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A new fundus perimetry device could provide reduced test-retest variability, increased sensitivity, higher accuracy, and simultaneous structure-function assessment.
Take-home message: A new fundus perimetry device could provide reduced test-retest variability, increased sensitivity, higher accuracy, and simultaneous structure-function assessment.
By Nancy Groves; Reviewed by Luca Rossetti, MD, and Murray Fingeret, OD
Padova, Italy- With a novel fundus perimeter (Compass, CenterVue SpA), clinicians can perform standard 24-2 visual field testing and deliver true color confocal images.
“Microperimetry has not until now been used in visual field testing for glaucoma, although it is used in testing of macular diseases,” said William Burnham, OD, chief executive officer of CenterVue’s U.S. subsidiary in Fremont, CA. “With the [novel device], we have expanded the testing into the 24-2 pattern, which is a standard for detecting glaucomatous field loss.”
The microperimetry pattern used for tracking the retina has also been adapted for the new device, another feature that is intended to lessen the variability of current visual tests.
“The promise of the [device] and fundus automated perimetry is that we are able to compensate for any fixation problem with the patient and we are certain to within 20 μm that we are testing the retinal sensitivity at a specific location,” Dr. Burnham said.
Testing of the device, conducted at the University of Milan San Paolo Hospital Eye Clinic, included a performance comparison with that of the Humphrey Field Analyzer (HFA) in more than 350 subjects (about 200 with normal vision and 150 with glaucoma).
“The [device] proved to be very similar to the HFA in testing retinal sensitivities and showed very good repeatability, indicating high precision,” said Luca Rossetti, MD, director of the Eye Clinic at the San Paolo Hospital and associate professor of ophthalmology, University of Milan. Dr. Rossetti had both a clinical and scientific role in the development of the device and was responsible for the clinical investigation performed to assess its safety and effectiveness.
One of the major features of the device is its ability to obtain a clear image of the central 30° of the retina, Dr. Rossetti said.
After autofocus, the device allows continuous infrared visualization of the central 30° during perimetric testing. When the quality of the images taken during the clinical trial was analyzed, it was found to be satisfactory in about 85% of cases and allowed the visualization of the fundus during perimetry and operation of the retinal tracker in 100% of the cases, he noted.
“The infrared image has the great advantage of helping better identify the optic disc and cup margins,” Dr. Rossetti said. “The quality of the color images was not sufficient in fewer than 10% of the cases.”
Imaging of the posterior pole has several advantages, Dr. Rossetti added.
“The first is the ability to compare the optic disc examination findings with the perimetric results,” he said. “This will reduce the number of false positive cases.”
Second, it may be possible to assess the development of other retinal diseases, such as myopic atrophy, diabetic retinopathy, or macular degeneration at an early stage. This will help explain an abnormal test result in patients with a normal optic disc, Dr. Rossetti added.
The third advantage is the possibility of assessing the retinal nerve fiber layer and searching for agreement with the perimetric test results. The images of the posterior pole might help to develop a guided grid to enhance the diagnostic capability of the functional assessment, he continued.
According to Dr. Rossetti, who has been using the perimeter for about 2 years, the device might challenge the standard instruments currently used for glaucoma diagnosis and management.
“This is mainly due to the possibility of viewing the fundus while examining retinal sensitivity,” he explained.
This-combined with modern software to robustly calculate the rates of disease progression-will enable reduced variability and increase the sensitivity in the detection of those patients getting worse with a consequent improvement of management, he noted.
“So, we will have a small machine with fast strategies and highly sensitive diagnostic performances allowing for assessment of the RNFL and of the optic disc and with the possibility of sending the output via Internet, for example to a reading center,” Dr. Rossetti said. “This new instrument has all the potential features to significantly improve the way we manage glaucoma.”
Another physician who has used the device is Murray Fingeret, OD, chief of the optometry section, Department of Veterans Affairs, New York Harbor Health Care System, Brooklyn, St. Albans campus.
Because the device is relatively new in North America, his clinical experience is limited to a few months. Dr. Fingeret describes the device’s hardware as advanced and noted that being able to obtain structure and function data in one printout aids in the diagnosis and assessment of disease severity.
The confocal scanning laser diode camera with a 60° view is also a bonus.
“It’s a digital camera and more,” Dr. Fingeret said. “It’s not false color. It’s real color, so you get an accurate representation of the color of the back of the eye.”
In practical terms, the device is easy to use because of the autofocus, he added, and technicians can be quickly trained to become competent in its use.
Dr. Fingeret concluded that it is too soon to determine if the device will be more effective than other perimetry devices but added that it has the potential to be an important tool in glaucoma management.
The device has been granted FDA 510(k) clearance and is available in the U.S. market.
Luca Rossetti, MD
Murray Fingeret, OD
Dr. Rossetti and Dr. Fingeret are both consultants for CenterVue.