About Corneal Diseases, Infections & Conditions

The cornea is the transparent dome at the front of the eye. It serves as the “windshield” of the eye and has an important role in focusing light rays onto the retina to form images. The cornea is covered by a thin layer of tears which prevent it from drying. Disturbances to the tear film or to the cornea itself interfere with vision and eye health.

The outermost layer of the cornea is called the epithelium. If it is damaged from trauma of any kind, such as:

  • Foreign body, including metal or dirt
  • a poke in the eye from a branch or a finger
  • an unclean or damaged contact lens

it is possible for bacteria, viruses or fungi to penetrate the cornea and cause an infection. An infection of the cornea is called Keratitis or a Corneal Ulcer. This can cause a painful inflammation with a discharge. If this is not treated quickly and appropriately, it may lead to corneal scarring or even loss of the eye

Dry Eye Syndrome is a very common eye condition that can affect the cornea.
To quote the American Academy of Ophthalmology: 

Our eyes need tears to stay healthy and comfortable. If your eyes do not produce enough tears, it is called dry eye. Dry eye is also when your eyes do not make the right type of tears or tear film.

How Do Tears Work?

When you blink, a film of tears spreads over the eye. This keeps the eye’s surface smooth and clear. The tear film is important for good vision.

The tear film is made of three layers:

  • An oily layer
  • A watery layer
  • A mucus layer

Each layer of the tear film serves a purpose.

The oily layer is the outside of the tear film. It makes the tear surface smooth and keeps tears from drying up too quickly. This protective lipid layer is made in the eye’s meibomian glands.

The watery layer is the middle of the tear film. It makes up most of what we see as tears. This layer cleans the eye, washing away particles that do not belong in the eye. This layer comes from the lacrimal glands in the eyelids.

The mucus layer is the inner layer of the tear film. This helps spread the watery layer over the eye’s surface, keeping it moist. Without mucus, tears would not stick to the eye. Mucus is made in the conjunctiva. This is the clear tissue covering the white of your eye and inside your eyelids.

Normally, our eyes constantly make tears to stay moist. If our eyes are irritated, or we cry, our eyes make a lot of tears. But sometimes the eyes don’t make enough tears or something affects one or more layers of the tear film. In those cases, we end up with dry eyes. 

The most common cause of dry is not under-production of tears, but rather over-evaporation. This occurs because the protective lipid layer of the tear film is not present to prevent tear evaporation. Typically, this is a result of the meibomian glands being blocked by hardened secretions. If left untreated, the blockage may damage the glands.

The symptoms of dry eyes include a scratchy, dry, sandy or gritty feeling that can be accompanied by a stringy clear white discharge with noticeable pain and redness. Often the irritation leads to excess tearing, but these tears in response to pain actually wash away the good, lubricating tears and the oily layer needed to prevent evaporation. Dry eye creates additional risk of corneal infection, as the tear film, which serves a protective mechanism and contains a number of antimicrobial components, is deficient.

Fortunately, our team of doctors has a great deal of expertise in the advanced diagnostic testing of dry eyes and will be able to make a treatment recommendation for your individual situation. For those patients with mild to moderate dry eyes the first course of treatment may be to use unpreserved artificial tears or lubricant eye drops. Depending on the nature of your tear film deficiency, they may prescribe a specific type of artificial tear that has different characteristics in terms of salt content, viscosity or lubricity. 

Because the most common cause of dry eye is over-evaporation of the tears, a mainstay of treatment is to restore the protective lipid layer of the tear film. Typically, this involves a combination of

  • nutritional supplementation with omega-3 fatty acids
  • warm compresses using a microwavable mask to help to “melt the butter”

Sometimes, it is helpful to perform a 12-minute in-office procedure called LipiFlow, in which warmth is applied to soften the hardened oil secretions which are blocking the oil glands. Once the secretions are softened, the LipiFlow device gently applies pulsations which express the thickened secretions so that they may exit the glands and allow normal oily secretions to reach the ocular surface.

Sometimes it is helpful to insert tiny “punctual plugs” into the openings of your tear ducts, in order to slow down or even stop the drainage of tears from the eye. Occasionally there are some cases that may not respond to the above sequence of treatment options because of some underlying low-grade inflammatory or infectious process. In these cases, it may be necessary to also prescribe an oral antibiotic such as a tetracycline or an anti-inflammatory eye drop such as a corticosteroid eye drop or another immune-modulating eyedrop, such as Xiidra or Restasis.

Herpes Zoster Keratitis is actually caused by the same virus that causes chicken pox, called Varicella-Zoster Virus. It is entirely possible that if as a child you had chicken pox , the Varicella-Zoster Virus may remain in the nerve cells of your body in an inactive state. The Varicella-Zoster Virus can reactivate later in life and travel through the nerves in your body causing a painful blistering rash. If the Varicella-Zoster Virus travels to your head or neck, it can affect the eye and thus cause a corneal infection. It is critical to have a physician diagnose this quickly as the infection can penetrate deeply into the cornea and cause scarring. The infection can also result in a loss of corneal sensation, which may be permanent. We may prescribe both oral medications and eye drops to treat the infection and prevent serious damage from occurring.

Ocular Herpes Simplex, or Herpes of the eye is caused by the Herpes Simplex Virus and is the most common cause of corneal blindness in the United States today. Up to 50% of people who have a single Herpes Simplex viral infection of the eye will experience a flare up or recurrence. The virus often leads to irreversible scarring of the cornea. Ocular Herpes may start as a painful sore on the eyelid or surface of the eye. If left untreated, it may multiply and begin to destroy epithelial cells and progress deeper into the cornea. If the Ocular Herpes penetrates the deeper layers of the cornea and causes a Stromal Keratitis, it may cause corneal scarring. Prompt diagnosis and treatment of Ocular Herpes is very important. We may prescribe both oral medications and eye drops to treat the infection and prevent serious damage.

Fuchs Dystrophy
Fuchs Dystrophy is a slowly progressive hereditary disease of the cornea that affects both eyes. . While Fuchs Dystrophy may be detected in people in their 30’s and 40’s, it usually does not compromise vision until people are in their 50’s or 60’s. The innermost layer of cells in the cornea, called the endothelium, are non-regenerating cells responsible for pumping water out of the cornea. This pump function is essential in maintaining corneal transparency. In Fuchs Dystrophy, as the abnormal endothelial cells die, the endothelium becomes progressively less adequate for pumping, and the patient begins to notice morning blurring which clears. Drops and ointments may help in providing clear vision and comfort. If and when these measures become inadequate, transplantation of the inner layer of the cornea may be necessary.

Map-Dot-Fingerprint Dystrophy
The outermost layer of the cornea, called the epithelium, is normally attached or anchored to an underlying basement membrane, called Bowman’s Layer, In the hereditary disorder known as Map-Dot-Fingerprint Dystrophy or Epithelial Basement Membrane Dystrophy, an abnormal basement membrane makes it difficult or impossible for the epithelium to adhere properly.. The area of poor adherence is called a Recurrent Corneal Erosion.. These distort the corneal surface, blurring vision. The poorly adherent area is likely to detach spontaneously, causing pain and foreign body sensation. If treatment is required to control the pain for those patients who are symptomatic, we may prescribe lubricating eye drops, patch the eye, apply a soft bandage contact lens or remove the layers of redundant epithelium either surgically or using a laser.

Keratoconus is an “ectasia” of the cornea in which the normally dome-shaped cornea progressively thins causing a cone-like bulge to develop, resulting in significant visual impairment. Keratoconus is caused by eye-rubbing, which commonly is in response to itching from allergic disease. The eye-rubbing usually begins in childhood, and the visual distortion from a progressively bowed-out cornea presents in the teens and twenties. Often the first sign is worsening nearsightedness and worsening astigmatism, followed by the onset of irregular astigmatism which cannot be fully corrected with glasses.

Certain specialized contact lenses may be of help; if a person is truly unable to wear them, we may consider a procedure called Intacs with CK. First CK (Conductive keratoplasty) applies radio frequency energy to the cornea so as to shrink and centralize the cone. Next, micro-thin prescription inserts call Intacs are implanted within the cornea to help hold the new shape. Sometimes, if the keratoconus is continuing to progress, a procedure called Corneal Collagen Cross-Linking (CXL) is performed to reinforce the structure of the cornea in the hope of slowing the progression of the disease. Regardless, it is crucial that eye-rubbing stop.

Management & Treatment of Keratoconus
Eyeglasses & Contact Lenses-Eyeglasses and soft contact lenses may be well tolerated and provide satisfactory comfort and vision when Keratoconus is mild. Most often, the quality of vision tends to decline so that patients require special keratoconus contact lenses.

Intacs for Keratoconus combined with Conductive Keratoplasty (CK)-When a person who requires special Keratoconus contact lenses becomes intolerant to wearing those lenses, another option is Intacs® for Keratoconus with CK. These micro-thin prescription inserts are made of the same material as a rigid contact lens, and are implanted within the cornea to make the shape less irregular. If the cone is located outside the center of the cornea, then performing Conductive Keratoplasty (CK) guided by an advanced technique known as intra-operative qualitative keratometry, devised by Dr. Anita Nevyas-Wallace, allows the corneal shape to be made more symmetrical and the Intacs to be placed in a more effective position. The purpose of Intacs® for Keratoconus with CK is to improve spectacle-corrected vision.

Collagen Cross Linking- Sometimes, if keratoconus is continuing to progress, a procedure called Corneal Collagen Cross-Linking (CXL) is performed to reinforce the structure of the cornea in the hope of slowing the progression of the disease. This treatment method works by increasing collagen cross-linking, which serve as the natural "anchors" within the cornea. These anchors are responsible for preventing the cornea from bulging and becoming steep and irregular and thus causing Keratoconus. Corneal Collagen Cross Linking is administered by placing riboflavin eye drops onto the surface of the eye and exposing the surface to a precise amount of ultraviolet light. The purpose of Corneal Collagen Cross Linking is to slow the progression of the disease. It often does not reverse visual distortion, and in the first year after this procedure, the vision may be worse than before.

Corneal Transplantation-When Keratoconus has progressed to the point that special keratoconus contact lenses no longer provide adequate vision, a corneal transplant may be the only option. In many cases of Keratoconus, a full thickness Penetrating Keratoplasty (PK) is the preferred surgical solution although sometimes the Cornea Surgeon may recommend a Lamellar Keratoplasty (LKP). With PK the cornea surgeon removes the central portion of the damaged cornea with a “cookie cutter” like instrument called a trephine and replaces it with a clear cornea obtained from the eye bank. The donor cornea is very carefully sewn into place using sutures that are thinner than a human hair PK is the most common type of corneal transplant for advanced keratoconus, as it has the potential to provide the clearest vision after healing because there is no interface (layer) to look through. However, the healing time is somewhat long and the use of a contact lens might be required for the clearest vision. Sometimes Lamellar Keratoplasty (LKP) may be used if the damaged corneal tissue is mainly located in the outermost (most superficial) 50% of the cornea. In LKP the outermost portion of the cornea is carefully dissected and removed along with any damaged tissue. Then a new donor cornea is gently sewn into place. This type of corneal transplant is less invasive and will allow your eye to be stronger after surgery than it would be with a regular full thickness transplant, or Penetrating Keratoplasty. However, in some cases there can be some loss of clarity from the interface between the new and remaining layers of the cornea.

Recurrent Corneal Erosion or Scratched Cornea
A corneal abrasion is a scratch or scrape on the surface of the cornea. Fingernails, makeup brushes and tree branches are common culprits of corneal abrasions.

Recurrent Corneal Erosion is a condition of the cornea in which there is a poor attachment of the outermost layer of the cornea, the epithelium, to Bowman’s Layer.

The area of poor adherence is called a Recurrent Corneal Erosions. These distort the corneal surface, blurring vision. The poorly adherent area is likely to detach spontaneously, causing pain and foreign body sensation. This often occurs when the eyes are first opened in the morning. Patients who experience Recurrent Corneal Erosion may experience sharp pain, light sensitivity, tearing and watering of their eyes, and a gritty sensation. Recurrent Corneal Erosion may develop after healing of a traumatic corneal abrasion, or it may be associated with Map-Dot-Fingerprint Dystrophy. The first line of treatment is salt solution eye drops or ointment. This medication helps the epithelium to adhere more firmly to Bowman's Layer. Usually artificial tears are also recommended to keep the cornea moist, and lubricating ointment at bedtime may be needed long term to prevent an area of epithelium from adhering to the eyelid and again detaching from the cornea when the lids are opened. Sometimes, a soft bandage contact lens will be used to help the healing process. Those patients who have a corneal dystrophy may require additional treatment. This usually includes an in-office procedure where the epithelium is gently removed and covered with a disk of amniotic membrane to promote healing. Patients who continue to suffer from Recurrent Corneal Erosions despite the treatments described, may benefit from Phototherapeutic Keratectomy (PTK). This involves removal of the redundant layers of corneal cells using the Excimer Laser to encourage proper healing.

A pterygium is a fleshy triangular growth of tissue on the cornea that may grow slowly throughout a person’s life. Rarely, a pterygium can grow across the cornea and block the pupil, but even less aggressive pterygia will distort the vision by inducing irregular astigmatism. People who live in sunny climates where they are exposed to a great deal of sunlight and other UV light sources along with wind are more prone to developing pterygia.

Pterygia may become red, swollen and inflamed, occasionally needing to be removed. Removal of a pterygium is a surgical procedure that has recently undergone medical advances. Our eye surgeons use a surgical technique called Amniotic Membrane Graft in order to prevent recurrences and obtain the best possible results for Pterygium surgery.