Amblyopia, also known as "lazy eye" is the lack of normal visual development in an eye, despite the eye being healthy. If left untreated, it can cause legal blindness in the affected eye. About 2% to 3% of the population is amblyopic.
Amblyopia signs and symptoms
Amblyopia generally starts at birth or during early childhood. Its symptoms often are noted by parents, caregivers or health-care professionals. If a child squints or completely closes one eye to see, he or she may have amblyopia. Other signs include overall poor visual acuity, eyestrain and headaches.
What causes amblyopia?
The most common cause of amblyopia is strabismus (intermittent or constant misalignment of the eyes). Another common cause is a significant difference in the refractive errors (nearsightedness, farsightedness and/or astigmatism) in the two eyes. It's important to correct amblyopia as early as possible, before the brain ignores vision in the affected eye.
Treatment of amblyopia
Amblyopic children can be treated with vision therapy (which often includes patching one eye), atropine eye drops, the correct prescription for nearsightedness or farsightedness or surgery.
Vision therapy exercises the eyes and helps both eyes work as a team. Vision therapy for someone with amblyopia forces the brain to use the amblyopic eye, thus restoring vision.
Sometimes the eye doctor or vision therapist will place a patch over the stronger eye to force the weaker eye to be used more. Patching may be required for several hours each day or even all day long, and may continue for weeks or months. If you have a lot of trouble with your child taking the patch off, you might consider a prosthetic contact lens that is specially designed to block vision in one eye but is colored to closely match the other eye.
In some children, atropine eye drops have been used to treat amblyopia instead of patching. One drop is placed in your child's good eye each day (your eye doctor will instruct you). Atropine blurs vision in the good eye, which forces your child to use the eye with amblyopia more, to strengthen it. One advantage of this method of treatment is that it doesn't require your constant vigilance to make sure your child wears an eye patch.
If your child has become amblyopic due to a strong uncorrected refractive error or a large difference between the refractive errors of their eyes, amblyopia can sometimes simply be treated by wearing eyeglasses or contact lenses full-time. In some cases, patching may be recommended along with the new glasses or contact lenses.
In cases when the amblyopia is caused by a large eye turn, strabismus surgery is usually required to straighten the eyes. The surgery corrects the muscle problem that causes strabismus so the eyes can focus together and see properly.
Amblyopia will not go away on its own, and untreated amblyopia can lead to permanent visual problems and poor depth perception. If your child has amblyopia and the stronger eye develops disease or is injured later in life, the result will be poor vision through the amblyopic eye. To prevent this and to give your child the best vision possible, amblyopia should be treated early on.
If amblyopia is detected and aggressively treated before the age of 8 or 9, in many cases the weak eye will be able to develop 20/20 vision.
Blepharitis is inflammation of the eyelids, occurring particularly at the lid margins. It's a common disorder and may be associated with a low-grade bacterial infection or a generalized skin condition.
Blepharitis occurs in two forms: anterior blepharitis and posterior blepharitis.
Anterior blepharitis affects the front of the eyelids, usually near the eyelashes. The two most common causes of anterior blepharitis are bacteria and a skin disorder called seborrheic dermatitis, which causes itchy, flaky red skin.
Posterior blepharitis affects the inner surface of the eyelid that comes in contact with the eye. It is usually caused by problems with the oil (meibomian) glands in the lid margin. Posterior blepharitis is more common than the anterior variety, and often affects people with a rosacea skin type.
Blepharitis signs and symptoms
Regardless of which type of blepharitis you have, you will probably have such symptoms as eye irritation, burning, tearing, foreign body sensation, crusty debris (in the lashes, in the corner of the eyes or on the lids), dryness and red eyelid margins.
It's important to see an eye doctor and get treatment. If your blepharitis is bacterial, possible long-term effects are thickened lid margins, dilated and visible capillaries, misdirected eyelashes, loss of eyelashes and a loss of the normal position of the eyelid margin against the eye. Blepharitis can also lead to styes and infections or erosions of the cornea.
Blepharitis can be difficult to manage because it tends to recur. Treatment depends on the type of blepharitis you have. It may include applying warm compresses to the eyelids, cleaning your eyelids frequently, using an antibiotic and/or massaging the lids to help express oil from the meibomian glands.
If your blepharitis makes your eyes feel dry, artificial tears or lubricating ointments may also be recommended. In some cases, anti-bacterial or steroid eye drops or ointments may be prescribed.
Always wash your hands before and after touching your eyelids when treating blepharitis. Your eye doctor will provide instructions on the products and techniques to use to relieve symptoms and get your blepharitis under control. Thereafter, a daily regimen of lid hygiene is helpful in preventing recurrences of blepharitis.
There is some evidence to suggest that taking a daily flaxseed oil supplement that contains omega-3 fatty acids may help prevent or reduce the severity of posterior blepharitis. Be sure to discuss any supplement use with your doctor.
Because blepharitis tends to be chronic, expect to keep up therapy for a prolonged period of time to keep it at bay. If you normally wear contact lenses, you may need to discontinue wearing them during the treatment period and even beyond. Sometimes, changing from soft contact lenses to rigid gas permeable (GP) contacts can be helpful, since GP lenses are less likely to accumulate lens deposits. In other cases, contact lens discomfort caused by blepharitis can be relieved by replacing soft contact lenses more frequently or changing to one-day disposable lenses.
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 allows light to 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.
Most cataracts occur gradually as we age and don't become bothersome until after age 55. However, cataracts can also be present at birth (congenital cataracts) or occur at any age as the result of an injury to the eye (traumatic cataracts). Cataracts can also be caused by diseases such as diabetes or can occur as the result of long-term use of certain medications, such as steroids.
Cataract Signs and Symptoms
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. However, as cataracts worsen, you are likely to notice some or all of these problems:
- Blurred vision that cannot be corrected with a change in your glasses prescription.
- Ghost images or double vision in one or both eyes.
- Glare from sunlight and artificial light, including oncoming headlights when driving at night.
- Colors appear faded and less vibrant.
What causes cataracts?
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 gathering information that may help to prevent them.
Many studies suggest that exposure to ultraviolet light is associated with cataract development, so eye care practitioners recommend wearing sunglasses and a wide-brimmed hat to lessen your exposure. Other types of radiation may also be causes. For example, a study conducted in Iceland suggests that airline pilots have a higher risk of developing a nuclear cataract than non-pilots, and that the cause may be exposure to cosmic radiation. A similar theory suggests that astronauts, too, are at greater risk of cataracts due to their higher exposure to 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 for cataracts include cigarette smoke, air pollution and heavy alcohol consumption.
When symptoms of cataracts begin to appear, you may be able to improve your vision for a while using new glasses, stronger bifocals and greater light when reading. But when these remedies fail to provide enough benefit, itâs time for cataract surgery.
Cataract surgery is very successful in restoring vision. In fact, it is the most frequently performed surgery in the United States, with nearly 3 million cataract surgeries done each year. More than 90% of people who have cataract surgery regain very good vision, somewhere between 20/20 and 20/40, and sight-threatening complications are relatively rare.
During surgery, the surgeon will remove your clouded lens and 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. Presbyopia-correcting IOLs not only improve your distance vision, but can decrease your reliance on reading glasses as well.
If you need cataracts removed from both eyes, surgery usually will be done on only one eye at a time. An uncomplicated surgical procedure lasts only about 10 minutes. However, you may be in the outpatient facility for 90 minutes or longer because extra time will be needed for preparation and recovery.
Presbyopia-correcting IOLs: Frequently asked questions
If you need cataract surgery, you may have the option of paying extra for new presbyopia-correcting IOLs that potentially can restore a full range of vision without eyeglasses.
Presbyopia-correcting IOLs are a relatively new option, so you may have questions such as:
1. What are presbyopia-correcting IOLs?
Presbyopia-correcting intraocular lenses (IOLs) are lens implants that can correct both distance and near vision, giving you greater freedom from glasses after cataract surgery than standard IOLs. They are available in two forms: multifocal lenses and accommodating lenses. Multifocal lenses are similar to multifocal contact lenses â they contain more than one lens power for different viewing distances. Accommodating IOLs have just one lens power, but the lens is mounted on flexible âlegsâ that allow the lens to move forward or backward within your eye in response to focusing effort to enable you to see clearly at a range of distances.
2. Aren't presbyopia-correcting IOLs a lot more expensive? How much extra do I have to pay?
Yes, presbyopia-correcting IOLs are more expensive than standard IOLs. Costs vary, depending on the lens used, but you can expect to pay up to 12,500 extra per eye. This added amount is usually not covered by Medicare or other health insurance policies, so it would be an âout-of-pocketâ expense if you choose this advanced type of IOL for your cataract surgery.
3. Why won't Medicare or health insurance cover the full cost of presbyopia-correcting IOLs?
A multifocal or accommodating IOL is not considered medically necessary. In other words, Medicare or your insurance will pay only the cost of a basic IOL and accompanying cataract surgery. Use of a more expensive, presbyopia-correcting lens is considered an elective refractive procedure, a type of luxury, just as LASIK and PRK are refractive procedures that also typically are not covered by health insurance.
4. Can my local cataract surgeon perform presbyopia-correcting surgery?
Not all cataract surgeons use presbyopia-correcting IOLs for cataract surgery. Make sure your eye surgeon has experience with these lenses if you choose a multifocal or accommodating IOL. Studies have shown that surgeon experience is a key factor in successful outcomes, particularly in terms of whether you will need to wear eyeglasses following cataract surgery.
5. Are any problems associated with presbyopia-correcting IOLs?
At a 2007 American Society of Cataract and Refractive Surgery conference, some reports indicated that even experienced cataract surgeons needed to perform enhancements for 13% to 15% of cases involving use of presbyopia-correcting IOLs. Enhancements don't mean that the procedure itself was a failure, because you likely will see just fine with eyeglasses even if your outcome is less than optimal. But itâs possible you may need an additional surgical procedure (such as LASIK) to perfect your uncorrected vision after cataract surgery with a presbyopia-correcting IOL. Depending on the arrangement you make with your eye surgeon, you also may need to pay extra for any needed enhancements.
If you have diabetes, you probably know that your body can't use or store sugar properly. When your blood sugar gets too high, it can damage the blood vessels in your eyes. This damage may lead to diabetic retinopathy. In fact, the longer someone has diabetes, the more likely they are to have retinopathy (damage to the retina) from the disease.
In its advanced stages, diabetes may lead to new blood vessel growth over the retina. The new blood vessels can break and cause scar tissue to develop, which can pull the retina away from the back of the eye. This is known as retinal detachment, and it can lead to blindness if untreated. In addition, abnormal blood vessels can grow on the iris, which can lead to glaucoma. People with diabetes are 25 times more likely to lose vision than those who are not diabetic, according to the American Academy of Ophthalmology.
Signs and symptoms of diabetic retinopathy
Anyone who has diabetes is at risk for developing diabetic retinopathy, but not all diabetics will be affected. In the early stages of diabetes, you may not notice any change in your vision. But by the time you notice vision changes from diabetes, your eyes may already be irreparably damaged by the disease.
That's why routine eye exams are so important. Your eye doctor can detect signs of diabetes in your eyes even before you notice any visual symptoms, and early detection and treatment can prevent vision loss.
Floaters are one symptom of diabetic retinopathy. Sometimes, difficulty reading or doing close work can indicate that fluid is collecting in the macula, the most light-sensitive part of the retina. This fluid build-up is called macular edema. Another symptom is double vision, which occurs when the nerves controlling the eye muscles are affected.
If you experience any of these symptoms, see your eye doctor immediately. If you are diabetic, you should see your eye doctor at least once a year for a dilated eye exam, even if you have no visual symptoms.
If your eye doctor suspects diabetic retinopathy, a special test called fluorescein angiography may be performed. In this test, dye is injected into the body and then gradually appears within the retina due to blood flow. Your eyecare practitioner will photograph the retina as the dye passes through the blood vessels in the retina. Evaluating these pictures tells your doctor or a retina specialist if signs of diabetic retinopathy exist, and how far the disease has progressed.
What causes diabetic retinopathy?
Changes in blood-sugar levels increase your risk of diabetic retinopathy, as does long-term diabetes. Generally, diabetics don't develop diabetic retinopathy until they have had the disease for at least 10 years. As soon as you've been diagnosed with diabetes, you need to have a dilated eye exam at least once a year.
In the retina, high blood sugar can damage blood vessels that can leak fluid or bleed. This causes the retina to swell and form deposits. This is an early form of diabetic retinopathy called non-proliferative or background retinopathy.
In a later stage, called proliferative retinopathy, new blood vessels grow on the surface of the retina. These new blood vessels can lead to serious vision problems because they can break and bleed into the vitreous, the clear, jelly-like substance that fills the interior of the eye. Proliferative retinopathy is a much more serious form of the disease and can lead to blindness.
Fortunately, you can significantly reduce your risk of developing diabetic retinopathy by using common sense and taking good care of yourself:
- Keep your blood sugar under good control.
- Maintain a healthy diet.
- Exercise regularly.
- Follow your doctor's instructions to the letter.
How is diabetic retinopathy treated?
According to the American Academy of Ophthalmology, 95% of those with diabetic retinopathy can avoid substantial vision loss if they are treated in time.
Diabetic retinopathy can be treated with a laser to seal off leaking blood vessels and inhibit the growth of new vessels. Called laser photocoagulation, this treatment is painless and takes only a few minutes.
In some patients, blood leaks into the vitreous humor and clouds vision. The eye doctor may choose to simply wait to see if the clouding will dissipate on its own, or a procedure called a vitrectomy may be performed to remove blood that has leaked into the vitreous humor.
Small studies using investigational treatments for diabetic retinopathy have demonstrated significant vision improvement for individuals who are in early stages of the disease. Two medications that are closely related, Lucentis and Avastin, may be able to stop or reverse vision loss, similar to very promising results that have been reported when the two drugs have been used as treatments for macular degeneration.
Glaucoma refers to a category of eye disorders often associated with a dangerous buildup of internal eye pressure (intraocular pressure or IOP), which can damage the eye's optic nerve â the structure that transmits visual information from the eye to the brain.
Glaucoma typically affects your peripheral vision first. This is why it is such a sneaky disease: You can lose a great deal of your vision from glaucoma before you are aware anything is happening. If uncontrolled or left untreated, glaucoma can eventually lead to blindness.
Glaucoma is currently the second leading cause of blindness in the United States, with an estimated 2.5 million Americans being affected by the disease. Due to the aging of the U.S. population, itâs expected that more than 3 million Americans will have glaucoma by the year 2020.
Signs and symptoms of glaucoma
Glaucoma is often referred to as the "silent thief of sight," because most types typically cause no pain and produce no symptoms. For this reason, glaucoma often progresses undetected until the optic nerve already has been irreversibly damaged, with varying degrees of permanent vision loss.
But there are other forms of the disease (specifically, acute angle-closure glaucoma), where symptoms of blurry vision, halos around lights, intense eye pain, nausea, and vomiting occur suddenly. If you have these symptoms, make sure you immediately see an eye care practitioner or visit the emergency room so steps can be taken to prevent permanent vision loss.
What causes glaucoma?
The cause of glaucoma is generally a failure of the eye to maintain an appropriate balance between the amount of fluid produced inside the eye and the amount that drains away. Underlying reasons for this imbalance usually relate to the type of glaucoma you have.
Just as a basketball or football requires air pressure to maintain its shape, the eyeball needs internal fluid pressure to retain its globe-like shape and ability to see. But when glaucoma damages the ability of internal eye structures to regulate intraocular pressure (IOP), eye pressure can rise to dangerously high levels and vision is lost.
Types of glaucoma
The two major types of glaucoma are chronic or primary open-angle glaucoma (POAG) and acute angle-closure glaucoma. The âangleâ refers to the structure inside the eye that is responsible for fluid drainage from the eye, located near the junction between the iris and the front surface of the eye near the periphery of the cornea. Some of the more common types of glaucoma include:
Primary open-angle glaucoma (POAG):
Angle-closure or narrow angle glaucoma produces sudden symptoms such as eye pain, headaches, halos around lights, dilated pupils, vision loss, red eyes, nausea and vomiting. These signs may last for a few hours, and then return again for another round. Each attack takes with it part of your field of vision.
Acute angle-closure glaucoma:
Angle-closure or narrow angle glaucoma produces sudden symptoms such as eye pain, headaches, halos around lights, dilated pupils, vision loss, red eyes, nausea and vomiting. These signs may last for a few hours, and then return again for another round. Each attack takes with it part of your field of vision.
Like POAG, normal-tension glaucoma (also termed normal-pressure glaucoma, low-tension glaucoma, or low-pressure glaucoma) is an open-angle type of glaucoma that can cause visual field loss due to optic nerve damage. But in normal-tension glaucoma, the eye's IOP remains in the normal range. Also, pain is unlikely and permanent damage to the eye's optic nerve may not be noticed until symptoms such as tunnel vision occur.
The cause of normal-tension glaucoma is not known. But many doctors believe it is related to poor blood flow to the optic nerve. Normal-tension glaucoma is more common in those who are Japanese, are female and/or have a history of vascular disease.
This inherited form of glaucoma is present at birth, with 80% of cases diagnosed by age one. These children are born with narrow angles or some other defect in the drainage system of the eye. It's difficult to spot signs of congenital glaucoma, because children are too young to understand what is happening to them. If you notice a cloudy, white, hazy, enlarged or protruding eye in your child, consult your eye doctor. Congenital glaucoma typically occurs more in boys than in girls.
This rare form of glaucoma is caused by pigment deposited from the iris that clogs the draining angles, preventing aqueous humor from leaving the eye. Over time, the inflammatory response to the blocked angle damages the drainage system. You are unlikely to notice any symptoms with pigmentary glaucoma, though some pain and blurry vision may occur after exercise. Pigmentary glaucoma affects mostly white males in their mid-30s to mid-40s.
Symptoms of chronic glaucoma following an eye injury could indicate secondary glaucoma, which also may develop with presence of infection, inflammation, a tumor or an enlarged cataract.
How is glaucoma detected?
During routine eye exams, a tonometer is used to measure your intraocular pressure (IOP). Your eye typically is numbed with eye drops, and a small probe gently rests against your eye's surface. Other tonometers direct a puff of air onto your eye's surface to indirectly measure IOP.
An abnormally high IOP reading indicates a problem with the amount of fluid inside the eye. Either the eye is producing too much fluid, or it's not draining properly.
Another method for detecting or monitoring glaucoma is the use of instruments to create images of the eye's optic nerve and then repeating this imaging over time to see if changes to the optic nerve are taking place, which might indicate progressive glaucoma damage. Instruments used for this purpose include scanning laser polarimetry (SLP), optical coherence tomography (OCT), and confocal scanning laser ophthalmoscopy.
Visual field testing is another way to monitor whether blind spots are developing in your field of vision from glaucoma damage to the optic nerve. Visual field testing involves staring straight ahead into a machine and clicking a button when you notice a blinking light in your peripheral vision. The visual field test may be repeated at regular intervals so your eye doctor can determine if there is progressive vision loss.
Instruments such as an ophthalmoscope also may be used to help your eye doctor view internal eye structures, to make sure nothing unusual interferes with the outflow and drainage of eye fluids. Ultrasound biomicroscopy also may be used to evaluate how well fluids flow through the eye's internal structures. Gonioscopy is the use of special lenses that allow your eye doctor to visually inspect internal eye structures that control fluid drainage.
Depending on the severity of the disease, treatment for glaucoma can involve the use of medications, conventional (bladed) surgery, laser surgery or a combination of these treatments. Medicated eye drops aimed at lowering IOP usually are tried first to control glaucoma.
Because glaucoma is often painless, people may become careless about strict use of eye drops that can control eye pressure and help prevent permanent eye damage. In fact, non-compliance with a program of prescribed glaucoma medication is a major reason for blindness resulting from glaucoma.
If you find that the eye drops you are using for glaucoma are uncomfortable or inconvenient, never discontinue them without first consulting your eye doctor about a possible alternative therapy.
All glaucoma surgery procedures (whether laser or non-laser) are designed to accomplish one of two basic results: decrease the production of intraocular fluid or increase the outflow (drainage) of this same fluid. Occasionally, a procedure will accomplish both.
Currently the goal of glaucoma surgery and other glaucoma therapy is to reduce or stabilize intraocular pressure (IOP). When this goal is accomplished, damage to ocular structures â especially the optic nerve â may be prevented.
Early detection is key
No matter the treatment, early diagnosis is the best way to prevent vision loss from glaucoma. See your eye care practitioner routinely for a complete eye examination, including a check of your IOP.
People at high risk for glaucoma due to elevated intraocular pressure, a family history of glaucoma, advanced age or an unusual optic nerve appearance may need more frequent visits to the eye doctor.
Presbyopia is a vision condition in which the crystalline lens of your eye loses its flexibility, which makes it difficult for you to focus on close objects. Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-40s. Presbyopia is a natural part of the aging process of the eye. It is not a disease, and it cannot be prevented.
Some signs of presbyopia include the tendency to hold reading materials at arm's length, blurred vision at normal reading distance and eye fatigue along with headaches when doing close work. A comprehensive optometric examination will include testing for presbyopia.
To help you compensate for presbyopia, your optometrist can prescribe reading glasses, bifocals, trifocals or contact lenses. Because presbyopia can complicate other common vision conditions like nearsightedness, farsightedness and astigmatism, your optometrist will determine the specific lenses to allow you to see clearly and comfortably. You may only need to wear your glasses for close work like reading, but you may find that wearing them all the time is more convenient and beneficial for your vision needs.
Because the effects of presbyopia continue to change the ability of the crystalline lens to focus properly, periodic changes in your eyewear may be necessary to maintain clear and comfortable vision.
Macular degeneration (also called AMD, ARMD, or age-related macular degeneration) is an age-related condition in which the most sensitive part of the retina, called the macula, starts to break down and lose its ability to create clear visual images. The macula is responsible for central vision â the part of our sight we use to read, drive and recognize faces. So although a personâs peripheral vision is left unaffected by AMD, the most important aspect of vision is lost.
AMD is the leading cause of vision loss and blindness in Americans of ages 65 and older. And because older people represent an increasingly larger percentage of the general population, vision loss associated with macular degeneration is a growing problem.
It's estimated that more than 1.75 million U.S. residents currently have significant vision loss from AMD, and that number is expected to grow to almost 3 million by 2020.
The two forms of AMD
Macular degeneration can be classified as either dry (non-neovascular) or wet (neovascular). Neovascular refers to growth of new blood vessels in an area, such as the macula, where they are not supposed to be.
The dry form of AMD is more common - about 85% to 90% of all cases of macular degeneration are the dry variety.
Dry macular degeneration.
Dry AMD is an early stage of the disease, and may result from the aging and thinning of macular tissues, depositing of pigment in the macula, or a combination of the two processes.
Dry macular degeneration is diagnosed when yellowish spots called drusen begin to accumulate in the macula. Drusen are believed to be deposits or debris from deteriorating macular tissue. Gradual central vision loss may occur with dry AMD. Vision loss from this form of the disease is usually not as severe as that caused by wet AMD.
A major study conducted by the National Eye Institute (NEI) looked into the risk factors for developing macular degeneration and cataracts. The study, called the Age-Related Eye Disease Study (AREDS), showed that high levels of antioxidants and zinc significantly reduce the risk of advanced dry AMD and its associated vision loss.
The AREDS study also indicated that taking high dose formulas containing beta carotene, vitamins C and E and zinc can reduce the risk of early stage AMD progression by 25%.
Wet macular degeneration.
Wet AMD is the more advanced and damaging stage of the disease. In about 10% of cases, dry AMD progresses to wet macular degeneration.
With wet AMD, new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive cells in the retina, causing blind spots or a total loss of central vision.
The abnormal blood vessel growth in wet AMD is the body's misguided attempt to create a new network of blood vessels to supply more nutrients and oxygen to the macula. But the process instead creates scarring and central vision loss.
Macular degeneration signs and symptoms
Macular degeneration usually produces a slow, painless loss of vision. Early signs of vision loss associated with AMD can include seeing shadowy areas in your central vision or experiencing unusually fuzzy or distorted vision. In rare cases, AMD may cause a sudden loss of central vision.
An eyecare practitioner usually can detect early signs of macular degeneration before symptoms occur. Usually this is accomplished through a retinal examination.
What causes macular degeneration?
Many forms of macular degeneration appear be linked to aging and related deterioration of eye tissue crucial for good vision. Research also suggests a gene deficiency may be associated with almost half of all potentially blinding cases of macular degeneration.
Who gets macular degeneration?
Besides affecting older individuals, AMD appears to occur in whites and females in particular. The disease also can result as a side effect of some drugs, and it appears to run in families.
New evidence strongly suggests that smoking is high on the list of risk factors for macular degeneration. Other risk factors for AMD include having a family member with AMD, high blood pressure, lighter eye color and obesity. Some researchers believe that over-exposure to sunlight also may be a contributing factor in development of macular degeneration, and a high-fat diet also may be a risk factor.
How is macular degeneration treated?
There is as yet no outright cure for macular degeneration, but some treatments may delay its progression or even improve vision.
There are no FDA-approved treatments for dry AMD, although nutritional intervention may be valuable in preventing its progression to the more advanced, wet form.
For wet AMD, there are several FDA-approved drugs aimed at stopping abnormal blood vessel growth and vision loss from the disease. In some cases, laser treatment of the retina may be recommended. Ask your eye doctor for details about the latest treatment options for wet AMD.
Testing and low vision devices
Although much progress has been made recently in macular degeneration treatment research, complete recovery of vision lost to AMD probably is unlikely. Your eye doctor may ask you to check your vision regularly with an Amsler grid â a small chart of thin black lines arranged in a grid pattern. AMD causes the line on the grid to appear wavy, distorted or broken. Viewing the Amsler grid separately with each eye helps you monitor your vision loss.
If you have already suffered vision loss from AMD, low vision devices including high magnification reading glasses and hand-held telescopes may help you achieve better vision than regular prescription eyewear.
Astigmatism is a vision condition that causes blurred vision due either to the irregular shape of the cornea, the clear front cover of the eye, or sometimes the curvature of the lens inside the eye. An irregular shaped cornea or lens prevents light from focusing properly on the retina, the light sensitive surface at the back of the eye. As a result, vision becomes blurred at any distance. Astigmatism is a very common vision condition. Most people have some degree of astigmatism. Slight amounts of astigmatism usually don't affect vision and don't require treatment. However, larger amounts cause distorted or blurred vision, eye discomfort and headaches.
Astigmatism frequently occurs with other vision conditions like nearsightedness (myopia) and farsightedness (hyperopia). Together these vision conditions are referred to as refractive errors because they affect how the eyes bend or "refract" light. The specific cause of astigmatism is unknown. It can be hereditary and is usually present from birth. It can change as a child grows and may decrease or worsen over time.
A comprehensive optometric examination will include testing for astigmatism. Depending on the amount present, your optometrist can provide eyeglasses or contact lenses that correct the astigmatism by altering the way light enters your eyes.Another option for treating astigmatism uses a corneal modification procedure called orthokeratology (ortho-k). It is a painless, non-invasive procedure that involves wearing a series of specially designed rigid contact lenses to gradually reshape the curvature of the cornea.Laser surgery is also a possible treatment option for some types of astigmatism. It changes the shape of the cornea by removing a small amount of eye tissue. This is done using a highly focused laser beam on the surface of the eye.
What causes astigmatism?
When the cornea or lens of an eye is irregularly shaped, vision may be out of focus at any distance.
Astigmatism occurs due to the irregular shape of the cornea or the lens inside the eye. The cornea and lens are primarily responsible for properly focusing light entering your eyes allowing you to see things clearly.
The curvature of the cornea and lens causes light entering the eye to be bent in order to focus it precisely on the retina at the back of the eye. In astigmatism, the surface of the cornea or lens has a somewhat different curvature in one direction than another. In the case of the cornea, instead of having a round shape like a basketball, the surface of the cornea is more like a football. As a result, the eye is unable to focus light rays to a single point causing vision to be out of focus at any distance.
Sometimes astigmatism may develop following an eye injury or eye surgery. There is also a relatively rare condition calledkeratoconus where the cornea becomes progressively thinner and cone shaped. This results in a large amount of astigmatism resulting in poor vision that cannot be clearly corrected with spectacles. Keratoconus usually requires contact lenses for clear vision, and it may eventually progress to a point where a corneal transplant is necessary.
How is astigmatism diagnosed?
A phoropter and a retinoscope are instruments commonly used by optometrists to measure refraction.
Astigmatism can be diagnosed through a comprehensive eye examination. Testing for astigmatism measures how the eyes focus light and determines the power of any optical lenses needed to compensate for reduced vision. This examination may include:
- Visual acuity - As part of the testing, you'll be asked to read letters on a distance chart. This test measures visual acuity, which is written as a fraction such as 20/40. The top number is the standard distance at which testing is done, twenty feet. The bottom number is the smallest letter size you were able to read. A person with 20/40 visual acuity would have to get within 20 feet of a letter that should be seen at forty feet in order to see it clearly. Normal distance visual acuity is 20/20.
- Keratometry - A keratometer is the primary instrument used to measure the curvature of the cornea. By focusing a circle of light on the cornea and measuring its reflection, it is possible to determine the exact curvature of the cornea's surface. This measurement is particularly critical in determining the proper fit for contact lenses. A more sophisticated procedure called corneal topography may be performed in some cases to provide even more detail of the shape of the cornea.
- Refraction - Using an instrument called a phoropter, your optometrist places a series of lenses in front of your eyes and measures how they focus light. This is performed using a hand held lighted instrument called a retinoscope or an automated instrument that automatically evaluates the focusing power of the eye. The power is then refined by patient’s responses to determine the lenses that allow the clearest vision.Using the information obtained from these tests, your optometrist can determine if you have astigmatism. These findings, combined with those of other tests performed, will allow the optometrist to determine the power of any lens correction needed to provide clear, comfortable vision, and discuss options for treatment.
How is astigmatism treated?
Persons with astigmatism have several options available to regain clear vision. They include:
- contact lenses
- laser and other refractive surgery procedures
Eyeglasses are a common form of correction for persons with astigmatism. Eyeglasses are the primary choice of correction for persons with astigmatism. They will contain aspecial cylindrical lens prescription to compensate for the astigmatism. This provides for additional lens power in only specific meridians of the lens. An example of a prescription for astigmatism for one eye would be -1.00 -1.25 X 180. The middle number (-1.25) is the lens power for correction of the astigmatism. The "X 180" designates the placement (axis) of the lens power. The first number (-1.00) indicates that this prescription also includes a correction for nearsightedness in addition to astigmatism.
Generally, a single vision lens is prescribed to provide clear vision at all distances. However, for patients over about age 40 who have the condition called presbyopia, a bifocal or progressive addition lens may be needed. These provide different lens powers to see clearly in the distance and to focus effectively for near vision work.
A wide variety of lens types and frame designs are now available for patients of all ages. Eyeglasses are no longer just a medical device that provides needed vision correction. Eyeglass frames are available in a many shapes, sizes, colors and materials that not only allow for correction of vision, but also enhance appearance.
For some individuals, contact lenses can offer better vision than eyeglasses. They may provide clearer vision and a wider field of view. However, since contact lenses are worn directly on the eyes, they require regular cleaning and care to safeguard eye health.
Soft contact lenses conform to the shape of the eye, therefore standard soft lenses may not be effective in correcting astigmatism. However, special toric soft contact lenses are available to provide a correction for many types of astigmatism. Because rigid gas permeable contact lensesmaintain their regular shape while on the cornea, they offer an effective way to compensate for the cornea’s irregular shape and improve vision for persons with astigmatism and other refractive errors.
Orthokeratology (Ortho-K) involves the fitting of a series of rigid contact lenses to reshape thecornea, the front outer cover of the eye. The contact lenses are worn for limited periods, such as overnight, and then removed. Persons with moderate amounts of astigmatism may be able to temporarily obtain clear vision without lenses for most of their daily activities. Orthokeratology does not permanently improve vision and if you stop wearing the retainer lenses, your vision may return to its original condition.Astigmatism can also be corrected by reshaping the cornea using a highly focused laser beam of light. Two commonly used procedures are photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).
PRK removes tissue from the superficial and inner layers of the cornea. LASIK does not remove tissue from the surface of the cornea, but only from its inner layer. To do this, a section of outer corneal surface is cut and folded back to expose the inner tissue. Then a laser is used to remove the precise amount of tissue needed and the flap of outer tissue is placed back in position to heal. Both procedures allow light to focus on the retina by altering the shape of the cornea.
Individuals with astigmatism have a wide range of options to correct their vision problem. In consultation with your optometrist, you can select the treatment that best meets your visual and lifestyle needs.
Dry eyes occur when your tears aren't able to provide adequate moisture for your eyes. Tears can be inadequate for many reasons. For example, dry eyes may occur if you don't produce enough tears or if you produce poor-quality tears.
Dry eyes feel uncomfortable. If you have dry eyes, your eyes may sting or burn. You may experience dry eyes in certain situations, such as on an airplane, in an air-conditioned room, while riding a bike, or after looking at a computer screen for a few hours.
Treatments for dry eyes may make you more comfortable. These treatments can include lifestyle changes and eyedrops. For more-serious cases of dry eyes, surgery may be an option.
Signs and symptoms, which usually affect both eyes, may include:
- A stinging, burning or scratchy sensation in your eyes
- Stringy mucus in or around your eyes
- Increased eye irritation from smoke or wind
- Eye fatigue
- Sensitivity to light
- Eye redness
- A sensation of having something in your eyes
- Difficulty wearing contact lenses
- Periods of excessive tearing
- Blurred vision, often worsening at the end of the day or after focusing for a prolonged period
When to see a doctor
See your doctor if you've had prolonged signs and symptoms of dry eyes, including red, irritated, tired or painful eyes. Your doctor can take steps to determine what's bothering your eyes or refer you to a specialist.