Puff test, Visual Field, OCT, Optomap... what is all of that?
I have heard of glaucoma before, but should I be concerned?
One of the most common eye health concerns I hear from patients is the fear that they may have glaucoma, and this is often followed by, “doc, what exactly is glaucoma?”. In order to explain what glaucoma is, and how it can damage your vision, it is important to understand a little bit about the eye anatomy. Glaucoma is a disease of the main nerve ending in the back of the eye that sends signals to the brain. This is called the optic nerve, and it generally has a predictable normal healthy appearance. Glaucoma damages this nerve ending to the point where visual signals cannot be properly sent to the brain, and over time this leads to vision loss. Unlike some eye diseases, however, the vision loss from glaucoma is permanent, so it is very important to address any potential concern as early as possible. In order to properly assess a patient’s risk, a standard battery of tests is ordered once there is a suspicion of glaucoma.
Do I really have to do the eye puff machine again this year?!?
There are several forms of glaucoma, but the most common form is related to optic nerve damage caused by high intra ocular pressure (IOP). Inside the eye there is fluid constantly created and drained from the eye in order to maintain the eye’s internal pressure. In glaucoma, the drainage system for this fluid begins to malfunction which in turn causes the eye pressure to increase. This increase in eye pressure causes stress on the optic nerve that can lead to tissue loss and eventual vision loss. In order to test the eye pressure to see if a patient falls outside of the normal range, the air puff test or Non-Contact Tonometer is used as a screening test. This test puffs a small amount of air at the cornea in order to slightly flatten it. The machine calculates the IOP based on the amount of air needed. There are several ways to measure IOP, and if a patient is suspected of having glaucoma these other methods may be used. I know that the air puff can be a stressful test, but the data is provides is very important to assess the risk of glaucoma.
This visual field test is like the worst video game ever!!
Even though glaucoma can cause permanent vision loss, the first signs of vision changes are often very subtle. In general, glaucoma first damages the far peripheral vision and only later in the disease causes loss of central vision. In order to test the peripheral vision a device called a Visual Field Analyser is used. During this test, a patient will look at a fixed central point, and press a button every time a flash is seen in the peripheral vision. These flashes start out bright and easy to see, and then eventually get dimmer and dimmer until they are not seen. The analysis takes about 5 minutes per eye, and yes I fully agree that it can be a pretty boring test! Once the testing is complete, it is analyzed to see if there are any areas of the visual field that were not seen as they should be. This is a very important way to track glaucoma progression over time. It is standard to perform the teat once per year for any patient suspected of having glaucoma, but it may be performed more often in certain cases.
You’re going to shoot a laser in my eye?!?
One of the final common tests used to measure glaucoma risk is called Optical Coherence Tomography (OCT). This device uses light waves to take very detailed images of various internal and external ocular structures similarly to how an ultrasound uses sound waves to take an image. The OCT uses safe noninvasive light waves to get an immediate high resolution image of parts of the eye not otherwise easily viewed. With regards to glaucoma, images of the optic nerve, the ocular drainage system, and the cornea can all be taken to assess glaucoma risk. Over time these images can be compared to see if there are changes to these structures occurring as a result of glaucoma. This test only takes a few minutes, but the data it provides is very important for correctly making a diagnosis of glaucoma.
When a patient hears that they may have glaucoma, it can be a shock. In many cases, a patient may look at risk for glaucoma, but after completing these tests it is determined that they actually have nothing to be worried about at this time. Glaucoma is a disease that is difficult to officially diagnose, and it take a large amount of data, sometimes collected over years, in order to make the proper diagnosis. If it is determined that a patient is at risk of glaucoma, a dedicated exam is usually scheduled to perform all of the needed tests and to go over the results with the patient. We are here to answer any questions you may have, and to ensure that all of the proper testing is performed in order to come to the correct diagnosis as early as possible. Please let us know if you ever have any questions about the tests we perform or why we are doing them because it is very important to all of us at Optique to keep patients involved in the process.