This is due to active corneal inflammation resulting in vascular invasion and stromal necrosis which can be diffuse or localized.
This causes the pinkish discoloration of what was a clear transparent normal corneal tissue (called Salmon patch of Hutchinson).
[citation needed] Such vascularization is likely to result in blurring of vision secondary to corneal stromal scarring, the presence of ghost vessels, and thinning of the cornea, especially if it involves the visual axis.
[1] Infectious causes include syphilis (commonest), followed by other bacterial infections (TB, Leprosy and Lyme disease) and parasitic infections (Acanthamoeba, Onchocerciasis or river blindness, Leishmaniasis, Trypanosoma cruzi or Chagas disease, Trypanosoma brucei or African sleeping sickness and microsporidia)[2] The corneal scarring is the result of the initial invasion of blood vessels into the corneal stroma as part of the inflammatory response.
[3] A positive VDRL of Treponema pallidum immobilization test confirms diagnosis of luetic(syphilitic) interstitial keratitis[citation needed] The underlying cause must be treated as soon as possible to stop the disease process.