Glaucoma

Glaucoma is a group of diseases that damage the optic nerve resulting in loss of vision or even blindness, often (but certainly not always) accompanied by an increase in intra-ocular pressure.

Glaucoma is the second leading cause of blindness in the world, affecting an estimated 65 million people worldwide. The disease is usually painless, and (like diabetic retinopathy, see the Diabetes page) often very advanced before the patient starts to notice changes in their vision. This is one reason we stress the importance of annual eye exams.

Anyone can develop glaucoma, but primary risk factors include:

• Race. Glaucoma is up to 8 times more common in the African American population than in Caucasians, and is the leading cause of blindness among this group.
• Age. Definitely more common after age 60, especially in the Hispanic population.
• Family History. 7% more risk if a family member has the disease, jumping to near 15% if that family member is a sibling.
• Steroid Users. This includes prescribed steroids for diseases like arthritis or asthma.
• History of Ocular Trauma.
• History of hypertension and/or diabetes.
• High myopia (nearsightedness).

There are basically four things we look at to determine the presence or absence of glaucoma:

1. Intra-ocular Pressure (IOP) – we do not weight IOP as heavily as we used to; we have learned that some patients will have an IOP within the expected range of normal, yet still have the disease (and we still are not certain why the optic nerve is being damaged in the presence of a normal pressure). This is called normal tension glaucoma – and is usually more difficult to treat, since most treatments focus upon lowering the pressure.
2. Optic Nerve Appearance – The optic nerve looks a bit like a donut where it enters the back of the eye. The outer circumference of the donut encapsulates the optic disk; the hole in the donut is called the optic cup. What we generally see as glaucoma progresses is an enlarging of the donut hole. So, patients with the disease often have a larger-than-average optic cup or perhaps a different cup size in one eye versus the other.
3. The Visual Field maps out each eye’s field of view, from extreme periphery in to center. There are very typical losses we will see in early glaucoma as opposed to a normal field – usually losses from the outside going in. This test is still considered critical to determine if the disease is present, and is quite simple and painless to administer.
4. The OCT takes a laser-scan at and adjacent to the optic nerve, analyzing the nerve fiber layer (NFL) thickness around the nerve.  It compares the patient’s NFL thickness to both age- and sex-matched norms and gives the doctor a color-coded analysis.  Significant thinning of that layer is usually indicative of the presence of the disease.

There are two main types of the disease: primary open angle glaucoma (POAG) and angle closure glaucoma. In the healthy eye, fluid moves through the pupil and drains from the eye in the angle formed between the iris and cornea.

1. In POAG (the most common type), the angle is not physically blocked, but the drainage canals that begin there are “clogged” deeper along their course, usually raising the pressure in the eye. This form progresses more slowly, causes a gradual loss of vision, and responds well to medication.
2. Angle closure glaucoma (or narrow angle glaucoma) is much rarer and is considered a medical emergency – the pressure rises quickly and significantly, and ocular pain and nausea accompany halos and blurred vision, and usually an angry red eye. This situation is caused by the pupil dilating slightly and the iris edges “bunching up” and blocking the angle.

Glaucoma can also occur as the result of something else, be it injury, other systemic disease, or even cataract formation. These are called the secondary glaucomas, and a few are listed below:

• Traumatic glaucoma. Caused by damage to the ocular anatomy; can occur immediately after the trauma or years later.
• Pigmentary glaucoma. Caused by pigment shedding from the rear of the iris; the pigment collects in the drainage canals and clogs them, raising pressure. This must be distinguished from the more common pigment dispersion syndrome, where pigment is shedding but glaucoma is not present.
• Neovascular glaucoma. Caused by abnormal new blood vessel growth across the iris and/or into the angle. It is often associated with a pre-existing problem like diabetes or retinal vein occlusion, and can be very difficult to treat.
• Pseudoexfoliative glaucoma. Much like pigmentary glaucoma except the blocked drainage comes from a flaky material peeling off the anterior surface of the lens.

Treatment options include medication (eye drops) and surgery. The current trend with medications is toward drugs with better pressure-lowering ability without such significant systemic side effects. Again, the medications are aimed at lowering the intra-ocular pressure, either by decreasing the amount of fluid made in the eye or by increasing the outflow of fluid from the eye.

Most surgical procedures are considered after it becomes clear the disease is not well-controlled with medication, and are aimed at increasing the outflow of fluid from the eye.

There are three important points to remember

1. The disease is generally painless (there are virtually no symptoms)
2. Glaucoma is never cured (i.e., treatment and monitoring never stop)
3. Treatment in the form of medication and/or surgery is usually effective in halting further vision loss (detection is key).