Open Angle Glaucoma

Tuesday, Sep 1, 2020 by Nisha Gupta, MD

This month we will begin our discussion about glaucoma. It is a leading cause of blindness in the world and approximately half of those with glaucoma do not realize they have it. There are two major types of glaucoma: open angle and angle closure. We will focus on open angle glaucoma first.

What is open angle glaucoma?

Open angle glaucoma is the most common type of glaucoma. Glaucoma means that there is damage to the optic nerve which causes loss of peripheral vision. The angle is the area formed by the iris and the cornea. If this is open on exam, the term open angle is used. This loss of vision is slow and happens over time.

What puts people at higher risk of developing glaucoma?

  • Older age
  • African American background
  • Family history
  • High intraocular pressure
  • Thin corneal thickness
  • Diabetes

What are the symptoms?

Most often, people do not have any symptoms. The vision loss is peripheral and may not be noticeable right away. Over time, one may notice that the vision is less in the periphery but can still have perfect vision looking straight ahead. Without treatment, glaucoma can lead to blindness. There is usually no pain associated with open angle glaucoma.

How is it detected?

A comprehensive exam including checking the vision, the pressure, and dilating the eyes are imperative to diagnose glaucoma. The dilated exam allows doctors to see the optic nerve. Doctors use a lens with mirrors to check if the angle is open.

Photos are taken to monitor the progression of the disease. This photo shows what a normal optic nerve looks like. The arrow points to the pale circle in the middle which is small in size.

Normal optic nerve

Normal optic nerve. Image Source 1

The following photo shows an optic nerve that is damaged by glaucoma. The pale circle is much larger than the normal nerve. The arrows point to the edge of the pale circle.

Optic nerve with glaucoma

Optic nerve with glaucoma. Image Source 1

In addition to monitoring the nerve on exam, doctors take a photo of the nerve to look deeper at the fibers that make up the nerve. As one gets older, it is normal to lose some of these fibers. With glaucoma, the fibers are damaged and lost more quickly. Optical coherence tomography (OCT) shows where the nerve has more damage due to the loss of these fibers. It shows the thickness of the retinal nerve fiber layer (RNFL).

This photo shows a healthy optic nerve. The nerve thickness is normal and is plotted in the green area.

Normal OCT

Normal OCT. Image Source 1

The next photo shows that there has been damage from glaucoma. The nerve thickness is much lower than normal and is plotted in the red area.

OCT of glaucoma

OCT of glaucoma. Image Source 1

Finally, doctors conduct a test to check the peripheral vision of patients to look for damage from glaucoma. When the optic nerve is damaged, the vision loss starts in the periphery and a formal visual field test is done to check this vision.

The next photo is a visual field of someone without glaucoma. The arrow points to the normal blind spot in the vision.

Normal visual field

Normal visual field. Image Source 1

The following is a visual field of someone with vision loss due to glaucoma. The arrow points to the area where the patient is not able to see.

Visual field of glaucoma

Visual field of glaucoma. Image Source 1

The exam and these tests should be done at least once a year to ensure that the disease is not progressing.

What are the treatments for open angle glaucoma?

It is important to note that there is no absolute cure for glaucoma. However, it is a disease that can be managed with appropriate treatment and regular follow up visits to an ophthalmologist. The mainstay of treatment is to lower the eye pressure, which prevents further damage to the optic nerve and subsequent vision loss.

Eye drops: The most common first line of treatment is to use medicated eye drops. There are several types of drops that work in different ways to lower the eye pressure. Some drops also come as a combination of two different medicines in one bottle. Depending on how severe the disease is, one may need to be on multiple drops at the same time. Occasionally, drops may be changed or stopped altogether. However, for most patients, once drops are started, they are a lifelong treatment.

Pills: Sometimes the eye pressures are too high, but a patient may not be able to endure treatments other than medications. There are some pills that work on the body to decrease the fluid in the eye and lower the eye pressure.

Laser: This is a procedure that is done in the eye clinic. The most common laser is called a selective laser trabeculoplasty (SLT). This laser creates tiny holes in the area of the eye where fluid flows. It allows for fluid to flow more easily in the eye and reduces the eye pressure. It can be used in combination with eye drops for treatment.

Surgery: This is the last option for treatment when all other methods have not worked. This is reserved for advanced cases where one is losing vision even when doing all other treatments. It requires going to the operating room and inserting a tube or valve in the eye to help the fluid flow more easily. This will then lower the eye pressure.

Glaucoma can be a complex disease and requires an individualized approach for treatment. Please be sure to discuss with your doctor all options to ensure the best treatment plan for you.

Return next month for our discussion on angle closure glaucoma!

  1. Image courtesy of Nisha Gupta, MD [return]

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