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S. Salvatore, U. De Marco, M. Marenco, E. M. Vingolo; Quantification of Fixation Stability by Bivariate Contour Ellipse Area (bcea) Using the Mp1 Microperimeter. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2219.
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© ARVO (1962-2015); The Authors (2016-present)
The Microperimeter MP1 (Nidek Instruments, Italy) is a microperimetry device that also assesses fixation stability. A new software upgrade of the instrument uses also the bivariate contour ellipse area (BCEA) to assess fixation. In recent studies BCEA has been demonstrated to be more accurate than the classic fixation classification. Here we evaluate the utility of BCEA to assess visual function in hypertensive retinopathy.
42 healthy people (group 1) and 22people (group 2) with hypertensive retinopathy were assessed. Groups were age and sex matched. Eye position was recorded using the MP1 during a fixation task. Fixation score and central 2 degrees and 4 degrees values were obtained from the MP1. Bivariate contour ellipse area values were automatically calculated. Patients were also assessed for BCVA, retinal sensitivity within central 2, 4 and 10 degrees. Statistical analysis was performed with student t test. Values < 0.05 were considered statistically significant.
fixation within the 2 degree diameter circle was 88.84 ±15.74 for group 1 and 76.50 ±16.27 (p <0.05), fixation within the 4 degree diameter circle was 95.79 ±11.23 and 92.98± 6.01 respectively (0.11), retinal sensitivity within the 2° was 17.30 ±2.56 dB and 16.75 ±2.68 dB respectively (0.58), retinal sensitivity within the 4° was 17.43± 2.29 dB and 17.26 ±2.20 dB respectively (0.680), retinal sensitivity within the 10° was17.37 ±2.09 dB and 16.97± 1.99 dB respectively (0.29), BCEA which contained 68%of fixation points was 2.20 ±2.71 deg2 and 5.13± 4.55 deg2 (0.0001) respectively, BCEA which contained 95% of fixation points was 5.97 7.34 deg2 and 11.63 ±7.39 deg2 (0.0002), BCEA which contained 99% of fixation points was 10.68 ±13.14 deg2 and19.94± 12.85 deg2 (0.0001) respectively. BCVA was 0 ±0.95 and 0 ±1.15 logMAR respectively.
Fixation can be better studied and characterized by BCEA rather than the old fixation classification, and fixation itself is more important than retinal sensitivity in the study of visual function. BCEA has proved to define very subtle changes in the macular function in moderate hypertensive retinopathy patients even in cases with good visual acuity, good retinal sentivity and good fixation assessed using the previous software version. We recommend that the BCEA technique is used to quantify fixation stability when using the MP1 microperimeter.
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