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DOCTOR, I HAVE A QUESTION
Questions answered by:
Murray Fingeret, OD, FAAO
VA New York Harbor Brooklyn Campus
Patients Chime in About Visual Field Tests
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 as it is non-specific. By the time vision is impacted, glaucoma may already be far advanced with almost all peripheral vision lost. Also, when the visual acuity is fine, the field of vision may still be affected.
During the visual field test, you look straight ahead into a lighted bowl and respond every time a light is flashed and perceived at different points of your peripheral (or side) vision. This help 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 again points that are missed. So, just because you miss a point, keep going because that point will be addressed again in the course of the test.
Visual field testing devices all incorporate an internal computer with the ability to store and analyze data. There are many variables involved in obtaining reliable results and it often takes several tests before a reliable initial baseline is established. This is a recognized phenomenon. Further field tests are then performed periodically, their frequency depending on factors such as the extent of loss. But they are typically done at least once a year to detect any new field defects, to compare to other field tests, and to look for changes in the field defect pattern that are indications if the disease is progressing.
The printout consists of a gray scale which is a rendering of the patient’s field of vision. It’s 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.
"I don't like to do fields - they are hard. Do I really need them?"
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 visual fields – i.e., a certain amount of damage needs to occur before field loss is present. Thus, structural testing and OCT (which stands for ocular coherence tomography) tend to be more sensitive to detect early loss. 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, OCT testing is a great method to monitor individuals with early to moderate loss but if the disease continues to advance, perimetry becomes the more useful test. This is why visual fields are necessary for monitoring moderate to advanced loss.
"Are there any advances in visual field testing?"
Carl Zeiss Meditec, Inc. has released new software that reduces the testing time to perform a visual field with little if any change in its ability to detect loss. This test is called SITA Faster. In addition, a new test pattern is about to be released. Here’s the background. The standard visual field test for glaucoma has been the 24-2 test pattern in which 55 points spaced 6° apart are tested in the central field. Small areas of glaucomatous loss (scotomas) may fall between the tested points and not be detected. The 10-2 test has been used in addition to the 24-2 with test locations spaced 2° apart. In the 10-2, because of the tighter spacing, it is difficult for loss to fall between the points. It has been challenging for the clinician and the patient to perform these two tests. Combining them into one simplifies management issues and improves patient care.
Also, advances in software are not far away that will allow assessment of OCT imaging and visual fields together to better understand if loss is present or getting worse. This is an exciting time in glaucoma diagnostics with changes seen with visual fields, allowing a timelier diagnosis to take place.
SECOND GENERATION iSTENT® APPROVED BY FDA
In 2012 iStent® was the first Micro-Invasive Glaucoma Surgery (MIGS) device approved by the FDA. With its goal of improving the eye’s natural outflow to safely lower increased intraocular pressure associated with glaucoma, iStent® created a permanent bypass through the primary blockage site (trabecular meshwork).
In recent years, as we have reported in this e-newsletter, minimally invasive glaucoma surgery has been gaining traction as a treatment approach for open-angle glaucoma, often in conjunction with cataract surgery. Among other MIGS devices now available in the US to doctors and their patients are Cypass® Micro-Stent and Xen® gel stent.
On June 25, the second-generation of iStent®, called iStent inject®, by Glaukos, was approved by the FDA. Designed to further optimize the natural outflow of aqueous humor, the iStent inject®, preloaded with 2 bullet-shaped stents, creates two bypasses through the trabecular meshwork for multidirectional flow through Schlemm’s canal. Glaukos expects the device to be commercially available in the US later this year.
ARE YOUR RX'S READY FOR TRAVELING?
It’s especially important for glaucoma patients to follow-through with their treatment plans – even while traveling. Here’s a checklist from The Glaucoma Foundation to help you prepare for a safe and healthy trip:
• Make a list of all medications you normally use, noting each prescription dosage, the medication’s trade name as well as the generic name for the drug. Generic names are especially important if you are traveling out of the country, where drug makers may use different names from those in the U.S.
• Bring a sufficient supply of each medication for the length of your trip, and talk to your doctor in advance about getting extra prescriptions, just to be safe.
• Pack your medications in their original drugstore containers rather than in pill cases or other unlabeled bottles.
• Never pack medications in checked baggage, which can be lost or stolen. Put them in your carry-on bag and always keep that with you.
• Store all medications in a dark, cool area – for example, among or inside clothing.
• If you’re crossing time zones, ask your doctor how you should take your medication. Many doctors recommend adapting your schedule to the local time at your destination, and not worrying about a missed dose due to time change. This can simplify your regimen during your stay as well as on your return.
And here are a few final eye care travel tips:
• Traveling on a plane will not affect your eye pressure (IOP) – it is a controlled atmosphere and compensates for changes in altitude. But open medication bottles carefully when you’re first back on land.
• The air on airplanes is very dry. If you wear contact lenses, frequently apply rewetting solution.
• Be safe rather than sorry. If you wear prescription eyeglasses, take an extra pair with you.
TGF'S 2018 INTERNATIONAL THINK TANK
The Glaucoma Foundation’s Annual International Think Tank provides a unique opportunity for scientists and clinicians from a variety of disciplines to apply their expertise and research to the challenge of glaucoma. Beginning in 2012, this interdisciplinary meeting has focused on exfoliation syndrome (XFS) -- the most common recognizable cause of open-angle glaucoma worldwide, comprising the majority of cases in some countries. XFS is an age-related disease characterized by deposits of a flaky, dandruff-like material in many ocular tissues.
This summer’s Think Tank in New York focused on genetic and biological aspects of the disease. It was the sixth Think Tank to deal with exfoliation, with some 40 participants from the United States, Canada, Germany, India, Ireland, Singapore and Spain.
The Think Tank aims at fostering new relationships among the attendees that will lead to continued communications across disciplines and between laboratories – long after the meeting has ended. In recent years, the Think Tank has stimulated research at a geometric level with TGF’s grants program now focused specifically on XFS. The number of researchers working on XFS has markedly increased.
In 2007 scientists identified genetic variants in the lysyl oxidase-like 1 (LOXL1) gene that have been strongly associated with XFS, but do not alone cause the condition. Environmental effects, such as lifetime ocular UV exposure, appear to play a role in whether or not someone predisposed to the disease will develop it. Collaborations have already advanced the understanding of exfoliation and provided new insights into the genetics, pathology and biology of XFS.
There was consensus that a major limitation has been the lack of animal models enabling experiments aimed at elucidating the cellular and molecular mechanism of XFS and identifying treatments to inhibit the production of exfoliation material. The potential of using induced pluripotent stem cells from exfoliation donors to generate a cell culture model for the disease is being investigated.
WE ARE LOOKING FOR STORIES TO SHARE
One of the most popular features of TGF’s Eye to Eye newsletter and electronic newsletter update has been our “Lifestyle Connection/Living with Glaucoma” series, in which glaucoma patients, inspiring and often courageous, have shared their personal stories. We’ve featured a teenager who lives life to the fullest, a triathlete who makes news, an active 90-year-old woman who shared fine advice, among others.
We are always looking for individuals whose lives have been impacted by glaucoma and whose experiences can inform others. If you would like to share your own story, or suggest another, email firstname.lastname@example.org.
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