Static and dynamic retinal fixation stability in microperimetry

Objective: To compare static (during a pure fixation task) versus dynamic (during microperimetry) quantification of fixation stability using microperimetry in normal and pathologic eyes, by means of 2 available (clinical and bivariate contour ellipse area [BCEA]) classification methods. Design: Prospective comparative observational study. Participants: One hundred and forty-nine eyes (110 patients) with different macular diseases and 171 normal eyes (109 subjects). Methods: In all eyes studied, fixation stability was acquired during an isolated fixation task (static fixation) and during microperimetry (dynamic fixation). All fixation data were analyzed and compared by means of a clinical classification and by means of BCEA quantification. Results: Pathologic eyes were classified as follows: 41 eyes with diabetic macular edema (DME group), 13 eyes with vitreoretinal interface disease, 60 eyes with age-related macular degeneration (AMD group), and 35 eyes with primary open-angle glaucoma. Fixation stability was not uniform among groups according to clinical classification in both static and dynamic modalities (p < 0.0001). AMD group showed larger BCEA areas compared with all other groups (p < 0.0001). All pathologic groups showed more unstable fixation in dynamic fashion according to both clinical and BCEA methods (p < 0.0001). The variation of fixation stability of control group in dynamic task was highlighted only by BCEA analysis (p < 0.0001). A deterioration of retinal fixation according to clinical method matches a significant increase in BCEA areas (p < 0.0001). Conclusions: The detection of clinical fixation stability changes improves when acquired in the dynamic modality. BCEA analysis provides more accurate evaluation of fixation stability and may detect minimal quantitative changes of the fixation area. However, a standard clinical classification can also detect changes in fixation stability in pathologic eyes. Both methods are useful tools in the evaluation of fixation stability.