Annie is a 50-year-old homemaker who wears reading glasses. She has no other problems with her eyes but she decides to go to the ophthalmologist (eye doctor) to check if her reading glasses are still the appropriate grade. She is shocked when the doctor tells her that she has glaucoma because her eye pressure is elevated and her optic nerves show signs of damage.
Glaucoma is the general term used for a large group of diseases that all result in progressive damage to the optic nerve. The optic nerve is the major nerve connecting the eye to the brain. Think of it as being like the power cord for your TV. The optic nerve progressively changes in appearance and progressively loses function as it slowly damaged by glaucoma. Damage to the nerve prevents the images received by the eye from reaching the brain in the same way that a TV with a damaged power cord will have no picture. If left untreated, glaucoma can lead to partial or complete blindness.
There are approximately one million nerve fibers in the eye that conduct light signals from the outside world. These nerve fibers come together to from the optic nerve which then connects to the brain. In glaucoma the number of living, functioning nerve fibers decreases at a rate much faster than would occur through the normal aging process. The death of these nerve fibers may be due to increased eye pressure (intraocular pressure or IOP), lack of blood flow, another mechanism not yet discovered, or a combination of mechanisms. When the nerve fibers die they leave an empty space where they used to be. If enough nerve fibers die the empty space on the optic disc becomes noticeable to the ophthalmologist examining the patient.
The exact biochemical and cellular mechanisms for the development of damage to the optic nerve are still being researched. Two of the main theories are: 1) increased intraocular pressure (pressure inside the eye) causing direct compression of the optic nerve or compressing the nerve’s blood supply and 2) blood vessel abnormalities causing decreased blood flow to the optic nerve.
Annie wonders how she can have glaucoma when her distance vision is perfect, her near vision is fine as long as she uses reading glasses, and her eyes feel normal. In most cases of glaucoma there are no symptoms. Because the optic nerve damage occurs slowly over a long period of time the visual loss develops very gradually and most patients don’t notice that they have already lost quite a lot of their peripheral vision. Some very observant patients may notice blind spots in their visual field or they may find that they have difficultly tracking small, fast moving objects such as golf or tennis balls. It is only in the very late stage of the disease that central vision becomes blurred. The eye pressure elevation can also occur very gradually or the pressure may not rise much so most patients don’t realize that they have elevated eye pressure. Because there are usually no symptoms, the only way for glaucoma to be discovered in these cases is if people have their eyes examined regularly by their eye doctor.
In some cases of a particular type of glaucoma called angle closure glaucoma, the intraocular pressure can rise very suddenly in one eye causing sudden blurred vision, eye redness, eye pain, headache on the side of the affected eye, seeing rainbows around lights (iridescent vision) and nausea or vomiting. If this happens, immediate consult with an eye doctor is warranted because delayed treatment is likely to produce a worse outcome.
In response to her doctor’s questions Annie recalled that her maternal grandmother had very poor vision in her old age and that it might have been due to glaucoma. Having a family member with glaucoma is one of the many risk factors for glaucoma that have been identified. Persons with one or more of these risk factors are more likely to develop the disease than those who have no risk factors. The major risk factors are older age, race (different types of glaucoma are more prevalent in different ethnic groups), a family history of glaucoma, and increased intraocular pressure. Other risk factors include some medical conditions especially those affecting the blood vessels such as diabetes, hypertension, and migraine headaches; certain eye conditions such as extreme myopia (near-sightedness) or hyperopia (far-sightedness) and previous eye trauma; and prolonged use of steroids whether as eye drops, tablets, nasal spray or inhaled. Smoking has also been implicated a risk factor for glaucoma (and other serious eye diseases as well) due to its deleterious effects on the circulation.
It would be prudent for people with one or more of the risk factors mentioned to have their eyes checked by an ophthalmologist. People with glaucoma should ask their eye doctor if they should have their children and other close blood relatives checked and at what age they should get checked.
Testing for Glaucoma
Annie’s doctor asked her to perform a visual field test, also called perimetry. It showed that there were some blind spots in the visual field of her right eye. Glaucoma usually affects the peripheral vision first. Our field of vision is made up of everything that we can see. The field of vision can be divided into central vision and peripheral vision. Central vision is what is seen in the area where the eyes are focused. Peripheral vision is what is seen to the right, left, above and below the area where the eyes are focused.
Various machines and methods can be used to test the visual field. The most common method involves asking the patient to look at a central target while flashes of light or other visual stimuli are projected all around the central target. The patient is asked to press a button whenever a stimulus is seen. The machine then records and analyzes the stimuli seen and not seen and the result is sent to the eye doctor for interpretation. The test is not painful or uncomfortable but it can be tiring or stressful due to the intense concentration required. Patients should try to get a good night’s sleep the night before the test. The test can take from 2 to 20 minutes for each eye depending on the machine, the test program used, and how quickly a particular patient responds.
The visual field test of Annie’s left eye did not show any abnormal blind spots. She recalled that her doctor had said that both of her optic nerves showed signs of damage and both of her eyes had high pressures. Her doctor explained that when an optic nerve is not too damaged is possible that the damage is not enough to be detected by visual field testing.
Annie’s doctor also asked her to have her optic nerves photographed. Because the optic nerve changes in appearance over time in patients with glaucoma, eye doctors often request for optic disc photographs or optic disc imaging tests. These tests enable the ophthalmologist to compare the patient’s disc appearance at every check-up with the baseline photos and/or imaging results taken during an earlier visit. Having a basis for comparison makes it easier to detect change.
Depending on the camera or machine to be used the patient’s pupils may need to be dilated using eye drops. If dilating drops are used there may be some discomfort due to excessive glare for several hours after the drops have been instilled. The patient’s cooperation is required during optic disc photography and imaging. The patient needs to focus on a particular spot and to avoid blinking when asked to keep his/her eyes open.
Increased eye pressure (intraocular pressure or IOP) is one of the major risk factors for glaucoma. There is a normal, healthy range of IOP that is needed to maintain the health and integrity of the eyeball and the structures inside it. The normal level of IOP varies from person to person. Too high or too low a pressure is detrimental to the health of the eye.
Fluid circulates inside the front part of the eye (anterior chamber) in order to nourish certain structures and to wash away toxins. This fluid is constantly being produced by the ciliary body and it is constantly being drained by the trabecular meshwork. The trabecular meshwork is a sieve-like structure located in anterior chamber angle. If the trabecular meshwork malfunctions or becomes blocked this can cause elevation of IOP because fluid production continues as usual despite the blockage or malfunction. There are two main types of glaucoma based on the status of the anterior chamber angle: open angle glaucoma and angle closure glaucoma. If fluid can reach the sieve-like trabecular meshwork but the fluid cannot pass through due to a malfunction that is called open angle glaucoma. If the fluid cannot even reach to the trabecular meshwork because the anterior chamber angle is obstructed by the iris, the colored part of the eye, that is called angle closure glaucoma.
The optic nerve damage can be caused by or can progress due to elevated intraocular pressure (IOP). The definition of “high” IOP can be relative or absolute. The statistically “normal” IOP is 16.5 mmHg (millimeters of mercury) with pressures above 20 mmHg considered statistically “elevated”. These values were obtained by averaging the IOPs of thousands of normal individuals who had a wide range of pressures (from 10 to 35mmHg). If a person with a usual IOP of 9 mmHg was found to have an IOP of 19 mmHg that would be a significant elevation even though it’s still a statistically normal IOP. That is an IOP that is increased relative to the person’s normal IOP but is still normal compared to the rest of the population. On the other hand, an IOP of 37mmHg is definitely abnormal (absolute increase). Ophthalmologists always keep this in mind when making the diagnosis of glaucoma and when deciding how to lower a particular patient’s IOP.
The actual level of IOP is not the only aspect of IOP that matters in glaucoma. Intraocular pressure normally fluctuates throughout the day. Glaucoma patients tend to have a larger daily fluctuation in their IOP (the difference between highest IOP and lowest IOP). This is called the diurnal variation. The IOP taken at the doctor’s office is the measurement for that specific moment only and does not necessarily indicate what the IOP levels have been the rest of the day and during the night. Glaucoma patients or glaucoma suspects are sometimes asked to have several IOP measurements taken in a single day in a procedure called phasing or diurnals.
Intraocular pressure is not the only risk factor for glaucoma but it is the one that ophthalmologists and glaucoma patients tend to obsess about. This is because IOP is still the only risk factor that we are able to manipulate. There are many drugs and treatments available that can lower IOP but there are still no treatments that can reverse or decrease the effects of aging or that can change a person’s genetic make-up. Research evidence has shown that lowering intraocular pressure and decreasing intraocular pressure fluctuation are effective for preventing glaucoma progression in most patients.
A workup for glaucoma includes checking the eye pressures, looking at the optic nerves, and looking at the anterior chamber angle inside the eye. Eye drops may be needed to dilate the patient’s pupils to get a better look at the optic nerves. If the eye doctor has any suspicions of glaucoma, diagnostic tests like those previously discussed might be requested. The diagnosis of glaucoma is made by analyzing the results of all of the eye examinations and tests together. Eye pressure measurements alone are not enough to detect, diagnose, or rule out the possibility of glaucoma. Unlike other diseases (e.g. diabetes) there is no single test (e.g. blood glucose test) that can definitely diagnose glaucoma.
After her visit to her doctor Annie became more informed about glaucoma. She advised her older brother and older sister to visit their ophthalmologists, to inform their doctors of their family history of glaucoma, and to have themselves screened for glaucoma. Her brother’s doctor found that he had slightly suspicious looking optic nerves, normal eye pressures, and open anterior chamber angles. His doctor diagnosed him as being a glaucoma suspect. Her sister’s doctor found that she had normal-looking optic nerves and eye pressures a bit on the high side. Her doctor initially diagnosed her as having ocular hypertension.
A primary open angle glaucoma (POAG) suspect is someone who has abnormal or borderline findings in some of the examinations or tests but has normal findings in other examinations. Like Annie’s brother, a person might have suspicious-looking optic discs but have a normal visual field test, open anterior chamber angles and an intraocular pressure within the normal range. Primary open angle glaucoma suspects fall within a spectrum ranging from low risk suspects to high risk suspects depending on the examination and test results and on the presence of risk factors in the patient’s medical and family history. Sometimes, an ophthalmologist may decide to begin treatment of a high risk suspect if the doctor thinks it’s highly likely that that person already has early glaucoma or will soon develop glaucoma.
Ocular hypertension is the condition where the intraocular pressure (IOP) is above the normal range but there are no other signs of glaucoma. This condition is usually found on routine check-up or when the person consults an ophthalmologist for an unrelated complaint. An ocular hypertensive can be considered an open angle glaucoma suspect. A recent large, randomized, controlled, study of ocular hypertensives found that approximately 10% of them developed open angle glaucoma in the next 5 years.
Ocular hypertensive individuals can be grouped into two categories: 1) those who simply have IOPs that are greater than the average for the population but which IOPs are normal for their eyes, and 2) those who have early open angle glaucoma but have not yet developed any obvious optic nerve or visual field changes. Because it is sometimes difficult to tell which category an ocular hypertensive belongs in, that person needs to be monitored regularly. Some ocular hypertensives have a higher risk of developing or having glaucoma than other ocular hypertensives so ophthalmologists may sometimes decide to treat high-risk ocular hypertensives even before any signs of glaucoma are detected. Moderate and low risk ocular hypertensives are usually just observed.
Annie’s sister’s doctor initially thought that she had ocular hypertension. However, when the doctor examined her anterior chamber angles he found that they were very narrow with her irises touching her trabecular meshwork in some places. So his diagnosis of Annie’s sister was changed to primary angle closure suspect.
A primary angle closure suspect is someone with a narrow anterior chamber angle. The iris is in a position where it could easily close off the anterior chamber angle. This person has no symptoms of angle closure and the risky iris position is only found on routine check-up or when the person consults an ophthalmologist for an unrelated complaint. The likelihood of angle occlusion varies. The ophthalmologist can simply observe the low-risk suspect or may decide to perform prophylactic laser treatment (laser iridotomy and/or iridoplasty) on a high-risk suspect.
There is no cure for glaucoma. The goal of treatment of glaucoma is to stop the disease from progressing any further than it already has at the time it was diagnosed. At present, the only proven method to prevent glaucoma progression is to lower the intraocular pressure (IOP) and/or prevent the IOP from rising.
Annie’s doctor advised her to use a medicated eye drop once a day. Eye drops are the most commonly used method of lowering IOP in glaucoma patients. Sometimes more than one type of eye drop may be needed. There are many different IOP-lowering eye drops available. Different cases of glaucoma need different eye drops. The patient’s ophthalmologist will choose the most appropriate one/s for that particular patient. Using eye drops rather than oral medications has the advantages of ease of use, fewer systemic side effects, and improved efficacy because the drug is delivered directly where it is needed.
Different eye drops each have different side effects. Some of these side effects affect only the area where they were placed (e.g. transient stinging after instillation of the drops). Other side effects are systemic, meaning they affect other parts of the body (e.g. slower heart rate). Always ask your doctor what side effects tend to occur when using the particular medication (not only eye drops) that has been prescribed to you. Preventing systemic side effects of glaucoma eye drops can be as simple as closing the eyes and pressing on the tear ducts for five minutes after instilling the eye drops. This will help keep the drops in the eyes where they are needed the most and keep the drops from flowing down the tear ducts to the nose where they can easily be absorbed into the bloodstream.
Different eye drops have different dosing regimens. Some drops are used only once a day while others need to be placed twice a day or more often. Placing the drops more frequently than prescribed will not improve the efficacy of the drug and will only increase the chances of a side effect or a bad reaction to the drug.
It is important that the eye drops go where they belong – in the eye, not on the eyelid, eyelashes, or cheek. Learning the proper technique of instilling eye drops is very important.
Continuity of treatment is extremely important. Glaucoma eye drops do not have a lasting effect, they only work while they are being used. Missing even just one dose can sometimes cause a sudden elevation of IOP that could be harmful especially in those with advanced glaucoma. The following are some tips to avoid missing a dose:
1. The use of eye drops can be linked with an activity that is performed every day at approximately the same time. For example, if a glaucoma patient takes a shower every morning at around the same time then that person could make it their habit to place the drops after every morning shower.
2. Many modern conveniences are available that can help a person remember when it’s time to use their eye drops (e.g. mobile phone’s alarm feature).
3. Buy the next bottle of eye drops before the current bottle runs out.
Some glaucoma eye drops lose their effectiveness after they have been used for several years. When this happens, a change of medications or a different type of treatment method may be needed.
Oral medication for glaucoma is rarely used due to the many unpleasant systemic side effects that can occur. It can be used for short term treatment or in special cases.
Current eye drug research is focusing on ways to improve the delivery of existing drugs to the eye (e.g. using eye medication once a month rather than daily) and looking for new drugs that can lower IOP, prevent damage, or make the optic nerve more resistant to damage better than the current drugs available.
Laser treatment can be used as the sole initial treatment in some cases of glaucoma, in combination with medical or surgical treatment, or it can be added after initial medical or surgical treatment. There are several different laser procedures for different types of glaucoma and the goals of the procedures vary depending on the type of glaucoma being treated.
Laser trabeculoplasty is performed on eyes with open angles. The goal of the procedure is to lower the intraocular pressure by stimulating the malfunctioning trabecular meshwork to improve its drainage of fluid. This procedure can lower intraocular pressure as much as some eye drops but it gradually loses its effect and may need to be repeated after a few years.
Laser iridotomy is performed on eyes that have narrow or partially closed angles. The goal of the procedure is to create a more direct route of intraocular fluid flow from behind the iris where it is produced to the anterior chamber angle. Once the fluid can easily flow into the anterior chamber, the fluid no longer has enough pressure to push the iris forward. So it helps the iris lie flat and keeps the iris from blocking the anterior chamber angle. If successful, this prevents intraocular pressure from rising suddenly or gradually.
Glaucoma surgery can be used as the initial treatment in some cases of glaucoma or it can be used after medical and/or laser treatment has turned out to be ineffective or inadequate. The various types of glaucoma surgical procedures all aim to lower intraocular pressure (IOP) by creating an alternative pathway for fluid drainage out of the eye.
Trabeculectomy is the most commonly performed glaucoma surgery. It can be done for practically all types of glaucoma, adult or pediatric, open angle or angle closure, primary or secondary. When a trabeculectomy is performed a tunnel-like pathway is created out of the eye’s own tissue. The new drainage pathway starts in the anterior chamber and ends under the conjunctiva, the transparent “skin” covering the sclera which is the white of the eye. The fluid collects in a pocket called a bleb. The fluid can now exit the anterior chamber, bypassing the diseased or blocked anterior chamber angle, and be absorbed from the bleb.
If successful, trabeculectomy provides superior IOP control that is rarely achieved by medications or laser. Improved IOP control means a lower and more stable IOP with fewer fluctuations. Improved IOP control means more effective prevention of further optic nerve damage. Usually, IOP-lowering medications are no longer needed or fewer medications are needed after the surgery.
The common complications of trabeculectomy are early failure and late failure. When this happens the IOP again becomes elevated. Other complications include development of a cataract or accelerated progression of an existing cataract, excessive fluid flow out of the eye (an extremely low IOP can be just as unsafe as a high IOP), and late infection of bleb. As with surgery in any other part of the body, surgical infection or severe bleeding during the surgery can also occur.
Trabeculectomy may be combined with cataract surgery for glaucoma patients who also have a significant cataract at the time of surgery.
Persons with glaucoma need to have checkups for the rest of their lives. Glaucoma suspects also need to have regular checkups to see if they have progressed from being a glaucoma suspect to actually having glaucoma.
Glaucoma is one of the leading causes of preventable, irreversible blindness in the world. In 2000, an estimated 90.8 million people worldwide were affected with glaucoma. According to the Third Philippine National Survey of Blindness it is the third leading cause of bilateral blindness, behind cataract and error of refraction, and is the leading cause of irreversible bilateral blindness in the Philippines (cataract and error of refraction are reversible types of blindness).
The economic impact of glaucoma is not simply the cost of medications and other treatments. There are many indirect costs such as the cost of transportation to and from clinic visits, the number of hours of work missed by the patient and the patient’s companion. Sometimes, for patients who have severe vision loss and are no longer able to work, two sources of income are lost: the patient’s income and the income of the person who stays home to take care of the patient. When multiplied by the number of persons with glaucoma all over the world the monetary cost of glaucoma is staggering.
Glaucoma cannot be cured but it can be controlled. Successful control of glaucoma can prevent further damage to the optic nerve and further loss of vision but it cannot restore lost vision.
Only a small percentage of treated glaucoma sufferers become completely blind especially those who are treated. Majority of glaucoma sufferers keep at least some vision throughout their lives although they may have blind spots (scotomas) in their peripheral vision.
Studies have shown that early detection and treatment of glaucoma, before it causes major vision loss, is the best way to control the disease. People with any of the risk factors of glaucoma should make sure they have their eyes examined periodically by an eye doctor.
In a way, Annie was lucky that she had a check-up when she did. If she had not gone for a check-up, her glaucoma might have been discovered much later when there was already advanced damage to her optic nerves. She wished that she had gone to the ophthalmologist several years earlier but at least she can ensure that her family members at risk have a better chance of having their glaucoma discovered much earlier or even prevented.
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