Keratitis

Keratitis is broadly divided into infectious and non-infectious forms. Infectious keratitis is most commonly bacterial (e.g., Pseudomonas aeruginosa, Staphylococcus aureus), viral (herpes simplex virus, varicella-zoster virus), fungal (e.g., Fusarium, Aspergillus), or protozoal (Acanthamoeba). Non-infectious causes include exposure keratitis (from incomplete eyelid closure), neurotrophic keratitis (due to corneal nerve damage), and ultraviolet keratitis (e.g., from welding arcs or sunlamps).² Contact lens wear is the leading risk factor for microbial keratitis in developed countries, accounting for up to 90% of cases in some series.

Typical symptoms include eye pain, redness, photophobia (light sensitivity), tearing, and a gritty or foreign-body sensation. Blurred vision may occur if the inflammation involves the central cornea. Slit-lamp examination reveals corneal epithelial defects, infiltrates, or ulceration; fluorescein staining highlights the damaged area. Microbial keratitis often presents with a corneal infiltrate and an overlying epithelial defect, whereas herpetic keratitis may show a characteristic dendritic (branching) pattern. Corneal scrapings for culture and sensitivity are indicated in severe or atypical cases, especially when contact lens wear is involved.³

Management depends on the cause. Bacterial keratitis is treated with intensive topical antibiotics, often fluoroquinolones or fortified aminoglycosides; fungal keratitis requires topical or systemic antifungals (e.g., natamycin, voriconazole). Herpetic keratitis is treated with antiviral agents such as acyclovir or ganciclovir, sometimes with debridement. Acanthamoeba keratitis is notoriously difficult to treat, requiring combination therapy with biguanides and diamidines.⁴ Preventive measures include proper contact lens hygiene, prompt removal of lenses at the first sign of redness or pain, and protective eyewear in occupational settings. Severe cases may require corneal transplantation.

Beyond the common causes, keratitis has several overlooked dimensions. Neurotrophic keratitis, often caused by herpes zoster ophthalmicus or trigeminal nerve damage, leads to reduced corneal sensation and can progress to perforation without pain. Exposure keratitis occurs in patients with Bell's palsy or proptosis. Ultraviolet keratitis, also called 'welder's flash' or 'snow blindness', typically resolves within 24–48 hours but can be intensely painful. A rare but serious form is interstitial keratitis, associated with congenital syphilis (as part of Hutchinson's triad) and other systemic infections.⁵ In tropical regions, fungal keratitis is more common, often following trauma with plant material. Onchocercal keratitis, caused by the filarial worm Onchocerca volvulus, is a leading cause of blindness in parts of Africa.⁵

Cornea

The transparent front part of the eye that covers the iris and pupil.

Infiltrate

An accumulation of inflammatory cells in the corneal tissue, visible as a white or yellow opacity.

Epithelial defect

A loss of the outermost layer of the cornea, often detected with fluorescein staining.

Dendritic pattern

A branching, tree-like corneal ulceration characteristic of herpes simplex keratitis.

Photophobia

Abnormal sensitivity to light, a common symptom of keratitis.