Convergence insufficiency with unilateral exophoria at near in schizophrenia and bipolar disorder - a preliminary study

The study describes an abnormal convergence symptom, i.e. unilateral exophoria at near, in patients with schizophrenia (SZ) and bipolar disorder (BD). The aim of this paper is to present the symptom and discuss its possible explanations. 29 patients with SZ, 15 patients with BD and 20 healthy controls (HC) took part in the study. The neurological assessment was done with International Co-operative Ataxia Rating Scale (ICARS) and Neurological Evaluation Scale (NES). The abnormal vergence pattern was observed in 12 patients with SZ, 1 patient with BD and 0 HC. Symptom appeared statistically more often in SZ patients than in BD patients and HC. SZ patients with vergence symptom performed significantly worst in oculomotor and dysarthia subscores of ICARS. The symptom can be linked to disruptions in cortico-ponto-cerebellar network and midbrain. It was the only neurological symptom that differed SZ and BD groups, thus it might be used in differential diagnosis. Further research is needed to obtain a full clinical description of the symptom.