Retinal vascular occlusions may involve both arteries and veins. Far more common are retinal vein occlusions. They occur when a retinal vein becomes obstructed by an adjacent blood vessel. This causes hemorrhage in the retina, which can result in swelling and lack of oxygen to the retina and sometimes glaucoma. Symptoms vary in severity from one person to another and are dependent on whether the central retinal vein or a branch retinal vein is involved. For a branch vein, the sudden onset of blurred vision or a missing area of vision is symptomatic. For a central vein occlusion, severe loss of central vision is characteristic. Common risk factors for vascular occlusion are hypertension, diabetes and cardiovascular disease.
Patients who suffer from a branch vein occlusion generally notice a gradual improvement in their vision as the hemorrhage resolves. Because the macula is often affected, recovery from a central vein occlusion is more difficult. It is important for follow-up care to be given in either of these cases to treat any complications. If areas of the retina have been oxygen-deprived, laser surgery may be used to prevent the growth of delicate vessels that could break, bleed or cause glaucoma.
Uveitis is an inflammation of the eye's structures responsible for its blood supply. The structures, called the uveal tract, include the iris, ciliary body and choroid. There are three major types of uveitis, each classified by the structures it affects.
- Anterior uveitis (also known as iridocyclitis) is the most common form of uveitis and affects the iris and ciliary body. It is characterized by symptoms including light sensitivity, blurred vision, redness, pain, small pupil and tearing.
- Posterior uveitis (also known as retinitis or chorioretinitis) involves the retina and choroid. Blurred vision and floaters are the most common symptoms.
- Pan uveitis affects structures in both the front and back of the eye. It can present with any combination of symptoms experienced with the other forms of uveitis.
Treatment for the different forms of uveitis is dependent on the severity of the disease and the ocular structures involved. Generally, topical eye drops and oral medications are prescribed to reduce the inflammation. In some cases, medicine that reduces intraocular pressure is used. After the inflammation has been treated, the eye should be evaluated for secondary conditions, such as scar tissue, cataracts or glaucoma. Many patients must also be evaluated for underlying systemic
One of the causes of a red eye is subconjunctival hemorrhage. This happens when a small blood vessel under the conjunctiva breaks and bleeds. A red patch of blood appears on the white of the eye, but causes no pain or change in vision. In some cases, the hemorrhage is caused by coughing, heaving lifting or vomiting. It may also develop following eye surgery or trauma.
While it may look frightening, a subconjunctival hemorrhage is essentially harmless. The blood becomes trapped underneath the clear conjunctival tissue, much like a bruise. No treatment is necessary as the blood naturally reabsorbs within several weeks
Need For Bifocals (Presbyopia)
Presbyopia is a difficulty in focusing that many people begin noticing after age 40. Most people first notice difficulty in reading very fine print. Print seems to have less contrast and a brighter, more direct light is needed for reading. In many cases, patients begin holding reading material further away to help them focus. Eye fatigue often occurs when reading a book or computer screen.
Presbyopia is a normal process that eventually everyone experiences. It can be detected with simple vision testing and a refraction. Depending on the patient's prior vision, reading or bifocal glasses or contact lenses are solutions. Monovision is another solution; using contact lenses or refractive surgery, one eye is adjusted for distance vision and the other eye is adjusted for reading vision.
Keratoconus is a degenerative disease of the cornea that causes it to gradually thin and bulge into a cone-like shape. This shape prevents light from focusing precisely on the macula. As the disease progresses, the shape becomes more pronounced, causing blurred or distorted vision. Patients with keratoconus are usually very nearsighted because of the cornea's irregular shape and have a high degree of astigmatism that is not correctable by glasses.
Keratoconus usually occurs in both eyes and is characterized by symptoms such as blurred vision (even when wearing glasses or contact lenses), glare at night, light sensitivity, frequent prescription changes or eye rubbing. Generally, this disease is diagnosed by the time patients reach their 20's. Because keratoconus is not usually visible to the naked eye, special testing is used for a detailed look at the shape of the cornea.
The first line of treatment for patients with keratoconus is to fit rigid gas permeable contact lenses. Because this type of contact is not flexible, it creates a smooth, evenly shaped surface to see through. However, because of the cornea's irregular shape, specialty contact lenses are often required. If vision deteriorates to the point that contact lenses no longer provide adequate vision, a corneal transplant may be necessary to replace the diseased cornea with a healthy one.
Nearsightedness occurs when light entering the eye focuses in front of the retina instead of directly on it. This is caused by a cornea that is steeper, or an eye that is longer, than a normal eye. Nearsightedness causes difficulty seeing at a distance. It is often discovered in school-age children who report having trouble seeing the board. Nearsightedness usually becomes progressively worse through adolescence and stabilizes in early adulthood.
Nearsightedness is characterized by blurry distance vision or squinting. A simple vision test and refraction are used to detect the problem. Vision is generally corrected with glasses or contact lenses. Refractive procedures, such as LASIK, can be considered for adults once the prescription has remained stable for at least one year.
Glaucoma is a disease caused by increased intraocular pressure (IOP) resulting either from an overproduction of fluid or from a malfunction of the eye's drainage structures. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers, which leads to progressive and permanent vision loss. Early detection and treatment can slow or halt the progression of the disease.
Essentially, glaucoma occurs when the delicate balance between the production and drainage of aqueous is thrown off-balance. Common types of glaucoma are open angle and acute angle closure.
Open angle glaucoma results from aqueous fluid building up within the anterior chamber, causing IOP to become elevated. Left untreated, this may result in permanent damage of the optic nerve and retina.
Acute angle closure occurs in only about 10% of the glaucoma population. It is the result of an abnormality of the structures in the front of the eye, collectively called the angle. In most of these cases, the angle space between the iris and cornea is more narrow than normal, leaving a smaller channel for the aqueous to pass through. If the flow of aqueous becomes completely blocked, IOP rises sharply, causing a sudden angle closure attack.
Two less common forms of glaucoma are secondary glaucoma, which results from another disease or problem in the eye and congenital glaucoma, a rare type that is seen in infants and requires surgery.
The danger of glaucoma lies in its lack of symptoms. Generally, it takes a routine eye exam to detect the disease. However, acute angle closure may cause a sudden decrease in vision, extreme eye pain, headache, nausea or vomiting, or acute glare and light sensitivity.
Most patients with glaucoma require only medication to control the eye pressure. Sometimes more than one medication will be prescribed. Surgery is indicated when medical treatment fails to lower the pressure satisfactorily. The purpose of surgery is to allow fluid to drain from the eye more efficiently so IOP is not elevated.
Inflamed Eyelids (Blepharitis)
Blepharitis is a common inflammatory condition that causes burning, itching and irritation of the eyelids. In severe cases, it may also cause styes and irritation or inflammation of the cornea (keratitis) or conjunctiva (conjunctivitis). Blepharitis is characterized by sandy, itchy eyes, red or swollen eyelids, and crusty or flaky skin on the eyelids.
Blepharitis is usually a chronic problem that can be controlled with extra attention to lid hygiene. Begin by soaking a clean washcloth in warm tap water. Place the compress on closed eyelids for five minutes and then repeat. Next, gently scrub the eyelids with a washcloth or cotton swab soaked in a mixture of equal parts of baby shampoo and water. Finally, rinse the eyelids thoroughly with warm water. Repeat the treatment two to three times daily for two weeks and then reduce to once daily. In some cases, anti-inflammatory and antibiotic drops or ointments may be necessary for flare-ups and more severe cases.
Floaters and Flashes
If you see black spots or spider webs that seem to float in a cluster or singly in your vision, or if you see spots that move or remain suspended in one place, or flickering or flashing lights that are most prominent when you look at a bright background, then you have experienced floaters and flashes.
A common cause of floaters and flashes is a condition called posterior vitreous detachment (PVD). The space between the lens and the retina of the eye is filled with a clear, jelly-like substance called vitreous. At birth, the vitreous has an egg-white consistency and is firmly attached to the retina. With age, the vitreous thins and may separate from the back of the eye. As the vitreous pulls free from the retina, it may be accompanied by light floaters and/or flashes. Floaters can be caused by tiny bits of vitreous gel or cells that cast shadows on the retina or from blood seeping into the vitreous. Flashes occur when the vitreous tugs on the sensitive retinal tissue.
In some cases, floaters and flashes may be symptoms of more serious problems, such as retinal tears or retinal detachment. Symptoms of a retinal detachment include sudden vision loss along with floaters and flashes, a veil or curtain that obstructs part or all vision, or a sudden increase in the number of floaters. All patients who notice floaters or flashes should seek immediate medical attention.
Diabetes Related Eye Problems
Patients with diabetes are more likely to develop eye problems such as cataracts and glaucoma, but the disease's effect on the retina is the main threat to vision. Over time, diabetes affects the circulatory system of the retina, and this effect is called diabetic retinopathy.
In its earliest phase, blood vessels in the retina become weakened and leak. These leaking vessels often lead to swelling (or edema) in the retina and cause decreased vision. As the condition worsens, circulation problems cause areas of the retina to become oxygen-deprived (or ischemic). New, fragile vessels (neovascularization) develop in an attempt to maintain adequate oxygen levels within the retina. These delicate vessels hemorrhage easily, causing blood to leak into the vitreous. The result causes symptoms of floaters or decreased vision. In the later phases of the disease, continued abnormal vessel growth and scar tissue may cause serious problems, such as retinal detachment.
Diabetic patients should have routine eye examinations so related eye problems can be detected and treated as early as possible. Retinal specialists rely on several tests to monitor the disease's progression and make treatment decisions. The most common cause of vision loss associated with diabetic retinopathy is diabetic macular edema. Laser treatment applied to the leaky blood vessels (focal photocoagulation) is helpful in preventing further vision loss. Two common procedures used in the treatment of proliferative diabetic retinopathy are pan retinal photocoagulation (PRP) and vitrectomy.
Pan retinal photocoagulation (PRP) is a type of laser surgery used to destroy oxygen-deprived retinal tissues outside of the patient's central vision. This treatment does create blind spots in the peripheral vision, but PRP prevents the continued growth of fragile vessels and seals the ones that leak.
Vitrectomy is used to remove the blood clots that occur in the gel-like substance that fills the center of the eye, called the vitreous. During a vitrectomy, the retina surgeon removes the blood and vitreous from the eye and replaces it with clear saline solution. The surgeon may also cut strands of vitreous attached to the retina that create traction, which may lead to retinal detachments if not removed.
Diabetic patients who are able to maintain appropriate blood sugar levels have fewer eye problems than those with poor control. Diabetic patients can also reduce the possibilities of eye complications by scheduling yearly dilated eye examinations with an eye doctor.
Farsightedness occurs when light entering the eye focuses behind the retina instead of directly on it. This is caused by a cornea that is flatter, or an eye that is shorter, than a normal eye. Farsightedness causes difficulty seeing up close.
Symptoms of farsightedness include blurred distance vision, eye fatigue when reading, difficulty seeing up close, eye strain and, in some cases with children, crossed eyes.
A simple technique called a refraction is used to diagnose farsightedness. Glasses or contact lenses are the most common type of treatment recommended. Refractive surgery may also be an option for adults.
Strabismus is caused by one or more eye muscles functioning improperly, resulting in a misalignment of the eyes. Each eye has six muscles that work in unison to control movements. The brain controls the eye muscles to keep the eyes properly aligned. These muscles must function together for the brain to superimpose the two images it receives from each eye.
Strabismus must be detected early in children because they are so adaptable. If a child sees double, his or her brain quickly learns to suppress or block out one of the images to maintain single vision. In a short time, the brain permanently suppresses vision from the turned eye, causing a weak or amblyopic eye. Trauma, certain diseases and occasionally eye surgery can cause strabismus. It can also be inherited.
Common signs of strabismus are turned or crossed eyes, a head tilt or turn, squinting, and in some cases, double vision. Treatment depends on the patient's age, cause of the problem, and type and degree of the eye turn. Treatment may include patching, corrective glasses, prisms, vision therapy or surgery.
A cataract is a clouding of the natural lens, the part of the eye responsible for focusing light and producing clear, sharp images. The lens is contained in a sealed bag or capsule. As old lens cells die, they become trapped within the capsule. Over time, the cells accumulate, causing the lens to cloud and making images look blurred or fuzzy. Cataracts are a natural result of the aging process, but may also be caused by diabetes. Occasionally, they are present at birth.
The most common symptoms of cataracts are a gradual decrease in vision and glare. Usually the decision to remove a cataract is based on the symptoms - once a person can no longer see well enough to do regular activities. Surgery is often performed on an outpatient basis. Using a local anesthetic, an incision is made and the opacified lens is removed. A clear, intraocular lens implant is inserted in its place. After surgery, new glasses are generally required.
Color Vision Deficiencies
Color vision deficiency is a term that is used to describe one of a number of hereditary or acquired color vision problems. The inherited form is the most common deficiency. It affects both eyes and does not worsen over time. This type of color vision deficiency occurs more in males than in females.
Color vision deficiencies may be partial (affecting only some colors) or complete (affecting all colors). Complete color deficiency, also known as color blindness, is rare. More often, individuals have a deficiency with one of the three photosensitive pigments in the eye: red, green or blue. Those people with normal color vision are referred to as trichromats. People with a deficiency in one of the pigments are called anomalous trichromats (the most common type of color vision deficiency). A dichromat has a complete absence of one cone pigment.
The most common signs of color vision deficiency are difficulty distinguishing between reds and greens or difficulty distinguishing between blues and greens. There is no cure for color vision deficiency. However, those with mild color vision deficiencies can be taught to associate colors with certain objects. In some cases, color vision deficiency can affect child development and career choice, which is why early detection is critical.
Astigmatism often refers to a cornea that is oval in shape, rather than round shaped. The oval shape of the cornea causes light to focus on more than one point in the eye, resulting in blurred vision. Astigmatism typically occurs along with nearsightedness and farsightedness.
Astigmatism can easily be detected in a routine eye examination, during refraction. Astigmatism can be corrected with glasses, contact lenses or refractive surgery, such as astigmatic keratotomy or LASIK. These surgeries essentially reshape the cornea, so it becomes more spherical and uniformly curved.
Age Related Macular Degeneration
Age-related macular degeneration (AMD) is the most common cause of blindness in individuals age 65 and older in the western world. It results from a hardening of the arteries that nourish the retina affecting the macula, part of the retina that is responsible for clear vision. Deprived of oxygen and essential nutrients needed for the retina to function, the central vision deteriorates. In addition to age, other risk factors for AMD include female gender, a family history of AMD, fair complexion, cardiovascular disease, smoking and (possibly) sunlight exposure.
There are two types of AMD.
- Non-exudative (also known as dry AMD) is the most common form of the disease and has a better long-term visual prognosis than wet AMD.
- Exudative (also known as wet AMD) is associated with the development of new blood vessels that grow beneath the retina leading to bleeding, scarring and severe reduction in central vision.
Signs of macular degeneration include loss of central vision (either gradually or suddenly), difficulty reading or performing tasks that require the ability to see detail and/or distorted or wavy vision. Presently there is no cure for AMD. Most individuals with reduced central vision benefit from low vision rehabilitative therapy.Some research also indicates the role of antioxidant vitamins and nutritional supplements may be helpful for the prevention of AMD in some patients.