News

THE GLAUCOMA FOUNDATION
OCTOBER 2019 NEWSLETTER

Doctor, I Have A Question.
Patients Chime in About Visual Field Tests

Questions answered by Murray Fingeret, OD, FAAO
Chief, Optometry
VA New York Harbor Brooklyn Campus
Clinical Professor, SUNY College of Optometry

Visual field testing is one of the key diagnostic tests for glaucoma. Some patients believe that the vision test with an eye chart may detect glaucomatous damage. Unfortunately, the Snellen chart is not useful as a diagnostic test for glaucoma. By the time visual acuity is impacted, glaucoma may already be far advanced. Also, when visual acuity is fine, the field of vision may still be affected.

During the visual field test, a person looks straight ahead into a lighted bowl and responds every time a light is flashed and they are perceived at different points of your peripheral (or side) vision. This helps draw a map of your field of vision.

"If I miss a point, is this test worthless?"

Visual field tests are designed to retest and retest points that are missed. So, just because you miss a point, keep going because that point will be addressed again later on.

Visual field testing devices incorporate an internal computer to store and analyze data. There are many variables involved in obtaining reliable results and it may take several tests to establish a baseline. Also, field tests are performed periodically, their frequency depending on factors such as the extent of loss. They are typically done at least once a year to detect any new field defects, to compare to field tests already done, and to look for changes in the field defect pattern.

The printout consists of a gray scale which is a rendering of the patient’s field of vision and which compares the tested points score to a reference database of healthy individuals based upon age. The grayscale is a visual graph of each eye’s field of vision. The fields are shown in shading that may be filled in gray to denote mild to moderate defects in the field or black to reflect severe loss.

The doctor is trained to look for patterns of loss, such as a cluster of points flagged in certain locations. There are also quality checks throughout the test that provide information to gauge if patients are performing the test properly. For example, are they holding their gaze steady or looking around; are they clicking randomly and not paying attention?

“Is there really a need for visual fields given all the other diagnostic tools? I don't like to do fields - they are hard.”

There are two kinds of tests to monitor individuals with glaucoma – structural testing (e.g. optic nerve assessment, fundus photos, OCT imaging) and functional testing (e.g. visual fields or perimetry). Structural testing often shows loss before functional testing (visual fields) – i.e., a certain amount of damage needs to occur before field loss is present. OCT, which stands for Optical Coherence Tomography, is a great test for recognizing loss in early to moderate glaucoma. But there is what is termed a floor effect, and OCT imaging in particular does not show loss after a moderate amount of damage has occurred. So, if the disease continues to advance, perimetry becomes the more useful test. This is why both tests are needed though one test may be more useful at a certain stage.

Patients with Glaucoma are at Higher Risk for Motor Vehicle Accidents

According to a study conducted at Wills Eye Hospital in Philadelphia, older drivers with moderate glaucoma are involved in automobile accidents at a higher rate than their similarly aged counterparts without glaucoma.

Of 142 patients with moderate glaucoma who reported driving, almost 11 percent reported involvement in at least one motor vehicle accident over the course of the study. The mean age of participants was 64 years. In contrast only 1.1 percent of drivers aged 61 years or older reported involvement in a motor vehicle accident in the 2017 Pennsylvania Crash Facts and Statistics report.

The study found a total of 25 percent of these patients gave up driving over the four year course of the study.

When Mark Lesselroth of Syracuse, New York, was diagnosed with narrow angle glaucoma 16 years ago, he shared the fears of many newly diagnosed patients. Would he lose his sight? Would his diagnosis impact his work? He was only 37 years old--would he see his children grow up?

“I was given a leaflet, but what I wanted was a folder full of information on what might happen and whether I was going to go blind. I wanted my health professionals to share all the information they had, and to be clear when they had no answer. In that way I could accept that my vision impairment could worsen.”

Almost immediately Mark began looking for answers to try and take control of his glaucoma. And to the extent possible, he’s done just that!

“Information gives hope,” Mark says. And he has been steadfast in his efforts to empower himself and the broader patient community to be well informed and to encourage a more open and honest relationship between patients and their doctors.

Early on he began to keep himself informed about the disease, its expected progression and available treatments as well as new advances in the pipeline. He also sought out and found a few support groups online and in 2011 started the Central New York Glaucoma Support Group with initial support from The Glaucoma Foundation – recognizing he was not unique in his efforts to look for answers. The group meets monthly.

As an advocate for educated patients and improving the relationship of patients with their doctors, Mark has some advice for both groups.

First and foremost, he urges doctors to provide educational materials to newly-diagnosed patients as well as a list of other available resources, including online support groups.

Also, Mark asks doctors to share what they know about current evidence on disease progression. “There are treatment advances in the pipeline – things are happening,” Mark says. “Share positive information. Listen to your patients and give them hope.”

Mark’s advice to patients? When diagnosed, make sure other family members get tested –some types of glaucoma have hereditary components.

And don’t be afraid to ask questions and tell doctors what you need to know. Look for local support -- there are numerous online groups and some others. If you cannot find one, consider starting a support group in your community.

Mark is doing well. He now takes one glaucoma medication – a generic form of Lumigan eye drops once a day. “While accepting my condition was initially difficult, having access to information about glaucoma and knowing what developments are being worked on gives me hope and peace of mind,” he says.

And, yes, there is some synchronicity between Mark’s glaucoma history and his professional life. He is currently the President and CEO of BioPortUSA, an international business development consultancy that facilitates United States entry for foreign-based life sciences companies.

Elevated eye pressure, the primary known risk factor for glaucoma nerve damage, is caused by a buildup of fluid known as aqueous humor. In a healthy eye, this fluid provides nourishment to cells before flowing out into the bloodstream through a drainage system made up of the primary outflow pathway, the trabecular meshwork, and the smaller uveoscleral pathway. When the drainage system is blocked, increased intraocular pressure (IOP) can put a person at risk of developing glaucoma.

The mainstay first step of glaucoma therapy has been the use of eye drops that either decrease the production of the aqueous humor or improve the drainage of aqueous humor through the uveoscleral pathway or trabecular meshwork in order to stabilize the intraocular pressure and prevent damage to the optic nerve.

There are numerous classes of eye drops and patients may take a combination of medications. These include prostaglandin analogs, beta blockers, alpha agonists, carbolic anhydrase inhibitors, and rho kinase inhibitors. Combination drugs are available for those who require more than one type of medication and numerous are available in generic form.

Prostaglandin analogs include Xalatan® (latanoprost), Lumigan® (bimatoprost), Travatan Z® (Travoprost), and Zioptan™ (tafluprost). They work by increasing the outflow of fluid from the eye.

Vyzulta, one of two new FDA-approved medications in 2018, works to lower intraocular pressure by opening the uveoscleral pathway much like other prostaglandin analogs. But another component of the drug is a nitric oxide donator which relaxes trabecular meshwork cells. Recent research has shown that an insufficient blood supply to the optic nerve may also contribute to the onset of glaucoma.

Beta blockers such as Timoptic® or Istalol® (timolol) and Betoptic® S (betaxolol) are the second most often used class of medication and work by decreasing production of fluid.

Alpha agonists [Alphagan®P (brimonidine), Lopidine® (apracionidine)] work to both decrease production of fluid and increase drainage.

Carbonic anhydrase inhibitors (CAIs) reduce eye pressure by decreasing the production of intraocular fluid. These are available as eye drops [Trusopt® (dorzolamide), Azopt® (brinzolamide)] as well as pills [Diamox (acetazolamide) and Neptazane® (methazolamide)].

Rho khinase inhibitors [Rhopressa® (netarsudil)], the second new class of medications, expands treatment options. Netarsudil is the first agent in the ROCK inhibitor class to be approved by the Food and Drug Administration for use in glaucoma and ocular hypertension.

Rhopressa reduces IOP specifically by improving outflow of the trabecular meshwork, a pathway from which most of the aqueous humor drains. Most other eye drops commonly used today target only the secondary drainage system, the uveoscleral pathway, or reduce aqueous production. In addition, Rhopressa also has an advantage in treating normal tension glaucoma, which results in damage to the optic nerve despite only slight elevations in intraocular pressure.

Your physician may change your medication prescriptions when they do not achieve the desired results or to reduce side effects they may cause. Still, they are key to controlling your eye pressure and keeping your vision.