Corneal Ulcer Management: Diagnosis And Treatment

A corneal ulcer, or ulcerative keratitis, or eyesore is an inflammatory or more seriously, infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma.

Aetiology: Causes of corneal ulcer include contact with vegetable matter, chemical injury, contact lenses’ wear and tear. Other eye conditions can cause corneal ulcers, such as entropion, distichiae, corneal dystrophy, and keratoconjunctivitis sicca (dry eye).

Many micro-organisms cause infective corneal ulcer. Among them are bacteria, fungi, viruses, protozoa, and chlamydia:

Bacterial keratitis is caused by Staphylococcus aureus, Streptococcus viridans, Escherichia coli, Enterococci, Pseudomonas, Nocardia and many other bacteria.
Fungal keratitis causes deep and severe corneal ulcer. It is caused by Aspergillus sp., Fusarium sp., Candida sp., as also Rhizopus, Mucor, and other fungi. The typical feature of fungal keratitis is slow onset and gradual progression, where signs are much more than the symptoms. Small satellite lesions around the ulcer are a common feature of fungal keratitis and hypopyon is usually seen.
Viral keratitis causes corneal ulceration. It is caused most commonly by Herpes simplex, Herpes Zoster and Adenoviruses. Also it can be caused by coronaviruses & many other viruses. Herpes virus cause a dendritic ulcer, which can recur and relapse over the lifetime of an individual.
Protozoa infection like Acanthamoeba keratitis is characterized by severe pain and is associated with contact lens users swimming in pools.
Chlamydia trachomatis can also contribute to development of corneal ulcer.

Depth: Superficial ulcers involve a loss of part of the epithelium. Deep ulcers extend into or through the stroma and can result in severe scarring and corneal perforation. Descemetoceles occur when the ulcer extends through the stroma. This type of ulcer is especially dangerous and can rapidly result in corneal perforation, if not treated in time.  Superficial ulcers may heal in less than a week. Deep ulcers and descemetoceles may require conjunctival grafts or conjunctival flaps, soft contact lenses, or corneal transplant.

Location: The location of the ulcer depends somewhat on the cause. Central ulcers are typically caused by trauma, dry eye, or exposure from facial nerve paralysis or exophthalmos. Entropion, severe dry eye and trichiasis (inturning of eyelashes) may cause ulceration of the peripheral cornea. Immune-mediated eye disease can cause ulcers at the border of the cornea and sclera. These include Rheumatoid arthritis, rosacea, systemic sclerosis which lead to a special type of corneal ulcer called Mooren's ulcer. It has a circumferential crater like depression of the cornea, just inside the limbus, usually with an overhanging edge.

Symptoms: Corneal ulcers are extremely painful due to nerve exposure, and can cause tearing, squinting, and vision loss of the eye. There may also be signs of anterior uveitis, such as miosis (small pupil), aqueous flare (protein in the aqueous humour), and redness of the eye. An axon reflex may be responsible for uveitis formation — stimulation of pain receptors in the cornea results in release inflammatory mediators such as prostaglandins, histamine, and acetylcholine.

Diagnosis:
Diagnosis is done by direct observation under magnified view of slit lamp revealing the ulcer on the cornea. The use of fluorescein stain, which is taken up by exposed corneal stroma and appears green, helps in defining the margins of the corneal ulcer, and can reveal additional details of the surrounding epithelium. Herpes simplex ulcers show a typical dendritic pattern of staining. Rose-Bengal dye is also used for supra-vital staining purposes, but it may be very irritating to the eyes. In descemetoceles, the Descemet's membrane will bulge forward and after staining will appear as a dark circle with a green boundary, because it does not absorb the stain. Doing a corneal scraping and examining under the microscope with stains like Gram's and KOH preparation may reveal the bacteria and fungi respectively. Microbiological culture tests may be necessary to isolate the causative organisms for some cases. Other tests that may be necessary include a Schirmer's test for keratoconjunctivitis sicca and an analysis of facial nerve function for facial nerve paralysis.

Treatment
Bacterial corneal ulcer require intensive fortified antibiotic therapy (Cefazolin 5% and Gentamycin 1.4% drops hourly) to treat the infection.

Fungal corneal ulcers require intensive application of topical anti-fungal agents (Natamycin 5%).

Viral corneal ulceration caused by herpes virus may respond to antivirals like topical acyclovir ointment instilled at least five times a day.

Alongside, supportive therapy like pain medications are given, including topical cycloplegics like atropine or homatropine to dilate the pupil and thereby stop spasms of the ciliary muscle.

Proper nutrition, including protein intake and Vitamin C are usually advised. In cases of Keratomalacia, where the corneal ulceration is due to a deficiency of Vitamin A, supplementation of the Vitamin A by oral or intramuscular route is given.

Role of Surgery:
Surgical procedures may include:
Debridement/superficial keratectomy: in Epithelial herpes simplex virus keratitis, Recurrent corneal erosion.

Superficial Keratectomy: Debulking of infective material.

Tarsorraphy: Exposure keratitis (Bells palsy)
Neuroparalytic keratitis

Patch Graft: in Descemetocele,Small perforation

Conjunctival flaps: in Non-healing superficial ulcer or peripheral corneal ulcers with descemetole or small perforation

Penetrating keratoplasty: Promotes healing of corneal ulcer by total removal of pathology

Corneal healing
An ulcer of the cornea heals by two methods: migration of surrounding epithelial cells followed by mitosis (dividing) of the cells, and introduction of blood vessels from the conjunctiva. Superficial small ulcers heal rapidly by the first method. However, larger or deeper ulcers often require the presence of blood vessels to supply inflammatory cells. White blood cells and fibroblasts produce granulation tissue and then scar tissue, effectively healing the cornea. The ulcer heals by the fourth day.

Complications: Untreated corneal ulcers and infections may lead to:

• Loss of the eye (rare)
• Severe vision loss
• Scars on the cornea