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FA remains gold standard for detecting new-onset CNV
The AMD DOC Study found that fluorescein angiography remains the best method of detection; however, the study did not evaluate spectral-domain OCT.
Among four technologies used to detect new-onset choroidal neovascularization, fluorescein angiography was determined to be the best, according to a literature review.
The review compared Amsler grid testing, preferential hyperacuity perimetry, time-domain optical coherence tomography and fluorescein angiography.
“Initially, we might have suspected that OCT would be very sensitive for detection; however, that is not the case,” Diana V. Do, MD, who authored the review that appeared in Current Opinion in Ophthalmology, told Ocular Surgery News.
This prediction was based on the results of the Age-Related Macular Degeneration: Detection of Onset of New Choroidal Neovascularization (AMD DOC) Study, published last year in Ophthalmology, for which Do served as study chair.
Spectral-domain OCT
In 2010, when the AMD DOC Study was under way, time-domain OCT was the method of choice, as well as the most readily available OCT system in the United States, Do said.
“However, since then, spectral-domain OCT has replaced time-domain OCT in the offices of many retina specialists,” Do said. “Spectral-domain OCT is likely superior to time-domain OCT because it provides higher resolution and it samples a greater area in the macular region. We suspect that spectral-domain, due to its higher resolution, is probably going to be able to detect more potential abnormalities associated with new-onset choroidal neovascularization (CNV) than time-domain OCT.”
Diana V. Do, MD, suggests using the AMD DOC Study as a guide but to also rely on clinical experience and higher resolution SD-OCT.
On the other hand, because spectral-domain OCT has a higher resolution, it also may pick up false-positive readings, Do said.
“But, there is no study that has evaluated spectral-domain OCT to detect new-onset CNV. Hopefully, such a study can be performed in the future,” she said.
Do, director of the Carl Camras Center for Innovative Clinical Trials in Ophthalmology at the University of Nebraska Medical Center, Omaha, personally prefers spectral-domain OCT over time-domain OCT because it provides a greater wealth of information for the physician.
Nonetheless, Do believes that retina specialists can continue to use the AMD DOC Study as a guide.
“However, they need to integrate their clinical experience with the higher-resolution spectral-domain OCT to determine how often they should follow their high-risk AMD patients in order to detect the earliest signs of conversion to CNV,” she said.
Other modalities
The review found that compared to fluorescein angiography, the other three techniques had low-to-moderate sensitivity for detecting new-onset CNV.
Amsler grid testing, which has been employed since the 1940s, is a simple, easy screening test that a patient can use at home daily, Do said.
“However, several studies have shown that the test is not very sensitive or specific, so we cannot rely on it completely for accuracy. It may have many false positives, as well as false negatives,” she said.
Do said it is important for the physician to instruct the patient how to correctly use the grid.
Similar to the Amsler grid, preferential hyperacuity perimetry is not perfect, either, but it may be a better tool because it can detect abnormalities in a more sensitive fashion, Do said. However, preferential hyperacuity perimetry is more complicated to perform.
Do recently evaluated an in-office version of the test (PreView PHP version 2.0, Carl Zeiss Meditec); a home version of the test intended to be performed daily is also being investigated as an alternative to in-office testing.
“Again, it is important that the patient is trained properly on how to perform the test — either for in-office or home use — because the results of the test are only as good as the patient’s understanding,” Do said.
Gold standard
Despite being an invasive imaging procedure, fluorescein angiography remains the gold standard for detecting CNV, Do said.
“It is a very sensitive test; therefore, I would encourage retina specialists and comprehensive ophthalmologists to continue to use this imaging tool if they suspect any possible conversion from non-neovascular AMD to neovascular AMD,” she said.
The valuable information that fluorescein angiography provides outweighs the minimal discomfort that may be experienced, according to Do.
For the AMD DOC Study, patients were tested every 3 months for 2 years.
“But in the real-world clinical practice, many physicians are using their own judgment to determine how often they should be monitoring the eye that is at high risk for conversion,” she said.
Do uses a combination of testing — spectral-domain OCT and fluorescein angiography — in conjunction with a detailed ophthalmic exam, which she conducts herself, to evaluate eyes that are at high risk for conversion.
“I am able to detect conversion fairly quickly with a combination of modalities,” she said. “[Spectral-domain OCT and fluorescein angiography] allow me to achieve a relatively high sensitivity and specificity.”
Despite advances in detection of new-onset CNV, Do believes there is always room for improvement.
“I am encouraged because in retina there is a constant evolution of ideas and scientific breakthroughs that we can bring to our clinical practice,” Do said. “Within the next several years, there will be additional tools and advances in ocular imaging and OCT that will further enhance our clinical skills to detect neovascular AMD. In addition, genetic testing may enable us to identify individuals who are at highest risk for conversion to advanced AMD.”
Do stressed that high-risk non-neovascular AMD patients need to be followed.
“We want to preserve their vision and improve their quality of life,” she said. – by Bob Kronemyer