Medications for Treatment of Glaucoma

ID-100112466The aim of treatment of glaucoma (if intra-ocular pressure or IOP, is more than 21 mm of Hg it is called glaucoma) is to reduce intra-ocular pressure to normal and to reduce complications (such as damage to optic nerve, loss of visual field and visual acuity, blindness etc.) due to increased intra-ocular pressure.

There are several groups of medications used as eye drops, which can be used to achieve the aim of glaucoma management. They include topical beta-blockers, prostaglandin analogs, carbonic anhydrase inhibitors, miotics, alpha agonists (more selective brimonidine, apraclonidine and less selective epinephrine), physostigmine etc.

Prostaglandin analogs in glaucoma:

Prostaglandin analogs (latanoprost, bimatoprost, travoprost etc.) are currently the first choice medication for treatment of glaucoma. They increase the outflow of aqueous humor through uveoscleral pathway without inducing inflammation (prostaglandins cause inflammation) and reduce intra-ocular pressure in glaucoma patients.

Beta-blockers in glaucoma:

Beta-adrenergic blockers (timolol, betaxolol and levobunolol) are among the first line medications (prostaglandin analogs are more preferred these days) for management of open angle glaucoma. They are used as topical eye drops. Beta-blockers reduce production of aqueous humor production by ciliary body and thereby reduce intra-ocular pressure. They do not have any effect on the eye such as size of the pupils, tone of ciliary muscle or outflow of aqueous humor.

Carbonic anhydrase inhibitors in glaucoma: 

Carbonic anhydrase inhibitors (acetazolamide, dorzolamide, brinzolamide etc.) reduce production of aqueous humor by inhibiting carbonic anhydrase enzyme in ciliary body and reduce synthesis of carbonic acid, which is an essential ingredient of aqueous humor.

Miotics in glaucoma:

Miotics (pilocarpine, ecothiophate) widen the irido-corneal angle to facilitate outflow of aqueous humor and reduce IOP. Due to high side effects (such as pupil size, effect on ciliary muscle tome, headache, fluctuation in IOP etc.), they are less commonly used these days. They were first line drug until 1970s for glaucoma.

Alpha agonists in glaucoma:

Alpha adrenergic agonists (more selective alpha agonists dipivefrine, brimonidine and apraclonidine and less selective alpha agonists epinephrine) reduce production of aqueous humor as well as increase outflow of aqueous humor through uveoscleral pathway.

Other medications used for glaucoma include physostigmine etc.

To reduce intra-ocular pressure to acceptable level (below 21 mm of Hg), sometimes tow or more medications of various groups (with different mechanism and site of action) may have to be combined. For example, prostaglandin analogs may be combined with beta-blockers as they have different mechanism of action and can have additive effect in lowering intra-ocular pressure.

“Image courtesy of marin /”.

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