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NEW PRODUCT APPLICATIONS: The Newest Frontier in Microperimetry

CenterVue’s intuitive MAIA can track a variety of macular pathologies.

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CenterVue’s MAIA is the most recent advancement in confocal microperimetry, combining the best aspects of its predecessors. It provides accurate perimetry results, independent of a patient’s fixation stability.

“The MAIA is advanced for many reasons, but primarily because of its active tracking while projecting onto the retina,” says David MacLellan, director of US marketing at CenterVue. “As the retina moves due to fixation instability, the projected points move with the retina, allowing for small areas of the retina to be tested very accurately.”

The MAIA, which stands for “macular integrity assessment,” is another name for a visual field for the macula or microperimeter. The device acquires retinal images using a scanning LED ophthalmoscope (SLO). A captured retinal image provides a correlation between structure and function, with the overlay of perimetry results registered to the SLO image. An eye tracker compensates for eye movements in real time. It can test under undilated conditions; confocality allows for superior imaging of unhealthy eyes.

The MAIA microperimetry device.
IMAGE COURTESY OF CENTERVUE

K. Bailey Freund, MD, an ophthalmologist fromVitreous Retina Macula Consultants of New York, tried the MAIA after other colleagues touted it as providing high-quality microperimetric studies more efficiently and on a broader range of patients than other devices they’ve used.

“Reliable eye tracking translates into more reliable measurements of retinal sensitivity, which are mapped to precise fundus locations,” he says. “Because traditional visual field devices don’t use eye tracking, the MAIA is particularly valuable in retinal practices like mine that see a high volume of patients with macular pathology.”

Dr. Freund says the device offers a broad range of adjustable examination parameters that are well suited to a wide variety of clinical situations. “When performing follow-up testing, the MAIA uses tracking to place its test pattern on the same retinal locations used during the baseline examination,” he says. “This feature enables longitudinal follow-up with precise comparison of retinal sensitivity over time.”

HOW IT WORKS

The MAIA is a subjective test during which patients respond by pushing a button when they see a small flash of light while fixating on a red target. If they respond, the light gets dimmer, and when they do not respond, the light brightens. “Called ‘thresholding,’ we use this to find what level of light a patient is able to see at a certain area of their retina,” MacLellan explains. The light randomly moves around a selected pattern until all points have been tested.

Once complete, results are viewed in dB values, where 0 dB is the brightest and 36 dB is the dimmest value. “The MAIA differs from traditional visual field units because it actively tracks a patient’s retinal position and adjusts the point of light within the pattern when the patient has unstable fixation,” MacLellan explains. “The MAIA assumes the patient has unstable fixation, where a traditional visual field assumes they are stable.”

Test results are displayed on an SLO image of the patient’s retina, providing the clinician with the exact anatomic location of function. The MAIA compares patient results to an age-related normal database and color codes results, making it easy to assess function quality.

Although there are test patterns and strategies for retina patients in most visual field units, MacLellan says the MAIA is specifically designed to assess the state of retinal disease, and how it impacts a patient’s visual function, more accurately than a visual acuity test.

Microperimetry has been recognized as a necessary component for testing the effectiveness of many treatments, particularly those involving AMD. The MAIA test is reimbursable under CPT codes 92083, 92082, and 92081, and also has applications used in low-vision therapy. The MAIA has also proven accurate in the early detection of retinal toxicity.1

“While micrometry is a valuable tool used in many ongoing clinical trials, I routinely use it in my daily practice when I see a benefit in measuring retinal sensitivity at specific locations within the macula,” Dr. Freund says. This information can be useful for a wide range of macular diseases, including AMD, macular dystrophies, hydroxychloroquine toxicity, macular telangiectasia type 2, macular hole, epiretinal membrane, and many retinal vascular diseases.

Dr. Freund finds microperimetry particularly helpful for difficult-to-diagnose macular disorders, such as acute macular neuroretinopathy, paracentral acute middle maculopathy, and reperfused macular branch artery occlusions, for which imaging findings may be subtle and difficult to localize. Microperimetry can localize the scotoma produced by these entities, which can help make a specific diagnosis.

EASE OF USE

Ophthalmic technicians or photographers typically operate the device. Compact and fully networkable, it can be adjusted to quickly assess macular function and fixation quality. Results can be opened remotely without the need of a viewing application and can be exported to most electronic medical record and image management systems.

“Our technicians have found the MAIA user interface to be simple and intuitive,” Dr. Freund says. “Autofocus eliminates the need for trial lenses. Since the MAIA is a nonmydriatic SLO-based device, there is flexibility with respect to when testing can be performed during an office visit.”

HOW PATIENTS BENEFIT

Most patients and technicians find perimetry testing cumbersome. The MAIA is designed to make this process quick without sacrificing clinical results — patients can be tested in less than 3 minutes per eye. The patient button, head rest, and chin rest are designed for patient comfort. Clinicians can use MAIA results to help explain to a patient how their vision is impacted by their retinal pathology by using easy-to-understand, color-coded graphical displays.

Microperimetry provides retinal sensitivity data in macular regions outside the foveal center. “These data can be used to detect potentially treatable diseases prior to symptomatic vision loss,” says Dr. Freund, who has found microperimetry to be the perfect complement to OCT. “The ability to correlate retinal function with anatomic structure helps me determine when treatment is achieving a visual benefit and when anatomic changes in retinal structure are best correlated with changes in retinal sensitivity.” Microperimetry can also be used in conjunction with OCT angiography to explore correlations between changes in retinal blood flow and visual function at specific macular locations. RP

REFERENCE

  1. Martínez-Costa L, Victoria Ibañez M, Murcia-Bello C, et al. Use of microperimetry to evaluate hydroxychloroquine and chloroquine retinal toxicity. Can J Ophthalmol. 2013;48(5):400-405.