FAQs About Glaucoma
Do you have questions about glaucoma or how glaucoma is treated? Click on a question below to learn more.
Can an optometrist treat me for glaucoma?
The optometric profession has evolved over the past two decades. Enhanced education and training allows optometrists to treat and manage glaucoma in 49 of the 50 United States. Massachusetts is the only state in which optometrists cannot prescribe medications used in the therapy of glaucoma.
When does my glaucoma test indicate I should see an opthamologist?
Elevation of eye pressure and asymmetry of the optic nerve appearance can be early signs of glaucoma. An examination by an ophthalmologist or glaucoma specialist is warranted to confirm or deny these findings.
Do all doctors use the same techniques to measure visual fields?
Visual field testing has advanced greatly in recent years. While Humphrey (and Octopus) perimeters are the most widely used devices by optometrists and ophthalmologists, several newer strategies – some using these same machines, others use different devices – have been introduced which allow for earlier detection of field defects and easier monitoring of field changes. These new technologies work by testing different groups or types of the retinal ganglion cells that are destroyed in glaucoma. One is blue-yellow perimetry, also known as Short Wavelength Automated Perimetry (SWAP), which uses blue light as the stimulus and yellow light as the background illumination. Another is Frequency Doubling Technology (FDT), which measures a form of contrast sensitivity. This test is especially useful for patients who have blurred vision or cataracts.
Do the newest imaging devices add to glaucoma diagnosis?
Are there advanced testing techniques in the pipeline to diagnose and assess visual field damage earlier?
Visual evoked potential (VEP) technology has been a promising avenue as we look for better ways to help identify early glaucoma visual field loss. VEP monitors the brain’s electrical response to a stimulus using electrodes placed on the scalp. So it, bypasses some of the problems associated with subjective standard visual field tests that require the subject to respond to stimuli by pushing a button. All the patient has to do is look straight ahead, look at the test object, and just have the electrodes measure the recordings from their scalp.
The best-known version of this technology has been multifocal VEP. But the chief problem with mfVEP has been that it’s a time-consuming test; it can take even longer than a standard visual field test, making it potentially difficult for some patients.
We have been engaged in Phase II clinical trials of an alternative called isolated-check VEP. The premise is similar—monitoring brain waves to evaluate retinal function in glaucoma—but the way the stimuli are presented is completely different. A patient can lose 30 or 40 percent of his ganglion cells before he has a visual field abnormality. We’re hoping that icVEP will be able to provide earlier evidence that a person has developed glaucoma so treatment can begin before the loss becomes that extensive.
This is not intended to replace visual field testing; it’s meant to be a complement to it. We’re interested in seeing whether this technology can provide another data point to help determine whether glaucoma is present or whether a therapy is slowing progression.
I've read that central corneal thickness (CCT) is an important factor in accurately diagnosing intraocular pressure (IOP). How is that measured?
Measuring CCT helps your doctor interpret your IOP levels. Thickness of the cornea can cause an inaccurate reading of IOP. Some people with thin central corneal thickness will have an IOP that is actually higher than when measured by tonometer. These patients are at greater risk for developing glaucoma although the tonometer measures IOP in the normal range. Likewise, individuals with thick CCT will have a true IOP that is lower than that measured. The most commonly used approach to obtaining reliable measurements of corneal thickness is ultrasonic pachymetry – a simple, quick and painless test. Your doctor will first anesthetize your eyes, and then place a small probe perpendicular to the central cornea on the surface of the eye to measure your corneal thickness. It only takes a minute or two to measure both eyes.
My doctor has different instruments he uses to look into my eyes. What are some of the tools he uses to look at my optic nerve?
We use an instrument called an ophthalmoscope to look directly through the pupil at the optic nerve. Its color and appearance can indicate whether or not damage from glaucoma is present and how extensive it is. This remains an important tool. Another very important diagnostic tool is the visual field test, which measures the function of the optic nerve. Stereoscopic photographs of the optic nerve are useful and can be repeated every two to three years for following up. Doctors also use advanced imaging devices such as the Heidelberg Retina Tomograph (HRT)and the Nerve Fiber Analyzer (GDx) which use laser disc confocal imaging. These tests measure optic nerve parameters and nerve fiber thickness.
Why do I need Visual Field Tests?
My recent eye exam included a visual field test, an eye pressure (IOP) measurement, and an exam to check my optic nerve for damage. Are there other tests for glaucoma I should have?
Optic nerve photographs are often taken using a retinal camera. By documenting the appearance of the optic nerve and retinal nerve fiber layer at a particular moment, such pictures can establish an initial baseline for future evaluation and can then help recognize progressive damage by allowing a comparison of the current optic nerve appearance to a prior photograph. Special imaging devices such as an Optical Coherence Tomograph (OCT), Heidelberg Retinal Tomograph (HRT), or a scanning laser polarimeter (GDx) may also be used to help assess the health of the optic nerve and retinal nerve fiber layer. These instruments take images of the optic nerve and retina similar to a photographic camera. The images quantify the amount of cupping, size of the optic nerve’s rim and thickness of the fibers that make up the nerve fiber layer. Research has shown that damage to the nerve fiber layer and optic nerve often occurs before visual field changes are recognized. While these devices are not essential for making an initial diagnosis of glaucoma, they can provide important findings for the clinician.
Other Ophthalmic Conditions
What is the relationship of conditions like sleep apnea and Raynaud's to glaucoma?
Recent studies suggest that certain types of glaucoma may result from insufficient blood supply to the optic nerve due either to increased intraocular pressure (IOP) or other risk factors. Sleep apnea, Raynaud’s syndrome, as well as migraine headaches and reduced nocturnal blood pressure are vascular factors that have been associated with glaucoma, particularly with normal-tension glaucoma,a form of glaucoma in which optic nerve damage and visual field loss progress despite seemingly normal IOP levels. Studies have shown that there is decreased ocular blood flow in sleep apnea, and that normal-tension glaucoma is more prevalent patients with sleep apnea than in patients without the disorder. Studies have also shown that the severity of sleep apnea correlates with the severity of glaucomatous damage.
Raynaud’s disease, characterized by abnormally cold hands and feet, may also be an indicator for normal-tension glaucoma, because decreased perfusion to the extremities could suggest a vascular disorder compromising blood flow to the optic nerve. Migraine headaches may also be associated with decreased blood flow to the optic nerve. And while not all patients with low blood pressure develop glaucoma, blood pressure is often significantly lower in patients with normal-tension glaucoma. In addition, patients who experience a decrease in blood pressure while sleeping may have a higher risk of glaucoma progression.
The subject of blood flow and glaucoma is currently an active field of scientific investigation. The impending results will be important in optimizing treatment to prevent development and/or halt glaucomatous progression.
Glaucoma and Children
How is an eye examination given to an infant or young child?
If glaucoma is suspected in a child under the age of four, it is often necessary to perform an examination with the child under anesthesia. Under anesthesia, the doctor is best able to test the child’s intraocular pressure (tonometry) and evaluate the angles or dimensions of the eye (gonioscopy).
Gonioscopy assists the doctor in determining whether the eye is functioning properly: producing, circulating, and draining the fluid or aqueous humor within the eye.
Should I allow my twelve year old participate in regular activities and sports, despite his glaucoma?
Your child’s participation level depends on his level of vision and the condition of his eyes. You should speak with your child’s ophthalmologist to determine what level of activity would be acceptable and what could be damaging. It is possible for a child to have a normal and active life if the glaucoma is under control and sight is good. If a child has had a corneal transplant, more caution is warranted and the child’s physical activity should not be strenuous or fast-paced.
Is there a surgery that can cure childhood glaucoma?
Congenital, or infantile, glaucoma can often be â€œcuredâ€? through a goniotomy or trabeculotomy surgical procedure, although it may be necessary to have more than one operation. These procedures are invasive and intended to cut the trabecular meshwork (eye’s drain) in order to improve its drainage function. If these procedures are unsuccessful, it will become necessary to perform a trabeculectomy, a filtering surgery traditionally given to adults. If surgery is successful, it is sometimes considered a “cure” because the glaucoma may never become problematic or vision threatening, but it never really goes away. There is still a chance that conditions will surface years later, and that further treatment with medication and/or surgery will be required.