👉 The Allan fluid, also known as Allan's fluid or Allan saline solution, is a sterile saline solution used primarily in ophthalmology for diagnosing and monitoring glaucoma. It consists of a 0.9% saline solution with added hyaluronidase, an enzyme that breaks down hyaluronic acid in the eye's fluid drainage system. By infiltrating the anterior chamber, the fluid helps visualize the trabecular meshwork and Schlemm's canal, allowing ophthalmologists to assess the rate of aqueous humor outflow and identify potential blockages or abnormalities that could lead to increased intraocular pressure, a hallmark of glaucoma.