January is National Glaucoma month a leading cause of blindness with an incidence 3 million however only half know they have it.
I invited a guest blogger, Meredith Rogers@GeriatricNursing.org to share her keen knowledge.
6 Glaucoma Tests Every Patient Should Know
Glaucoma refers to a group of illnesses that damage the optic nerve of the eyes. This disease affects millions of people, causing pain, vision problems and long-term vision loss. There are several different types of glaucoma that can impact vision, but fortunately there are effective tests that can diagnose glaucoma early on.
An ophthalmologist (eye doctor) can usually identify those people who are at higher risk for getting glaucoma (due to, for instance, an increased intraocular pressure or a narrow drainage angle) before nerve damage happens. The doctor can also diagnose individuals who have glaucoma already by noting their visual field loss or nerve damage.
The following eye examination tests, which are painless, can be used as part of this evaluation:
This test is done by a device known as a tonometer to determine the pressure inside the eye by measuring the firmness and tone of its surface. Various kinds of tonometers can be used to perform this test; however, the applanation tonometer is the most widely used. Once anesthetic eye drops are applied to numb the eye, the sensor of the tonometer is placed just against the eye’s front surface. A firmer tone of the eye surface indicates a higher intraocular pressure inside the eye.
Performed using a pachymeter, Pachymetry is a measure of the central corneal thickness. Like in tonometry, the eyes are first anesthetized using eye drops before the tip of the pachymeter probe is touched lightly on and perpendicularly to the eye’s front surface (cornea). Multiple studies indicate that corneal thickness is often a variable of intraocular pressure. Thinner corneas may falsely report low-pressure readings while thicker corneas may give false high-pressure readings. However, the importance of this test is getting to know the width of the corneas. Thinner corneas increase the risk factor of getting glaucoma. Once the doctor establishes the width of the cornea, they can use this information to interpret the individual’s tonometry more accurately.
This is a procedure done to scrutinize the trabecular meshwork and note the angle at which the fluid flows out of the eye. It is done by first numbing the eye using anesthetic drops and then placing a specific type of hand-held contact lens, that has mirrors, on the eye. These mirrors allow the doctor to monitor the eye’s interior from different directions. This test aims to observe the drainage area and angle of the eye. In this method, the doctor will find out whether the angle is narrow or open and look for other abnormalities, such as damage to the angle from previous injuries.
People who have narrow angles are at more risk of having their angles suddenly close which might cause an acute glaucoma attack. Gonioscopy is also useful in determining whether the eye is susceptible to chronic angle closure, whether there are abnormal blood vessels, and if there might be hidden tumors that are blocking the flow of the aqueous fluid.
This technique is done using an ophthalmoscope which looks directly into the eye through the pupil. The purpose of ophthalmoscopy is to examine the optic nerve. Any damage to the optic nerve can be observed using this procedure. Cupping (damage to the optic nerve), which is indicated by an indented optic disc, occurs as a result of increase in the intraocular pressure. Additionally, the color of the optic nerve can also be used to tell whether there is damage from glaucoma and how extensive it is. This is the most important technique for monitoring and diagnosing glaucoma.
- Visual Field Test
It is an important measure of damage to the optic nerve as a result of elevated IOP. Glaucoma tends to target the peripheral vision first, and it is for this reason that your doctor tests your visual field to know whether your side vision is being lost. There are several techniques available for this test.
- Imaging Technology
A group of new and highly sophisticated image analysis software is now available. These imaging systems are used to evaluate the retinal nerve fiber layer and the optic nerve; the area damaged by glaucoma. These devices assist the doctor by producing three-dimensional images of the anatomical structures inside the eye. These photographs can be used to track the progression of damage over time. These images are also put in large databases to compare individuals’ anatomic structures within the same age group.
Knowing the different types of glaucoma tests will assist you in choosing the one which you feel is the most appropriate one for you. Consult with your doctor further as you might need a combination of these tests to get an accurate diagnosis.