Glaucoma is the diagnosis given to a group of ocular conditions that contribute to the loss of retinal nerve fibers with a corresponding loss of vision. Glaucoma therefore is a disease of the optic nerve, the nerve bundle which carries images from the eyes retina to the brain.
The eyeball is basically a rigid sphere filled with fluid. As the total amount of fluid within the eye increases, so does the pressure, similar to over inflating a tire. Many people know that glaucoma has something to do with increased pressure inside the eye. The higher the pressure inside the eye, the greater the chance of damage to the optic nerve. Glaucoma is said to be one of the leading causes of blindness in people over the age of 40. It affects approximately 2% of that population. Loss of peripheral (vision off to the side) is the earliest symptom. Left untreated the field of vision will continue to narrow leading to tunnel vision. If detected early, loss of vision can most often be prevented.
GLAUCOMA AND THE OPTIC NERVE
COLUMN 1- ARTIST DRAWING OF OPTIC NERVE HEAD
COLUMN 2- ACTUAL PHOTO OF OPTIC NERVE HEAD
COLUMN 3- EFFECTS ON PERIPHERAL VISION
The above photographs demonstrate various degrees of optic nerve head cupping caused by increased intraocular pressure.
Glaucoma is most common in people with a family history of the disease, and in nearsighted patients. Patients with systemic diseases such as diabetes, anemia, or hardening of the arteries are at a higher risk of developing glaucoma. African-Americans tend to develop glaucoma more often than other racial groups. A comprehensive eye examination from your eye care provider is required for diagnosis due to the fact, the eye will become severely damaged before visual loss is first noted. Early treatment is the best way to preserve vision once the diagnosis has been made.
What Causes Glaucoma?
(Image complements of anaesthesia.com)
The front portion of the eye is filled with a nourishing, protective fluid called aqueous humor. This transparent fluid is continuously circulated through the inner eye, flowing in and draining out, much like a sink with the faucet turned on all of the time. If the “drainpipe” gets clogged, water collects in the sink and pressure builds up. If the drainage area of the eye called the Trabecular Meshwork is blocked, the fluid pressure within the inner eye may increase, resulting is decreased blood supply to the eye’s optic nerve and damage. The optic nerve will no longer be able to transfer the information form the retina to the brain. This damage can result in partial or complete blindness.
Common Types of Glaucoma
Open Angle Glaucoma or Primary Open Angle glaucoma
The most common type of glaucoma, known as chronic open angle (COAG) or primary open angle, occurs when the canals draining the eye of aqueous humor become clogged. This blockage can gradually increases pressure within the eye to damaging levels. No pain occurs so individuals are usually unaware these changes are occurring. There are no early signs or symptoms but over the years vision will be lost starting in the periphery and moving toward the central vision (see above chart). With early treatment, you can often protect your eyes against serious vision loss and or blindness. Periodic eye examinations from your eye care provider are the best method for early detection of glaucoma. Over 90% of adult glaucoma patients have this type of glaucoma. This affects about 3 million Americans—half of whom don’t know they have it.
Closed Angle Glaucoma or Narrow Angle Glaucoma
When eye pressure builds up rapidly, it is called acute angle-closure glaucoma. This type of glaucoma commonly occurs in individuals who have narrow anterior chamber angles. In these cases, aqueous fluid behind the iris cannot pass through the pupil thus pushing the iris forward, preventing aqueous drainage through the angle. It is as though a sheet of paper floating near a drain suddenly drops over the opening and blocks the flow out of the sink. In cases of acute angle closure glaucoma, one may experience blurred vision, halos around lights, deep pain behind an eye, nausea, and vomiting. If you have any combination of these symptoms, call your eye care provider immediately. If pressure within the eye is not immediately relieved, blindness may result in a matter of days.
Glaucoma resulting from congenital, ocular or systemic conditions represent the Secondary glaucoma’s. The six most common forms of the disease:
- Exfoliation syndrome
- Pigmentary glaucoma
- Neovascular glaucoma
- Lens induced glaucoma
- Glaucoma accompanied by ocular inflammation
- Trauma induced glaucoma
Who Is at Risk For Glaucoma?
High pressure alone does not mean that you have glaucoma. Your eye care provider puts together many kinds of information to determine your risk for developing this disease. The most important risk factors include: Age, near-sightedness, African ancestry, a family history of glaucoma, past injuries to the eyes, or a history of severe anemia or shock. Your eye care provider will weight all of these factors before deciding whether you need treatment for glaucoma, or whether you should be monitored closely as a glaucoma suspect. This means your risk of developing glaucoma is higher than normal, and you need to have regular examinations to detect the early signs of damage to the optic nerve.
How is Glaucoma Treated?
As a rule, damage caused by glaucoma cannot be reversed. Therefore, the goal in the management of glaucoma is to reduce the intraocular pressure to the point whereby the remaining healthy nerve fibers are able to receive proper nourishment and therefore maintain function.
Glaucoma is usually controlled with eye drops taken several times a day (see: Proper eye drop insertion), sometimes in combination with pills. These medications are used to prevent damage to the optic nerve by decrease eye pressure, either by slowing the production of aqueous fluid within the eye or by improving the flow leaving the eye. Recently there have been a few brand new medications which show great promise for more effectively and
It is important to tell all of your doctors about the eye medications that you are using for glaucoma control. In order for these medications to work, you must take them regularly and continuously as they were prescribed. Quite simply, the key to the success of medication therapy is patient compliance.
Information on commonly used glaucoma medication:
- ALPHAGAN (Brimonidine)
- Azopt (Brinzolamide)
- Combigan (brimonidine tartrate.2% / Timolol Maleate)
- Cosopt (Dorzolamide .2% / Timolol Maleate)
- Iopidine (Apraclonidine)
- Lumigan (Bimatoprost)
- Rescula (Unoprostone)
- Travatan (travoprost)
- Trusopt (dorzolamide)
- XALATAN (latanoprost)
- Beta Blockers
- Timoptic XE (Timolol Maleate)
- Ocupress (Carteolol)
- Betoptic S (Betaxolol)
- Betaxon (Levobetaxolol)
- Betimol (Timolol Hemi-Hydrate)
- Betagan (Levobunolol)
- OptiPranolol (Metipranolol)
- Glaucoma Treatment During Pregnancy And Breastfeeding.
Laser treatment for glaucoma
If topical and/or oral therapy is not controlling the intraocular pressure (IOP), or if the patient is not taking their medicine according to schedule, laser surgery treatment may be an effective alternative or adjunct. The laser is usually used in one of two ways. In open-angle glaucoma, the laser is used to enlarge the drain (argon laser trabeculoplasty) to help control eye pressure. In angle-closure glaucoma, the laser creates a hole in the iris (iridotomy) to improve the flow of aqueous fluid to the drain.
|Laser treatment for Glaucoma|
|Laser Trabeculoplasty For open angle glaucoma|
|Laser Iridotomy for narrow angle glaucoma|
When operative surgery is needed to control glaucoma, your eye care provider creates a new drainage channel (bleb) through which the aqueous fluid can leave the eye, thereby lowering the IOP.
Fortunately, technology has improved significantly for both the medication and laser treatment alternatives in glaucoma, so that only a very few individuals need ever progress to the point of needing surgery. The key to a lot of these successes however, lie in prevention; specifically, the earlier that glaucoma can be diagnosed, the more effective the treatment through either medications or laser.
How Is Glaucoma Detected?
Most people think that they have glaucoma if the pressure in their eye is high, this is not always true.High pressure only puts you at risk for glaucoma. It may not mean that you have the disease. Whether or not you get glaucoma depends on the level of pressure that your optic nerve can tolerate without being damaged. This level is different for each person. Although normal pressure is usually between 12-21 mm Hg, a person might have glaucoma even if the pressure is in this range. That is why regular eye examinations are so important.
There are several tests which your eye care provider may perform to confirm a diagnosis of glaucoma.
Since a large percentage of glaucoma sufferers do indeed have elevated intraocular pressure, careful measurement of the eye pressure on a regular basis (for high risk people) is a crucial step in early detection. This pressure is measured using an instrument called a tonometer. This standard test determines the fluid pressure inside the eye. There are many types of tonometry. The most common type called application tonometry uses a blue light to measure pressure. Another type is the “air puff tonometer,” which measures the resistance of the eye to a puff of air to determine pressure.
The back of the eye can also be observed directly through an eye microscope or ophthalmoscope. This is to insure that the optic nerve is healthy.
HRT laser Scanning Ophthalmoscopy
During the past decade, major eye centers around the world have used scanning laser systems from Heidelberg Engineering for their research and clinical work.
For exact data in glaucoma research the Heidelberg Retina Tomograph has become the system of choice. In more than 150 peer-reviewed papers and hundreds of abstracts, study results have confirmed unsurpassed reproducibility and consistent longitudinal data. As a result, the highest diagnostic precision to differentiate between normal eyes and early glaucomatous eyes – even before any visual field defect has been confirmed.
Three-dimensional optic nerve head topography analysis by laser scanning tomography has been shown to be superior to all other imaging technologies. Because of its advantages, this technology is now generally accepted and used to provide the best service possible for glaucoma patients and patients at risk.
Heidelberg Engineering integrated the experience from more than one million exams, advice from hundreds of users, and research data from around the world. Adding the latest available technology in electronics, optics, and software the standard glaucoma detection system of the future has been created: the Heidelberg Retina Tomograph II.
The drainage angle of the eye is also inspected with a special type of “contact lens” (gonioscopy). This test is performed on patients who have glaucoma or when the disease is suspected. A special mirrored contact lens is used to allow the doctor to examine the angle, a drainage structures in the front of the eye. With this lens, the doctor can assess the eye’s drainage system.
This test measures your side (peripheral) vision. It helps youreye care professional find out if you have lost side vision, a early sign of glaucoma.
This examination provides your eye care professional with the best view of your optic nerve enabling damage to be spotted as early as possible. To do this, your eye care professional places drops into the eye to dilate (widen) the pupil. After the examination, your close-up vision may remain blurred for several hours.
Some of these tests may not be necessary for every person, and others may need to repeat these tests on a regular basis, to determine if glaucoma damage is increasing over time.
Treatment for glaucoma requires a “team” made up of both you and your doctor. Your eye care provider can prescribe treatment for glaucoma, but only you can make sure you take your eye drops or pills (see: Proper eye drop insertion). Never stop taking or change your medications without first consulting your eye care provider.
Periodic eye examinations and tests are critical to monitor your eyes for any changes because glaucoma can worsen without your being aware of it. Your eye care provider will schedule frequent short exams in which they will monitor the pressure within the eye. Remember, regular eye exams may help prevent unnecessary vision loss.