Fourth Cranial Nerve Palsy: Surgical Outcome Quantification

Abstract

Introduction: Fourth cranial nerve (CN4) palsy is one of the main causes of vertical diplopia in adults and children. While some cases present spontaneous recovery, the remaining are not self-limited and require extraocular surgery. We propose to apply a quantitative evaluation method to binocular visual field (BVF), thus defining surgical outcome on a group of patients diagnosed with CN4 palsy and treated by the Strabismus Department of Instituto de Oftalmologia Dr. Gama Pinto.
Methods: A retrospective study was conducted. The exclusion criteria were previous strabological surgery, absence of fusion and inability to perform a kinetic perimetry. The BFV was performed after surgery through a personalized kinectic perimetry software on Octopus 900, Haag Streit® (vectors with a radiant direction, pointing from the center to the periphery, stimuli III4e; angular velocity of 5o/s). The exam was performed with green/red filters. Thereafter, the Binocular Single Vision (BSV) Score was calculated as proposed by Sullivan et al (1992). We defined good surgical outcome: BSV Score > 50% and heterophoria in the primary position; moderate outcome: BSV Score 1%-50% but with correctable diplopia with prisms or head tilt; poor outcome: BSV Score = 0% and/or intractable diplopia.
Results: Six patients were included. The mean age was 36.5 ± 23.0 years and 66.7% were males. Mean preoperative deviation was 10.7 ± 5.6 prismatic diopters of vertical deviation and -4.0 ± 9.4 DP of horizontal deviation. After surgery, mean vertical deviation was 3.0 ± 3.5 DP and mean horizontal deviation was -1.0 ± 2.5 DP. Five patients achieved good outcome and one patient had moderate outcome. Mean BVS Score was 67.8 ± 24.9.
Conclusion: We concluded that BVF evaluation allow us to quantify surgical outcome in patients with CN4 palsy. This method may be applied to other pathologies with diplopia.