Common Corneal Conditions

Fuchs' Corneal Dystrophy | Bullous Keratopathy
Corneal Edema | Keratoconus

Fuchs' Corneal Dystrophy

Fuchs’ dystrophy is an inherited condition that affects the thin, fragile inner layer (endothelium) of the cornea. The endothelium functions as a pump mechanism to keep the cornea clear. As we age, all individuals gradually lose endothelial cells. Fortunately, for most people this loss is gradual enough to maintain a clear cornea through their lifetime. In Fuchs' dystrophy, the endothelial cells degenerate more rapidly. Once lost, the endothelial cells do not grow back, but instead spread out to the fill empty spaces. When there are insufficient endothelial cells the cornea becomes swollen. See below to learn more about corneal edema.

Cornea with Fuchs' Dystrophy

Fuchs’ is slightly more common among women and affects both eyes. It is usually first detected in the 5^th or 6^th decade of life (40 – 59 years of age). It generally progresses quite gradually. The incidence of cataracts and glaucoma is slightly higher in patients with Fuchs' dystrophy. If the vision becomes significantly impaired, a corneal transplant may be indicated. Sometimes cataract surgery is performed in conjunction with the corneal transplant. Learn more about corneal transplants or cataracts.

Bullous Keratopathy

Bullous Keratopathy (Aphakic or Pseudophakic): In some individuals who undergo cataract surgery, the thin fragile inner layer (endothelium) of the cornea is damaged by the surgical procedure or implanted lens. The endothelium functions as a pump mechanism to keep the cornea clear. As we age, all individuals gradually lose endothelial cells. Fortunately, for most people this loss is gradual enough to maintain a clear cornea through their lifetime. If the endothelial cells become too damaged, the effect is corneal clouding or swelling. Eventually, this process can result in reduced vision and discomfort. See below to learn more about corneal edema.

With the modern techniques of cataract surgery, bullous keratopathy has become quite uncommon. Some risk factors for the development of bullous keratopathy include increasing age, dense cataract, and previous eye trauma. Certain older types of intraocular lenses were associated with the development of bullous keratopathy. They include certain models of the Leiske and Azar lenses. These lenses have not been implanted for many years.

Corneal Edema

Corneal Edema may occur transiently with cataract surgery, inflammation, increased intraocular pressure, or trauma. Permanent corneal edema may develop with Fuch's Dystrophy or Bullous Keratopathy. (See above).

Signs and Symptoms of Corneal Edema
In the early stages, patients notice glare, light sensitivity, and a mild decrease in vision. The symptoms are greatest in the morning and improve as the day progresses. During the daytime our eyes are open. Evaporation eliminates the excess corneal fluid that cannot be removed by the damaged endothelial cells. During sleep the eyelids are closed. There is no evaporation to assist the damaged cells. As the dystrophy worsens, evaporation is not sufficient to thin the cornea and vision becomes continuously blurred. Pain may also develop from the corneal thickening or vesicles (‘blisters’) that form on the surface of the eye. Other symptoms include:

• Hazy vision that is often most pronounced in the morning
• Fluctuating vision
• Glare when looking at lights
• Light sensitivity
• Sandy, gritty sensation

 
Detection and Diagnosis

Treatment

Medical Treatment: Permanent corneal edema from Fuchs’ corneal dystrophy nor bullous keratopathy cannot be cured with medication. However certain medications can reduce the corneal swelling. Concentrated (hypertonic) salt solutions such as sodium chloride drops or ointment are often prescribed to draw fluid from the cornea and reduce swelling. Another simple technique that reduces moisture in the cornea is to hold a hair dryer at arm’s length, blowing air into the face with the eyes closed. This technique draws moisture from the cornea, temporarily decreases swelling, and improves the vision.

The standard regimen of treatment is as follows:

Upon Awakening: Hypertonic Sodium Chloride Drops (Muro 128) - one drop every 5 minutes for 3 doses

Lunch Time: Hypertonic Sodium Chloride Drops
(Muro 128) - one drop

Dinner Time: Hypertonic Sodium Chloride Drops (Muro 128) - one drop

Bedtime: Hypertonic Sodium Chloride Ointment (Muro 128) - 1/2 inch inside lower lid

Bandage Contact Lens: In patients who develop significant discomfort,a soft contact lens can be placed over the cornea. The lens stabilizes the corneal surface reducing erosions and irritation. The lens is usually worn for 1-2 months and then exchanged. With this prolonged use of contact lenses, there is a small, but not insignificant, risk of infection or the formation of blood vessels.

Surgical Treatment: Two options are presently available for patients:

• Corneal Transplant: The central cornea is replaced with a similar sized portion of donor cornea. This is indicated when the vision deteriorates to the point that it impairs the patient’s ability to function normally. Click here to learn more about corneal transplants.
  
• Amniotic Membrane Graft: In cases of substantial discomfort, a smooth layer of tissue can be placed over the corneal surface. This membrane will reduce surface swelling and discomfort; however, since it does not replace the endothelial cells, visual function is usually not restored to a level greater than 20/40-20/100. This procedure is usually indicated in patients where a corneal transplant is not advisable.

Keratoconus

Keratoconus is a condition caused by an abnormal change in the cornea. The cornea is the major component involved with focusing images on the retina so that we see clearly. Normally, the cornea is round like a baseball.

Photokeratoscope with normal round curvature

Cornea with keratoconus.
Note the steeper curvature.

In keratoconus, the cornea gradually becomes thinner and conical in shape. The thinnest aspect of the cornea is usually in the middle or slightly below the middle portion of the cornea. Keratoconus is usually progressive, with the cornea becoming more steep and irregular over time. With early or mild keratoconus, patients may have normal vision with glasses. As the disorder advances, vision may become distorted. The vision may be corrected with a variety of methods that will be discussed below.

Note the distorted pattern of the rings

Etiology and Prevalence

Doctors at EDOW treat keratoconus patients on a daily basis. Keratoconus has been reported to affect approximately 1 in 5, 000 to 10,000 persons. Onset is usually during the late teenage years; however, it has occurred in children as young as 6 years of age. Keratoconus rarely develops after the age of 30. It affects men and women equally. Keratoconus is present in both eyes in over 90% of cases; however the onset is not always at the same time or to the same magnitude.

Keratoconus is usually progressive from the late teenage years until the mid thirties. Then, in approximately 75% of cases, the disease becomes stable. During the active stage, changes may be rapid. The thinning process is non-inflammatory; therefore, patients do not feel any pain or discomfort.

The cause of keratoconus is unknown. It has been found to be familial (meaning it is more common in certain families), but the exact mode of genetic transmission is unknown. It is associated with certain medical conditions such as atopy, Erlos-Danlos, and Downs Syndrome. It may also be associated with long-term use of rigid contact lens wear.

Keratoconus has no known cure. Fortunately, almost all patients with keratoconus live a normal, active life due to the variety of treatments at their disposal. See below to learn more about the present options.

Diagnosis

The doctors at EDOW have advanced diagnostic equipment
to assist in the diagnosis and treatment of keratoconus. In
moderate or advanced keratoconus, making the diagnosis
is fairly simple due to the classic findings on physical examination with a slit lamp. These findings include the following:

Fleisher ring: this ring is a yellow-brown to olive-green ring of pigment which surrounds the base of the cone. It is formed from the iron in the tear film.

Vogt Striae: Small stress lines on the inner portion of the cornea.

Corneal thinning. In advanced cases, the thinning of the central cornea can be seen on examination.

Corneal scarring – in advanced keratoconus – the cornea develops central scarring.

Diagnosing keratoconus in its early stages is more difficult. It requires a thorough history and examination. Patients with undetected early keratoconus will often visit a variety of eye doctors over a short period of time. They often receive several different spectacle prescriptions that do not provide satisfactory vision. The irregular shape of the cornea causes refractions to be variable and inconsistent because the image with any lens prescription is distorted. Keratoconus patients often report (monocular diplopia) ghost images and distortions rather than blur at both distance and near vision.

A variety of diagnostic tests can be performed to assist in the diagnosis of keratoconus.

Computerized corneal topography can provide an overview of the cornea and can show the relative steepness of any corneal area. EDOW has the most advanced topography units, an Orbscan. This unit can simultaneously measure the curvature and thickness of the cornea over the entire surface.

Photograph of normal cornea

Topography of mild keratoconus

Topography of intermediate keratoconus

Topography of advanced keratoconus

In mild keratoconus, wavefront analysis can be determined to quantify the amount of aberration caused by irregular astigmatism.


Treatments:

Glasses: In mild or early keratoconus, glasses can be used for vision correction. Unfortunately, as keratoconus progresses, the irregular shape of the cornea cannot be corrected with glasses.

Contact Lenses:

Soft contact lenses may be worn with early or mild keratoconus. Since soft contact lenses conform to the shape of the cornea. They are not able to eliminate visual distortion created by the irregular shape. For this reason, patients usually require the use of a rigid contact lens.

Rigid contact lenses (hard and gas permeable) create a stable surface upon which light can be focused into the eye. With mild or moderate keratoconus, a rigid lens can reduce or eliminate the distortion created by the abnormal corneal curvature. The optometrists at EDOW can fit patients with rigid contact lenses. They are experts in this field and receive referrals from patients throughout the world.

Surgical Intervention:

A variety of surgical procedures are available for patients with keratoconus. Penetrating keratoplasty is the most common. Recently, less invasive procedures, such as Intacs, have been developed.

Penetrating keratoplasty: In this procedure, the central area of the cornea is excised and a full-thickness corneal button is sutured into the recipient. For a complete description, see the corneal surgery section of this website.

Lamellar keratoplasty: A partial thickness portion of the cornea is excised and a partial thickness donor corneal button is sutured into the recipient transplant.

Intacs: Two arc shaped segments of inert plastic are inserted into the peripheral (outer) cornea. These segments add volume to the thinned cornea. This flattens the steep curvature and educes the irregular shape. For a complete description see the corneal surgery section of this website.

Phototherapeutic Keratectomy (PTK): Excimer laser procedures can remove superficial corneal scars. PTK is often helpful in rigid contact lens wearers who have developed a central plaque-like scar. These scars can reduce vision and irritate the cornea via mechanical rubbing.