Computational principles in Purkinje I and IV reflection pattern evaluation for the assessment of ocular alignment.

PURPOSE To develop a standardized reasoning for the evaluation of Purkinje I and IV Reflection Pattern data in primary, secondary, and tertiary positions of gaze in the diagnosis of strabismus with a mathematical approach. To demonstrate the applicability of certain mathematical relations and the appropriate graphic representation of computed ocular alignment data. METHODS Starting from the known Reflection Pattern Evaluation formulae, equations were derived that allowed for the computation of the relative and absolute positions of the optical and visual axes of both eyes from original data in binocular and monocular fixation. These equations were simplified for clinical use. RESULTS The authors obtained a set of equations that could be applied to the objective, quantitative analysis of eye alignment in screening for microtropia, in concomitant and incomitant diagnoses of strabismus in primary and nonprimary positions. CONCLUSIONS Purkinje I and IV Reflection Pattern Evaluation can be extended to the diagnosis of strabismus in nonprimary positions with sufficient clinical accuracy. The newly presented principles and equations serve as a basis for a convenient graphic representation of Purkinje I and IV Reflection Pattern data. These principles of evaluation may be applied to any data dealing with ocular alignment, independently of the method.