SELF-ASSESSMENT OF ANGLES OF STRABISMUS WITH PHOTOGRAPHIC PURKINJE-I AND PURKINJE-IV REFLECTION PATTERN EVALUATION

Background: Accurate assessment of the angle of strabismus, e.g. of va riable angles of strabismus, is crucial in preoperative patient manage ment and is usually performed in a clinical environment, Objective ass essment by patients themselves, under everyday conditions, could contr ibute to a better preoperative work-up, A new objective evaluation pro cedure for the measurement of manifest angles of strabismus for near a nd distance fixation by the patient himself is presented. Methods: To account for the modified experimental setup used for the self-assessme nt, an amended computation procedure of Purkinje reflection pattern ev aluation was developed. For measurement, patients and controls placed their head on a head/chin rest and fixated at 33 cm or 4 m distance in primary position. A reflex camera and three photo flash units were po sitioned on a special frame underneath the visual axis and in front of the subject so that both eyes could be photographed simultaneously, T he camera's remote shutter control was released together with the phot o flash units by the properly fixating subject, The angles of strabism us were obtained from the series of pictures through later evaluation of the Purkinje I and IV reflection patterns recorded in the photograp hs of the eyes. Results: Measurements of the ocular alignment in two c ontrol groups and in a group of strabismic subjects showed satisfactor y accuracy of the ''self-assessment'' method compared to ''standard'' Purkinje reflection pattern evaluation and orthoptic measurements of t he angle of strabismus. Conclusion: The modified ''self-assessment'' m ethod can be used for the objective recording of angles of strabismus as needed in the preoperative work-up of patients with variable angles of strabismus, over prolonged periods of time, and outside a clinical setting.