Analysis of ocular objective torsion and near stereopsis function in primary superior oblique overaction

AIM: To investigate the relationship between objective ocular torsion and near stereopsis in patients with primary superior oblique overaction(PSOOA).METHODS: Retrospective study. A total of 59 strabismus patients with PSOOA who underwent strabismus surgery at Renmin Hospital of Wuhan University between January 2019 and November 2023 were collected. Based on the collected fundus photographs and the position of the fovea relative to the horizontal line through the optic disc, the eyes were categorized as incyclotorsion, excyclotorsion, or no cyclotorsion. Additionally, the fovea-disc angle(FDA)and the relationship between objective ocular torsion status, FDA, and near stereopsis function in the patients were further measured and analyzed.RESULTS: Totally 59 patients(92 eyes)showed superior oblique overaction. There were no cases of excyclotorsion, 32 cases with no cyclotorsion, and 27 cases with incyclotorsion. The total binocular FDA was significantly smaller in the no-cyclotorsion group compared with the incyclotorsion group(2.83°±2.89° vs 16.12°±5.74°, P<0.001). The preservation rates of near stereopsis were 66% and 15% in the no-cyclotorsion and incyclotorsion groups, respectively, with a significant statistical difference(P<0.001), and the preservation rates of fine near stereopsis were 38% and 11% in the no-cyclotorsion and incyclotorsion groups, respectively, with a significant statistical difference(P=0.02). Among all patients, near stereopsis was correlated with total binocular FDA(r=-0.526, P<0.001), with the strongest correlation observed with the FDA of the incyclotorsion(r=-0.546, P<0.001). In the incyclotorsion group, there was no correlation between near stereopsis and total binocular FDA(r=-0.366, P=0.060), with a negative correlation between near stereopsis and the FDA of both the incyclotorsion and the overaction(r=-0.424, P=0.028; r=-0.485, P=0.010). In the no-cyclotorsion group, near stereopsis was not correlated with total binocular FDA, incyclotorsion FDA, or overaction FDA.CONCLUSION:PSOOA patients with incyclotorsion have a lower preservation rate of near stereopsis than those without cyclotorsion. Near stereopsis function of patients with PSOOA is negatively correlated with total binocular FDA, especially the greater the FDA of the incyclotorsion and overaction, the worse the near-stereoscopic function.