General Ophthalmologists and AMD Diagnosis

These simple tests can help you help your patients.

By Jerry Helzner, Senior Editor

While the treatment of age-related macular degeneration remains squarely in the realm of retina specialists, the growing incidence of AMD in an aging population creates opportunities for general ophthalmologists to help their patients in the areas of disease detection and progression. While the simple paper Amsler Grid has been in use since the 1940s and still stands as the most basic method of self-testing for retinal disease, recent years have seen the application of technology to several newer home- and office-based diagnostic tests for AMD that can be incorporated into a general ophthalmology practice with a minimal cost of time or expense.

Here, we will explore five of the quickest, simplest tests that can indicate the presence or progression of AMD and that, at a minimum, can result in referral to a retina specialist and the initiation of treatment at an earlier stage of the disease — certainly a feather in the cap of any general ophthalmologist who can play a key role in the disease detection process.

The Amsler Grid

The Amsler grid is the oldest, simplest and most basic self-administered diagnostic test for detecting retinal disease. Developed by a Swiss ophthalmologist named Marc Amsler in the 1940s, it is almost always given to patients by eyecare practitioners at no cost and is often magnetized to a refrigerator door in seniors' homes for regular testing. Amsler Grids can also be easily downloaded from Web sites such as allaboutvision.com.

The Amsler grid dates back to the 1940s. Today, it is considered a rather primitive and inaccurate test that has been surpassed by newer home- and office-based tests. However, it is still in wide use and is usually given to at-risk patients by their eyecare practitioners.

Essentially, the Amsler Grid is a rectangle filled with horizontal and vertical lines and is used to monitor a person's central visual field.

In performing the test, the person looks with each eye separately at the small dot located in the center of the grid. Patients with macular disease may see wavy lines or they may perceive some lines as missing.

Though the original Amsler grid was a black and white pattern, a blue and yellow grid has been developed and is considered to be a somewhat more sensitive and accurate test. The color version can be used to test for a range of visual deficits, including some associated with the retina and the optic nerve.

The overall problem with the Amsler grid is its low sensitivity and what retina specialists call its “too little and too late” detection of changes in vision that could be effectively treated if identified earlier.

MyVisionTest

Richard Trevino, OD, thinks that a home test for macular degeneration can be “engaging, interesting, informative and perhaps even fun.” He says that the traditional Amsler grid is none of those.

Dr. Trevino, who is employed by the Veterans Administration in Evansville, Ind., has been a pioneer in developing online home tests for macular degeneration that can either replace or be used as a supplement to the Amsler grid.

Dr. Trevino has put two tests that he has created on a free Web site whose address is MyVisionTest.com. On the site, he provides a tutorial with complete instructions on how to take both tests, plus an automatic scoring system that immediately delivers the results. The tests can be retaken periodically and all scores can be recorded and reviewed. Thus, a “red flag” is raised if the individual sees recent scores that indicate a change in vision. Ophthalmologists may want to check out the site before recommending it to their patients.

MyVisionTest employs a technique known as “entoptic perimetry” to detect defects in vision. Dr. Trevino asserts that research has found entoptic perimetry to be superior to the traditional Amsler grid in detecting such defects. (The value of entoptic perimetry in identifying diabetic retinopathy has been validated in a study conducted at the Shiley Eye Center at the University of California San Diego and published in the British Journal of Ophthalmology).

Mixed-Contrast Reading Cards

Because studies have shown that a decline in contrast sensitivity is a strong predictor of macular degeneration, a simple and inexpensive test that general ophthalmologists can administer quickly uses a set of mixed-contrast reading cards.

While most patients' ability to read high-contrast cards will be slightly greater than their ability to read low-contrast cards (perhaps a difference of a line or two), AMD patients with a contrast deficit often demonstrate a five- or six-line difference. Patients who have not been diagnosed with AMD and who have great difficulty in reading the low-contrast cards should be referred to a retina specialist for further evaluation.

The Foresee PHP

Moving from the simplest tests to office-based tests using far more advanced technology, the FDA-approved Foresee PHP from Reichert Instruments was originally developed by Notal Vision, an Israeli company. Retina specialists say its chief value is in detecting the progression of dry AMD to the choroidal neovascularization (CNV) of wet AMD.

“The low reliability of the Amsler grid encouraged the development of the Foresee PHP, a medical device that was shown to have higher sensitivity and specificity in detection of a new CNV,” wrote Michael Waisbourd, MD, in a recent article in Retinal Physician.

“The Foresee PHP uses patented technology called preferential hyperacuity perimetry (PHP), which has demonstrated an ability to distinguish intermediate AMD from neovascular AMD with a high degree of sensitivity in numerous peer-reviewed studies,” adds Anat Loewenstein, MD, of Tel Aviv, an investigator for the device. “Early detection and early treatment of wet AMD, when lesions are small and visual acuity is still good, will hopefully result in the best possible visual outcome for patients.”

The Foresee PHP uses a method based on the human visual function of hyperacuity, which gives it the capability of detecting functional changes. Hyperacuity, also known as Vernier acuity, is defined as the ability to perceive a difference in the relative spatial localization of two or more visual stimuli.

The Foresee PHP, an office-based test from Reichert Instruments, is accurate in detecting the progression from dry to wet AMD.

The Foresee test, administered in the office by a tech, requires only a few minutes for each eye, measuring 500 retinal data points covering the central 14 degrees of the macular visual field. The patient's response patterns are automatically recorded, analyzed and compared to the patient's previously established baseline, producing a visual field map and report revealing the relative location and intensity of defects in the macular area.

The Foresee PHP repeatedly presents very brief visual stimuli on a touch screen positioned in front of the patient being tested. Each stimulus is presented as a line consisting of dots. But while most of the dots are arranged along a straight line, several are presented out of alignment, creating a small “bump” of misaligned dots on the screen.

The patient must quickly indicate the distorted area on the touch screen. The very brief time of each presentation of dots means that the patient reacts only after the stimulus has already disappeared. A patient with wet AMD may see distortion as well as a bump. If the distortion is more apparent to the patient than the bump in the dots, the patient may be more attracted to the distortion than to the bump.

The data from a patient's Foresee PHP test are compared to a normative database comprised of tests taken by patients with dry AMD and by newly diagnosed wet AMD patients. The comparison can indicate a probability that the test belongs to a patient with wet AMD.

Reichert says the Foresee PHP costs about $13,000 and that reimbursement for the test is available in a number of states. For reimbursement, use CPT code 92082 and any of the three ICD-9 codes for intermediate visual fields relevant to AMD.

Reimbursement runs $45 to $65 an eye, depending on the local Medicare carrier.

ForeseeHome Monitoring

Notal Vision has retained the rights to the home-based, FDA-approved ForeseeHome device, which uses the same PHP technology as the Foresee PHP. However, the home-based device is intended for individuals with advanced AMD who are at risk for further vision loss. These are individuals who are seeking to save whatever sight they have retained through daily monitoring. The test is self-administered but results are checked remotely at a Notal Vision Data Monitoring Center.

The ForeseeHome program is marketed through a unique program that includes a one-time activation fee and a monthly subscription fee. A patient can cancel at any time with no further obligation.

The ForeseeHome is a home-based test from Notal Vision. It is offered on a subscription basis, primarily to patients who already have vision loss from AMD and are seeking to save whatever vision they have left.

Patients take the test daily in their homes. Information from the tests are sent by phone lines to a Notal Vision reading center.

A Digital iPhone “App”

A convenient device may be able to help patients who have a degenerative eye disease better track vision changes. The investigational device is currently in a one-year clinical trial designed to confirm a recently completed eight-month trial of a prototype.

The handheld digital device is called myVisionTrack. With it, patients can perform an accurate self-test in less than 90 seconds, said Yu-Guange He, MD, associate professor of ophthalmology at UT Southwestern and an inventor of the device.

“Many patients do not have timely eye exams and end up suffering preventable vision loss,” he said. “Careful self-monitoring is critical because treatment for age-related macular degeneration and diabetic retinopathy is most effective when given at precise stages in the disease's progression.”

Supplied as an “app” on an iPhone or iPod touch, the prototype device displays three circles on a screen, one of which is markedly different from the others. Patients cover one eye, then touch what they perceive to be the odd-shaped circle on the screen. With each click, the differentiation becomes more subtle. The test is then repeated with the other eye. Results are stored in the device so patients do not have to memorize scores. If a significant vision change is detected, patients are instructed to see their doctor.

myVisionTrack's “shape discrimination” tests are twice as sensitive as the paper eye chart in detecting small changes in vision, Dr. He said.

Researchers at UT Southwestern and the Retina Foundation of the Southwest tested the prototype device in an eight-month clinical study funded by the National Institutes of Health's National Eye Institute. Forty diabetic patients diagnosed with retinopathy used the monitoring device at home each week. Their test results showed a high correlation with an ophthalmologist's reading of their retinal images, taken at the beginning, midpoint and end of the study.

Diagnostic Tests Continue to Improve

As illustrated by the progression from the almost primitive Amsler grid to the iPhone app, the quickest and simplest tests for AMD detection and progression are encompassing more advanced technologies. This trend should continue, opening up possibilities for more timely treatment for those afflicted. General ophthalmologists can play a greater role in AMD detection and monitoring by making their senior patients aware of the simple self-tests and by also integrating an office-based test into their practice. OM