Why is the Cornea Important?
It is important to understand the crucial role that the cornea plays in a patient’s ability to see. The cornea is the transparent sheath that covers the front surface of the eye. From the side, the cornea is the clear, circular structure, which seems to protrude. It is often compared to a window since the light must pass through the cornea in order to enter the eye. Because the cornea is a covering layer, it serves as protection to the rest of the eye against foreign materials. The cornea is also responsible for beginning to bend, or refract, the incoming light rays so that they will ultimately focus on the retina. The retina converts light images into electrical signals that are sent to the brain for interpretation. Thus, if the cornea does not bend the light appropriately, vision may be blurred.
The cornea has five layers:
1) Epithelium: the outermost layer of the cornea that serves as a boundary against infection and foreign materials such as dust and water
2) Bowman’s layer: the transparent layer made up of strong collagen fibers
3) Stroma: the collagen layer that comprises the majority of the cornea
4) Descemet’s membrane: the thin layer of tissue that protects the eye from infection and holds the endothelium in place
5) Endothelium: the thin, innermost layer of the cornea. It is made up of cells (endothelial cells) that are responsible for pumping water out of the cornea and keeping it from swelling.
What is Blepharitis?
Blepharitis is an inflammation along the lash line of the eyelids caused by the build-up of the normal secretions of your eyelids. Blepharitis may also be secondary to bacteria (i.e. an infection).
Signs & Symptoms
Blepharitis often causes symptoms such as irritation, foreign body sensation, redness of the eyelids and/or eyes, itching, excessive tearing, blurred vision, and crusting of the eyelashes, especially during sleep.
The treatment of blepharitis involves keeping the eyelids clean. This is most effectively done with warm compresses, used to loosen oil and crust, followed by lid hygiene with either commercially available lid scrubs or a solution of water and baby shampoo. In severe cases, or ones with infection, topical and/or oral medications may be prescribed.
Dry Eye Syndrome
What is Dry Eye Syndrome?
The tear film keeps the eye moist, creates a smooth surface for light to pass through the eye, nourishes the front of the eye, and provides protection from injury and infection. It is composed of three layers: oil, water, mucus. The innermost mucus layer helps the tears adhere to the eyes. The middle layer is water and the outermost oil layer seals the tears and keeps them from evaporating.
Dry eye is a condition caused mainly by either a deficiency in the amount of tears, known as aqueous deficiency, an unstable tear film, in which portions of the eye dry too rapidly, or a combination of the two. Oftentimes there is an inflammatory component to the Dry Eye Syndrome.
Signs & Symptoms
Pain/burning, foreign body sensation, light sensitivity, excessive tearing, and blurred vision are all common symptoms of Dry Eye Syndrome. This condition may also cause increased discomfort in contact lenses and eye fatigue, especially when reading, driving, watching television, or working on the computer.
The treatment of Dry Eye Syndrome varies depending on the cause. If the cause is another condition such as an autoimmune disease, thyroid disease, or estrogen deficiency that condition will be treated. However, most people with dry eye have no underlying disease. They may be treated with over-the-counter artificial tears or lubricating gels/ointment or anti-inflammatory prescription eye drops. Punctal plugs which block the drainage of tears from the eye, punctal cautery which permanently closes the drain from the eye, or a change in diet and supplements including increasing omega 3 fatty acid intake may also be recommended.
What is Fuchs’ Dystrophy?
Fuchs’ Dystrophy is a slow progressive disease that usually affects both eyes. It occurs when the natural pumping activity of the endothelial cells (the innermost layer of the cornea) begins to deteriorate. Excess fluid begins to accumulate causing the cornea to become swollen and less transparent. This condition is most commonly seen in men and women between the age of 40 and 50 although it typically does not become visually significant until later in life. Having Fuchs’ Dystrophy may be significant if cataract surgery is being considered.
Signs & Symptoms
Fuchs’ Dystrophy is most often associated with blurred vision upon awakening that gradually clears during the day. In more advanced stages, the blurred vision persists throughout the day. Pain, foreign body sensation, and light sensitivity may develop in the advanced stages.
Treatment for Fuchs’ Dystrophy varies depending on the severity of the condition. Hypertonic saline eye drops or ointments are often the first treatment utilized to decrease swelling of the corneas. When a patient’s vision begins interfering with their day-to-day activities and/or they begin experiencing painful symptoms they may need a corneal transplant. Oftentimes, an Endothelial Keratoplasty such as DSAEK or DMEK would be the preferred procedure.
Herpes Simplex Virus
What is Herpes Simplex Virus?
There are two types of Herpes Simplex Virus (HSV): HSV-1 and HSV-2. HSV-1 has manifestations above the neck (i.e. the face, such as mouth sores) and is not an STD. HSV-2 causes genital herpes.
Signs & Symptoms
While 90% of adults have been exposed to HSV-1 by the age of 21, the virus often remains dormant therefore causing no symptoms. Active inflammations from HSV-1 may affect the eye casing lid swelling, crusting, redness, and/or decreased vision.
The Herpes Simplex Virus is treated with topical and/or oral anti-viral medication. Some patients are left on these medications long-term to prevent reactivation of the virus.
Herpes Zoster Virus
What is Herpes Zoster Virus?
Herpes Zoster (HZV) is acquired primarily during childhood where it is more commonly known as Chicken Pox. The virus remains latent in the nervous system until activated later in life, either spontaneously or due to immunosuppression. At this time, it is often referred to as Shingles.
Signs & Symptoms
The Herpes Zoster Virus can affect any part of the body causing painful blistering of the skin, fever, and inflammation of nerve fibers. If the rash is present on the face it may also affect the cornea. An infection such as this could cause decreased or hazy vision and decreased corneal sensation in the affected eye.
HZV is often treated with oral anti-viral medications to decrease the risk of scarring to the cornea. Since the Herpes Zoster Virus can decrease corneal sensitivity, it is important for these patients to have regular follow-up visits to ensure the continued health of the eye.
What is Keratoconus?
The word “keratoconus” comes from the Greek words “kerato”, which means cornea and “konos,” which means cone. Though the disorder was identified two hundred years ago, it was not well distinguished from other known eye problems until 1864. Keratoconus refers to the progression of a conical shape to the cornea. The characteristically round smooth shape of the cornea bulges in the center due to thinning of the tissue. The corneal tissue can become as thin as half of its original thickness.
Signs & Symptoms
With keratoconus, the uniform transparent corneal surface becomes distorted causing increased astigmatism, decreased vision and sometimes scarring. These symptoms typically occur in both eyes, however, one eye may be affected more severely.
Who has keratoconus?
Keratoconus most commonly begins in the teens around the onset of puberty or in the twenties. One out of 2,000 people in the general population have been reported to have Keratoconus. Roughly one out of every 10 patients with Keratoconus has family members with the disease as well. The condition has not been associated with any particular social, cultural or geographical background.
Unfortunately, we do not know what causes Keratoconus. A genetic basis has been speculated due to a higher familial pattern of occurrence than the general population. Some physicians are exploring the possibility of endocrine involvement since the disease often occurs with puberty. Keratoconus may also be associated with other disorders such as eczema. It is possible that rubbing the eyes contributes to the disease as well. One of the latest research efforts explores the relationship of Keratoconus with the activity of certain enzymes in the eye. Although the causes of keratoconus may not be known, treatments for it are available.
Glasses and contact lenses may be effective treatment for the early stages of Keratoconus. As the condition progresses, contact lenses generally are more effective than glasses. Usually gas permeable lenses are used, but this depends upon the patient. Fitting contact lenses in Keratoconus patients can be difficult because so many trials are often necessary. In some cases, contact lenses may need to be custom made. The lenses may feel uncomfortable (especially at first) or they may have a tendency to fall out of the eyes. However, 90% of the time successful lenses can be fitted.
About 10% of the time, corneal transplant surgery becomes necessary. Corneal transplants for Keratoconus patients may be full-thickness (PK – Penetrating Keratoplasty) or partial-thickness (DALK – Deep Anterior Lamellar Keratoplasty). This surgical procedure has about a 95% success rate in Keratoconus patients. Like any surgical procedure, corneal transplant surgery involves certain risks.
Collagen Cross Linking
Our practice is now involved in collagen cross linking studies. Collagen cross linking is a new procedure that is becoming available in the United States through IRB approved research trials. Keratoconus and ectasia are conditions in which the cornea is weakened and thinned, which can result in bulging. The protruding shape can distort vision and lead to corneal scarring. Collagen cross linking is a normal part of the aging process that helps to strengthen adjacent collagen fibers in the cornea. The collagen cross linking treatment helps to accelerate this process in corneas weakened by disease. The proposed treatment was first described in 1992 and has since undergone multi-center trials that have been submitted to the Food and Drug Administration in order to be approved for use in the United States. Though the procedure has not yet been approved by the FDA, it is being widely used throughout Europe and Canada.
When a patient is entered into the study, we will first remove the front layer of the cornea (the epithelium). The patient will then receive riboflavin (vitamin B2) eye drops every two minutes for thirty minutes. During this treatment a UV light is shined on the eye for thirty minutes. The patient will receive regular follow-ups to compare their visual acuity and progression pre- and post-treatment. For many patients this procedure may delay or prevent the need for a corneal transplant.
Collagen cross linking can also be used in select cases of corneal infection that are not responsive to conventional medications.
We welcome you to make an appointment for further discussion on your specific treatment options.
Recurrent Erosion Syndrome
What is Recurrent Erosion Syndrome?
Recurrent Erosion Syndrome (RES) is a spontaneous breakdown of the corneal epithelium (the outermost layer of the cornea). This occurs because the outer layer is weakly attached to the underlying membrane. The most common cause of Recurrent Erosion Syndrome is an initial minor corneal injury or abrasion, such as that caused by a fingernail. Other disease processes that can elicit Recurrent Erosion Syndrome include dystrophies, infections, diabetes, and dry eyes.
Signs & Symptoms
Recurrent Erosion Syndrome is typically characterized by an abrupt onset of ocular discomfort including foreign body sensation, sharp stabbing pain, excessive tearing, redness, light sensitivity, and/or blurred vision. These symptoms usually occur during sleep or upon awakening. The episodes usually heal within one or two days but episodes tend to recur at irregular intervals from several days to weeks or months later.
Treatment varies depending on the severity of the condition. It can include over-the-counter eye drops, a long-term bandage contact lens to protect the surface of the eye from being damaged further, or a surgical procedure to scrape the epithelium (outermost layer of the cornea) away allowing new, healthy epithelium to replace the damaged portion.