A cataract is a cloudy area in the lens of the eye. You cannot see it because it is located behind the iris, but as it grows, it can affect your vision. Cataracts are not:

• A film over the eye
• Caused by overuse of your eyes
• Spread from eye to another

What Causes Cataracts? The cause of cataracts is unknown, but cataracts are very common with aging. Having diabetes can put you at a higher risk for developing cataracts. Also, certain prescription medications may affect cataract formation.

• Blurred vision
• Sensitivity to light
• Frequent changes in your eyeglass prescription
• Changes in your color vision (yellow, orange and red may appear brighter; blue appears duller)
• Double vision in one eye
• Needing brighter light to read
• Trouble driving at night

Cataracts develop gradually and don’t cause pain, so they often go undiagnosed for years. But, they can be diagnosed early during routine eye exams. If you are over age 55, you should have an eye exam every year. If you notice a change in your vision, schedule an appointment immediately. Don’t wait for your next scheduled exam.

Prescription Glasses If a cataract is mild, a new prescription for eyeglasses may be all you need.

Cataract Extraction Surgery When glasses are no longer able to improve your vision, surgery is the only way to restore it. During cataract surgery, the cloudy lens is removed and often replaced with a permanent lens implant.

The cornea is the eye’s outermost layer. It is the clear, dome-shaped surface that covers the front of the eye. Although the cornea is clear and seems to lack substance, it is actually a highly organized group of cells and proteins. Unlike most tissues in the body, the cornea contains no blood vessels to nourish or protect it against infection. Instead, the cornea receives its nourishment from the tears and aqueous humor (a fluid in the anterior portion of the eye) that fills the chamber behind it. The cornea must remain transparent to refract light properly, and the presence of even the tiniest blood vessels can interfere with this process. To see well, all layers of the cornea must be free of any cloudy or opaque areas. The corneal tissue is arranged in five basic layers, each having an important function. These five layers are: Epithelium The epithelium is the cornea’s outermost region, comprising about 10 percent of the tissue’s thickness. The epithelium functions primarily to: (1) block the passage of foreign material, such as dust, water, and bacteria, into the eye and other layers of the cornea; and (2) provide a smooth surface that absorbs oxygen and cell nutrients from tears, then distributes these nutrients to the rest of the cornea. The epithelium is filled with thousands of tiny nerve endings that make the cornea extremely sensitive to pain when rubbed or scratched. The part of the epithelium that serves as the foundation on which the epithelial cells anchor and organize themselves is called the basement membrane. Bowman’s Layer Lying directly below the basement membrane of the epithelium is a transparent sheet of tissue known as Bowman’s layer. It is composed of strong, layered protein fibers called collagen. Once injured, Bowman’s layer can form a scar as it heals. If these scars are large and centrally located, some vision loss can occur. Stroma Beneath Bowman’s layer is the stroma, which comprises about 90 percent of the cornea’s thickness. It consists primarily of water (78 percent) and collagen (16 percent), and does not contain any blood vessels. Collagen gives the cornea its strength, elasticity, and form. The collagen’s unique shape, arrangement, and spacing are essential in producing the cornea’s light-conducting transparency. Descemet’s Membrane Under the stroma is Descemet’s membrane, a thin but strong sheet of tissue that serves as a protective barrier against infection and injuries. Descemet’s membrane is composed of collagen fibers (different from those of the stroma) and is made by the endothelial cells that lie below it. Descemet’s membrane is regenerated readily after injury. Endothelium The endothelium is the extremely thin, innermost layer of the cornea. Endothelial cells are essential in keeping the cornea clear. Normally, fluid leaks slowly from inside the eye into the middle corneal layer (stroma). The endothelium’s primary task is to pump this excess fluid out of the stroma. Without this pumping action, the stroma would swell with water, become hazy, and ultimately opaque. In a healthy eye, a perfect balance is maintained between the fluid moving into the cornea and fluid being pumped out of the cornea. Once endothelium cells are destroyed by disease or trauma, they are lost forever. If too many endothelial cells are destroyed, corneal edema and blindness ensue, with corneal transplantation the only available therapy.

Because the cornea is as smooth and clear as glass, but is strong and durable, it helps the eye in two ways:

1. It helps to shield the rest of the eye from germs, dust, and other harmful matter. The cornea shares this protective task with the eyelids, the eye socket, tears, and the white part of the eye (sclera).
2. The cornea acts as the eye’s outermost lens. It functions like a window that controls and focuses the entry of light into the eye. The cornea contributes between 65-75 percent of the eye’s total focusing power.

When light strikes the cornea, it bends– or refracts– the incoming light onto the lens. The lens further refocuses that light onto the retina, a layer of light-sensing cells lining the back of the eye that starts the translation of light into vision. For you to see clearly, light rays must be focused by the cornea and lens to fall precisely on the retina. The retina converts the light rays into impulses that are sent through the optic nerve to the brain, which interprets them as images. The refractive process is similar to the way a camera takes a picture. The cornea and lens in the eye act as the camera lens. The retina is similar to the film. If the image is not focused properly, the film (or retina) receives a blurry image. The cornea also serves as a filter, screening out some of the most damaging ultraviolet (UV) wavelengths in sunlight. Without this protection, the lens and the retina would be highly susceptible to injury from UV rays.

INJURIES The cornea copes very well with minor injuries or abrasions. If the highly sensitive cornea is scratched, healthy cells slide over quickly and patch the injury before infection occurs and vision is affected. If the scratch penetrates the cornea more deeply, however, the healing process will take longer, at times resulting in greater pain, blurred vision, tearing, redness, and extreme sensitivity to light. These symptoms require professional treatment. Deeper scratches can also cause corneal scarring, resulting in a haze on the cornea that can greatly impair vision. In this case, a corneal transplant may be needed. DISEASES AND DISORDERS Some diseases and disorders of the cornea are:

• Allergies
• Conjunctivitis (Pink Eye)
• Corneal Infections
• Dry Eye
• Fuchs’ Dystrophy
• Corneal Dystrophies
• Herpes Zoster (Shingles)
• Iridocorneal Endothelial Syndrome
• Keratoconus
• Lattice Dystrophy
• Map-Dot-Fingerprint Dystrophy
• Ocular Herpes
• Pterygium
• Refractive Errors
• Stevens-Johnson Syndrome

CORNEAL TRANSPLANT A corneal transplant involves replacing a diseased or scarred cornea with a new one. When the cornea becomes cloudy, light cannot penetrate the eye to reach the light-sensitive retina. Poor vision or blindness may result. In corneal transplant surgery, the surgeon removes the central portion of the cloudy cornea and replaces it with a clear cornea, usually donated through an eye bank. A trephine, an instrument like a cookie cutter, is used to remove the cloudy cornea. The surgeon places the new cornea in the opening and sews it with a very fine thread. The thread stays in for months or even years until the eye heals properly (removing the thread is quite simple and can easily be done in an ophthalmologist’s office). Following surgery, eye drops to help promote healing will be needed for several months. Corneal transplants are very common in the United States; about 40,000 are performed each year. The chances of success of this operation have risen dramatically because of technological advances, such as less irritating sutures, or threads, which are often finer than a human hair; and the surgical microscope. Corneal transplantation has restored sight to many, who a generation ago would have been blinded permanently by corneal injury, infection, or inherited corneal disease or degeneration. PHOTOTHERAPEUTIC KERATECTOMY Phototherapeutic keratectomy (PTK) is one of the latest advances in eye care for the treatment of corneal dystrophies, corneal scars, and certain corneal infections. Only a short time ago, people with these disorders would most likely have needed a corneal transplant. By combining the precision of the excimer laser with the control of a computer, doctors can vaporize microscopically thin layers of diseased corneal tissue and etch away the surface irregularities associated with many corneal dystrophies and scars. Surrounding areas suffer relatively little trauma. New tissue can then grow over the now-smooth surface. Recovery from the procedure takes a matter of days, rather than months as with a transplant. The return of vision can occur rapidly, especially if the cause of the problem is confined to the top layer of the cornea. Studies have shown close to an 85 percent success rate in corneal repair using PTK for well-selected patients. The Excimer Laser One of the technologies developed to treat corneal disease is the excimer laser. This device emits pulses of ultraviolet light– a laser beam– to etch away surface irregularities of corneal tissue. Because of the laser’s precision, damage to healthy, adjoining tissue is reduced or eliminated. The PTK procedure is especially useful for people with inherited disorders, whose scars or other corneal opacities limit vision by blocking the way images form on the retina. PTK has been approved by the U.S. Food and Drug Administration.

Electrophysiology testing includes a battery of tests, which can be used to provide information about the visual system beyond the standard clinical examination of the eye. The primary objective of the electrophysiologic examination is to assess the function of the visual pathway from the photoreceptors of the retina to the visual cortex of the brain. Information obtained from these diagnostic tests helps establish the correct diagnosis or may rule out related ophthalmic diseases. Electrophysiologic testing is useful in diagnosing a variety of inherited retinal and optic nerve diseases, toxic drug exposure, inflammatory conditions, intraocular foreign bodies, and retinal vascular occlusions. Electrophysiologic testing is performed most often in large referral centers, which have expertise in obtaining and interpreting these data. The data are used in conjunction with the clinical examination and other tests (perimetry, dark adaptometry) to establish a correct diagnosis. The following tests are performed in the Electrophysiology laboratory:

• Electroretinography (ERG)
• Visually Evoked Potential (VEP)
• Electrooculography (EOG)
• Electroretinography (ERG)

The Kresge Eye Institute Photography Department features state-of-the-art ophthalmic imaging that provides photographic and digital documentation for patient care, clinical research, and vision research activities. The department has one of the busiest and most advanced ophthalmic photography programs in the nation. Our ophthalmic photographers perform film and digital photography for both clinical and research purposes. The Photography department offers:

• Fundus photography
• Fluorescein and indo-cyanine green (ICG) angiography
• Slit-lamp photography
• OR photography
• HD Digital video imaging
• Optical Coherence Tomography (OCT)
• Scanning laser ophthalmoscope (SLO)

The full-service digital and film lab furnishes the faculty, residents, and fellows with prints and PowerPoint presentations and for publication and teaching purposes respectively.

The following is an explanation of the various examinations performed by our ultrasound department: CONTACT B-SCANS For this test the patient is reclined in the chair with eyes opened or closed, depending on the physician or technician. A probe that is covered with a coupling gel is placed in contact with the eye or eyelid. This allows us to examine the patient’s globe and orbit for various abnormalities. The test is usually painless and comfortable for the patient. BIOBETRIC A-SCANS This test allows the measurement of the axial length of the eye (from front to back). The patient places their chin in a chin rest and photographs are taken. The measurements obtained from these photographs are used to determine the power of an intraocular lens implant. CONTACT A-SCANS This test is performed in the same manner as the contact B-scans. However, this test allows the quantitative measurement of various structures and abnormalities of the eye. KERATOMETRY This allows us to measure the curvature of the cornea. The patient places their chin in a chin rest and looks through the center of the tunnel. These measurements are obtained along with the biometric A-scan for the determination of the power for an intraocular lens implant.

The optic nerve carries vision signals from your eyes to your brain. Glaucoma can interfere with the optic nerve, causing vision loss. If left untreated, the vision loss can lead to blindness. Increased pressure in the eye – known as intraocular pressure – is often associated with glaucoma. People without increased intraocular pressures have been known to experience vision loss. Early detection and treatment are critically important in preventing glaucoma-related vision loss. Once vision is lost, it cannot be reversed. Who is at risk? Anyone can develop glaucoma, but some people are at a higher risk than others, including:

• African Americans over age 40
• Anyone over age 60
• People with a family history of glaucoma

An ophthalmologist can perform a special exam to detect the warning signs of glaucoma – including increased pressure in your eyes. This is the only way to detect glaucoma before vision loss occurs. An ophthalmologist can also examine the drainage channels in your eyes and perform a visual field test to detect changes in your peripheral vision. It’s important to get an annual exam from an ophthalmologist, especially if you have high-risk factors. If you experience any symptoms of glaucoma, you should immediately schedule an appointment with an ophthalmologist. Kresge Eye Institute glaucoma specialists provide advanced patient care by conducting continuous research and using the latest technology.

Glaucoma is treatable, but not curable. Early detection can delay progression of the disease. The goal of treatment is to lower pressure in your eyes. Techniques include:

• Eye drops
• Oral medications
• Laser surgery
• Conventional surgery

Physicians from the glaucoma service at Kresge Eye Institute are testing several drugs such as those designed to prevent wound-healing following filtration surgery and those used to lower eye pressure. Our ophthalmologists are also experimenting with various intraocular tubes designed to lower pressure as well as combining glaucoma surgery with cataract removal. Open Angle is the most common type of glaucoma. In its early stages, it has no symptoms and your vision remains normal. However, as open-angle glaucoma progresses, you may notice tunnel vision. Closed-Angle glaucoma affects the iris of the eye. It may come on suddenly and result in blindness quickly. Symptoms may include severe eye pain, seeing halos around lights, nausea, vomiting and blurred vision. Anyone experiencing these symptoms should see an ophthalmologist immediately.

Tumors of the eyelids may be benign (not cancerous) or malignant (cancerous). The most common types of eyelid cancers are:

• Basal cell carcinoma
• Squamous cell carcinoma
• Sebaceous carcinoma
• Melanoma

Tumors known as Orbital Tumors may also occur in the eye socket, behind or around the eye. Ophthalmic Plastic Surgeons are qualified to diagnose and treat most types of eyelid and orbital tumors, including complex surgical reconstruction of the eyelids and reconstruction of eyelids after dermatologic procedures such as Mohs’ micrographic surgery.

Thyroid eye disease is a potential problem in patients with Graves’ disease. Symptoms include inflammation and swelling of the tissues surrounding the eyeball(s), protrusion of the eyes, retraction (stare) of the eyelids, double vision, and in severe cases, vision loss. Women are more likely than men to have thyroid eye disease, although men tend to have a more severe version of the disease. Cigarette smoking has been shown to make thyroid eye disease worse.

Tearing problems can involve one or both eyes. This can be due to problems with the tear drainage system (nasolacrimal duct obstruction) or with tear production (allergy, reflex tearing from dry eye, and others). One can be born with a tearing problem, or it may develop as an adult.

Blepharoptosis (or Ptosis) is a drooping of the upper eyelid that can affect an individual’s line of sight. Common causes include age, detachment or stretching of the eyelid muscle (levator muscle) nerve damage, and trauma. This condition can occur in children and adults and is treated with surgical lift of the eyelid.

Dermatochalasis is excessive skin in the eyelid, and may involve upper or lower eyelids. When excessive in the upper lids, it may affect an individual’s line of sight.

Ectropion is the outward turning of an eyelid, usually the lower lid. The out-turning of the eyelid exposes part of the inner lid and the eye to the air causing dry eyes, blurred vision, tired burning eyes, red eyes and eyelids and sometimes tearing.

Entropion is the inward turning of the eyelid, usually the lower lid, resulting in eyelashes and skin to rub against the eye’s surface. Irritation, pain and damage to the surface of the eye may occur. Left untreated, permanent scarring and loss of vision is possible.

Eyelid retraction may be caused by several conditions including Graves’ disease, scar tissue and previous surgery. This condition shortens the eyelids vertically, exposes the eye to the air thereby causing decreased vision and irritation.

Laser in-Situ Keratomileusis, or LASIK, is one of the most innovative and effective treatment options for vision correction. LASIK uses a microsurgical instrument and an excimer laser. First, a thin flap of corneal tissue is created and folded back to reveal the underlying corneal tissue. The laser is then precisely manipulated to reshape the cornea and improve the way the eye focuses light rays onto the retina. The laser treatment often takes less than one minute. The corneal flap is gently put back in place and allowed to heal. This outpatient surgical procedure is used to treat nearsightedness (myopia), farsightedness (hyperopia) and astigmatism.

Photo Refractive Keratectomy, PRK, was the first procedure to use the excimer laser. This procedure corrects vision by reshaping the surface of the cornea. Unlike LASIK, no corneal flap is created. Instead, the protective skin (epithelium) which covers the cornea is completely removed. Then, the laser reshapes the surface and the protective skin grows back over the treated area. A protective soft contact lens is placed over the cornea to make the eye more comfortable as it heals.

Laser Epithelial Keratomileusis, LASEK, is an excimer laser vision procedure that combines elements from both PRK and LASIK surgeries. Similar to PRK, there is no flap and the epithelium is loosened to perform the laser procedure on the underlying tissue. Unlike PRK, the epithelium is put back to its original position after the procedure. A protective soft contact lens is placed over the cornea to make the eye more comfortable as it heals.

Diabetes causes dramatic changes in the blood vessels throughout the body and can impact vision. Diabetic retinopathy can begin without symptoms and become progressively worse over time. To protect and preserve your eyesight, follow your doctor’s treatment plan for controlling your blood sugar, have regular eye exams and learn more about your eyes.

Macular degeneration typically causes loss of vision in people over the age of 65 but can affect younger people. It is defined as wear and tear in the macula, the central part of vision in the eye. Onset can be gradual or abrupt and usually occurs in one of two ways. The dry type causes a gradual loss of vision; the wet type causes a sudden loss of vision. Macular degeneration affects your ability to read, drive and see fine details; it usually does not affect side vision and typically does not lead to total blindness.

Retinal vascular occlusions are caused by closure or blockage of the central retinal vein; this vein is responsible for draining the retina. This condition can affect people of all ages, although it is most common in people over the age of 50. A physical exam, which includes complete blood tests and glucose tolerance tests for non-diabetic patients are used to diagnose the condition and regular follow-up exams are required to monitor the condition.

Detached retinas are most common in people with a family history of the condition or who are nearsighted; detached retinas sometimes happen after cataract surgery. Retinal detachment can also occur because of a direct hit to the eye. If the condition is not diagnosed or treated, impaired vision or complete loss of vision may occur.

The macula is specific area in the retina responsible for clarity of vision and the ability to see details. A macular hole is an irregular opening that occurs in the center of the macula over a period of time ranging from weeks to months. These holes are typically caused by vitreous jelly within the eye pulling on the macula and creating a hole or by scar tissue on top of the retina. Treatment options typically include reattachment of the retina, if needed, and vitrectomy.

When ordinary eyeglasses, contact lenses or intraocular lens implants cannot provide sharp sight, an individual is said to have low vision. This condition should not be confused with blindness. People with low vision still have useful vision, which can often be improved with aids. 
Visual impairment may be mild or severe, but in each case, visual performance does not meet the individual’s needs. Improving vision with visual aids is usually undertaken after your ophthalmologist has completed medical or surgical procedures or determined that such procedures are unwarranted. What Causes Low Vision? Though most often experienced by the elderly, people of all ages may be affected. Low vision can occur from birth defects, inherited diseases, injuries, diabetes, glaucoma, cataract and aging. The most common cause is macular degeneration, which is a deterioration of the retina, the light-sensitive tissue in the back of the eye. Vision loss from macular degeneration is limited to central vision and fortunately does not cause total blindness since side (peripheral) vision is not affected. Are There Different Types of Low Vision?

 Yes. Although reduced central or reading vision is most common, low vision may also result from decreased side (peripheral) vision, a reduction or loss of color vision, or the eyes’ inability to properly adjust to light, contrast or glare.

Different types of low vision may require different kinds of assistance. For example, people born with low vision have different needs than those who develop low vision later in life. What Is a Low Vision Aid? A low vision aid is a device that improves vision. There is no single aid that magically restores normal vision in all circumstances. In fact, you may need different aids for different purposes. A low vision exam will determine what aid is beneficial before you buy it. Optical Low Vision Aids Optical Low Vision Aids use lenses or a combination of lenses to provide magnification. They should not be confused with standard eyeglasses. There are five main kinds of optical aids: magnifying spectacles, hand magnifiers, stand magnifiers, telescopes and closed circuit TV (CCTV).

• Magnifying spectacles are stronger than ordinary glasses. They require that reading material be held very close otherwise the print is out of focus. This position may feel awkward at first, but the awkwardness can be overcome with some initial effort. Designed for close work, magnifying spectacles leave both hands free to hold reading material.
• Hand magnifiers are familiar to most people. They allow you to hold reading material at a normal distance.
• Stand magnifiers rest on the reading material and are used with a near spectacle correction (for example, the bottom part of bifocal glasses). Some have a self-contained light source.
• Telescopes are used for distance magnification. They may be handheld for viewing distant objects such as street signs, or mounted in spectacles.
• Closed circuit television produces an enlarged image on a television screen. With the added advantage of adjustable magnification and contrast, a closed circuit television is often easier to use and less fatiguing than other aids.

Non-optical Low Vision Aids

• Large print books, newspapers and magazines
• Check writing guides
• Large playing card
• Enlarged telephone dials and high contrast watch faces
• Auditory aids, such as machines that talk (timers, clocks, computers) and even machines that scan print and read aloud, are also available.

The simplest non-optical technique is getting closer to what you want to see. Holding reading material very close to your eyes or sitting as close as one foot from the television screen will not cause eye damage contrary to popular belief. Is Lighting Important for People with Low Vision? Correct lighting is as important as a low vision aid. Without an eye disorder, a 60-year-old person may need twice the illumination they needed at 20 to comfortably perform the same task. Remember to place the light source close to your reading material for greatest visibility. High intensity lights with adjustable arms work well for this purpose. Visors and hat brims block annoying overhead light and absorptive lenses are useful in controlling glare. What Is Large Print? Large print is oversize type that enables people who cannot comfortably read regular size print to enjoy all the pleasures and conveniences of reading. Technically speaking, large print is 14-point type, about twice the size of type you find printed in most books, magazines, and newspapers. What Services Are Available for Low Vision Patients? A complete eye examination is essential. Once the cause of your low vision is determined, your doctor may suggest low vision aids or may refer you to other low vision specialists or agencies for help. Governmental and private agencies provide social services for low vision patients. These include talking books, independent home-living instruction, and in some cases, orientation and mobility training. For additional information, contact:

• Your local State Commission for the Blind and Visually Impaired
• Commission for the Blind 1-800-292-4200
• American Foundation for the Blind, New York, NY, 1-800-AFB-BLIND
• National Association for Visually Handicapped
• National Library Service for the Blind and Physically Handicapped, Library of Congress, Washington, DC
• National Center for Vision and Aging, The Lighthouse, New York, NY 1-800-334-5497
• Dialogue Publications, Berwyn, IL

(The above information is from the American Academy of Ophthalmology, PO Box 7424, San Francisco, CA)