Glaucoma has caused 7.7 million people to go blind globally. So what’s glaucoma?
Firstly, we know that the fluid in the eye is known as aqueous humor, which helps to provide nutrition to the eye. As new aqueous flows into your eye, the same amount should drain out. The fluid drains out through an area called the drainage angle. This process keeps pressure in the eye (called intraocular pressure or IOP) stable.
Simply put, glaucoma happens when the drainage angle is not working properly. The fluid builds up and leads to increased pressure in the eye, damaging the main nerve in the eye known as the optic nerve.
You may imagine the optic nerve as an electric cable made up of many small wires. As these nerve fibers die, you will develop blind spots in your vision and impact your vision. You may not notice these blind spots until most of your optic nerve fibers have died. If all of the fibers die, you will become blind.
Image via https://www.aao.org/eye-health/diseases/what-is-glaucoma
Glaucoma can be further classified into a more common type known as the open-angle glaucoma and the rarer type known as angle-closure glaucoma.
Angle-closure glaucoma happens when someone’s iris is very close to the drainage angle in their eye. The iris can end up blocking the drainage angle. You can think of it like a piece of paper sliding over a sink drain. When the drainage angle gets completely blocked, eye pressure rises very quickly. This is called an acute attack. It is a true eye emergency, and you should call your ophthalmologist right away or you might go blind.
On the other hand, pressure in the eyes builds up slower in open-angle glaucoma, and it is a more common and less severe form of glaucoma.
Fortunately, there are various types of medical treatments available for glaucoma today, and most of them are in the form of eye drops.
Eye drops for glaucoma
The main aim of treating glaucoma is to decrease the pressure within the eye, thereby slowing down the progression of glaucoma. In fact, study found that for each mmHg reduction in the eye pressure, the risk of glaucoma progression is decreased by 10%. Hence, it’s important to remind your loved ones with glaucoma to use their eye drops according to the doctor’s instructions.
Prostaglandin analogues
E.g. Latanoprost (Xalatan®), bimatoprost (Lumigan®), travoprost
Eye drops containing prostaglandin analogues such as latanoprost and bimatoprost are the first go-to for glaucoma treatment. Prostaglandin analogues work by increasing uveoscleral outflow, thereby reducing pressure in the eyes.
They're a famous choice for glaucoma because not only they can greatly reduce pressure in the eye while giving minimal to no side effects; patients only need to use it once daily– which is convenient and can enhance compliance to treatment. It’s more effective to use a prostaglandin analogue eye drop in the evening.
Note: Prostaglandin analogues eyedrops are generally avoided during pregnancy due to a theoretical risk of miscarriage and premature labor, although no human studies are available to prove it is dangerous (or safe) for pregnant women and babies.
Beta-blockers
E.g. Timolol (Timo-COMOD®), levobunolol, betaxolol
Beta-blockers eye drops work by reducing the production of fluids (aqueous humor) in the eyes. They can be used alone or in combination with other types of glaucoma eye drops. One of the common combinations in treatment of glaucoma is beta-blocker and prostaglandin analogues eye drops. Beta-blockers eye drops are a preferred choice in treating glaucoma in pregnancy as compared to prostaglandin analogues. However, if the glaucoma patient has:
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Respiratory disorders such as asthma and chronic obstructive pulmonary disorder (COPD)
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Heart disorders such as heart block, heart failure or bradycardia (slow heartbeat)
Then the use of beta-blockers eye drops should be avoided.
Beta-blocker eye drops should be used once to twice daily, and they generally come with more systemic side effects (i.e. side effects that involve more than just the eyes) compared to prostaglandin analogues. The systemic side effects may be bronchospasms (sudden narrowing of airway), heart failure, syncope (temporary loss of consciousness), increased blood sugar level and increased risk of falls in elderly.
Alpha-adrenergic agonist
E.g. brimonidine (Alphagan®)
Brimonidine is more commonly used in combination with other glaucoma eye drops. It's generally used 2-3 times daily. Brimonidine works by reducing fluid production in the eye and promoting outflow of the fluid. Its side effects may include eye allergy, redness in eye and burning sensation in the eye after using the eye drop. Brimonidine should not be used if the patient with glaucoma is also taking a type of medication called monoamine oxidase inhibitor (e.g. selegiline), which is commonly used in treating Parkinson’s disease.
Carbonic anhydrase inhibitors
E.g. Acetazolamide (available as pills), brinzolamide, dorzolamide (Trusopt®)
Carbonic anhydrase inhibitors also work by reducing fluid production in the eyes, and they’re commonly used together with other types of glaucoma eye drops. This group of eyedrops is rarely used for long-term due to their possible serious side effects, such as Stevens-Johnson syndrome (a rare but life-threatening skin reaction), angioedema (severe swelling involving lip, eyes, face and breathing tracts), metabolic acidosis and electrolyte imbalance.
Fixed combination
E.g. latanoprost + timolol (Xalacom®), brimonidine + brinzolamide (Simbrinza®), bimatoprost + timolol (Ganfort®), Dorzolamide + timolol (Cosopt®), Travoprost + timolol (Duo-Trav®)
Combination eye drops offer convenience for glaucoma patients, thereby improving their compliance to the treatment. Most fixed combination medications contain timolol as one of its components. They’re equally safe and efficacious compared to the non-fixed combination counterparts.
Never change or stop taking your glaucoma medications without talking to your ophthalmologist. If you are about to run out of your medication, ask your ophthalmologist if you should have your prescription refilled.
Non-medication treatment
Besides eye drops, laser surgeries and operating room surgeries are also commonly used to treat glaucoma. These procedures help to improve drainage for the eyes, so that fluids can leave the eyes and thus lead to drop in pressure.
How to use an eye drop the right way
To maximise your glaucoma eye drop, make sure you follow the steps below:
For more information, read our article here
A word from Doc2Us
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References
Cover image credit: Photo by Todd Cravens on Unsplash
