To see clearly, light rays must be bent or refracted to focus on the retina, the light-sensitive nerve layer that lines the back of the eye. The cornea and lens of the eye work together to bend or refract light rays and bring them together on the retina. If a refractive error is present, the light is not focused directly on the retina, so images appear blurry.

Myopia (nearsightedness): Distance vision is impaired when the eye is too long in relation to the curvature of the cornea. This causes light to focus before it reaches the retina. Close objects look clear but distant objects appear blurry.

Myopia (nearsightedness)

Hyperopia (farsightedness): Close vision is impaired, with some impairment of distance vision, as well. The eye is too short in relation to the curvature of the cornea. Light rays are not yet in focus when they reach the retina, so images appear blurry.

Hyperopia (farsightedness)

Astigmatism (the cornea is oval shaped instead of round): The irregular curvature of the cornea causes light to focus on more than one point on the retina. Uncorrected astigmatism impairs both distance and near vision.

Astigmatism

Presbyopia (aging eyes): When young, the lens of the eye is soft and flexible, allowing people to see objects both close and far away. After the age of 40, the lens of the eye becomes more rigid, making it more difficult for the lens to change its shape, or accommodate to do close work such as reading. This condition is known as presbyopia and is the reason reading glasses or bifocals are necessary at some point after age forty.

Over 24 million people choose contact lenses to correct vision. When used with care and proper supervision, contacts are a safe and effective alternative to eyeglasses. And with today's new lens technology, many people who wear eyeglasses can also successfully wear contacts.

Contacts are thin, clear discs that float on the tear film that coats the cornea, the curved front surface of the eye. Contacts correct the same refractive conditions eyeglasses correct: myopia (nearsightedness), hyperopia (farsightedness) and astigmatism (an oval, rather than round-shaped cornea).

Contact lenses can be made from a number of different plastics. The main distinction among them is whether they are hard or soft. Most contact lens wearers in the United States wear soft lenses. These may be daily wear soft lenses, extended wear lenses or disposable lenses. Toric soft lenses provide a soft lens alternative for people with slight to moderate astigmatism.

Hard lenses are usually not as comfortable as soft lenses and are not as widely used. However, rigid gas permeable lenses provide sharper vision for people with higher refractive errors or larger degrees of astigmatism.

The majority of people can tolerate contact lenses, but there are some exceptions. Conditions that might prevent an individual from successfully wearing contact lenses include dry eye, severe allergies, frequent eye infections or a dusty and dirty work environment.

Individuals who wear any type of contact lens overnight have a greater chance of developing infections in the cornea. These infections are often due to poor cleaning and lens care.

Some people do not consider wearing contact lenses because they think the required cleaning, disinfecting, storing and inserting are too much trouble. They may also want the option of occasionally napping or sleeping with their contacts in their eyes.

Extended-wear contacts are designed to appeal to these people. They require less maintenance than daily wear lenses and because they are thinner and allow more oxygen to reach the eyes, they may be left in the eye overnight.

To use extended-wear contact lenses, you must be free of external eye disease, have normal tear function and be motivated to take care of them.

Infection is the most significant complication of extended-wear contact lens use. They must be removed at least once a week and thoroughly cleaned and disinfected. Many studies show the cornea is put at increased risk of infection by wearing contact lenses overnight. The risk of developing an infection in the cornea is 10-15 times greater for those who wear extended-wear contacts overnight than for those who use daily wear soft lenses. This risk increases with the number of consecutive days the contacts are worn overnight. Infections may range from simple conjunctivitis to blinding endophthalmitis, which is a serious infection that travels through all layers of the eye.

The decision to accept the risks and benefits of extended-wear contacts requires a process of evaluation between you and Dr. Najafi-Tagol. Once you are carefully fit for your contact lenses, follow-up exams with Dr. Najafi-Tagol to ensure continuing eye health is important. As with any contact lens, extended-wear contacts should be removed at the first sign of redness or discomfort.

Contact lens wearers who wear cosmetics on a daily basis may be especially vulnerable to eye problems. Misuse of products and adverse reactions to ingredients used in cosmetic formulas cause lens deposits, eye irritation, allergy, dryness, injury and infection. Knowing which products to use and how to use them is important for long-term, problem-free contact lens wear.

Before handling lenses, wash your hands with a mild soap such as Neutrogena, Ivory or a clear glycerin soap. Or, use one of the specialty soaps for contact lens wearers such as AOSoap or Optisoap. Avoid soaps containing cream, deodorant, antiseptics, or heavy fragrances.

Contact lenses should be inserted before any cosmetics are applied to prevent contaminating the lens by makeup and disrupting makeup by tears. Mascara should be used sparingly and only on the outer half of the lashes. Besides being a potential irritant, mascara is frequently a source of infection. Even with the best of care, mascara and eyeliner should be replaced every three months. Use a light touch with eyeliners and shadows, as they may cause blepharitis, an infection of the eyelid that can lead to styes and chalazion. Don't use eyeliner pencils inside the lower eyelid. Color pigments can cause irritation, damage contact lenses or lodge underneath the contact lens and scratch the cornea.

Prevent contamination of your makeup by keeping it dry and avoiding contact with fingers. Keep applicators clean and replace them after approximately three months. Hair spray, deodorant, cologne, mousse, nail polish and nail polish remover should be used before inserting your lenses. If one of these products gets into your eye, it can cause permanent damage to the contact lens surface. If you must use hair spray while wearing contacts, close your eyes tightly while spraying and then leave the area quickly. Aerosol mist lingers in the air for some time after spraying.

Never wear contacts when using hair dyes, permanent wave lotions or medicated shampoos.

Use cosmetics labeled "hypoallergenic," "for contact lens wearers," or "for sensitive eyes." Approximately one in ten women have either a respiratory or skin allergy to perfume. Hypoallergenic brands are designed to be free of irritants such as perfumes and lanolin. Lanolin may be used in cosmetics and soaps and is one of the most common allergens, causing redness, itching and blotchy skin spots.

Wash your hands and remove contact lenses before removing make-up. Your fingers are less likely to be contaminated by pigments, creams and oils from cosmetic products when the lenses are removed first.

Many types of tinted contact lenses are available. They can enhance and even change the color of one's eyes for cosmetic purposes, for costumes or provide special effects for the movie industry.

Tinted contacts can make light eyes more blue, green or hazel. They can alter the color of the eyes, such as making brown eyes blue.

Tinted lenses have been used in the movies since 1939. In the movie "Ghostbusters," actors playing gargoyles wore red contact lenses. Reptile lenses were crafted for the commander in "Star Trek" and white contact lenses were used for the Hulk in "The Incredible Hulk." Recently, these costume lenses have become available to the general public.

Tinted contacts may also be used to disguise or improve the appearance of an abnormal eye. They can be used to conceal corneal scars, irregular pupils and to hide shrunken, unsightly eyes. Sometimes tinting a lens can make the lens easier for a person with poor vision to handle. These tints are more subtle handling tints.

Contact lenses for the general public, including those with no correction, are considered medical devices. They must undergo clearance for safety by the Food and Drug Administration (FDA). Color additives used by the manufacturers of costume contact lenses must also be approved for use. Additives in unapproved lenses may be toxic.

Purchase only tinted contacts prescribed by an ophthalmologist and never share lenses with someone else.

The key to avoiding the irritation and infection sometimes associated with contact lens wear is proper cleaning.

There are two main types of lens care systems: heat and chemical disinfection. The appropriate choice depends on the lens type, duration of lens wear and an individual's own biochemistry. Regardless of the type of disinfection system you choose, there are a number of common steps that must be followed.

• Always wash your hands prior to handling your contact lenses.
• Remove one lens and place it in the palm of your hand. Apply a few drops of contact soap, usually called cleaning solution. Rub the soap onto both sides of the lens surface to help remove deposits, debris, protein build-up and any bacterial film. Removing surface deposits and other debris not only contributes to improved vision and comfort but also reduces the risk of infection and allergy. Soft extended-wear contacts may be the most likely to develop a protein build-up that can lead to lens-related allergies.
• After thoroughly cleaning the lens, rinse it with commercially available sterile saline solution. Homemade saline solutions have been linked to serious eye infections and should never be used.
• After cleaning and rinsing, lenses need to be disinfected. You and Dr. Najafi-Tagol will pick the best system for you, but make sure you understand the instructions and follow them. Heat and chemical disinfection methods each require several hours of disinfection time.
• After disinfecting, rinse the lens with sterile saline before putting it in your eye.
• Your empty contact lens case should be thoroughly rinsed with warm water and allowed to air dry. All contact lens cases need to be cleaned frequently, including disposable lens cases.

Color blindness (color vision deficiency) is a condition in which certain colors cannot be detected. There are two types of color vision difficulties: inherited (congenital) problems that you have at birth, and problems that develop later in life.

People born with color vision problems are unaware what they see is different from what others see unless it is pointed out to them. People with acquired color vision problems are aware that something has gone wrong with their color perception.

Congenital color vision defects usually pass from mother to son. These defects are due to partial or complete lack of the light-sensitive photoreceptors (cones) in the retina, the layer of light-sensitive nerve cells lining the back of the eye. Cones distinguish the colors red, green and blue through visual pigment present in the normal human eye. Problems with color vision occur when the amount of pigment per cone is reduced or one or more of the three cone systems are absent. This limits the ability to distinguish between greens and reds and occasionally blues. It involves both eyes equally and remains stable throughout life.

There are different degrees of color blindness. Some people with mild color deficiencies can see colors normally in good light but have difficulty in dim light. Others can't distinguish certain colors in any light. In the most severe form of color blindness everything is seen in shades of gray.

Except in the most severe form, color blindness does not affect the sharpness of vision at all. It does not correlate with low intelligence or learning disabilities.

Most color vision problems that occur later in life are a result of disease, trauma, toxic effects from drugs, metabolic disease or vascular disease. Color vision defects from disease are less understood than congenital color vision problems. There is often uneven involvement of the eyes and the color vision defect will usually be progressive. Acquired color vision loss can be the result of damage to the retina or optic nerve.

There is no treatment for color blindness. It usually does not cause any significant disability. It can, however, prevent employment in an increasing number of occupations.

Change in color vision can signify a more serious condition. If you are experiencing a significant change in color perception, contact Dr. Najafi-Tagol.

Giant papillary conjunctivitis (GPC) is an inflammation of the inner surface of the eyelids, most frequently associated with contact lens wear. It can develop in people who wear either soft or rigid gas permeable contact lenses and can occur at any time, even if an individual has successfully worn contacts for a number of years. Although not vision threatening, GPC can be inconvenient and may require one to stop wearing contacts temporarily or even permanently.

The typical symptoms of GPC include red, irritated eyes, often with itching and mucus discharge. Blurred vision and light sensitivity can also occur. GPC is not an infection, but a hypersensitivity of the membrane covering the inner lids and the whites of the eyes. The inner lining of the eyelid becomes roughened and inflamed by constant blinking over a contact lens or other foreign body such as an artificial eye. Hard, flat elevations in a cobblestone pattern develop on the undersurface of the upper eyelid. Eventually the entire eye becomes irritated.

In most cases, treatment of GPC involves discontinuing the use of contact lenses to allow the eye to rest. Eyedrops are frequently prescribed to control inflammation. Many people find their symptoms are relieved when contact lens wear is discontinued. Unfortunately, the symptoms can return when lens wear is resumed.

Once GPC is under control, it may be helpful to consider changing to new contacts or disposable contacts. Changing lens care systems and cleansing solutions can also be helpful. After an episode of GPC, limit the amount of time lenses are worn, and increase the time slowly.

Once it develops, GPC may be an ongoing problem. Prolonged GPC may be more difficult to treat.

People with low vision still have useful vision that can often be improved with low-vision devices.

Low vision can result from birth defects, inherited diseases, injuries, diabetes, glaucoma or macular degeneration. Although reduced central or reading vision is most common, a person can have low vision in their side (peripheral) vision, or a loss of color vision or contrast sensitivity.

Low vision devices or aides are available in optical and non-optical types. Optical devices use lenses or combinations of lenses to provide magnification. They should not be confused with standard eyeglasses. There are five main kinds of optical devices: magnifying spectacles, hand magnifiers, stand magnifiers, telescopes and closed-circuit television. Different devices may be needed for different purposes. If possible, try the optical device before purchasing it and be sure you understand how to use it.

The simplest non-optical technique is to bring the object of interest closer. Non-optical low vision devices include large print books, check writing guides, enlarged phone dials, talking appliances (timers, clocks, computers) and machines that scan print and read out loud.

Government and private agencies have social services available for people with low vision. For more information, you may contact the following resources:

• American Foundation for the Blind
  (800) 232-5463
• National Association for Visually Handicapped
  (212) 889-3141
• National Library Service for the Blind and Physically Handicapped
  (800) 424-8567
• Lighthouse International
  (800) 334-5497
• Prevent Blindness America
  (800) 331-2020
• Visions/Services for the Blind and Visually Impaired
  (212) 425-2255

Veterans may contact the Visual Impairment Services coordinator at their local VA facility.

Myopic degeneration is an uncommon condition characterized by progressive stretching of the eye that damages the retina, the layer of light-sensitive cells that lines the back of the eye. People with severe nearsightedness (high myopia) are at greater risk for myopic degeneration.

Myopic degeneration commonly occurs during young adulthood with a gradual decrease in central vision. Vision can decrease more abruptly, but typically vision loss is gradual. Although central vision may be lost, side (peripheral) vision usually remains unaffected. Remaining sight can still be very useful and with the help of low-vision optical devices, people can continue many of their normal activities.

The causes of myopic degeneration are not clearly understood but may include biomechanical abnormalities or hereditary factors. The biomechanical theory assumes that the retina, in a myopic eye, is stretched over a larger than normal area because the eye is longer than usual. Over time, the outer coat of the eye, known as the sclera, also stretches in response to forces like internal eye pressure. This stretching of the sclera is thought to lead to retinal degeneration. In the hereditary theory, the retinal changes are thought to be an unavoidable, inherited process.

The only treatment for myopic degeneration is surgery to reinforce the scleral wall. This has been performed with varying degrees of success.

Strabismus refers to misaligned eyes. If the eyes turn inward (crossed), it is called esotropia.

Esotropia left

If the eyes turn outward (wall-eyed), it is called exotropia.

Exotropia left

Or, one eye can be higher than the other which is called hypertropia (for the higher eye) or hypotropia (for the lower eye). Strabismus can be subtle or obvious, intermittent (occurring occasionally), or constant. It can affect one eye only or shift between the eyes.

Strabismus usually begins in infancy or childhood. Some toddlers have accommodative esotropia. Their eyes cross because they need glasses for farsightedness. But most cases of strabismus do not have a well-understood cause. It seems to develop because the eye muscles are uncoordinated and do not move the eyes together. Acquired strabismus can occasionally occur because of a problem in the brain, an injury to the eye socket, or thyroid eye disease.

When young children develop strabismus, they typically have mild symptoms. They may hold their heads to one side if they can use their eyes together in that position. Or, they may close or cover one eye when it deviates, especially at first. Adults, on the other hand, have more symptoms when they develop strabismus. They have double vision (see a second image) and may lose depth perception. At all ages, strabismus is disturbing. Studies show school children with significant strabismus have self-image problems.

Amblyopia, or lazy eye, is closely related to strabismus. Children learn to suppress double vision so effectively that the deviating eye gradually loses vision. It may be necessary to patch the good eye and wear glasses before treating the strabismus. Amblyopia does not occur when alternate eyes deviate, and adults do not develop amblyopia.

Strabismus is often treated by surgically adjusting the tension on the eye muscles. The goal of surgery is to get the eyes close enough to perfectly straight that it is hard to see any residual deviation. Surgery usually improves the conditions though the results are rarely perfect. Results are usually better in young children. Surgery can be done with local anesthesia in some adults, but requires general anesthesia in children, usually as an outpatient. Prisms and Botox injections of the eye muscles are alternatives to surgery in some cases. Eye exercises are rarely effective.

Visual Field Test

The visual field is the entire area one can see. It includes central and peripheral (side) vision. A visual field test can detect problems with vision in any part of the visual field. Changes in the visual field may be difficult to notice since both eyes are generally used at the same time. One eye can sometimes compensate for some vision loss in the other. A problem may not be detected until each eye is tested separately.

The visual field test provides information that no other test can. It is used to detect many diseases, such as glaucoma or retinitis pigmentosa, which affect the eye, optic nerve, and brain. It can also help diagnose brain tumors, strokes and other conditions. Visual field testing helps diagnose the disease and can follow the progress of the disease and its treatment.

During a visual field test, one eye is temporarily patched while the other eye is being tested. You are asked to look straight ahead at a fixed spot and watch for targets to appear in your field of vision.

There are two kinds of visual field tests. One method uses moving targets. Targets are moved from outside the visual field (where you can't see them) toward the center of your vision. When you see them, you press a button. The test can be done using a dark screen on a wall (called tangent screen testing) or using a large bowl-shaped instrument (called Goldmann testing).

The other testing method uses small fixed targets that appear briefly as bright or dim lights (called computerized static perimetry). You sit in a chair facing either a bowl-shaped instrument or a computer screen and indicate when you see the targets appear.

Prescription eyeglasses help improve the focusing power of the eyes for patients who have vision problems due to refractive errors. With today’s advancements in eye care, a variety of lenses and frames are available.

Types of Lenses

Aspheric Lenses — Unlike traditional lenses, the front surface of aspheric lenses is not completely round. This results in better vision. The shape of the lens gradually changes starting from the center and extending to the edge. Aspheric lenses are thinner and flatter, and are positioned closer to the face. This eliminates the unattractive magnified look associated with traditional lens prescribed for extreme farsightedness, and the small look of the eyes associated with traditional lens prescribed for nearsightedness.

High-index Lenses — High-index lenses have a thinner edge, which reduces the total weight of the lenses, making them significantly lighter and more comfortable to wear.

Multifocal Lenses — Multifocal lenses include bifocals to correct near and distance vision and trifocals to treat near, intermediate and distance vision.

Generally, in bifocals, a small region of the lens is preserved for near, while the reminder of the lens is reserved for distance vision.

The region of the lens preserved for near-vision can be shaped like a:

1. Flat-top or D segment
2. Round segment
3. Narrow rectangle or Ribbon segment
4. Full bottom half lens, known as the Franklin or Executive E-style

Typically, bifocals are positioned so that the line rests at the lower eyelid. Trifocals are placed a little higher; with the intermediate area positioned level to the pupil.

Polycarbonate Lenses - Polycarbonate lenses are thin and light weight. They are also scratch resistant, making them a suitable choice for children and athletes. These lenses also provide UV protection.

Progressive Lenses - Also known as no-line bifocals, Progressive lenses not lonely provide correction for near and distance vision, but intermediate as well.