Classification of eccentric fixation.

The literature on eccentric fixation includes numerous systems of classification devised by different workers. At the orthoptic and pleoptic centre at this hospital, we have tried to use some of these classifications, but have observed certain discrepancies which are discussed below. Some classifications are based on anatomical landmarks (Mayweg and Massie, 1958; von Noorden, 1959; Scully and Naylor, I96I; von Noorden and Lipsius, I964) and others on the relationship of the fovea with the fixation target (Byron, I960; Agarwal, Khosla, and Angra, I964). Table I (opposite) shows much disparity in nomenclature. The same degree ofeccentric fixation has been differently described by different workers: e.g. 30 eccentric fixation was included under paramacular fixation by Byron (I960) but under parafoveal fixation by Agarwal and others (I964). Similarly, 5' eccentric fixation was termed "centrocaecal" by Byron (I960) and "paramacular" by Agarwal and others (I964).