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IU Optometry Clinics & Patient Care: Patient Education Angle on Glaucoma: Types |
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Mechanism of Angle Closure Glaucoma
A pupillary block is just that. It is where the posterior side of the iris and the anterior surface of the crystalline lens are completely pushed up against one another causing no aqueous humor to pass out of the posterior chamber. In the posterior chamber, there is a buildup of aqueous humor which is being produced by the ciliary body. This pressure pushes the iris forward and creates what is known as iris bombe as seen in the image at the right. As the pressure builds, there will also be adhesions of the anterior surface of the iris to the cornea and the trabeculum. If these Peripheral iris apposition is an iris root block of the trabecular meshwork that is usually caused by a plateaued iris which is an anomaly or secondary to inflammation. If a patient has an iris plateau, when the eye is dilated (either due to being in darkness, an autonomic response, or by use of certain drugs) the angle will be closed off. Inflammation can lead to "creeping" adhesions of the iris root toward the trabecular meshwork and cornea. Anterior uveal displacement can be caused by the anterior swelling of the ciliary body or even an anterior displacement of the vitreous body. Additionally, if a ciliary body ring melanoma is present, it will increase in size, causing the anterior movement of the iris which will lead to angle blockage. What Is Glaucoma? | Types of Glaucoma | Diagnosing Glaucoma | Treatments | Research & Links | Glaucoma Home 
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Angle closure occurs when the iris root completely blocks the trabecular meshwork and thus prevents aqueous humor from leaving the anterior chamber of the eye. This blockage can occur via three different mechanisms: (1) a pupillary block, (2) peripheral iris apposition, or (3) the anterior displacement of the uvea. 
adhesions are not broken within approximately 48 hours or if they occur frequently, the adherence becomes permanent to the trabecular meshwork, allowing no aqueous to pass through. A secondary pupillary block can occur as part of the inflammatory process of uveitis by creating a posterior synechia. 