Interstitial keratitis
Interstitial Keratitis (IK) basically means corneal scarring due to chronic inflammation of the corneal stroma. Interstitial means space between cells i.e corneal stroma which lies between the epithelium and the endothelium. Keratitis means corneal inflammation.
Pathophysiology
The corneal scarring is the end result of the initial invasion of blood vessels into the corneal stroma as part of the inflammatory response. Since normal corneal tissue should be avascular (no blood vessel) and therefore clear to allow light to pass, the presence of blood vessel and the infiltration of cells as part of the inflammatory process results in scarring or hazing of the cornea [1].
Aetiology
By far the most common cause of IK is syphilitic disease. However the corneal inflammatory response can be of 2 reason, infection and/or immunological response from hypersensitivity type reaction. Infectious cause due to syphilis (commonest) followed by other bacterial infection (TB, Leprosy and Lyme disease)and parasitic infection (Acanthamoeba, Onchocerciasis or river blindness, Leishmaniasis, Trypanosoma cruzi or Chagas disease, Trypanosoma brucei or African sleeping sickness and microsporidia)[2]
History
Previous long-standing eye infection which possibly during childhood time recalled as being treated with antibiotic and/or hospitalized over long period of time.
Symptoms and signs
Acutely or at the early sign includes painful, photophobic, red and watery eye. This is due to active corneal inflammation resulting in vascular invasion and stromal necrosis which can be diffuse or localized. This cause the pinkish discoloration of what was a clear transparent normal corneal tissue (called Salmon patch of Hutchinson).
Chronically or the end result will cause blurring of vision secondary to corneal stromal scarring, presence of ghost vessel and thinning of the cornea especially if it involves the visual axis.
Treatment
The underlying cause must be treated as soon as possible to stop the disease process. Corticosteroid drop can be use to minimize the scarring on the cornea along with antibiotic cover. However, residual scarring cannot be avoided which can result in long term visual impairment and corneal transplantation is not suitable due to high rejection rate from the corneal vascularization.[3]
