Factors influencing fixation stability area: a comparison of two methods of recording

Significance: The authors analyze factors influencing bivariate contour ellipse area (BCEA) in healthy and pathologic eyes and how such factors may affect isolated (static BCEA) or microperimetric fixation (dynamic BCEA). They conclude that aging increases both dynamic BCEA and examination time, whereas static BCEA offers less variance and the maximum distinction with pathologic eyes. Purpose: The aim of this study was to assess factors influencing BCEA and the recording method that offer less variability and thus maximum distinction between healthy and pathologic eyes. Methods: A total of 136 eyes were retrospectively reviewed, 85 eyes without ophthalmic disorders (logMAR acuity ≦0.0) and 51 eyes with late age-related macular degeneration (AMD) were enrolled. All patients underwent two consecutive examinations, a 30-second isolated fixation (static BCEA) and a microperimetric test with continuous fixation recording (dynamic BCEA). All the examinations were carried out using MP1 microperimeter (NAVIS software version 1.7.6; Nidek Technologies, Padova, Italy). Results: Dynamic BCEA was significantly correlated with age (r = 0.38, P <.001), total (r = 0.32, P =.03), and tracking time (r = 0.33, P =.02) in controls, whereas no significant relationships were found in the AMD group. The greatest difference between static and dynamic BCEA was observed in 70- to 79-year decade in healthy subjects (P <.01). Logistic regression analysis showed that late AMD status was significantly predicted by ±2 SD and ±3 SD static BCEA (both P =.03). Conclusions: Dynamic BCEA is influenced by a certain degree of variability in advanced-age healthy subjects. In such cases, the use of ±2 SD and ±3 SD static BCEAs seems to offer a more accurate detection of fixation stability changes in the AMD group with respect to normal subjects.