Vergence Eye Movement Deficits Observed in Schizophrenia, Bipolar Disorder

Patients with schizophrenia or bipolar disorder demonstrate vergence eye movement deficits, according to a study published in the Journal of Psychiatric Research. These deficits are particularly severe among men with schizophrenia, according to the study. 

Researchers enrolled 85 participants consisting of individuals with schizophrenia (n=28; mean age, 37.32 years; 11 women), patients with bipolar disorder (n=32; mean age, 42.15 years; 16 women), and healthy control individuals (n=25; mean age, 35 years; 14 women). All participants underwent optometric examinations consisting of visual acuity measurement, retinoscopy, ocular dominance testing, and prism cover test at far and near. An infrared tracker with a dedicated vergence stimuli generator was used to measure vergence eye movements. 

Patients with schizophrenia had a higher mean break time and recovery points of fusion (P =.008 and P =.0097, respectively) and shorter correct tracking time (P =.0022) compared with participants in the control group. Participants with bipolar disorder demonstrated a higher number of saccades while tracking in both convergent (P =.03) and divergent (P =.04) states compared with control individuals. They also showed higher eye positioning errors (P =.02) and adjusted gain (P =.05) on convergence compared with the control group. 

Men with schizophrenia presented more severe eye movement deficits, according to the report, demonstrating decreased break point of fusion (P =.035), maximal convergence and divergence achieved (P =.03 and P =.015, respectively), and correct tracking time in divergence (P =.043) compared with men with bipolar disorder.

The study authors state that these deficits have “been considered as objectively measured biomarkers that support uncovering of the neurobiological basis of mental disorders,” and suggest that “[s]everity of those oculomotor deficits may reflect common structural and functional abnormalities of brain areas associated with vergence eye movements that were identified in previous studies.”

Study limitations include a small sample size, the use of convenience sampling in the control group, and potential confounding due to pharmaceutical use.