All-in-one system provides microperimetry, color fundus imagery, and fixation analysis.
Although visual acuity tests are useful for testing retinal function, they can show only the status of a small part of the retina. This limitation prompted Srinivas Sadda, MD, ophthalmologist at the Doheny Eye Institute in Los Angeles, to try NIDEK’s MP-3 Microperimeter all-in-one system. “There is a lot of important real estate in the retina outside of the central area,” he says. “I wanted to have the capability to test the function of other retinal areas.”
The system, ideal for patients with atrophic macular degeneration, can detect damage to the macula outside of the fovea. “MP-3 gives us a more complete picture; it’s the next generation of microperimetry,” Dr. Sadda says.
NIDEK’s MP-3 includes a wider range of stimulus intensity, from 0 dB to 34 dB, compared to the MP-1, says Keith Effert, senior product marketing manager of NIDEK Inc., based in Fremont, California. It can measure perimetric threshold values even for normal eyes. In addition, a maximum stimulus luminance of 10,000 asb enables physicians to evaluate low-sensitivity areas.
AUTOMATION SIMPLIFIES THE TESTING PROCESS
Another reason that MP-3 is a significant advancement over previous versions is that it automates many functions, Dr. Sadda says. The auto-alignment feature aligns on the selected eye, moves in to focus on the retina, selects the infrared fundus image as a tracking reference, starts presenting stimuli directly onto the retina at the exact location, and automatically takes a color fundus image. The perimetry exam registers precisely to the color fundus image.
For earlier versions, a highly skilled operator would conduct microperimetry tests to properly line up the patient. “The new system eliminates the chance for operator error; you no longer need to have a technician run the test,” Dr. Sadda says. “By not having to line up the patient, the testing process is expedited.”
The MP-3 can measure fixation and determine the preferred retinal locus by asking the patient to fixate on a target. “Any change in fixation can be compared pre- and post-treatment because the patient’s eye is constantly tracked during microperimetry,” Effert explains. “The test can also evaluate fixation in patients with central visual field defects and determines whether fixation improved after treatment. The MP-3 indicates the percentage of fixation points within 2° and 4° in diameter to help confirm fixation stability.”
The system also has a broader dynamic range. “It tests the dimmest light that a patient can see,” Dr. Sadda says. “This improves the physician’s ability to distinguish between disease and normalcy. Ultimately, results are more reliable.”
The MP-3 can perform 3 different exams: color fundus image (morphology), fixation analysis (functional), and microperimetry (functional). “It’s a subjective, quantitative, noninvasive diagnostic exam aimed at assessing retinal functionality and puts it in strict correlation with retinal morphology,” Effert says.
The 12-megapixel fundus camera in the MP-3 acquires high-resolution images of retinal pathology and allows for easy image acquisition, Effert says. After taking measurements, physicians can evaluate results in a specific region of interest and easily compare them with other pathology images. By specifying the region of interest, average results in the region are displayed.
Physicians can perform a follow-up test on the same area using the same parameters as a previous test. This feature allows physicians to evaluate disease progression or assess pre- and post-treatment outcomes. Any differences in 2 microperimetry images are displayed for interpretation. This reduces variations between examiners.
The MP-3 has an easy-to-use touchscreen interface that permits customization. Patterns are customizable and the perimetry exam can be automatically overlaid onto a color fundus image.
In addition to atrophic macular degeneration patients, physicians can use the system to study patients with inherited retinal degeneration and map out functional defects in patients who may be normal otherwise but complain of a symptom such as a blank spot in their vision. “We can use microperimetry to determine exactly which part of the retina the functional problem is related to,” Dr. Sadda says.
Ultimately, the system enables physicians to get a better diagnosis and track how a patient’s eyes change over time. “MP-3 is being used in clinical trials to monitor atrophic macular degeneration patients for new treatments,” Dr. Sadda concludes. RP