The cornea is a round convex transparent structure forming anterior one-sixth of the outer fibrous envelope of an eye.
Centrally it is spherical and in periphery becomes flatter.
Thinnest at its center and thickness increases gradually from the center to periphery. Corneal thickness is important for the diagnosis of keratoconus, primary open-angle glaucoma, and refractive laser surgery.
Composed of five layers Epithelium, bowman’s membrane, stroma, Descemet membrane, and endothelium.
Corneal transparency is maintained by
1. Regular orientation of stromal collagen fibers
2. Active endothelial pump mechanism.
3. Regular arrangement of epithelial and endothelial cells.
4. Absence of blood vessels and lymphatics.
Keratitis (inflammation of the cornea)
Etiology (Infective causes)
1. Bacteria: Gram-positive and Gram-negative organisms.
2. Viruses: Herpes simplex and herpes zoster virus.
3. Fungi: Aspergillus fumigatus and Candida albicans.
4. Chlamydia trachomatis.
2. Autoimmune disease.
4. Chemical burns.
5. Eyelid abnormalities.
Bacterial corneal ulcer
The most common bacteria responsible are (Staphylococcus aureus, Streptococcus pneumonia, pseudomonas aeruginosa, and proteus)
1. Rapid onset of pain due to exposure and stimulation of corneal nerves.
1. Reduced vision.
2. Conjunctiva is red and congested.
3. Purulent discharge.
Intraocular pressure may be raised due to the development of secondary glaucoma.
Blood CP, ESR, blood sugar, and urine D/R.
Gram and Giemsa staining.
Culture and sensitivity.
1. Antibiotic ointment: Poleax, tobramycin, ciprofloxacin, and moxifloxacin.
4. Antiglaucoma drugs
Steroids are contraindicated for long use because it prolongs the danger of perforation.
Caused by Herpes simplex (type 1 and type 2)
Foreign body sensation.
The corneal sensation is reduced.
Mild to moderate pain.
2.Corneal sensitivity is reduced.
3.Fluorescein stains ulcer(club-shaped ulcer).
1.Topical antiviral drugs( acycloguanosine and acyclovir)
2. Topical antibiotics for secondary infection.
Caused by filamentous fungi (Aspergillus, Fusarium, Curvularia) and yeasts(Candida SPP.)
1: Ocular trauma with agriculture material.
2: Ocular surface disease.
3: Long term use of topical steroids.
4: Systematic immunosuppression and diabetes.
Signs and symptoms
1: Filamentous keratitis
1: It frequently appears as a greyish white ulcer that has feathery edges.
2: Superficial lesion may appear as grey-white strands elevating the surface of the cornea.
3: Deep lesions are often accompanied by an endothelial plaque and hypopyon.
4: Occasionally, multifocal or satellite lesions may be present.
5: Progressive infiltration is associated with hypopyon and may be surrounded by satellite lesions.
6: Immune ring surrounding the lesion may be present.
2: Candidal keratitis
Characterized by yellow-white infiltration associated with dense suppuration that resembles keratitis caused by the Gram-positive bacteria.
Laboratory examination should be performed before starting the antifungal therapy.
Corneal scraping is obtained for the identification of organisms.
1: Topical antifungal therapy( Natamycin, Fluconazole, Amphotericin B ).
2: Subconjunctival fluconazole may be used in severe cases with hypopyon.
3: Systemic antifungals are used for severe cases(Ketoconazole and fluconazole).