Selection of drugs for glaucoma
The different types of drugs for glaucoma are in use. The drug is selected for the treatment after understanding the type of glaucoma in the eye of the patients.
Glaucoma is a group of disease associated with optic nerve neuropathy along with rise in intra-ocular pressure of the eye. It can cause visual field defects. Initially it remains undiagnosed. However the persistent increase in the intra-ocular pressure can damage the nerve fibers of optic nerve.
Understanding aqueous humor dynamics
The anterior segment of eye has two chambers.
- Posterior chamber
- Anterior chamber
Posterior chamber
The posterior chamber of the eye is present between the anterior part of lens and posterior part of iris. The ciliary processes of the ciliary body produce and secrete aqueous humor in this part.
Anterior chamber
The anterior chamber of the eye is present between the cornea and and iris. Between them there is an angle and a drainage organ for the aqueous humor which is trabecular meshwork.
There are two types of pathways for the aquous flow. These are
- Trabecular outflow pathway
- Uveoscleral outflow pathway
Choice of drugs for glaucoma
If the glaucoma occurs due to increase in the production of aqueous humor then we chose the drugs to decrease its production.
Ocular beta blockers
Ocular beta blockers are very useful to achieve the target. these drugs act on the sympathetic nerve endings in the ciliary epithelium of the ciliary body. This overall decrease the IOP by decreaing aqueous humor production. These drugs are
- Timolol
- Betaxolol
- Levobunolol
- Carteolol
Alpha2 selective blockers
They are the vasoconstrictors. They work as sympathomimetic drugs and make the blood vessels of the eye to contract. As a result there is a decrease in aqueous humor production. They also decrease the redness in the eyes. The drugs available for this class are
- Apraclonidine
- Brimonidine
Carbonic anhydrase inhibitors
The production of aqueous humor involves bi-carbonate ion secretion. This class of drugs block the activity of enzyme (carbonic anhydrase) that help in producing these ions. Thus there is a decrease in the secretion of these ions followed by decrease in the transport of fluid. This overall decreases IOP of the eye. The drugs of this class are
- Acetazolamide
- Brinzolamide
- Dorzolamide
If there is a need to increase the outflow of aqueous humor which is secreted by the ciliary body in a normal range then we use the drugs to increase its outflow. The choice of drugs depends upon the fact if we want to increase trabecular outflow or uveoscleral outflow.
Trabecular outflow drugs
The classes of drugs to increase trabecular outflow are following
Non-selective alpha agonists
These include epinephrine and dipivefrine
Cholinomimetic drugs
The first drug is direct acting cholinergic drug which acts on the cholinergic receptors to increase trabecular outflow. These drugs cause the constriction of pupillary sphincter that moves iris in such a way to increase the site of trabecular meshwork for the greater outflow. The other two drugs are indirect acting cholinergic drugs. They increase the concentration of acetylcholine by inhibiting acetylcholinesterase. They do not directly stimulate cholinergic receptors.
- Pilocarpine
- Physostigmine
- Echothiophate
Uveoscleral outflow drugs
There is only one class of drugs which is prostaglandin analogues.
Prostaglandin (PGF2a) analogues
These drugs widen intermuscular space in the ciliary body to increase the outflow of aqueous humor. These include
- Latanoprost
- Tafloprost
- Bimatoprost
Founder of EyesMatterMost- an optometry student who loves talking about eyes. I tend to cover topics related to optometry, ophthalmology, eye health, eyecare, eye cosmetics and everything in between. This website is a medium to educate my readers everything related to eyes.
