How does Glycerine (Osmoglyn) lower intraocular pressure (IOP)?

Glycerine (Osmoglyn) lowers intraocular pressure (IOP) primarily by causing hypertonicity of plasma, which creates an osmotic gradient. When glycerine is administered, it increases the osmolarity of the blood, leading to the movement of water from the intraocular space into the bloodstream. This shift of fluid helps to reduce the volume of aqueous humor in the anterior chamber of the eye, thereby lowering IOP.

The mechanism involves the principle of osmosis, where water moves from an area of lower solute concentration (inside the eye) to an area of higher solute concentration (the bloodstream). This effect is particularly useful in conditions such as acute glaucoma, where rapid reduction of IOP is necessary to prevent damage to the optic nerve.

In contrast, increasing aqueous humor production would have the opposite effect by raising IOP, while reducing retinal blood flow is not a direct mechanism for lowering IOP but instead may have implications for ocular health. Decreasing pupil size relates to the actions of specific medications affecting the iris but does not contribute to lowering IOP directly. Thus, the effectiveness of glycerine in lowering IOP stems from its osmotic properties, which create an ideal scenario for fluid movement out of the eye.