context: Periodic comprehensive eye exams by an eye doctor are essential to monitor the health of your eyes and diagnose suspected problems. Checking the position of each eye and its movements will reveal crossed eyes or other forms of strabismus. The exam may include these parts: An eye chart uses letters of decreasing size to determine the sharpness of your vision at a distance. The retinoscope projects a thin beam of light into the eye. When used with the rotating lens dial (called the phoropter) the eye doctor measures any refractive error like nearsightedness, farsightedness, or astigmatism. A slit-lamp microscope exam of the surface of each eye. The same device is used to inspect the eye's internal structures. This is how changes in the clear cornea and lens are identified. Pressure inside the eye is measured using one of several devices. Exams with an ophthalmoscope can reveal abnormalities of the retina, the macula, the optic nerve, and other structure inside the eye. Dilating eye drops may be given in order for the doctor to complete a full exam. The purpose of dilation is to open the pupil or âwindowâ to allow a much better view of the lens, retina, and optic nerve. Although this can cause some temporary blurriness, it is a very important evaluation. Typically, sunglasses are given at the end of an exam to help protect the eyes from sensitivity after the dilation until the effect wears off. If routine testing indicates that you have a refractive error, conventional treatment calls for wearing corrective glasses or contact lenses. Over 150 million people in the US wear corrective lenses. In many cases, surgical correction of refractive errors is possible using modern surgical techniques such as LASIK. Conventional treatment for disorders such as nearsightedness, farsightedness, and astigmatism typically relies on corrective prescription lenses. Disorders such as cataracts, glaucoma, macular degeneration, and retinal detachment require advanced medical and surgical treatments. Enormous progress in eye surgery has been made over the past few decades. Many people with eye problems previously felt to be untreatable now enjoy improved eyesight and an improved quality of life. This applies to individuals of every age -- infants to senior citizens! To treat nearsightedness, your eye doctor will usually prescribe lenses to focus visual images correctly on the retina. Depending on the specifics of your eye exam, you may have a choice between wearing conventional eyeglasses and contact lenses. As an alternative to corrective lenses, surgery can sometimes be performed to treat nearsightedness. Excimer laser treatment (like LASIK) uses a laser beam to remove microscopic amounts of tissue from the cornea. This effectively flattens or steepens the cornea as needed so that light rays focus correctly on the retina. LASIK is safe and effective for most patients with nearsightedness, but only up to a certain level. Some patients with thin corneas and extreme nearsightedness may be better served with a variant of LASIK called PRK or they may not be good laser candidates at all. There are advanced options for these patients, including surgical correction with implantable contact lenses. To treat farsightedness that does not resolve itself naturally, glasses or contact lenses can be prescribed. People typically seek treatment for farsightedness when they begin to complain of eyestrain, especially at the end of the day, or when they have trouble focusing while reading. LASIK can also be used to treat lower levels of farsightedness. Higher levels of farsightedness can only be surgically corrected with a refractive lens exchange -- the natural lens is replaced with an intraocular lens that is more powerful, thereby focusing the light on the retina. To treat astigmatism, the accepted prescription is a lens that will correct or neutralize the effect of the uneven cornea. Again, you will typically have a choice between glasses and contact lenses. Surgery for astigmatism can include limbal relaxing incisions, LASIK, and toric intraocular lenses. With cataracts, the eye's natural lens becomes cloudy, obscuring vision. Correcting the problem was once a complex procedure requiring general anesthesia and a week of hospitalization. Today, a process called "phacoemulsification" uses ultrasound to break up the cataract and remove the tiny lens fragments through an incision so small that it usually requires no stitches. Some people mistakenly call this laser cataract surgery. The surgeon then inserts an artificial lens implant. Local anesthesia is used and the patient goes home from an outpatient facility typically within an hour or two after surgery. For macular degeneration, there is currently no cure for age-related macular degeneration ( AMD), but new treatments are sometimes able to prevent severe visual loss. Treatment depends on the type of AMD, but may include: Injections of medication into the eye -- to prevent the formation of new, leaky blood vessels Laser therapy -- to destroy abnormal blood vessels Photodynamic therapy -- injection of medications that are activated by light exposure Submacular surgery (very rarely done) -- to remove blood under the retina, abnormal blood vessels or scar tissue Retinal translocation (very rarely done) -- surgical rotation of the damaged retinal tissue away from the macula Low-vision aids -- to help people with partial vision make the most of their remaining vision. These devices have special lenses or electronic systems that magnify images so they can be seen by the parts of the retina that are still functioning. Vitamins -- to help reduce or delay the risk of severe vision loss. Some evidence suggests that certain vitamins and antioxidants -- vitamins C and E, beta-carotene, and zinc -- may help. However, more current research replaced beta-carotene with lutein and zeaxanthin with similar results. Other ways to protect your eyes from AMD include the following: Eating vegetables high in carotenoids, such as spinach and collard greens Wearing sunglasses with an ultraviolet filter when outdoors Not smoking Having regular visits to an eye care specialist to detect AMD and other eye diseases in the early stages For retinal detachment, some cases can be corrected with laser surgery, which has a high rate of success. If the peeling or tearing of the retina is more advanced, more extensive corrective surgery may be necessary. Treating glaucomausually includes using a series of eye drops over time to keep the disease under control. In many cases of glaucoma, fluid in the eye fails to drain properly, causing pressure to build up. Laser surgery for this form of the disease, called chronic open-angle glaucoma, has been available since 1979, but ophthalmologists generally use it as an alternative or addition to drug therapy, not as the first line of treatment. There is no single, surefire remedy for glaucoma. Much remains to be learned about this disease. Glaucoma therapies evolve and change continuously. One long-term study, however, indicates that treating people with laser surgery first works just as well, if not better, to keep glaucoma in check. But medication in the form of eye drops is still the primary and most common treatment of COAG. Because the disease can strike people at any age and there is no cure, treatment for glaucoma may need to continue for several decades. Although some researchers express concern that the laser's effects may last only three to five years before the eyes need to be treated again, drugs may become less effective over time as well. While people just diagnosed with glaucoma may be reluctant to try surgery first, there are good reasons to consider it. Some patients with heart problems or asthma may not be able to take topical beta-blockers, a commonly used glaucoma drugs, and drug treatment can be expensive for some medications, so surgery may be cheaper in the long run.