Stereopsis deficits in schizophrenia: a systematic review with exploratory meta-analysis

Early sensory processing abnormalities are increasingly recognized as core features of schizophrenia. While impairments in contrast sensitivity, color vision and visual integration are well established, stereopsis (depth perception) has received limited systematic evaluation. This study systematically reviews and synthesizes available evidence on stereopsis deficits in schizophrenia, combining narrative synthesis of all eligible studies with an exploratory meta-analysis of studies reporting sufficiently comparable quantitative data. This review followed PRISMA 2020 guidelines and was prospectively registered in PROSPERO (CRD420251065135). PubMed, Scopus, and Embase databases were searched, alongside Google Scholar and ClinicalTrials.gov.in, from inception to 16 April 2026. Studies were imported to Rayyan for screening. The Newcastle-Ottawa Scale was used to assess the risk of bias. Random-effects meta-analysis pooled standardized mean differences in stereopsis thresholds. Studies unsuitable for pooling were narratively synthesized. This systematic review included six studies that assessed stereopsis in individuals with schizophrenia (n = 200) and compared with healthy controls (n = 167). Reduced stereopsis was reported across the included studies. Four studies were eligible for exploratory quantitative synthesis. The pooled standardized mean difference (SMD = 0.824, 95% CI: 0.605 to 1.043) suggested poorer stereopsis performance in schizophrenia. The heterogeneity was low to moderate (I2 = 25.9%, τ² = 0.0013, p = 0.2563). Subgroup analysis suggested a deficit with Titmus Stereotest (SMD = 0.890, 95% CI 0.637 to 1.143; I2 = 0%) and Graded Circles tests (SMD = 0.608, 95% CI -0.083 to 1.300; I2 = 63.3%). Leave-one-out analysis indicated directionally stable effects (SMD range 0.703 to 0.898). Overall methodological quality was good (NOS > 6) with low risk of bias. However, given the small number of studies, this estimate should be interpreted cautiously as preliminary and hypothesis-generating. This systematic review suggests that currently available studies generally report reduced stereopsis in individuals with schizophrenia. The exploratory meta-analysis, based on only four studies, provides preliminary quantitative support but is insufficient for definitive inference. Larger, methodologically harmonized studies are needed. Not applicable.