Actions and Uses
Increased serum osmolarity reduces IOP and vitreous volume by drawing fluid across vascular barriers and out of the eye. The osmotic activity of a drug depends on the number of particles in the solution and the maintenance of an osmotic gradient between the plasma and the intraocular fluids. This activity is independent of molecular weight. Low-molecular-weight agents such as urea, which penetrate the blood–ocular barrier, produce a small increase in IOP after an initial reduction because of a reversal of the osmotic gradient when the kidneys clear the blood of excess urea.
Osmotic drugs are FDA approved for the short-term management of acute glaucoma in adults and may be used to reduce vitreous volume before intraocular surgery.
The hyperosmotic drugs glycerin, mannitol, and urea are currently available for ophthalmic use in the United States (Table 16-13). Osmotic drugs should be used with care in patients in whom cardiovascular overload can occur with moderate vascular volume expansion; this includes patients with a history of congestive heart failure, angina, and systemic hypertension or recent myocardial infarction.
Lichter PR. Glaucoma clinical trials and what they mean for our patients. Am J Ophthalmol. 2003;136(1):136–145.
Netland PA. Glaucoma Medical Therapy: Principles and Management. 2nd ed. Ophthalmology Monograph 13. San Francisco: American Academy of Ophthalmology; 2008.
Table 16-13 Hyperosmotic Drugs
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.