Glaucoma Information for Patients

Overview

  • What is glaucoma
  • What causes glaucoma
  • How is glaucoma diagnosed
  • How is glaucoma treated
  • Summary and final thoughts
  • Frequently asked questions

What is Glaucoma

Glaucoma is a characteristic optic neuropathy.

Optic neuropathy means a disease or damage of the opitc nerve.  The optic nerve is a cable composed of more than a million axons, or connections, that transmits the information from the eye to the parts of the brain that interpret visual information.  There are many diseases the affect the optic nerve and glaucoma is one of them.  There are several characteristics typically associated with glaucomatous optic neuropathy:


  • Characteristic optic nerve appearance (see photos below)
  • Association with long standing increase in intraocular pressure
  • Slow progressive and  irreversible damage to the optic nerve (many years)
  • Loss of peripheral vision initially followed by central vision and blindness
  • Association with certain risk factors, including age, race, and family history

Glaucoma is actually not a single disease entity.  There are many subtypes of glaucoma and they are all related because they have the same end point- damage to the optic nerve resulting in a characteristic appearance.  The above is a generalization of glaucoma and applies to the most common type of glaucoma- primary open angle glaucoma.  Some subtypes of glaucoma can progress quickly.  For example, when someone has an acute angle closure glaucoma, the rise in intraocular pressure can inrreversibly damage the optic nerve in hours to days.


Normal Optic Nerve

The apperance of the normal optic nerve by ophthalmosocopy.  The optic nerve is composed of 1.2 million axons, or nerve connections, betwee the eye and the brain.  The thick rim of nerve tissue around the central cup in this photo indicates no axons have been lost.  The pink-orange hue suggests the nerve is healthy.




Advanced Glaucomatous Optic Neuropathy

Notice the thinning of the rim of nerve tissue in this photo, indicating axons have been lost and damaged.  When this occurs, visual information in the form of nerve impulses cannot travel from your eye to your brain and loss of vision occurs.  This is a  case of advanced disease and not all glaucomatous optic nerves are easily and readily diagnosed based on the size of the rim (or the degree of cupping) alone.  There are many other subtle clues in early glaucoma, which your ophthalmologists look for during a dilated ophthalmic examination.


What Causes Glaucoma

There are many factors that contribute to glaucoma and we are finding out more about the disease as research is being conducted.  At the present time, intraocular pressure is the most important and the only modifiable risk factor.  The other factors that contribute to this disease and its progression are more theoretical in nature and we cannot alter them with the current medical technology.
  • Intraocular pressure- glaucoma has traditionally been associated with an increased intraocular pressure and this is the only risk factor that your doctors can alter in order to halt or slow the progression of the disease.
  • Blood flow-  the optic nerve is supplied by a rich network of blood vessels.  Blood vessels become damaged and less effective with diseases such as chronic high blood pressure and diabetes.  Optic nerve blood vessels are very small and it is not possible to open these vessels to improve flow as in blood vessels around the heart.  Poor circulation likely makes the optic nerves more susceptible to damage from increased intraocular pressure and other factors.
  • Neurogenic factor- all nerves in our body are believed to need neurogenic factors- small signal molecules from surrounding nerves and support tissues- to function and survive.  Stress to the optic nerve such as from increased pressure and poor circulation may decrease the amount of neurogenic factors reaching the optic nerve and contribute to disease progression.
  • Mechanical support- the optic nerve is support by a porous bony plate called the cribiform plate.  Over time, this structure weakens and is believed to physically damage the nerve or decrease the amount of blood or neurogenic factors that flow through the plate.
It is impossible to really say exactly what causes glaucoma- there are many contributing factors and further study and understanding of the disease are needed.

How is Glaucoma Diagnosed

Glaucoma is best diagnosed by your eye care professional with a complete ophthalmic examination.  This includes a dilated fundus examination which allows your doctor to obtain a stereoscopic view of the optic nerves in your eyes.  This stereoscopic examination of the optic nerves is crucial in the detection of the characteristic appearance of the nerves in its earliest stages of glaucomatous damage. 

Sometimes your doctor may also order a visual field test (a test for side or peripheral vision).  Early glaucoma produces damages to side vision that is not noticeable to the patient because the side vision in our two eyes overlap and complement each other.  The visual field test allows your doctors to detect this early damage to your side vision.  The ophthalmic examination and the visual field test complement each other.  Sometimes damage is first detected through the exam and sometimes it is first detected through the visual field.

There are several other tests that one may order in addition to the ophthalmic exam and the visual field.  These tests are supplemental in nature and whether your doctor performs these tests are strictly based on his or her clinical preference.

How is Glaucoma Treated

At the present time, the only modifiable risk factor is intraocular pressure and if you are diagnosed with glaucoma, it is likely your doctor will suggest one of several ways to lower you intraocular pressure.  Again, this is a generalization of the disease.  Depending on the subtype of glaucoma you have, a different treatment maybe required.  For example, if someone has narrow angle, a laser treatment maybe required to prevent acute angle closure.  In neovascular glaucoma where diabetic eye disease has caused the drain of the eye to be closed by blood vessels and scar tissue, surgery is most likely required along with laser treatment of the retina.

There are three ways to lower the intraocular pressure:

  • Medicine- several classes of medications are available to lower eye pressure.  Eye drops are most commonly employed.  Medications by mouth are also available but are not typically used on a long-term basis.
  • Laser- laser treatment can allow the natural drain of your eye to work better and lower the intraocular pressure.
  • Surgery- a cutting surgery typically involves making an accessory drain to your eye because the natural drain is not working well enough to allow the fluid inside your eyes to egress.

Typically meidinces and lasers are offered first prior to deciding whether surgery is needed.

Perhapss more important than the technical aspects of glaucoma management are the characteristics of the disease that you need to understand in order to facilitate proper follow-up and compliance with treatment.  Here are the important points for you to understand:

  • Glaucoma is a slow and progressive disease.  Follow-up with the same physician is very important to ensure that your disease is being monitored and treatment is escalated if progression occurs.  If you need to move, make sure you obtain records or ask for a dictated summary letter for your new doctor.  Information such as your highest intraocular pressure, what surgeries you have had, and serial visual fields are all important pieces of information that will help your physician take the best care of you.
  • Glaucoma is asymptomatic in its earliest stages but it is a potentially devastating and blinding disease.  The disease course is very similar to other serious systemic conditions such as high blood pressure and diabetes.  People are often not compliant with their diabetes and high blood pressure medications early on because they don't feel like they have any problems.  However, once they notice they have advanced disease, it is often too late to control the diseases well  because vitals organs such as the kidneys have been damaged and heart failure has already started.  Compliance is a big issue in glaucoma and research shows a large percentage of patients and doctors do not address the issue adequately. By the time you can tell you have central visual loss from glaucoma, you already have advanced disease.  The ideal outcome of glaucoma is to detect it early and to stop it from ever reaching its advanced stages.  In its early stages, patients are functionally normal- this means that although we can detect glaucoma on examination and visual field tests, you do not suffer any limitations from your condition. 
  • Glaucomatous optic nerve damage is not reversible.  Nervous tissues do not regenerate and optic nerve damage cannot be reserved with the current available technology.  One more important reason for you to be vigilant about your compliance and follow-up.

  • Summary and Final Thoughts

    • Glaucoma is a term used to describe a family of diseases that cause optic nerve damage with certain characteristic appearances.  It is a chronic disease that is slowly progressive and asymptomatic in its early stages.  Your job as a patient to manage glaucoma is to understand the above characteristics of the disease- this will ensure appropriate compliance with prescribed treatment and continued follow-up with your physician.  This in turn will halt glaucoma in its early stages where patients are not functionally impaired.


    More research is needed to better understand glaucoma and to hopefully derive better means of diagnosis and treatment for this condition.  This is important because glaucoma currently ranks as the second cause of blindness and visual impairment in the United States.  If you are able to do so, donations to your local glaucoma research fund or academic institution will allow physicians and researchers to advance their knowledge and your generosity will be much appreciated. 

    Frequently Asked Questions

    My parents have glaucoma, what should I do?
    You should have a complete ophthalmic exam, including a dilated fundus exam.  Primary open angle glaucoma is not typical before the age of 40 but it doesn't hurt to have a screening exam a little earlier, especially if you have a strong family history and/or if you are worried about having the condition.

    Can I have my optic nerve checked by my primary care physician?
    You primary care physician can examine your optic nerve with the direct ophthalmoscope.  While this exam is useful in many ways, it is not an adequate exam to screen for glaucoma.

    What is the normal eye pressure?  Why is my doctor not worried that my pressure is elevated?
    Normal eye pressure based on population average is about 16 with a range of 10-21 (2 standard deviations from the mean).  However, glaucoma is defined by a characteristic damage to the optic nerve and NOT an increase in intraocular pressure.  Therefore, intraocular pressure must be interpreted in the context of each individual patient.  Someone who has increased intraocular pressure without optic nerve damage has ocular hypertension. 

    My husband and I both have glaucoma.  Why is my doctor not worried about my intraocular pressure of 18 but he wants to perform surgery on my husband who has a pressure of 14?
    A term you may hear from your doctor is damaging pressure- it is the pressure that causes damage to your optic nerve.  Damaging pressure differs in different patients and treatment for glaucoma must be individualized.  For example, if you started with a pressure of 35 and it is now lowered to 18 and no further damage has occurred, your damaging pressure is >18 and your current therapy is adequate.  However, if your husband has a pressure of 14 and has progressive changes on his visual field, then the current therapy is not sufficient and needs to be escalated.

    Can the eye drops I take have side effects?
    Yes, the eye drops can have both local (i.e. eye irritation) and systemic (i.e. decreased heart rate) side effects.  You should discuss the specific side effects of each medication with your doctor.

    Additional FAQ will be added- please leave your questions in the guestbook.  Only general questions that maybe beneficial to other readers wil be posted.  Please direct your personal questions to your eye care professional.