Interstitial keratitis (IK) is 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. Signs and symptoms
Acutely, early symptoms include a painful, photophobic, red watery eye. 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).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. Cause
By far the most common cause of IK is syphilitic disease. However, there are two possible causes of the corneal inflammatory response: an infection and/or an immunological response, such as a hypersensitivity type reaction, or (rarely) Cogan syndrome. 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)

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.
Ranolazine, sold under the brand name Ranexa among others, is a medication used to treat heart related chest pain. Typically it is used together with other medications when those are insufficient. Benefits appear smaller in women than men. It is taken by mouth.Common side effects include constipation, headache, nausea, and dizziness. Serious side effects may include QT prolongation. Use is not recommended in those with liver cirrhosis. How it works is not clear but may involve adenosine triphosphate.Ranolazine was approved for medical use in the United States in 2006. In 2019, it was the 211th most commonly prescribed medication in the United States, with more than 2 million prescriptions. Medical uses
Ranolazine is used to treat chronic angina. It may be used concomitantly with β blockers, nitrates, calcium channel blockers, antiplatelet therapy, lipid-lowering therapy, ACE inhibitors, and angiotensin receptor blockers. It is also effective at preventing atrial fibrillation, and has been studied as monotherapy as well as in combination with other medications used to treat irregular heartbeat.Its use is not recommended in Scotland as of 2019. Contraindications
Some contraindications for ranolazine are related to its metabolism and are described under Drug Interactions. Additionally, in clinical trials ranolazine slightly increased QT interval in some patients and the FDA label contains a warning for doctors to beware of this effect in their patients. The drugs effect on the QT interval is increased in the setting of liver dysfunction; thus it is contraindicated in persons with mild to severe liver disease.