The Nidek microperimeter (MP1, Nidek Instruments, Italy) is a microperimetry device that also assesses fixation stability. The MP1 does not use the method of quantifying fixation stability by calculating a bivariate contour ellipse area (BCEA). Here we compare the MP1 fixation quantification with the BCEA technique by correlating these values to various parameters of reading known to be related to fixation stability.
Twenty-five people with age-related macular disease were assessed. Eye position was recorded using the MP1 during a fixation task. Fixation score and central 2° and central 4° values were obtained from the MP1. Bivariate contour ellipse area values were calculated from raw fixation data. Reading was assessed using MNREAD, Rapid Serial Visual Presentation, and European reading tests.
Fixation data could not be collected for two observers. For the other 23 participants, the MP1 fixation scores were very poorly related to reading parameters. In contrast, there was a significant relationship between fixation stability assessed using the BCEA technique and Rapid Serial Visual Presentation reading speed (r = −0.59, P < 0.01), European reading test reading error rate (r = 0.66, P < 0.01), and MNREAD peak reading speed (r = 0.55, P < 0.05).
Using the software supplied with the MP1 does not adequately quantify fixation stability in people with age-related macular disease. We recommend that the BCEA technique is used to quantify fixation stability when using the MP1 microperimeter.