Purulent keratitis is an acute, severe form of keratitis. The disease commonly begins with a bacterial infection of the lacrimal sac. Characterized by a severe purulent reaction, it occurs frequently in the elderly and patients with poor nutrition. It is distinguished by a nebula in the cornea with the appearance of congealed fat on the surface, along with upward-rushing, yellow pus. Purulent keratitis can occur at any age and in any season; however, it is especially common in elderly patients with a weak constitution who are predisposed to chronic dacryocystitis. If not treated immediately and appropriately, it can lead to rupture of the cornea and iris. Even spillage of the vitreous humor can occur, leading to corneal perforation, iridoptosis and a sunken pupil. This disease will severely afect visual acuity even afer recovery, and constitutes one of the main causes of blindness.

Treatment consists of antibiotics as a frst measure and then antimicrobial drugs specific to the causative pathogen. If left untreated, purulent keratitis will develop into a pus-producing ulcer that will lead to disintegration of the cornea.

In TCM, this disease pertains to níng zhī yì (凝脂翳, congealed-fat nebula). It usually results from an invasion of wind heat pathogen after external injury to the cornea. This allows hidden pathogens from chronic dacryocystitis to easily invade the injured eye. An external atack of wind heat may move inward to transform into heat, or the excessive intake of spicy-hot food may cause heat accumulation in the zang-fu organs. These result in burning fre in the liver and gall bladder that rises upward to the eyes to damage the cornea. Alternatively, chronic illness can result in qi defciency, yin defciency or upright qi defciency, allowing external pathogens to reside in the eye and cause the cornea to become purulent and sunken. Recovering from this condition is, therefore, long term and challenging.