From the Guidelines
Pupillary constriction is a crucial mechanism in managing glaucoma, particularly in acute angle-closure attacks, as it helps reduce intraocular pressure (IOP) by opening the drainage angle and allowing better outflow of aqueous humor through the trabecular meshwork. This is achieved through medications called miotics, such as pilocarpine, which activate the parasympathetic nervous system, causing the iris sphincter muscle to contract 1. According to the primary angle-closure disease preferred practice pattern, pupillary constriction can be induced using parasympathomimetics, but their effectiveness may be limited in cases of markedly elevated IOP or secondary pupillary block 1.
The configuration of the iris becomes less bowed with pupillary constriction, which may open the angle and improve drainage, as noted in the primary angle closure preferred practice pattern guidelines 1. However, miotic therapy may be ineffective in certain cases, such as secondary pupillary block due to intraocular gas, oil, or vitreous, or if the intraocular lens or crystalline lens is blocking the pupil 1.
In such cases, other treatments like laser iridotomy, which has a favorable risk-benefit ratio, may be preferred 1. Laser iridotomy can relieve pupillary block, prevent or retard the formation of peripheral anterior synechiae (PAS), and result in significant angle widening and iris-profile flattening 1.
While modern glaucoma treatment often relies on other medication classes like prostaglandin analogs and beta-blockers as first-line options, miotic agents remain useful in certain cases, particularly for angle-closure glaucoma 1. The pupillary constriction effect is especially beneficial during acute angle-closure attacks when rapid pressure reduction is needed, but miotic drugs can cause side effects, including reduced night vision, headaches, and brow pain, which limits their widespread use in chronic glaucoma management 1.
Key points to consider in glaucoma management include:
- Reducing IOP is crucial in preventing glaucoma and its progression 1
- Prostaglandin analogues are effective in lowering IOP 1
- Laser trabeculoplasty is as effective as medical treatment in controlling IOP 1
- Pupillary constriction, achieved through miotics like pilocarpine, can be beneficial in certain cases, particularly acute angle-closure glaucoma 1
From the FDA Drug Label
INDICATIONS AND USAGE: Pilocarpine hydrochloride can be used in the medical management of glaucoma, especially open-angle glaucoma, in those cases in which the intraocular pressure can be controlled adequately by the topical administration of pilocarpine Pupillary constriction, caused by pilocarpine, helps glaucoma by reducing intraocular pressure. This is the main mechanism by which pilocarpine aids in the management of glaucoma, especially open-angle glaucoma 2.
From the Research
Pupillary Constriction and Glaucoma
- Pupillary constriction is related to the use of miotic drugs, such as pilocarpine, which are used to treat glaucoma 3.
- Miotics work by constricting the pupil, which increases the outflow of aqueous humor from the eye, thereby reducing intraocular pressure (IOP) 3.
- In the context of acute closed-angle glaucoma, pupillary constriction induced by miotics can help to open the blocked trabecular meshwork, allowing for increased outflow of aqueous humor and reduction of IOP 3.
- The use of miotics, such as pilocarpine, in combination with other medications, like timolol, can be an effective treatment for acute closed-angle glaucoma 3.
Mechanism of Action
- The exact mechanism by which pupillary constriction helps in glaucoma is not fully understood, but it is thought to be related to the increased outflow of aqueous humor through the trabecular meshwork 4, 5.
- Prostaglandin analogs, which are also used to treat glaucoma, work by increasing the outflow of aqueous humor through the uveoscleral outflow pathway, and may also have an effect on the trabecular meshwork 5.
Treatment of Glaucoma
- The primary goal of glaucoma treatment is to reduce IOP, which can be achieved through various means, including medication, laser therapy, and surgery 4, 6, 7.
- Pupillary constriction, induced by miotic drugs, is just one aspect of glaucoma treatment, and is often used in combination with other therapies to achieve optimal IOP reduction 3.