Glaucoma is an eye condition which affects the ability of the eye to send pictures to the brain, interfering with a person’s vision.
Glaucoma is not a simple eye disease. Glaucoma is the name given to a group of eye diseases in which the optic nerve at the back of the eye is slowly destroyed. Glaucoma is an eye disease that involves damage to the optic nerve, which sends visual signals to the brain. No one knows exactly what causes this damage, but pressure building up in the eye is proven to be one of the major risk factors associated with glaucoma. When the optic nerve gets damaged by increased pressure inside the eye, some signals from the eye aren’t transmitted to the brain. This can result in visual field loss, and if not managed, could eventually lead to blindness. This high intraocular pressure (IOP) is a result of blockage of the circulation of aqueous, or its drainage. In other patients the damage may be caused by poor blood supply to the vital optic nerve fibres, a weakness in the structure of the nerve, and/or a problem in the health of the nerve fibres themselves.
Why common is so important to detect glaucoma?
Glaucoma affects around 70 million people worldwide and is the second biggest cause of blindness, having taken the sight of over 6 million people.
There is no cure for glaucoma, but treatments are available which can help lessen the deterioration of sight. Usually there are in form of eye drops which can help lower pressure in the eye.
Glaucoma can affect people of any age and has a high prevalence globally. At least half of glaucoma patients are undiagnosed yet early diagnosis and treatment will help reduce progression of the eye condition.
What are the symptoms of glaucoma?
Chronic (primary open-angle) glaucoma is the most common type. It has no symptoms until eye sight is lost at a later stage.
Damage progresses very slowly and destroys vision gradually, starting with the side vision. Patient with cronic open angle glaucoma may experience a gradual narrowing of their peripheral vision, which many call “tunnel vision”, or areas of vision loss. One eye covers for the other, and the person remains unaware of any problem until a majority of nerve fibres have been damaged, and a large part of vision has been destroyed. This damage is irreversible. It is progressive and usually relentless. Treatment cannot recover what has been lost. But it can arrest, or at least, slow down the damage process. That is why it is so important to detect the problem as early as possible, to be able to start treatment with as little damage to the vision as possible. This damage is permanent but if detected early, further damage can be minimised.
Who is at risk?
Although anyone can get glaucoma, some people have a higher risk. Could you be one of those people? Only your doctor can help you find out, but some people are at greater risk than others. Studies have proven that anyone who meets one or more of the following criteria is at increased risk:
- Over the age of 40
- A family history of glaucoma
- African, Asian or Hispanic descent
- Short sightedness (myopia)
- Long sightedness (hyperopia)
- Eye injuries
- Blood pressure
- Past or present use of cortisone drugs (steroids)
People in these groups should have their first eye check no later than the age of 35. For most people, it is recommended to have an eye check for glaucoma by the age of 40. If no signs of glaucoma are not detected at the first visit, t is important to continue follow up with a complete eye examination every 2 years if you fall into any of these groups.
What are some of the forms of glaucoma?
The most common is called open-angle glaucoma, which accounts for about 80% of all cases. However, other forms occur:
- Low-tension or normal tension glaucoma. Occasionally optic nerve damage can occur in people with so-called normal eye pressure. This form of glaucoma is treated in the same manner as open-angle glaucoma.
- Acute (angle-closure) glaucoma. Acute glaucoma is when the pressure inside the eye rapidly increases due to the iris blocking the drain. An attack of acute glaucoma is often severe. People suffer pain, nausea, blurred vision and redness of the eye. Immediate medical help should be sought. If treatment is delayed there can be permanent visual damage in a very short time. Usually, laser surgery performed promptly can clear the blockage and protect against visual impairment.
- Congenital glaucoma. This is a rare form of glaucoma caused by an abnormal drainage system. It can exist at birth or develop later. Parents may note that the child is sensitive to light, has enlarged and cloudy eyes, and excessive watering. Surgery is usually needed.
- Secondary glaucomas. These glaucomas can develop as a result of other disorders of the eye such as injuries, cataracts, eye inflammation. The use of steroids (cortisone) has a tendency to raise eye pressure and therefore pressures should be checked frequently when steroids are used.
Why is IOP such an important clue?
The front of the eye is filled with a liquid called the aqueous humor. This is produced by the eye to bathe and nourish its different parts. The aqueous humor normally flows out of the eye through various paths and chambers. When these paths get clogged, aqueous humor gets trapped in the eye. This causes a pressure build up and leads to high IOP.
Doctors can easily measure IOP, and use it as an important clue in the diagnosis and treatment f glaucoma. Normal IOP is about 12 to 22 mm HG (millimetres of mercury, which is the unit to measure IOP). One of the most common and important tests for measuring IOP is tonometry. Tonometry is a procedure in which your doctor uses a tonometer to measure IOP. This test is important because high IOP is a major risk factor for glaucoma. However, high IOP doesn’t necessarily mean you will have glaucoma, nor does normal IOP mean you don’t have glaucoma. Controlling IOP is the major goal of glaucoma therapy. When IOP is controlled, the optic nerve is less at risk of being damaged, so vision may be preserved.
How can glaucoma be stopped?
It’s awfully hard to stop glaucoma completely, but we have years of research that shows that treating the disease early helps preserve vision. The primary effect of any glaucoma treatment is lowering IOP. This has been proven over the years to be an effective way to help prevent or slow down vision loss in glaucoma patients. IOP can be lowered with medication and/or surgery. IN most cases medication is used before surgery, which is often reserved for patients who haven’t responded adequately to or are intolerant of medications.
There are several different types of glaucoma medications. A few of them are highlighted here. Your eye doctor should prescribe the treatment that best fits your needs.
This is the newest class of antiglaucoma drugs. Prostalandin analogues were first introduced in the US in 1996. These drugs are usually prescribed when patients have trouble tolerating their current medication or when that medication is not working well enough. All work by increasing the flow of aqueous humor out of the eye, this lowering the IOP.
Prostaglandin analogues may gradually darken eye color by increase the amount of brown colouring in the iris. Although these changes can occur slowly, they may be permanent. They may also cause redness in the eye.
These drugs have been around to treat glaucoma for over two decades. The most commonly used beta blocker is timolol. The dosing of beta blockers ranges from once daily to twice daily. Beta blockers work by decreasing production of the aqueous humor, which lowers IOP. Some of the side effects include low blood pressure, slow heart rate, and general fatigue. If you have asthma, let your doctor know.
Brimonidine is the most common alpha agonist. It should be dosed teo times a day in the eye. Alpha agonists cause an increase outflow, as well as a decrease in production, of aqueous humor to lower IOP. Brimonidine can cause ocular allergic reactions and drowsiness.
Carbonic anhydrase inhibitors
Carbonic anhydrase inhibitors are available in oral formulations or eye drops like brinzolamide or dorzolamide. Dosing for these eye drops is three times a day. Carbonic anhydrase inhibitors lower IOP y decreasing the production of aqueous humor. The severe side effects, such as nausea and diarrhoea, common with the oral forms, are largely avoided with eye drops. The eye drops are fairly well tolerated, causing a minor ocular stinging or burning sensation.
Pilocarpine is the most common miotic. It has been around for decades, and is usually dosed in the eye three to four times a day. Miotics decrease IOP by increasing outflow of aqueous humor. Side effects include blurred vision, brow ache, and small pupil size.
Talk to your doctor before it’s too late
The best way to control glaucoma and preserve your vision is through early detection and treatment. Glaucoma is often referred to as “the sneak thief of sight” because it strikes without any obvious symptoms. Luckily, your doctor, who is a great detective, has tools to catch the early warning signs of glaucoma.
If you have one of the risk factors for glaucoma or are over age 40, you should schedule an exam with an eye care professional.
If our doctor determines that you have glaucoma, he or she may prescribe a treatment regimen. This will most likely include one or more medications to help lower IOP.
Using the glaucoma treatment your doctor prescribes to control your IOP should help preserve your eyesight.