Eye Disorders

This information is neither comprehensive nor intended to replace the professional examination and diagnosis by an eye doctor. It is presented here strictly for informational purposes. This information should not be taken as a recommendation to self-diagnose or self-treat a condition. A misdiagnosed or improperly treated eye condition can result in permanent loss of vision.

CLICK ON THE FOLLOWING TO VIEW VIDEO ABOUT SOME COMMON EYE CONDITIONS:

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CLICK ON THE FOLLOWING TO VIEW TEXT ABOUT SOME COMMON EYE CONDITIONS:

Allergies

Astigmatism

Blepharitis

Cataracts

Chalazion

Color Blindness

Diabetes

Dry Eyes

Farsightedness (Hyperopia)

Flashes and Floaters

Glaucoma/Ocular Hypertension

Keratoconus

Macular Degeneration

Migraine Visual Disorder

Nearsightedness (Myopia)

Pinguecula

Pink Eye (Conjunctivitis)

Presbyopia

Pterygium

Refractive Error

Stye

Allergies

An allergy is the body’s overreaction to a substance. A substance that triggers an allergic reaction is called an “allergen”. Some of the most common airborne allergens include pollen, mold, dust and pet dander. When the eye reacts to an allergen it is called “allergic conjunctivitis”. Over 22 million Americans suffer from allergies, and most of those also have allergic conjunctivitis, according to the American Academy of Ophthalmology.
The most common symptoms of allergic conjunctivitis are:

  • Itching
  • Burning
  • Tearing
  • Redness
  • Puffiness
  • Increased Mucus

The severity of the allergic reactions can vary significantly from mild, moderate to severe.

The best treatment is to avoid the allergen, however, this is not always possible. We cannot cure your allergy, but, there are medications we can prescribe to help your discomfort.

Astigmatism

For us to see clearly, light rays enter the eye, are bent by the cornea and lens (“refracted”) and focus to one point on the retina. The retina converts the light rays into impulses that are sent to the brain, where they are recognized as images. If the light rays don’t focus on the retina, the image is blurry. With astigmatism light enters the eye and focuses at two points instead of one. In between these two points the image is spread out and therefore blurry. This usually occurs because the cornea (the clear front part of the eye) is warped. We typically say that the astigmatic cornea is shaped more like a football rather than a basketball…it is curved more in one direction than another. Glasses, contact lenses and refractive surgery (e.g. LASIK) attempt to reduce this error by making the light focus at one point on the retina.

See “refractive error” for more illustrations.

Blepharitis

We all have normal bacteria on our skin, but for some of us there is an overgrowth of this normal bacteria. This causes a chronic inflammation of the eyelids which we call “blepharitis” (sometimes called “granulated” eyelids). The most common symptoms of blepharitis are:

  • Itching
  • Burning
  • Tearing
  • Gritty/Sandy Irritation
  • Redness
  • Mattering (especially in the mornings)

The picture on the top right shows what a lid with blepharitis can look like. Note that the edge of the lid is red, lashes are missing and there is debris at the edge of the lid. This appearance comes after long-standing inflammation.

This is a chronic condition….we cannot cure blepharitis but we can help you manage it to be more comfortable. People with blepharitis look like they have dandruff/debris on their lashes. This debris harbors the bacteria, so treatment involves cleaning the lashes to eliminate this debris. Many times this strict lid hygiene is enough to control the condition.

In more severe cases it may be necessary for us to prescribe antibiotic and steroid drops or ointments. Once the acute phase is controlled by the medications, the lid hygiene may be sufficient to control the blepharitis.

Cataracts

When we are born the lens inside the eye is clear. As we grow up the lens inside the eye becomes cloudy…this is a cataract. It is simply a cloudy lens. We will all develop cloudy lenses, or cataracts, if we live long enough. But not everybody needs surgery….it just depends on how cloudy the lens gets and how much it is interfering with your life. If surgery is done they simply remove that cloudy lens and typically replace it with a clear manufactured one (this is called an “implant”). With today’s surgical techniques the success rate of cataract surgery is very high and the complication rate is very low. Our doctors will advise you if you are a candidate for cataract surgery.

Chalazion

A chalazion is a painless, hard round bump that can appear anywhere on the eyelid. It can vary in size from very small to quite large. It is an enlarged, clogged oil gland and is not an infection. The exact cause is unknown, but several conditions are associated with chalazia: seborrhea, chronic lid inflammation, dry eyes and acne. A chalazion may last weeks to months and can sometimes resolve on its own without any treatment. It is often very helpful to apply frequent warm compresses. In some cases oral antibiotics, steroid injection or surgical removal is necessary.

There are other more serious conditions which can look like a chalazion, so it is important to have this evaluated by an eye doctor.

Color Blindness

Color blindness is really not blindness at all. A more appropriate term is “color defective”. People who are color defective have difficulty distinguishing certain colors. Most commonly they confuse red and green and less commonly blue and yellow. It is extremely rare for a color deficient person to see only in shades of gray (“monochromat”) or no color at all (“achromat”) . People are born with color blindness. It is a genetic disorder that is gender-linked (X-linked recessive) and is, therefore, much more prevalent in boys than girls (about 8% males and 0.5% females in North America). The mother is either color deficient herself or has normal color vision but carries the defective gene. Color deficient fathers never pass the gene directly to their children, although daughters will carry the color deficient gene. Color deficiency can never be cured and usually does not create a major problem in a person’s life. A child may require special help in school since some learning materials rely heavily on color.

The picture on the top right is an example of a color vision test plate. To a person with normal color vision some of the dots will appear dissimilar enough from the other dots to form a distinct figure (in this case the number 25). To a color deficient person all the dots will appear so similar that they cannot distinguish the image.

(Note: You cannot test your color vision on this plate. This is for illustration purposes only and even a color defective person can see this number).

Diabetes

Diabetes can have profound effects on eye health. Specifically, diabetes can make the blood vessels in the retina leaky. The vessels can then leak blood, fluid and fatty substances which we call hemhorrage, edema and exudate, respectively. This damage is called “diabetic retinopathy” and is typically not seen in the first five to ten years after being diagnosed with diabetes. The longer somebody has been diabetic the greater the likelihood that we will see these changes. However, it is possible to see this damage early on. Of those who have had diabetes for over 15 years, 60% will have some signs of retinal damage.

There are two types of diabetic retinopathy:

  • Non-Proliferative
  • Proliferative

Proliferative retinopathy is the more advanced form and is more sight-threatening. It usually has severe hemorrhaging and scar tissue formation. The picture on the top right demonstrates what a normal retina should look like. The picture on the bottom right shows a severe retinal hemorrhage from diabetic retinopathy.

We have proof now that, the better control someone has over their blood sugar, the better the health of the retina. We think that the damage comes from long-standing poor sugar control. Therefore, it is imperative to KEEP YOUR BLOOD SUGAR UNDER STRICT, TIGHT CONTROL.

There is no pain associated with diabetic retinopathy and often there are not even any symptoms in the early stages. It is therefore very important that all diabetics have at least an annual dilated eye examination, or more frequently if advised by your eye doctor.

Dry Eyes

Dry Eye Syndrome is a chronic condition which is probably the most common ocular disorder in the general population. The front of the eye is covered by a tear film that has three layers. The top layer consists of oil to help keep the moisture from evaporating. The middle layer is watery to provide lubrication. The bottom layer is mucus to help spread the tear film over the front of the eye evenly. If there is a problem with any of these three layers, dry eye symptoms can occur.

Some of the most common symptoms of Dry Eye Syndrome are:

  • Burning
  • Tearing
  • Gritty, Sandy
  • Itchy
  • Redness
  • Dryness
  • Irritated
  • Scratchy
  • Light sensitivity
  • Foreign body sensation (feeling like there is something in your eye)
  • Variable blurred vision
  • Lids that stick together, especially in the morning

Dry eyes can be caused or affected by:

  • Age
  • Air conditioners
  • Heaters
  • Fans
  • Humidity
  • Wind
  • Smog
  • Allergies
  • Hormonal changes
  • Illness (especially Arthritis, Rosacea, Lupus and Sjogren’s Syndrome)
  • Fatigue
  • Medications (especially antihistamines, antidepressants and birth control pills)
  • Sun
  • Pregnancy
  • Lid problems

Because dry eyes are affected by so many factors, the discomfort may be variable in severity or frequency. Dry eyes cannot be cured, but, the symptoms can be controlled or managed. The most common way to alleviate dry eye symptoms is to artificially lubricate the eyes with drops, gels or ointments. Sometimes this lubrication isn’t adequate and we will insert a temporary plug in the lid ducts where the tears drain from the eye. This preserves the tears that are already there. If the temporary plugs help we can insert permanent (although removable) plugs. Additionally, permanent closure of the ducts with the use of laser or cautery surgery can be performed.

There is now one prescription medication to help dry eyes:

Farsightedness (“Hyperopia”)

For us to see clearly, light rays enter the eye, are bent by the cornea and lens (“refracted”) and focus to one point on the retina. The retina converts the light rays into impulses that are sent to the brain, where they are recognized as images. If the light rays don’t focus on the retina, the image is blurry. With farsightedness (“hyperopia”) the light comes into the eye and focuses BEHIND the retina. Glasses, contact lenses and refractive surgery (e.g. LASIK) attempt to reduce this error by making the light focus on the retina.

See “refractive error” for more illustrations.

Flashes and Floaters

Inside the eye there is a clear gel called the vitreous. When we are born the vitreous has a firm solid shape to it (like jello) even though it is 98-99% water. Starting at about age four this gel begins to liquify. Bits and pieces of this gel break off and float around inside the eye. This will cast a shadow on the retina and cause you to see something moving in your vision. So, although floaters appear to be in front of the eye, they are actually floating in the fluid inside the eye. These “floaters” come in many sizes and shapes and are described by people in different ways: spots, dots, circles, lines, strands, strings, cobwebs, clouds, amoeba and dust-like specks. They are most apparent against a light background like a blue sky, lightly painted walls, white tiles in a bathroom or white background of a page in a book. Because they are inside your eye, they move with your eyes when you try to look at them. With time floaters will usually diminish because:

  • They break up into smaller pieces or,
  • Gravity will pull them down out of your line of sight or,
  • The brain just ignores them

Some people feel their floaters do not change at all. They are typically no more than an aggravation or annoyance and are not treated.

The vitreous gel is firmly attached to the retina in three spots. As the gel becomes more liquid and shrinks with age, it tugs at these attachments and eventually will detach. It is the GEL detaching from the retina and not the retina itself detaching, however, retinal detachment has similar symptoms. When this tugging and detachment occur you will usually see more floaters and flashes of light because the retina is being stimulated. These flashes are similar to the sensation of “seeing stars” when one is hit on the head. Most people will eventually see flashes and/or floaters in their lifetime.

If you should suddenly see a shower of new floaters, especially in conjunction with flashes of light and a black curtain or veil over your vision, it could indicate something more serious. Your eye doctor will need to examine you to diagnose this properly.

Flashes of light which appear as jagged lines or “heat waves” lasting 5-60 minutes are likely to be a result of a migraine. This can occur with or without a headache (see “Migraine Visual Disorder”), is usually of no clinical significance and does not need treatment.

Glaucoma/Ocular Hypertension

It is estimated that millions of people have glaucoma and half of them don’t even know it. This is because usually there are no symptoms until it is very advanced. Glaucoma means that there is damage to the optic nerve. The optic nerve is like an electrical cable that plugs into the back of the eye and transmits visual information to the brain so we can see. It consists of about one million nerve fibers. In glaucoma, there is damage to the optic nerve and individual nerve fibers begin to die and disappear. When these nerve fibers are lost there is no way for visual information to transmit to the brain, so blind spots develop. Eventually, after the disease has run its course, a glaucoma patient is left with tunnel vision….like looking through a straw. Ultimately, in the worst case scenario, when that last nerve fiber goes, vision is completely lost. This vision loss is not reversible.

The image to the right shows a normal optic nerve. The pinkish “rim” tissue are the actual nerve fibers diving into the nerve. The “cup” is empty space where there are no nerve fibers. In a normal eye the cup and rim will always look the same. However, because glaucoma is a progressive disease, the appearance of the cup and rim tissue will change over time. These changes occur very gradually and subtly over time making it difficult to detect. Imaging devices like retinal cameras have aided us in photodocumenting the appearance of the nerve so we can monitor any changes.

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The image to the right shows a damaged glaucoma nerve. As the damaged nerve fibers gradually die and disappear, the empty space [or “cup”] will get larger. Note how large the white cup area is compared to the normal nerve. This is what we are looking for in your annual eye exams: a large cup that is increasing in size as the rim tissue is decreasing in size.

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Most people with glaucoma have elevated pressure inside their eye. This pressure inside the eye is a fluid pressure. The fluid is produced in the eye in order to maintain its shape and to nourish the eye tissues. The amount of fluid produced and going into the eye should equal the amount leaving the eye. If too much fluid is produced or not enough drains out, the pressure builds up. Over time this chronic elevated pressure pushes on the delicate optic nerve, causing damage which results in vision loss.

Often the diagnosis of glaucoma is not straightforward. It is possible to have NORMAL pressures and HAVE glaucoma (“Low Tension Glaucoma”). It is also possible to have ELEVATED pressures and NOT have glaucoma (“Ocular Hypertension”).

The diagnosis of glaucoma is therefore far more complicated than simply measuring the pressure inside the eye. In order to diagnose glaucoma, these and other tests may be performed:

  • Measurement of the intraocular pressure (“IOP”)
  • Evaluation of the optic nerve
  • Mapping of the visual field (a test that looks for blind spots)
  • Measurement of corneal thickness (“pachymetry”)

Sometimes all of these tests have abnormal results and the diagnosis is clear. But more often only some of these test results are abnormal. This person is considered to be a “glaucoma suspect” and is examined more often than they otherwise would be.

Once glaucoma is diagnosed the main goal of treatment is to lower the eye pressure. Treatment may include medicated eyedrops, oral medications or surgery.

In most cases glaucoma can be controlled and managed, but not cured. It is typically a very slowly progressive disease, taking many years to run its course. It is not fully understood what causes glaucoma.

Because you can see well and feel fine even if you have glaucoma, is important to have regular eye examinations.

Keratoconus

The cornea is the clear front part of the eye (like a watch crystal is to a watch). It is normally spherical like a basketball. In people with astigmatism it’s more like a football. In people with keratoconus it is abnormally thin, bulging, distorted and shaped like a cone. It causes vision to be distorted and blurry. It is usually diagnosed in the early teens or early twenties and it’s cause is not clear. As the disease progresses the cornea gets more thin, bulgy and conically shaped. As the distortion increases the vision declines. In its very early stages glasses or soft contact lenses may help, but, as the disease progresses, they become ineffective. Eventually a rigid contact lens is necessary as this creates an undistorted surface on the cornea. These are very difficult custom contact lens fits which require many office visits and a skilled doctor. As the corneal degeneration progresses it may become impossible to keep a contact lens on the eye and a corneal transplant may be necessary. After the transplant another complex custom contact lens fitting is usually needed.

The picture on the top right shows the profile of an advanced keratoconic eye. Note how much the cornea is shaped like a cone. It is so pointy that it becomes very difficult and eventually impossible for a contact lens to balance on that cone without teetering so much that it falls off.

Macular Degeneration

The retina is the tissue in the back of the eye that contains the receptor cells for seeing. These receptor cells are called rods and cones. The rods are more effective in dim light and provide our less clear peripheral vision. The cones are responsible for providing our sharp, central 20/20 vision. The heaviest concentration of the cone receptors is located in the macula, a very small (about 1.5 mm) but important part of the retina. Macular Degeneration never affects the peripheral retina so, although the vision loss can be catastrophic, it does not result in total blindness. As we age the macula produces some yellowish-white particles called “drusen”. Drusen can be small (hard) or large (soft) and they collect in the retinal tissue as the degeneration progresses. These drusen deposits can be an early sign of age-related macular degeneration, or ARMD, although not all people with drusen go on to develop ARMD.

The picture on the top right shows a normal retina.

There are two types of ARMD:

  • Dry or Atrophic
  • Wet or Exudative

Dry ARMD accounts for about 90% of all macular degeneration. It is the more mild, typically slowly progressive form and usually affects vision to a lesser degree. It develops as the drusen deposits cause the macula to thin and break down, slowly leading to the loss of these receptors and eventually vision. It is sometimes hard to tell the difference between early ARMD drusen and that drusen which is seen in most normal aging eyes. There is currently no medical or surgical treatment for dry ARMD and it can progress to the wet form.

The picture on the top right shows dry ARMD. Note the small yellowish lesions. These are drusen.

Wet ARMD accounts for about 10% of all macular degeneration. It is the more severe form and can have a devastating effect on vision. In wet ARMD the macula grows abnormal, fragile blood vessels which eventually leak causing hemorrhage. This leakage, which can occur very suddenly, causes the retinal receptor cells to die and the resultant vision loss.

The picture on the top right shows wet ARMD. Note the reddish areas. These are hemorrhages.

The most common treatments are:

    • Laser Therapy

This technique uses high energy lights to destroy the abnormal blood vessels.

    • Photodynamic Therapy

In this technique a light-activated drug called Visudyne is injected into the patient’s arm. It travels through the bloodstream to abnormal blood vessels in the retina. A cold laser (one that does not burn the retina) is then focussed on the drug in the abnormal vessels and destroys only these blood vessels, leaving the healthy blood vessels unharmed. This therapy may need to be repeated.

Other methods of treatment are also currently being used and investigated, but the laser techniques described above remain the mainstays of treatment.

Many researchers and eye doctors have believed that certain vitamins and/or minerals could help prevent or slow down the progression of ARMD, but had no scientific studies to support their theory. A study published in the August 2001 issue of Archives of Ophthalmology found that consuming omega-3 fatty acids, such as is found in fish like salmon, had a protective effect against advanced ARMD. Conversely, omega-6 fatty acids, as is found in vegetable oils, was associated with an increased risk of ARMD.

THE AREDS STUDY

In 2001 the National Eye Institute completed a 10-year study called AREDS (“Age-Related Eye Disease Study”). This research was sponsered by the National Eye Institute (NEI) and studied the effects of antioxidants and zinc on vision loss from ARMD.

The AREDS study concluded:

  • High levels of antioxidants and zinc reduced the risk of progression to advanced ARMD by about 25%
  • High levels of antioxidants and zinc reduced the risk of vision loss from ARMD by about 19%
  • High levels of antioxidants and zinc did not provide any significant benefit for those with early ARMD or no ARMD
  • These supplements do not prevent the initial development of ARMD
  • These supplements do not improve vision that was already lost due to ARMD
  • A few patients taking zinc alone had urinary tract problems
  • Some patients taking large doses of antioxidants had some yellowing of their skin
  • Long-term effects of taking these supplements are still unknown

The vitamins used in this study were:

    • Vitamin C, 500 mg
    • Vitamin E, 400 IU
    • Beta-Carotene, 15 mg

NOTE: Beta-carotene becomes vitamin A in the body.

    • Zinc,as zinc oxide, 80 mg
    • Copper, as cupric oxide, 2 mg

NOTE: Copper must be taken with zinc because high-dosage zinc is associated with copper deficiency.

Lutein and zeaxanthin (natural pigments found in the macula) were not evaluated in AREDS, however, there is uncontrolled scientific data to suggest that they may be helpful for patients with ARMD.
Although these supplements are available without a prescription, you must first check with your physician to ensure it is safe for you to take these supplements. Some may interfere with certain medications.

Smokers and ex-smokers should not take beta-carotene, as studies have shown a link between beta-carotene use and lung cancer among smokers.

Finally, although the incidence of ARMD is quite high (about 20% of the senior population), the exact cause of this condition is not known.

Migraine Visual Disorder

A migraine is a vascular event. The blood vessel will suddenly constrict limiting the blood supply to the involved tissue. The symptoms that result are dependent on which specific blood vessels and tissues are involved. If it happens in the retina it is called a visual migraine, or ophthalmic migraine, or retinal migraine. This usually causes a dramatic visual disturbance such as flashing or flickering lights, “heatwave” wavy vision and complete loss of vision in spots. This visual symptom typically lasts from 5 minutes to an hour (average is 15-20 minutes). When the visual disturbance is followed by a headache it is called a “classic” migraine. Visual migraines do not require treatment. However, if the classic migraine sufferer takes their medication during the visual disturbance, they may be able to prevent the subsequent headache.

Nearsightedness (“Myopia”)

For us to see clearly, light rays enter the eye, are bent by the cornea and lens (“refracted”) and focus to one point on the retina. The retina converts the light rays into impulses that are sent to the brain, where they are recognized as images. If the light rays don’t focus on the retina, the image is blurry. With nearsightedness (“myopia”) the light comes into the eye and focusses in FRONT of the retina. Glasses, contact lenses and refractive surgery (e.g. LASIK) attempt to reduce this error by making the light focus on the retina.
See “refractive error” for more illustrations.

Pinguecula

A pinguecula is an extremely common small lump on the white part of the eye. It is usually located towards the nose or ear. These elevations often have a yellowish color and range in size from barely visible to very large. When they become inflammed they will appear quite bloodshot. This inflammation usually goes away on its own and does not require medication. Pingueculae are usually caused by dryness, exposure to the environment and ultraviolet light. They occur most frequently in warm, dusty dry climates. There are usually no symptoms, but some people report burning and stinging as a result of the dryness. If there are no symptoms these are not treated. Some people will need to use artificial tears (over-the-counter moisture drops) to be comfortable. Glasses with ultraviolet (UV) protection are also recommended.

Pink Eye (Conjunctivitis)

“Pink Eye” is the common term for conjunctivitis. The conjunctiva is the thin, clear membrane lining the inside of the eyelids as well as the white of the eye. When this membrane is inflammed it is called “conjunctivitis”. The most common types of conjunctivitis are:

  • Allergic
  • Bacterial
  • Viral

Any inflammation of the conjuctiva causes it to appear red because the blood vessels in the tissue become dilated. This redness can be mild to severe. All three types of conjunctivitis make the eye appear pink or red. The vision is usually normal (although it can be blurry) and the discomfort is relatively mild.

ALLERGIC conjunctivitis generally causes itching as its primary symptom.

BACTERIAL conjunctivitis generally has a pus discharge.

VIRAL conjunctivitis generally has a watery discharge.

Bacterial and viral conjunctivitis are infections and are highly contagious. People who have it should not share towels, pillowcases, washcloths, eyeliner, eye shdow, mascara and should wash their hands frequently. Children may need to stay home from school.
Allergic conjunctivitis is an inflammation and is not contagious.
Treatment will vary depending on the cause of the infection/inflammation.
It is extremely important to understand that there are many things that can cause the eye to appear pink/red. Some of these conditions are very serious and require rapid medical treatment. The specific cause and necessary treatment of the red eye can only be determined after an eye doctor has examined you. Please do not diagnose yourself…this can be very dangerous.

Presbyopia

presbyopiaWhen we look further than 20 feet away the focussing mechanism inside the eye is totally relaxed. We don’t start to focus until we look closer than 20 feet. The closer something is to us, the more we need to focus. The way we focus is that the lens inside the eye changes its shape. One of the changes that occurs as we age is that the lens inside the eye gets stiffer and the muscles that control it don’t work as well. The result is that we lose our ability to focus. This loss of focussing ability is called “presbyopia”. By about age 40 we have lost enough focussing power that it begins to affect our life. Small print is more difficult to see, you may develop headaches and fatigue more quickly when doing near work. You may also push things further away (until your arms get too short!) because you don’t have to focus as much at that further distance. This is a normal, gradual physiological process and not a disease process. It occurs whether you are nearsighted, farsighted or astigmatic. When it begins to cause you difficulty glasses and/or contact lenses can provide the focussing power that your natural lens can no longer provide. The lens inside your eye will continue to do less and less focussing until about age 65 and the prescription we provide will do more and more focussing for you until it eventually flip-flops: the lens inside your eye will do little to no focussing and your prescription will do all of it.

Pterygium

A pterygium is a fleshy growth that begins on the white part of the eye and grows onto the surface of the cornea (the clear front part of the eye). This is a degenerative change that we think is related to exposure to wind, sun and ultraviolet light. They are three times more common in men than women. Pterygia are generally slowly progressive and typically stabilize before they can affect vision. Usually they have no symptoms and no treatment is needed. Sometimes they make the eye feel dry and the use of artificial tear drops can help. Occasionally they can become inflammed and a prescription anti-inflammatory drop is necessary. Rarely, a pterygium grows so far onto the cornea that it can threaten sight and is therefore surgically removed. Pterygia often recur and the irritating symptoms persist in spite of their removal.
The use of ultraviolet blocking lenses is highly recommended.

Refractive Error

For us to see clearly, light rays enter the eye, are bent by the cornea and lens (“refracted”) and focus to one point on the retina. The retina converts the light rays into impulses that are sent to the brain, where they are recognized as images. If the light rays don’t focus on the retina, the image is blurry. There are three types of refractive error: nearsightedness (“myopia”), farsightedness (“hyperopia”) and astigmatism. Glasses, contact lenses and refractive surgery (e.g. LASIK) attempt to reduce these errors by making the light focus on the retina.

The animation on the right illustrates how the light image lands incorrectly when a refractive error is present. You can see how in a normal eye the image lands on the retina.
In a nearsighted (“myopic”) eye the image lands in front of the retina.
In a farsighted (“hyperopic”) eye the image lands behind the retina.
In an astigmatic eye the image lands in two points of focus.

In all of these instances the vision will appear blurry because the image does not come to one point of focus on the retina.

Stye

A “stye” is the common term used for an acute infection of the hair follicle or gland at the edge of the eyelid. The medical term for this condition is “hordeolum”. Initially they are usually tender, small, red painful bumps on the inside or outside edge of the lid. This condition is caused by bacteria (staphylococcal) which is often found in the nose. It is easily transferred to the eye by first rubbing your nose and then your eye. It is common among the following groups: children, people with chronic lid infections, diabetics and debilitated patients with poor hygiene. The first line of treatment is to use aggressive warm compresses as well as plucking out the lash from the middle of the infected lash gland. This can bring the stye to a head which will then usually rupture, drain and heal. This discharge is loaded with bacteria and is therefore highly contagious. Never squeeze a stye to pop it; allow it to rupture on its own. Sometimes an antibiotic drop is needed to protect the rest of the eye. Surgery is rarely needed. It is important to prevent the spread of this infection to the rest of the lid. If the entire lid surrounding the stye is swollen, red, painful and also seems infected your doctor may prescribe oral antibiotics.

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