Nearsightedness (myopia) is an eye condition in which the steep curvature of the cornea and/or the long length of the eye cause light rays to focus in front of the retina. The optical power of a myopic eye is too strong resulting in near images appearing clear and distant images appearing blurred.
In farsightedness (hyperopia) the flatness of the cornea and/or the short length of the eye cause the point of focus of the eye to fall beyond the retina. The optical power of the hyperopic eye is weak making up-close objects appear blurred. Distant objects can also sometimes be blurred.
Astigmatism is a condition in which both the cornea and the lens have an irregular curvature, causing light to focus on more than one point of the eye and distort vision. In an astigmatic cornea, instead of having a spherical curve like a basketball, the curvature is more like a football. Most corneas affected by astigmatism have both a steeper curve and a flatter curve which generate the multiple points of focus. Astigmatism often occurs in combination with myopia or hyperopia. The result is blurred, distorted vision near or far.
Presbyopia is a naturally occurring eye condition that usually affects individuals beginning in their 40’s. The natural lens of the eye losses flexibility and the ability to change its focusing distance as we age. This is known as accommodation. When presbyopia develops, close-range activities such as reading a book may become increasingly difficult. Unlike a refractive error such as near-sightedness, far-sightedness or astigmatism, there are no changes to the shape of the cornea or natural lens in presbyopia. People often have one or more refractive errors in combination with presbyopia.
Chronic Dry Eyes is known by the scientific name keratoconjunctivitis sicca. It is a common condition that can result in localized inflammation of both the eye surface as well as the tear-producing glands. This inflammation over time can decrease the eye’s ability to produce tears which protect the surface and keep it lubricated. This can cause damage to the eye’s surface, and severe forms of the condition can lead to increased risk of infection and possibly vision impairment if left untreated. Chronic dry eye affects millions of Americans and is one of the most common complaints seen by eye care professionals.
Diagnosing Chronic Dry Eyes
If a patient reports that their eyes feel dry or that they are using artificial tears frequently throughout the day, the doctor may do one or more of the following tests:
- The Schirmer’s test which consists of placing filter paper inside the lower lid of the eye to test for moisture content.
- Measure the amount of time a tear maintains a coating over the eye with or without fluorescein stain.
- Use either rose Bengal, Lissamine green, or fluorescein dyes to stain the damaged area of the ocular surface.
Treating Chronic Dry Eye
Treatment options for patients experiencing chronic dry eye include:
- Artificial tears
- Oral supplements
- Occlusion of tear outflow
- Serum tears
With age, chemical changes occur in the lens of the eye which make the lens less transparent. The loss of transparency may be so mild that vision is hardly affected or so severe that shapes can be seen only as light and dark. When the lens becomes so cloudy that vision is significantly obstructed, it is referred to as a cataract. The eye is like a camera, focusing light rays through the lens onto the retina. The retina allows the image to be seen by the brain. Over time, if the lens becomes cloudy, preventing light rays from passing through it clearly, the cloudy lens is called a cataract.
Glasses or contact lenses will not sharpen one’s vision if a cataract is present. The only cure for a cataract is surgical removal. The risk for developing a cataract may be decreased by limiting the amount of ultraviolet light exposure and by wearing sunglasses and a wide-brimmed hat. Early symptoms of cataracts can often be managed, but when vision loss from a cataract interferes with a patient’s normal activities, surgical removal of the cataract is the only treatment.
Most cataracts are caused by aging, affecting millions of Americans over the age of 40 each year.
Other causes include:
- Certain medications such as steroids
- History of smoking
- Systemic diseases, including diabetes
- Prolonged exposure to ultraviolet light
- Congenital cataract
Symptoms of Cataract Formation
Cataract formation is characterized by a slow, painless, but progressive decrease in vision.
- Cloudy or blurred vision
- Glare, particularly at night
- Frequent eyeglass prescription changes
- Yellowing of images
- Decrease in color intensity
- Double vision
Glaucoma is a group of diseases that can damage the optic nerve, resulting in vision loss or blindness. Millions of Americans have glaucoma, but only half of them know it. If caught early, glaucoma can be effectively treated. The earlier the disease is found, the greater the chances for preventing serious vision impairment. Scheduling regular eye exams is very important for this reason.
Some populations are at greater risk of developing glaucoma than others. African-Americans over the age of 40, everyone over age 60, and people with a family history of glaucoma are among these groups. Other risk factors include high eye pressure, a thin cornea or an abnormal optic nerve.
The most common form of glaucoma is called open-angle glaucoma which occurs when normal fluid pressure in the eye begins to rise and subsequently damages the optic nerve. The fluid passes too slowly through the angle resulting in increased eye pressure that may damage the optic nerve and cause vision loss overtime.
There are no symptoms in the early stages of glaucoma. As the disease progresses, peripheral vision may begin to decrease and eventually may be lost, creating tunnel vision. In the final stages of glaucoma, straight-ahead vision may decrease to the point where no vision remains at all. Once vision is lost to glaucoma, there is no way to restore it. Early intervention can significantly delay progression of vision loss. The most common treatment for glaucoma is eye drops or oral medication. The medicine is intended to either lower eye pressure or to cause the eye to make less fluid. Doctors sometimes treat glaucoma with Selective Laser Trabeculoplasty (SLT), which uses a laser to stretch drainage holes in the meshwork for better fluid drainage.
When glaucoma develops without increased eye pressure, the condition is called low-tension or normal-tension glaucoma. It has similar symptoms to open-angle glaucoma and is usually treated the same way by decreasing eye pressure. Less common forms of glaucoma include angle-closure glaucoma, congenital glaucoma and secondary glaucoma.
Visual Field Testing
Visual field testing (perimetry testing) is a diagnostic tool used to measure a patient’s scope of vision, side or periphery. This test can be used to detect and monitor optic nerve damage and peripheral vision loss due to glaucoma. A visual field test takes less than 30 minutes to complete and is normally performed on one eye at a time. While resting the chin on a small cup and looking into an instrument called a perimeter, the patient stares straight ahead as a series of flashes appears. When the patient sees a flash, he clicks a handheld button. Each response is recorded and a report is generated detailing possible patterns of vision loss.
Optical Coherence Tomography (OCT)
Optical coherence tomography (OCT) is a non-invasive imaging tool used to diagnose and monitor the progression of retinal and optic nerve diseases, including glaucoma. High-resolution, three-dimensional maps of the optic nerve are created by beams of light and retinal nerve fiber thickness is measured. In addition, OCT provides cross-sectional studies of the retinal structure which give doctors precise and detailed images to aid in the diagnosing and treatment of ocular diseases even in their early stages.
Selective Laser Trabeculoplasty (SLT)
Selective Laser Trabeculoplasty (SLT) creates high-resolution, three-dimensional maps of the optic nerve and measures retinal nerve fiber thickness. It is a type of laser surgery used in the treatment of open-angle glaucoma. SLT offers an alternative for glaucoma patients whose condition has not responded to pressure-lowering eye drops or for patients unsuccessfully treated with traditional laser surgery. In this procedure, the surgeon holds a special lens to the eye, aiming a high-intensity beam of light at the lens which is reflected onto the trabecular meshwork. The laser then creates a series of evenly spaced burns in the meshwork, stretching the hole to allow better drainage.
SLT is an outpatient procedure using a local anesthetic and takes about fifteen minutes to complete. Separate surgeries will be scheduled if glaucoma is present in each eye, usually one to two weeks apart. Several post-operative visits will be scheduled so the doctor can monitor the patient’s eye pressure. Patients must continue to use pressure-lowering eye drops as prescribed by the doctor. SLT surgery can be repeated when effects diminish. The most common side effect of SLT is inflammation which can be successfully treated with eye drops.
Keratoconus is a degenerative disorder of the eye in which the normal round shape of the cornea thins and develops a cone-like bulge. The disease, which generally appears in teens and young adults, can cause significant visual impairment including distorted and blurred vision and corneal scarring. Progression of the disease generally occurs gradually and can slow or stop at various stages, resulting in mild to severe impairment.
The exact cause of keratoconus is not known, although a number of scientific theories point to a combination of factors including genetics and environmental and cellular causes. Approximately one out of every 2,000 people will develop keratoconus with most cases starting to appear spontaneously. Some cases appear to have a genetic link. Other risk factors include excessive eye rubbing, a history of rigid contact lens wear, and the presence of one or more atopic diseases such as asthma and eczema. Also, people with Down syndrome are more likely to develop keratoconus than those in the general population.
Symptoms of Keratoconus
The symptoms of keratoconus begin with blurred or distorted vision. Patients often experience progressive worsening of nearsightedness and astigmatism in the early stages as well. Frequent eyeglass prescription changes are required to improve vision. The thinning of the cornea progresses over a period of 10-20 years before slowing or stopping. If progression is rapid and the disease moves into an advanced stage, patients can develop hydrops which is a clouding of vision in one eye caused by a sudden infusion of fluid into the stretched cornea.
Treatment of Keratoconus
Mild myopia (nearsightedness) and astigmatism are corrected in the early stages with eyeglasses or contacts. As the condition progresses, rigid gas permeable (RGP) contact lenses can be prescribed to manage the distorted vision caused by increased astigmatism. Intacs is another treatment option. Intacs are tiny plastic inserts that are placed in the periphery of the cornea to help re-shape the cornea to improve vision. If none of the available treatment options work, or the disease progresses to an advanced stage, corneal transplant may become necessary.
Rigid gas permeable (RGP) lenses are often used in treatment to mitigate the visual distortion created by keratoconus. RGP lenses can be customized to the unique shape of the eye to correct the myopia and astigmatism associated with keratoconus. The permeable surface of RGP lenses allows oxygen to reach the cornea. These lenses are easy to insert, to remove and to clean, making them a good treatment option. Custom soft contact lenses, large scleral lenses, hybrid contact lenses, and piggyback lenses are also available to treat keratoconus.
Uveitis, also known as iritis, is an inflammation of the uvea which is a well vascularized structure in the eye. The Iris, the colored part of the eye, is a visible part of the uvea. The rest of the uvea is between the retina and the sclera, the white part of the eye. Uveitis can be a serious condition resulting in permanent vision loss or blindness if not treated. The treatment of uveitis is determined after a detailed evaluation. Most uveitis cases respond to topical corticosteroids. More serious cases may require oral corticosteroid. This condition can become chronic or recurring and should be carefully monitored for steroid side effects.
Fuchs’ Corneal Dystrophy is a slowly progressing eye disease that occurs when endothelial cells lining the inside of the cornea begin to die off. The disease generally affects people over 50, although early signs may appear in the thirties or forties. The cause of Fuchs’ dystrophy is unknown but the disorder is often inherited. Fuchs’ dystrophy affects women more than men and generally will involve both eyes. The disease is one of the leading causes of corneal transplant surgery.
In Fuchs’ dystrophy, cells in the endothelium gradually deteriorate, the cornea begins to swell and cloud and vision is distorted. As the disease progresses, the endothelium may begin taking on water, causing further vision loss and pain.
The early stages of Fuchs’ dystrophy are treated with drops, ointments and/or contact lenses to reduce corneal swelling. As the disease progresses, vision impairment may begin to affect the patient’s quality of life making corneal transplant surgery the best option for restoring vision.