Inherited Corneal Diseases and Related Conditions
Genetics are believed to play a role in a number of corneal diseases, including the following disorders and related conditions.
Keratoconus is a non-inflammatory eye condition where the central or paracentral cornea undergoes progressive thinning and steepening. This abnormal curvature of the cornea can result in blurred or distorted vision, nearsightedness, high irregular astigmatism, and increased sensitivity to light. The condition usually occurs in both eyes, but may be asymmetrical.
What Causes Keratoconus?
While the exact cause is unknown, genetics are believed to play a role. Keratoconus is commonly associated with “atopy” (the genetic tendency to develop allergic diseases, such as allergic rhinitis, asthma, and atopic dermatitis, or eczema), Down syndrome, Leber’s congenital amaurosis, and Ehler’s Danlos/connective tissue disorders. The hereditary pattern is neither prominent nor predictable, but positive family histories have been reported. The incidence of keratoconus is often reported to be 1 in 2,000 people.
What is the Treatment for Keratoconus?
Keratoconus usually progresses slowly for the first 5-10 years, then stabilizes without causing severe vision problems. It can initially be corrected with glasses or soft contact lenses. If the disease progresses, rigid, gas-permeable contact lenses may be needed to improve vision. One of the most recent developments in the treatment of keratoconus is a procedure called corneal cross-linking, which has proven to halt the progression of the disease. The cornea specialists of NYEE offer this latest technology to patients whose disease has not progressed too far. In the most advanced cases of keratoconus, typically when scarring of the cornea develops, corneal transplantation may be necessary.
Fuchs' (pronounced "fooks") dystrophy, also called endothelial dystrophy, is a condition where the endothelial cells that line the inner surface of the cornea slowly start to die off. As more and more cells are lost, fluid begins to build up, causing swelling in the cornea. Most patients with Fuchs’ dystrophy have a very mild form that never affects vision. When it does, it usually occurs in middle age or later. Over time, vision will worsen, along with glare, sensitivity to light and difficulty seeing at night, and is often worse in the morning than later in the day. Pain or severely decreased vision can occur later in the course of the disease. Fuchs’ dystrophy can be inherited, though it also occurs in people without a known family history of the disease. It is more common in women than in men.
How is Fuchs’ Dystrophy Diagnosed?
Your ophthalmologist can diagnose the disease through a slit-lamp exam, which uses a high-intensity beam to show the eye structure in great detail. Other tests may include pachymetry, which measures the thickness of the cornea; specular microscopy, which examines the thin layer of cells that line the back part of the cornea; and a visual acuity test.
What is the Treatment for Fuchs’ Dystrophy?
Eye drops or ointments that draw fluid out of the cornea are the first step in relieving the swelling from Fuchs’ dystrophy. Blowing cool or warm (not hot) air from a blow dryer upon wakening can often improve vision earlier in the day in the early stages of the disease. If blisters develop on the cornea, soft contact lenses may temporarily help reduce the pain.
Because the condition worsens over time, a corneal transplant may be necessary to prevent blindness or severely reduced vision. Currently, the surgical treatments of choice are endothelial transplants (Descemet’s stripping endothelial keratoplasty [DSEK] or Descemet’s membrane endothelial keratoplasty [DMEK]). If your eyes show significant corneal scarring, you may need a full thickness corneal transplant to achieve good vision.
AKC is the result of atopy, a genetic condition in which the immune system produces higher than normal antibodies in response to a given allergen. Although AKC is a year-round disease, symptoms may worsen in the winter. Unlike atopic dermatitis, which is generally seen early in childhood, atopic keratoconjunctivitis appears during late adolescence and early adulthood. Men are more commonly affected than women.
How do I Know if I Have Atopic Keratoconjunctivitis?
With AKC, the conjunctiva lining the eyelids is usually red and swollen, with the lower eyelid generally more affected than the upper. AKC can progress to ulceration, scarring, cataract, keratoconus, and corneal vascularization.
The most common symptoms of atopic keratoconjunctivitis include:
- light sensitivity
- itching, burning, tearing
- red and thickened eyelids
Risk factors of keratoconjunctivitis include a family history of multiple allergies, eczema or asthma, and a previous diagnosis of atopic dermatitis.
How is Atopic Keratoconjunctivitis Treated?
AKC is usually treated with a combination of oral and topical antihistamines along with topical mast cell stabilizers. These are normally effective in controlling most symptoms. In more severe cases, there is the potential for damage to the eye caused by scratching and rubbing. An ophthalmologist may advise you to:
- Wear cotton gloves at night to prevent unintentional damage to the ocular surface.
- Apply cold compresses and saline irrigation to lower the elevated tear pH.
- In more severe cases, consider topical steroid therapy. Other steroid-sparing agents may be helpful, including cyclosporine or tacrolimus.
Be aware that systemic treatment of the conditions that accompany AKC may be very helpful.
Epithelial Basement Membrane Dystrophy (Map-Dot-Fingerprint Dystrophy)
Epithelial basement membrane dystrophy (EBMD) affects the anterior (transparent front part) of the cornea, resulting in decreased vision and/or recurrent corneal erosions. In EBMD, extra layers of basement membrane (or “maps”) extend abnormally into the corneal epithelium. Maturing epithelial cells become entrapped in these extra layers and form cysts (or "dots"). Parallel or concentric lines of thickened basement membrane appear as "fingerprints."
What are the Symptoms of EBMD?
This disorder may cause blurred vision and, most dramatically, may interfere with adherence of the epithelial cells to the basement membrane and thus lead to painful recurrent corneal erosions. Approximately 10 percent of patients with map-dot-fingerprint dystrophy experiences recurring erosion of the cornea.
How is Map-Dot-Fingerprint Dystrophy Treated?
Treatment for map-dot-fingerprint dystrophy is usually not required since the majority of patients have no symptoms and may not even be aware they have the condition. Epithelial erosions, when they occur, can be managed with topical lubricating eye drops and ointments. If those fail to relieve the pain and discomfort, then several surgical procedures may be performed. They include corneal scraping to remove the eroded areas of the cornea and allow healthy tissue to regrow, and laser surgery to remove surface irregularities on the cornea.
Recurrent Corneal Erosion Syndrome (RCES)
This common clinical disorder involves the corneal epithelium (the thin, outer protective layer of the cornea) and the epithelial basement membrane to which it is anchored. RCES is characterized by the repeated breakdown of the epithelium due to an underlying weakness of the attachments of the epithelium to its basement membrane.
What are the Symptoms of RCES?
The most common symptoms of RCES are a mild foreign body sensation and severe pain that can be fleeting or last for days, typically occurring during sleep or upon wakening. In addition to pain it may cause photophobia (discomfort or pain to the eyes due to light exposure), chronic tearing, and corneal scarring leading to visual changes.
What Causes RCES and How is the Diagnosis Made?
The most common causes are ocular trauma from foreign bodies, fingernails, tree branches, and paper cuts. Several corneal dystrophies may also predispose you to the condition, most notably epithelial basement membrane dystrophy, or EBMD (also known as Map Dot Fingerprint Dystrophy). Patients with diabetes, dry eye syndrome, and ocular rosacea are also at risk to develop RCES. Diagnosis of this condition is mostly made by slit lamp examination; findings could range from normal or mild irregularity to a large area of loose epithelium to a large corneal defect. Fluorescein stain will help to reveal the corneal defect.
What is the Treatment for RCES?
Treatment usually begins with artificial tear drops/gels during the day and artificial tear or 5 percent sodium chloride ointment at bedtime. Occasionally, a short course of anti-inflammatory drops may help. A bandage or soft contact lens may be helpful temporarily, but does not generally yield a long-term cure. A procedure known as anterior stromal puncture, in which hundreds of small micropunctures are made with a blunt needle into the superficial corneal surface, can be very successful in treating some cases. Other possible treatments include epithelial debridement removal and excimer laser phototherapeutic keratectomy (PTK).