What is glaucoma, how to manage it and what are the precautions that need to be taken
What is glaucoma?
Glaucoma is a group of ocular conditions where there is damage to your optic nerve(the nerve responsible for your eyesight). This is also referred to as the “silent killer of sight”. Glaucoma has affected more than 70 million people worldwide, from which 10 per cent are classified as blind in both their eyes.
This condition rarely shows any symptoms and can be hereditary. In glaucoma, The damage to the optic nerve occurs due to increased eye pressure(intraocular pressure, also referred to as IOP ).
But in some cases, glaucoma-related damage to the optic nerve can also occur in patients with normal eye pressure. The damage to the optic nerve is slowly progressing, leading to irreversible loss of side vision. Although the damage is irreversible, it can be controlled to prevent further vision loss.
Chronic (Long-standing) types of glaucoma are often painless and are discovered by chance during the comprehensive eye examination. During the initial stages of the study, glaucoma may not have any immediate effects on the eye. As the disease progresses, the person’s side vision gradually reduces and ultimately leaves the person with tunnel-like vision if left untreated.
Figure 1: What a person with normal vision sees what a person with glaucoma sees
Because of this slow and quiet damage, glaucoma is difficult to detect in the early stages and is left undetected until the damage becomes quite severe.
Figure 2: Nature of glaucoma
What causes glaucoma?
The eye produces a fluid called aqueous humour. The aqueous humour creates pressure inside that helps maintain the eye’s structure. If there is any excess production of this fluid or any difficulty in drainage of this fluid, the pressure inside the eye goes up. This pressure is called intraocular pressure or, simply, IOP. Like blood pressure, it is harmful to the eyes when it is above the normal range. This increase in IOP over a long time causes damage to the optic nerve. If it not treated on time, it can lead to blindness.
Figure 3: Normal eye versus eye with glaucoma
Types of glaucoma
There are several types of chronic glaucoma. The most common two types are primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG).
In primary angle-closure glaucoma, the pressure increases due to a block caused in the angle between the cornea and iris of the eye, which prevents the fluid from draining efficiently.
In primary open-angle glaucoma, the reason for the increase in pressure is still unclear. Although the area between the iris and cornea is free from any blockage, the IOP increases because the trabecular meshwork (responsible for the drainage of the aqueous humour) is partially or entirely obstructed.
In the acute form of the disease, eye pressure shoots up quickly because the drainage of the liquid in the eye is obstructed. Acute angle-closure glaucoma is considered an ocular emergency. It may lead to blindness within a short period if it is not given immediate attention. The patient usually experiences severe ocular pain and redness, seeing halos around lights, blurred vision, headaches, vomiting and nausea.
Secondary glaucoma – In some cases, the patients may get glaucoma due to the presence of another eye or systemic condition. This type is referred to as secondary glaucoma. Some types of secondary glaucoma include glaucoma after intraocular surgery like cataract or retina surgery, after an eye injury, or an existing inflammation in the eye (such as in uveitis), pseudoexfoliative glaucoma, pigmentary glaucoma etc. to name a few.
The only way to control glaucoma is by controlling the eye’s pressure. The management options include:
- Antiglaucoma medications (AGMs)
Anti-glaucoma medications are medications used to lower your eye pressure(IOP). They reduce the eye pressure to a level where damage to the optic nerve is not likely, which preserves your side vision. These medicines work by either reducing the amount of fluid (aqueous humour) your eye makes, by increasing the drainage of the fluid(aqueous humour) or by both ways. AGMs are usually prescribed as eye drops, or in some rare cases, as oral medication. They are usually the first-line management in adults. There are several different classes of anti-glaucoma medications. Your practitioner will decide the most suitable AGM for you depending on several factors such as how effective are those drops, their frequency of use, their price and type of glaucoma, amongst few others.
The different types of Antiglaucoma medications are :
a. Prostaglandin analogues – This type of medication reduces eye pressure by improving the drainage of the fluid. These medicines are often the first choice of treatment as it has to be applied only once a day.
Examples: Xalatan® (latanoprost), Lumigan® (bimatoprost), Bimat® (bimatoprost), Travatan Z® (Travoprost), and Zioptan™ (tafluprost), and Vyzulta™ (latanoprostene bunod)
b. Beta-Blockers – Beta-blockers reduce eye pressure by reducing the fluid production at the source of production. They are prescribed during the waking hours of the day and are often given twice a day for ideal results. There are two types of beta-blockers: Selective (Betaxolol) and Non-selective beta-blocker (Timolol, Levobunolol, Metipranolol). Your ophthalmologist will decide which one to prescribe based on your health history (i.e.) if you have any other medical conditions.
Timolol is the most widely prescribed beta-blocker. It is an FDA-approved drug that provides a reduction of 25-30 per cent on average. Some patients may experience side-effects such as difficulty in breathing, headache, dizziness, bradycardia (Slow or irregular heart rhythm), hypotension(low blood pressure) with the use of these drugs. Hence they are used with caution.
The symptoms can be reduced effectively by applying the punctal occlusion technique. (Discussed below in precaution
c. Combination drugs – For best results, beta-blockers are also combined with other classes of drugs. Some famous commercially available combinations are Combigan™(Brimonidine + Timolol), Cosopt™ ( Dorzolamide + Timolol), DuoTrav™(Travoprost + Timolol) , Xalacom™ (Latanoprost + Timolol), Ganfort ™ Bimatoprost + Timolol)
d. Alpha Agonists – These medicines reduce the flow majorly by reducing the fluid production and minorly by improving the drainage of the fluid.
Example: Alphagan, Brimodin, Iobrim, Alfa drops
e. Carbonic anhydrase inhibitors – CAIs help to reduce the pressure by controlling the production at the source. They are available as prescription eye drops, injections and as oral tablets. They are ideally prescribed as eye drops 3-4 times a day to achieve reasonable control of the pressure. CAI’s as eye drops are generally preferred due to fewer side effects than the other types of CAIs. CAIs, when used as eye drops, could cause side effects like blurred vision, bitter taste and changes in the cornea.
Examples – Dorzox ( Dorzolamide), Azopt ( Brinzolamide)
f. Miotics – Miotic drugs are a part of glaucoma treatment for more than 100 years. Miotic drugs are often used to constrict the pupil of the eye(Insert image of the constricted pupil). However, it is also used as an anti-glaucoma drug to reduce pressure by improving fluid drainage.
E.g. Pilocarpine Due to its several side effects and disturbances to the vision, other drugs are preferred over it.
g. Hyperosmotic drugs – This class of drugs is only used to control sudden episodes of increased eye pressure. These drugs help draw more water from the eye, reducing eye pressure. These drugs are often used only for a few hours as their effect reduces over time. Headache, mental confusion, heart problems and backache are some of the side effects of the drugs. E.g., Oral glycerine, Intravenous mannitol.
Rho Kinase Inhibitors – This class of drugs is newly introduced and improves the outflow of the fluid from the eye. Eg. Rhopressa ( Netarsudil)
Laser and Surgical Options for glaucoma: Laser and surgical treatment for glaucoma are recommended when medical treatment is not appropriate, insufficient, not well-tolerated or when the patient is not compliant. When the eye pressure cannot be under control despite giving maximum medical treatment, laser and surgical options are considered.
YAG-Pi – YAG Peripheral iridotomy
YAG-Pi is a standard outpatient procedure performed to improve the outflow mechanism of the eye. This procedure is advised as a preventive measure when there is a chance of a sudden block in the drainage of the fluid inside the eye (angle-closure glaucoma) by disturbing the free flow of the fluid drainage.
The ophthalmologist will use a LASER beam to make a small hole in the iris of the eyes. This size of the hole is tiny and is covered by the eyelid making it invisible to the naked eye(unless seen with a microscope!)
Rarely this procedure may have some complications like IOP spikes, Laser-induced inflammation (Iritis), Double vision (Diplopia), bleeding, lens opacities, Injury to the cornea(transparent front part of the eye), and cataract(clouding of the lens).
Laser trabeculoplasty (LTP) is performed to treat the trabecular meshwork (TM) with a laser beam to improve the outflow facility. The laser is fired on the TM through a special contact lens. This unclogs the pores for the fluid drainage.
The trabecular meshwork is a part of the eye that works like a sieve for fluid drainage. Treating this part of the eye would help the fluid to exit freely. Argon laser trabeculoplasty and Selective laser trabeculoplasty are the two commonly practised techniques.
Trabeculectomy – Glaucoma filtering surgery
Trabeculectomy is a surgical procedure done to remove a part of your trabecular meshwork. This procedure is advised when the patient’s eyes are not responsive enough to the prescribed medications, leaving the IOP out of control.
The procedure is roughly 45-60 minutes long. The surgeon creates an opening on the eye, under the lid, to create a reservoir called “the bleb”. This drains the fluid from the eye. Once the procedure is complete, the surgeon will stitch the area to keep the flap” in place. The stitches will stay in place until the surgeon removes them during your post-surgery visit to the clinic. After the surgery, the doctor will prescribe some anti-inflammatory eye drops(corticosteroids) whose dosage will be reduced gradually.
Figure: Trabeculectomy procedure
Image courtesy: https://www.drsimonskalicky.com.au/glaucoma-specialist/trabeculectomy/
Last accessed on 10/3/2021
Glaucoma Tube shunt Surgery (Ahmed glaucoma valve)
This surgical procedure is done in advanced glaucoma cases where other treatment options are insufficient. It consists of installing a small silicone device to allow free flow of the fluid inside the eye. The device consists of a small tube and a reservoir, both made of a biocompatible material, silicone and is not visible from outside to others. This tiny device drains the fluid outside the eye, reducing the workload of the eye’s internal drainage system.
1. Apply drops regularly
The golden key to good management of glaucoma is to apply the drops regularly as advised. Glaucoma medications need to be used every day and at the time suggested by your doctor.
Try to coordinate the time of applying drops with other activities in your daily routine like before/after eating your meals, waking up and bedtime. Set reminders on your phone if you find it challenging to remember to take them. Keeping the drops at a visible place you frequent could also help you regularly use them.
2. Get your follow-up examination done regularly – IOP and field examination!
As glaucoma is a slowly progressive disease without any significant symptoms, the only way to keep track of the condition is regular follow-ups. Timely follow-up comprehensive eye examinations and tests( Visual field tests and OCT) as advised are crucial to maintaining the eye’s health.
It is best advised to schedule your next appointment before you exit your doctor’s clinic
3. Time interval between the drops
If you are prescribed more than one drop, you must maintain a 5 minute time difference between the two drugs. This time interval will help to prevent the effect of one drop being washed away by the immediate use of the other eye drop. This exercise will help you get the maximum effect out of your multiple eye drops.
4. Punctal occlusion and gentle eyelid closure to prevent systemic side effects.
Some eye drops tend to cause side effects in the other parts of the body. These side effects can be controlled using the punctal occlusion technique. After applying the drops, close your eyes for 1-3 minutes and gently apply pressure to the bridge of your nose. This will help the drop to be retained on the eyes surface for a more extended period. It also increases the availability of the drug to the maximum.
5. Changing medications
Let’s face it. Some glaucoma drugs may not be suitable for you. In case you develop side effects like redness, tendency to fall asleep, irritation, etc., please report it to your ophthalmologist. Your ophthalmologist will change the drug to your convenience. Even in cases where the eye drops are too expensive, inconvenient to use, or simply not available in your area, please share them with your doctor. Your ophthalmologist could help you in such situations by changing the medications.
Glaucoma is a life-long disease but can be controlled with a few lifestyle changes. Keeping eye pressure in control is the most important part of glaucoma treatment.
There are several drugs and surgical procedures to manage the condition. Suppose you are suspected of having the condition. In that case, it is best to get a complete eye examination once every six months. Otherwise, it is sufficient to get yourself tested once a year.
Do not panic. With regular treatment and follow-ups, you can win the battle against this silent killer of vision!
Further reading :
1. Smartsight by American Academy of Ophthalmology.