to be removed. Some patients, in fact, don't even need sutures, and the "no suture" surgery is popular today.

But the sophisticated and most popular type of extracapsular cataract extraction is phacoemulsification (often just called "phaco"), where the surgeon removes the cataract through an even smaller incision than the one used in conventional surgery. In this procedure, the surgeon uses a computerized instrument consisting of a needle about the size of a ballpoint pen tip, which vibrates at about 40,000 times a second.

This ultrasonic vibration dissolves the cataract into fine particles, which are then vacuumed through an opening in the instrument.

The benefits of the phaco approach include an early restoration of vision and return to normal activities. Phaco is well suited for patients with a less-advanced cataract, when an earlier return to activity is required or when increased physical activity is part of the convalescent period.

At its onset, conjunctivitis is usually painless and does not adversely affect vision. The infection will clear in most cases without requiring medical care. But for some forms of conjunctivitis, treatment will be needed. If treatment is delayed, the infection may worsen and cause corneal inflammation and a loss of vision.

As a general rule, the deeper the corneal infection, the more severe is the symptoms and complications. It should be noted that corneal infections, although relatively infrequent, are the most serious complication of contact lens wear.

Minor corneal infections are commonly treated with anti-bacterial eye drops. If the problem is severe, it may require more intensive antibiotic or anti-fungal treatment to eliminate the infection, as well as steroid eye drops to reduce inflammation. Frequent visits to an eye care professional may be necessary for several months to eliminate the problem.

Many people wear contact lenses in place of glasses for cosmetic or aesthetic reasons. But there are also medical indications for the wearing of contact lenses.

About 26 million people in America wear contact lenses, and that number is constantly increasing. This popularity is due to the many improvements made in the design and availability of contact lenses and the fact that they have been made more comfortable and easier to wear. Contact lenses are also suited for people with medical conditions where eyeglasses do not provide adequate clarity of vision.

Ninety-five percent of those who want to wear contact lenses and who are well motivated can do so successfully, under ideal circumstances. The key for successful wearing rests with the wearer. However, for others, some organic or systemic disease may bar the use of contact lenses.

Contact lenses are tiny, curved plastic discs which are microthin, very light and barely visible. There are two major types: hard and soft.

Hard Lenses

The hard lens covers about two-thirds of the cornea and may be clear or tinted. This lens has been improved so that it can be made into a bifocal, toric or bitoric lens.

The hard, gas-permeable ( RGP) lens resembles the hard contact lens but is made of a material that allows oxygen to cross through the lens to the cornea, which is healthier for the cornea. Today, virtually all hard lenses are made in gas permeable plastics.

The scleral contact lens covers the whole front of the eye and is still used for certain medical conditions. The latest version of this lens design is used in the management of advanced Keratoconus.

The X-chrome lens is a hard, red contact lens which, when fitted on the non-dominant eye, allows people who have a particular kind of "color blindness" (those who can't discriminate between red and green) to partially distinguish colors. It is worn in only one eye (the weaker, "non-dominant" eye) and may be made with a prescription for patients who would also need eyeglasses to correct for vision.

Soft Lenses

The soft, or hydrophilic, lens is made of a special thin and very flexible plastic which absorbs water. It is larger than the hard lens and covers all of the cornea and extends to the sclera. Soft astigmatic lenses (Toric) are also available.

Daily-wear lenses were the first type of soft lenses available. These lenses are approved to be worn and removed on a daily basis. Patients may not sleep or nap with these lenses and are expected to clean and disinfect them whenever handled. A wide variety of soft daily-wear lenses are currently available on the market, including colored, bifocal and toric.

Extended wear lenses have been approved for patients after cataract surgery and for patients with myopia, hyperopia and astigmatism. These are soft lenses that allow better oxygen transmission to the cornea and need not be removed on a daily basis. They provide the visual benefits of contact lens wearing for many patients who cannot or do not wish to handle daily wear lenses. Because of the nature of these lenses, more frequent return visits are necessary. Extended-wear, hard, gas-permeable lenses are also available.

The disposable contact lens is one of the latest soft lenses available and may be worn as extended wear, daily wear or single-use lenses.

When removed daily, they must be soaked in disinfecting solution overnight. They are available for myopic and hyperopic patients.

Single-use lenses are designed to be worn for one day and then thrown away. These lenses are currently available only in limited prescriptions.

The latest innovation in soft lenses is the Silicone gel lens. These lens have a silicone backbone and are much more biocompatible than traditional soft lens. These lenses are used for extended wear, dry eyes and eyes that need more oxygen.

Contact Lens Fitting Procedure

Before contact lenses can be prescribed, a complete eye examination is required. No contact lens should be fitted without a thorough eye exam as a first step. The type of lens best suited for you should be the subject of a discussion between you and your doctor. Your eye doctor will determine the strength of the lenses, and inspect your eyes and lids for possible allergies or infections. The curvature of the eye must be measured and other special tests may have to be performed.

Contact lenses, both hard and soft, are held in place by adhering to the film of tears that normally covers the front of your eye. A membrane that lines the front half of the eyeball and lines the underside of the eyelid makes it impossible for the contact lens to go behind the eye or to wander anywhere but under the lid.

After you are fitted, there may eye discomfort, but there should be no pain. As you become accustomed to the lenses, wearing time should increase and discomfort decrease until maximum wearing time is finally reached. This may take three to four days for soft lenses, and two to four weeks for hard lenses.

Some symptoms experienced during the adaptation period are tearing, blinking, sensitivity to light, head tilt, and a slight redness of the eye. All of these symptoms are temporary and should disappear by the end of the third week. If not, notify your eye doctor.

Patients should be alert to any signs of infection, corneal abrasion and swelling.

A small percentage of patients have a great degree of sensitivity and never quite adapt to contact lenses. They are usually told that they are not ideal candidates and should not be wearing contacts.

Lens Care Guidelines

• Always wash, rinse and dry your hands thoroughly before handling your contact lenses.

Hard Lenses

• Hard lenses scratch easily, so don't wipe them with hard or rough cloths.
• Hard lenses should be cleaned daily and soaked in a commercial sterilizing solution.
• Use a wetting agent before insertion.
• Periodically have contacts examined by a professional to ensure comfort and good vision. It may be necessary to have rigid lenses cleaned and polished professionally.
• If you live in a polluted area, your lenses may need to be cleaned more frequently.

Soft Lenses

• Always store soft lenses in disinfecting solution, not saline solution.
• Never prepare homemade solutions. Use only commercially prepared products and saline solutions.
• Because soft lenses are absorbent, never use water or any solutions without your physician's approval.
• Soft lenses must be cleaned daily.
• After cleaning, soft lenses must be disinfected using either heat or chemical methods, as recommended by your physician.
• In addition to the daily cleaning, soft lenses require a weekly enzymatic cleaning to remove protein deposits and to ensure clean, healthy lenses.

When Should Contacts Not Be Worn

As a rule, lenses should not be worn while swimming, or sitting in a hot tub. Under special circumstances and only with a eye doctor’s permission, some patients may be able to wear their lenses while swimming, if they wear good protective goggles.

Advice for Contact Lens Wearers

• Do wash, rinse and dry your hands before handling the lenses.
• Do carry identification stating that you wear contacts, so they can be removed in case of an accident.
• Do follow your doctor's instructions about regular checkups.
• Do learn to insert and remove lenses correctly.
• Do keep a backup pair of glasses.
• Do be careful applying makeup; apply after insertion of the lenses.
• Do carry your contact lens case and glasses at all times.
• Do use only those solutions recommended by your doctor.
• Do use commercially prepared saline and other cleaning solutions.
• Don't rub eyes while wearing lenses.
• Don't wear damaged lenses.
• Don't wear lenses while sleeping, or continuously, unless specifically prescribed by your doctor.
• Don't use any eyedrops on your lenses without your doctor's approval.
• Don't insert, remove or work with lenses over a wash basin.
• Don't place lenses on top of anything warm; they will melt.
• Don't wear lenses while under a hair dryer or around harsh fumes.
• Don't use saliva or tap water on your lenses as a wetting agent.
• Don't use homemade saline solution or distilled water in preparing your lens care products.
• Don't reinsert your lenses without disinfecting them.

The tear film consists of three layers--an outer, oily (lipid) layer that keeps tears from evaporating too quickly and helps tears remain on the eye; a middle (aqueous) layer that nourishes the cornea and conjunctiva; and a bottom (mucin) layer that helps to spread the aqueous layer across the eye to ensure that the eye remains wet. As we age, the eyes usually produce fewer tears. Also, in some cases, the lipid and mucin layers produced by the eye are of such poor quality that tears cannot remain in the eye long enough to keep the eye sufficiently lubricated.

The main symptom of dry eye is usually a scratchy or sandy feeling as if something is in the eye. Other symptoms may include stinging or burning of the eye; episodes of excess tearing that follow periods of very dry sensation; a stringy discharge from the eye; and pain and redness of the eye. Sometimes people with dry eye experience heaviness of the eyelids or blurred, changing, or decreased vision, although loss of vision is uncommon.

Dry eye is more common in women, especially after menopause. Surprisingly, some people with dry eye may have tears that run down their cheeks. This is because the eye may be producing less of the lipid and mucin layers of the tear film, which help keep tears in the eye. When this happens, tears do not stay in the eye long enough to thoroughly moisten it.

Dry eye can occur in climates with dry air, as well as with the use of some drugs, including antihistamines, nasal decongestants, tranquilizers, and anti-depressant drugs. People with dry eye should let their health care providers know all the medications they are taking, since some of them may intensify dry eye symptoms.

People with connective tissue diseases, such as rheumatoid arthritis, can also develop dry eye. It is important to note that dry eye is sometimes a symptom of Sjögren's syndrome, a disease that attacks the body's lubricating glands, such as the tear and salivary glands. A complete physical examination may diagnose any underlying diseases.

Artificial tears, which lubricate the eye, are the principal treatment for dry eye. They are available over-the-counter as eye drops. Sterile ointments are sometimes used at night to help prevent the eye from drying. Using humidifiers, wearing wrap-around glasses when outside, and avoiding outside windy and dry conditions may bring relief. For people with severe cases of dry eye, temporary or permanent closure of the tear drain (small openings at the inner corner of the eyelids where tears drain from the eye) may be helpful.

How does Glaucoma cause damage?

Normally, watery fluid (aqueous humor) constantly flows through the eye. This fluid keeps the eye firm and clear so the eyeball can function well visually. The relative state of inflow and outflow of aqueous humor partially determines how firm the eye is. If the outflow is blocked, pressure inside the eye builds up.

The pressure within the eye, the intraocular pressure, can directly damage the optic nerve, the nerve that carries the electrical impulses from the light-sensitive part of the eye to the brain, where the electrical impulses are put together to form a picture. Even when the intraocular pressure is not above average, it may still be high enough to cause optic nerve damage. Elevated intraocular pressure can damage other tissues as well, such as the cornea and the lens, and can squeeze out of the eye the blood needed to keep the nerves healthy, resulting in damage to the nerves or retina (the light-sensitive part of the eye).

Outflow of fluid, aqueous humor, can be blocked in different ways: The pupil, the hole through which the fluid flows as it passes from the back to the front of the iris (the colored part of the eye) can get blocked by adhesions or by a cataract. The sieve through which the fluid drains can become blocked by debris caused by inflammation, by deposits which are due to aging, by abnormal material which is sometimes the result of certain drugs, or by the iris itself. The veins into which the fluid flows when it leaves the eye can be partially blocked by other disease, or by pressure on the large veins in the orbit.

Average normal intraocular pressure in adults is 15 mm Hg (mercury). If the pressure is below 8 mm Hg or so, the eye may be too soft to function well. The actual upper limit of normal, however, is difficult to pinpoint.

If the pressure is consistently above 21 mm Hg, the chance of eye damage is probably around 10 percent. When the pressure inside the eye is above 26 mm Hg, the likelihood of eye damage increases to about 50 percent. When the intraocular pressure is above 30 mm Hg, the chance that damage will eventually develop may be close to 100 percent if the elevated pressure persists long enough.

What constitutes normal intraocular pressure is an individual matter for each person. For example, some persons with an intraocular pressure of 16 mm Hg may need surgery; others with a pressure of 30 mm Hg may not even need any treatment.

Studies indicate that keratoconus stems from one of several possible causes:

An inherited corneal abnormality. About seven percent of those with the condition have a family history of keratoconus.
An eye injury, i.e., excessive eye rubbing or wearing hard contact lenses for many years.
Certain eye diseases, such as retinitis pigmentosa, retinopathy of prematurity, and vernal keratoconjunctivitis.
Systemic diseases, such as Leber's congenital amaurosis, Ehlers-Danlos syndrome, Down syndrome, and osteogenesis imperfecta.

Keratoconus usually affects both eyes. Keratoconus is a disease which causes the cornea to protrude and become progressively thinner and cone-shaped. Eyeglasses usually cannot fully correct this condition, and in advanced cases, patients can only obtain useful vision with specially designed hard lenses. Very severe cases that cannot be fit with lenses or cannot get useful vision with contact lenses may require a corneal transplant.

At first, people can correct their vision with eyeglasses. But as the astigmatism worsens, they must rely on specially fitted rigid ( hard) contact lenses (RGP Contact Lenses) to reduce the distortion and provide better vision. Although finding a comfortable contact lens can be an extremely frustrating and difficult process, it is crucial because a poorly fitting lens could further damage the cornea and make wearing a contact lens intolerable.

In most cases, the cornea will stabilize after a few years without ever causing severe vision problems. But in about 10 to 20 percent of people with keratoconus, the cornea will eventually become too scarred or will not tolerate a contact lens. If either of these problems occur, a corneal transplant may be needed. This operation is successful in more than 90 percent of those with advanced keratoconus. Several studies have also reported that 80 percent or more of these patients have 20/40 vision or better after the operation.

Pterygia are more common in sunny climates and in the age group of 20-40. Scientists do not know what causes pterygia to develop. However, since people who have pterygia usually have spent a significant time outdoors, many doctors believe ultraviolet (UV) light from the sun may be a factor. In areas where sunlight is strong, wearing protective eyeglasses, sunglasses, and/or hats with brims are suggested. While some studies report a higher prevalence of pterygia in men than in women, this may reflect different rates of exposure to UV light. Lubricants can reduce the redness and provide relief from the chronic irritation.

Because a pterygium is visible, many people want to have it removed for cosmetic reasons. It is usually not too noticeable unless it becomes red and swollen from dust or air pollutants. Surgery to remove a pterygium is indicated if it affects vision or in cases of considerable irritation. If a pterygium is surgically removed, it may grow back, particularly if the patient is less than 40 years of age.

The most successful surgery technique is to removal/ excision of pterygium with conjunctival transplantation. This technique reduces the risk of pterygium recurrence to approximately 2% - 5%.

A retinal detachment, should it occur, can be vision threatening. That is why it is important to know the signs and symptoms of a retinal detachment. They are:

• Brief flashes of light in your vision (if you have a known posterior vitreous detachment, watch for increasing frequency of light flashes)
• A sudden shower of new floaters
• A grey or black curtain or shade coming into your vision from any direction
• A new blind spot in your vision
• Blurring of your vision which does not clear with blinking or artificial tears

If you see any of these retinal detachment symptoms, consult with an eye doctor immediately.

Treatment of Retinal Tears to Prevent Retinal Detachments

Usually, retinal tears affect the only peripheral vision. Symptoms include unexplained flashes of light and moving black spots (floaters). If you suspect you have a retinal tear, it is important to see your ophthalmologist as soon as possible.

Sometimes, doctors will simply monitor a retinal tear and elect not to treat it. However, if your retina specialist is concerned that the tear will lead to a retinal detachment, the recommended treatment is either cryosurgery (a "freezing" technique) or laser treatment.

Both cyrosurgery and laser may be performed on an outpatient basis. Cryosurgery involves the use of a local anesthetic to numb the eye. The area around the site of the retinal tear is then frozen using a probe. As the treated area heals, scar tissue is formed which helps to seal the tear. Laser surgery uses an intense but precisely focused beam to form the scar tissue that seals the tear.

Scleral Buckle Surgery for Retinal Detachments

Scleral buckle is a surgical procedure that has been used for more than 30 years. It involves the placement of silicone onto the outer wall of the eyeball to create a buckle effect inside the eye. The buckle pushes against the retinal tear or detachment, helping to push it back into a more normal position. Once the tear is sealed, the eye completes the healing process by resorbing the fluid inside the retina (the subretinal fluid).

Scleral buckle surgery can usually be done under local anesthesia and on an outpatient basis.

Vitrectomy for Retinal Detachments

For certain types of retinal detachments ("traction" retinal detachments and detachments that involve the loss of the natural fluids inside the retina), vitrectomy is a commonly used surgical procedure.

Sometimes referred to as "pars plana vitrectomy or PPV," this procedure was developed about 20 years ago. Small incisions are made to allow access into the center of the eyeball. The surgeon removes the vitreous and repairs the detachment. After surgery, the patient will need to use certain precautions and maintain specific head positions to prevent another retinal detachment. Within days-to-weeks of surgery, the eye will replace its own fluids inside the retina.

During a routine eye examination, your ophthalmologist will test your eyesight and the health of your eyes. At this time, you should discuss any chronic illnesses you have and any medications or dietary supplements you may be taking. Even if you feel your eyesight is good, it is always helpful to have an open discussion about your family history, health problems, profession and lifestyle because these things may have an impact on your eyes now and in the future.

Your eye doctor will test your visual acuity, which is the clarity of your vision. You will probably be asked to read the letters on an eye chart. These letters vary in size, becoming increasingly smaller as you read from row to row. At some point, you will probably tell the doctor that you can't see clearly or at all. Based on this test, the doctor will be able to determine whether your visual acuity is normal or whether you are nearsighted (myopic) or farsighted (hyperopic).

The doctor will also examine your eyelids and use various lights and instruments to look into your eyes, on the eye surface and even behind the eye. Just as you have your blood pressure taken at your primary care physician's office, the ophthalmologist will use a device that measures the pressure inside your eye to check for glaucoma.

At some point in the exam, your doctor will also check the muscles of your eyes.

None of the tests used during a routine eye examination are painful or uncomfortable. There is a possibility that the doctor may use eyedrops that will dilate (widen) your pupils, which may make it difficult for your eyes to focus properly for several hours after the exam.

If your ophthalmologist believes you need to have eyeglasses or contact lenses to correct your vision, you will receive a prescription for the appropriate strength based on your exam.

However, if you are in good health and have no known eye problems and no vision problems, an exam every two to four years is adequate. The elderly should have eye examinations at least every two years because cataracts and other eye problems may develop as we age.

Because vision is so related to learning, children should have yearly eye examinations.

For people with special health problems, such as diabetes, frequent eye examinations are necessary to maintain good eye health. Finally, anyone with known eye problems, such as glaucoma, will need to see their ophthalmologist on an ongoing basis.