Fixation Stability: A Comparison between the Nidek MP-1 and the Rodenstock Scanning Laser Ophthalmoscope in Persons with and without Diabetic Maculopathy

Abstract

Impaired fixation stability is associated with reduced reading speed. In previous research, fixation stability has been assessed using an infrared eye tracker or a confocal scanning laser ophthalmoscope. The new MP-1 microperimeter from Nidek Technologies (Padova, Italy) provides another option for the assessment of fixation. Here the authors compare fixation stability values measured using the MP-1 microperimeter and the Rodenstock scanning laser ophthalmoscope (SLO; Rodenstock GmbH, Munich, Germany) in persons with and without diabetic maculopathy. Sixteen normally sighted volunteers and 21 patients with diabetic maculopathy were recruited. Fixation stability was recorded monocularly on the SLO and the MP-1 in counterbalanced order while participants fixated a red 1 degree cross. Fixation data collected from each instrument were used to calculate a bivariate contour ellipse area (BCEA) that encompassed 68% of fixation points. For control subjects, MP-1 BCEA values were larger than SLO by 0.25 log min arc(2), though the difference was small (10%) and of borderline significance (MP-1, 2.51 log min arc(2); SLO, 2.26 log min arc(2); P = 0.06). In patients with diabetic maculopathy there was no significant difference between MP-1 and SLO values (MP-1, 2.94 log min arc(2); SLO, 2.90 log min arc(2); P = 0.88). No significant difference was found in BCEA values from the SLO and MP-1 in control subjects and patients with diabetic maculopathy. The authors suggest that the similarity between BCEA values, together with the consistent and reliable operation of the MP-1, make it a useful and viable alternative to the SLO in the assessment of fixation.