Effectiveness of prisms in relieving diplopia in superior oblique palsies

Abstract

Aim: To study the effectiveness of prisms in relieving diplopia in patients with superior oblique palsies. Materials and Methods: This was a retrospective study of all patients with superior oblique palsies who were prescribed prisms for relief of symptomatic diplopia in our institute from September 2013 to March 2015. A detailed analysis was performed of demographic features of the patients; nature, onset, duration, and course of diplopia; measurement of deviation in all gazes; diplopia charting; assessment of torsion; systemic risk factors; and amount and type of prism given. The effectiveness of prisms was measured by an objective score by the examiner as well as a subjective score reported by the patient. Results: Among the total 25 patients, 21 patients had acquired superior oblique palsies and 4 patients had congenital causes. Males outnumbered females. Majority had unilateral involvement. Deviation in primary position ranged from 3 Prism Dioptre to 25 PD with 80% having less than 10 PD. Seventy-six percent had less than 10° torsion in primary gaze. Eighty-eight percent were given less than 10 PD prisms, 12% were given more than 10 PD, of which two were Fresnel Prisms. Seventy-six percent were satisfied with the prisms. Fifty-two percent had spontaneous improvement whereas 16% needed surgery. Conclusion: Prisms were effective in relieving diplopia in most of the acquired unilateral superior oblique palsies where the primary deviation was less than 10 PD and torsion was less than 10°.