How Do Antiglaucoma Beta Blockers Work?

Antiglaucoma beta blockers reduce the pressure inside the eye (intraocular pressure) by decreasing the production of aqueous humor. Aqueous humor is a clear fluid that forms and fills the posterior and anterior chambers of the eye, which are located between the lens and the cornea.

A part of the eye known as the ciliary body produces aqueous humor, which supplies oxygen and nutrients to the lens and cornea and removes waste products. Aqueous humor inflow and outflow are a continuous process that maintains an optimum pressure in the eye, and the eye’s spherical shape.

Antiglaucoma beta blockers decrease the production of aqueous humor by blocking beta receptors, which are protein molecules on the membranes of epithelial cells in the ciliary body. The ciliary body has two types of beta receptors, beta-1 and beta-2. Some antiglaucoma beta blockers selectively block beta-1, while some block both types of receptors.

Beta receptors in the ciliary body activate production of aqueous humor in response to stimulation by hormones such as epinephrine and norepinephrine (catecholamines). Beta receptors are found in many organs of the body, including the heart, lungs and kidneys.

Antiglaucoma beta blockers are topical solutions or suspensions administered in the eye to reduce intraocular pressure. High intraocular pressure increases the risk of damage to the optic nerve. Antiglaucoma beta blockers are usually the first-line treatment for the following eye conditions:

• Open-angle glaucoma: Glaucoma is a disease that damages the optic nerve and can lead to vision loss if left untreated. Open-angle glaucoma is the most common type of glaucoma in which the drainage angle through which the aqueous humor drains remains open, but the drainage channels are partially blocked.
• Intraocular hypertension: Elevated intraocular pressure due to imbalance in the production and drainage of aqueous humor.

Side effects of antiglaucoma beta blockers may include the following:

Ocular side effects:

• Irritation, discomfort and foreign body sensation
• Blurred and cloudy vision
• Reduced night vision
• Double vision (diplopia)
• Itching and redness
• Inflammation
• Pain, stinging or burning
• Tearing and/or discharge
• Light sensitivity
• Corneal inflammation (keratitis)
• Infection
• Dry eyes
• Cataract
• Conjunctival hyperemia (dilation of blood vessels in the conjunctiva, the membrane that lines the eye and inner surface of eyelids)
• Conjunctivitis (inflammation of the conjunctiva)
• Blepharitis (inflammation of the eyelids)
• Blepharoconjunctivitis (inflammation of the eyelid margin and the surrounding conjunctiva)
• Droopy eye (blepharoptosis)
• Redness of eyelids
• Reduced corneal sensitivity
• Cystoid macular edema (thickening of macula, the central portion of the retina)
• Pseudopemphigoid (scar tissue formation)
• Abnormal blood vessel formation in the retina (retinal vascular disorder)
• Corneal degeneration (band keratopathy)
• Inflammation of iris (iridocyclitis)

Systemic side effects:

• Slow heartbeat (bradycardia), heart failure, heart block
• Dizziness, vertigo and headache
• Insomnia, lethargy and depression

Hypersensitivity reactions such as:

• Hair loss
• Hives
• Toxic epidermal necrolysis, a rare and serious skin condition with skin peeling and blistering
• Tongue inflammation (glossitis)
• Bronchial spasms, shortness of breath (dyspnea), respiratory failure
• Aggravation of symptoms in myasthenia gravis, a neuromuscular disease
• Abnormal coordination
• Abnormal skin sensation (paresthesia)
• Impotence
• Cerebral ischemia (reduced blood supply to the brain)
• Reduced blood pressure (hypotension)
• Fainting (syncope)

Systemic side effects may be reduced by applying a finger on the inside corner of the eye or keeping the eyes closed for three minutes after drug application. It can help block the lacrimal puncta, which are small openings in the inner margin of the eyelids through which tears drain into the nasal passage, and may prevent the medication from getting into the system through the puncta.

The information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of some antiglaucoma beta blockers include:

• Betaxolol hydrochloride (Betoptic, Betoptic S)
• Carteolol hydrochloride
• Levobunolol hydrochloride (Betagan, AKBeta)
• Timolol (Betimol, )
• Timolol maleate (Timoptic, Timoptic in Ocudose, Timoptic XE, Istalol)

Betaxolol is a selective beta-1 blocker, while all the other drugs block both beta-1 and beta-2 receptors.