The sub-specialty of Cornea and External Disease refers to the medical and surgical management of the full range of routine, complex and high-risk corneal and external eye diseases.  The cornea is the clear, dome-like structure on the front of the eye through which we see. Corneas can be damaged through inflammation, degeneration, allergies, infections, injuries and inherited dystrophies. External disease refers to conditions of the conjunctiva and eyelids that affect the function of the eyes themselves.

WHAT ARE THE COMMON CORNEAL AND EXTERNAL DISEASE CONDITIONS?

The corneal can be affected by a wide range of conditions including:

  • Dry eye
  • Infections such as cornea ulcers caused by bacteria, viruses, fungi, and protozoa
  • Allergic and atopic conditions
  • Auto-immune conditions
  • Hereditary conditions and dystrophies such as Fuchs’ dystrophy, epithelial basement membrane dystrophies, map-dot-fingerprint dystrophy, Reis-Bucklers corneal dystrophy, stromal cornea dystrophies, lattice corneal dystrophy, granular corneal dystrophy, congenital stromal corneal dystrophy, posterior corneal dystrophies, posterior polymorphous corneal dystrophy, and congenital hereditary endothelial dystrophy, for example
  • Herpes zoster (shingles) and herpes simplex infections
  • Iridocorneal endothelial syndromes (ICE syndromes)
  • Keratoconus
  • Growths and tumors including ptyergia and nodules.
  • Scarring following trauma and complications from prior eye surgery

External disease conditions encountered include:

  • Blepharitis, including difficult to treat conditions such as Demodex folliculorum
  • Ocular pemphigoid
  • Limbal stem cell deficiency
  • Trichiasis
  • Atopic conjuctivitis

These conditions can cause significant symptoms of ocular irritation and pain, and can lead to significant vision loss.  While all of the ophthalmologists of Richmond Eye Associates can diagnose and treat these conditions, consultation and referral to the Cornea and External Disease specialist may be necessary to help manage difficult or complex cases.

MEDICAL TREATMENT OF CORNEAL AND EXTERNAL DISEASE CONDITIONS

There are a wide variety of medical treatments for corneal and external disease conditions, ranging from over the counter artificial tears of different types to prescription medications to specially formulated eye drops made only by compounding pharmacies.  Other non-surgical treatments include bandage contact lenses to protect the cornea and punctal plugs for dry eye.

Microscopic and immunologic diagnostic tests are also available through the Cornea and External Disease specialists.

SURGICAL OPTIONS FOR CORNEAL AND EXTERNAL DISEASE CONDITIONS

The Corneal and External Disease specialist of Richmond Eye Associates is fellowship trained in advanced surgical management of corneal conditions such as penetrating and lamellar keratoplasty (corneal transplant), DSEK procedures, amniotic membrane procedures, and anterior segment reconstruction procedures.  In some cases corneal, scleral, or conjunctival biopsy might be necessary for diagnostic purposes. Therapeutic laser procedures (PTK) are available as well.

Corneal and external diseases involve various parts of the eye including the cornea, iris, lens, anterior chamber, conjunctiva and eyelids. Corneal and external diseases can include corneal allergies, cataracts, infections, conjunctivitis and dry eye. There can also be refractive maladies like near sightedness, far sightedness and astigmatism. Other related disorders include keratoconus, pterygium, endophthalmitis and Fuch’s Dystrophy apart from other ailments.

The Cornea

The cornea is the dome-shaped, outermost, transparent layer that covers the iris and pupil. The corneal tissue itself consists of five basic layers called the epithelium, Bowman’s layer, stroma, Descemet’s membrane and endothelium in that order. Although it is transparent, the cornea contains a highly complex group of cells and proteins. However, unlike most tissues in the human body, the cornea contains no blood vessels to nourish it or to guard against infection. The cornea receives its nourishment from the aqueous humor that fills the chamber behind it. Human tears also provide the cornea with nourishment

Dual Function

The cornea serves two purposes: First, in tandem with the eyelid, eye socket, the tear film and the white part of the eye called the sclera, the cornea shields the eye from dust, germs and other harmful substances.

Secondly, since it is outermost lens of the eye, it serves as the point of entry for light. When a ray of light strikes the cornea, it refracts, or bends the ray onto the lens. The lens refocuses the light onto the retina, the tissue of light-sensing cells lining the anterior of the eye. Clear vision requires the cornea and lens to focus the light rays precisely on the retina. The way a camera takes a picture is modeled on this refractive process, with the cornea and lens of the eye acting like the lens of a camera. The retina is the film, if the cornea cannot focus the light properly, the retina receives a blurred image.

Irregularities of the Cornea

Any trauma like foreign projectiles, lacerations and blunting can result in scarring, which clouds the cornea. Hereditary conditions can also cause dystrophies and degenerations, which can also cause scarring. In young people, the most common hereditary corneal disorder is keratoconus, in which the cornea becomes cone-shaped. This is common in children in Down’s syndrome and in patients with allergic conjunctivitis. Such patients may be able to see with contact lenses or glasses for a period of time, but may eventually develop scarring or high astigmatism. These conditions can only be rectified with a corneal transplantation.

A corneal transplant can sometimes become necessary following cataract surgery, if bullous keratopathy occurs. In this condition, the endothelial cells at the back of the cornea decrease in number as a result of the surgery. However, with the invention of improved lens design an new techniques, bullous keratopathy is less common today.

Corneal Damage

The cornea or surface of the eye can be afflicted with a number of problems including:

Chemical and thermal injuries

  • Corneal inflammations
  • Chronic infections
  • New tissue growth like pterygium, which is considered to be related to sun damage
  • Neurotrophic conditions caused by damage to optical sensory nervesli>
  • Hereditary conditions like aniridia (absence of the iris at birth)
  • Tumour

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These disorders can cause extensive damage to the eye surface and lead to the formation of new blood vessels. Severe scarring may result in loss of vision. Researchers at (Name of eye hospital) are exploring the possibility of normal tears being able to modulate and heal these conditions. A better understanding of the precise role of tears in the healing process may lead to the innovation of new techniques for visual recovery. It may also increase the number of successful surgeries.