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

PURPOSE: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.