In most patients, the iridotomy is placed in the upper portion of the iris, and cannot be seen under the upper eyelid. Aqueous humor leaves the eye through a tiny drain called the trabecular meshwork, which is located just in front of the iris. In the normal eye, fluid passes between the iris and lens before leaving through the trabecular meshwork in the front of the eye. As it rises, the iris is pushed forward. The balance between how much fluid is made, and how much leaves the eye, determines the pressure within the eye.
All eyes have measurable pressure.
However, when the amount of aqueous humor draining from the eye is reduced, the pressure within the eye can increase. This high pressure often leads to glaucoma. Although many people think of glaucoma as just one single disease, in fact there are many different forms of glaucoma. Differences depend upon where in the eye the blockage to the drainage occurs. Both the border between the iris and lens as well as the trabecular meshwork are areas where the flow of aqueous can be limited, leading to increased eye pressure.