¹Unidade Local de Saúde Gaia e Espinho, Psychiatry, Vila Nova de Gaia, Portugal, ²Unidade Local de Saúde de Matosinhos, Psychiatry, Matosinhos, Portugal

Background: Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder whose diagnostic criteria primarily focus on cognitive and behavioural symptoms. However, increasing evidence suggests that non-cognitive systems are also affected, particularly visual function. Studies have reported a higher prevalence of abnormalities in retinal structure, pupillary dynamics, oculomotor control, and visual processing speed in individuals with ADHD, as well as a potential role of psychostimulants in improving these deficits. These findings highlight possible benefits of psychostimulant treatment beyond cognitive and behavioural symptom management.

Aims & Objectives: Through a scoping review, we aim to address the latest evidence about the effects of psychostimulants on the visual function of patients with ADHD, highlighting the systemic nature of this condition and the non-cognitive and non-psychiatric benefits of its treatment.

Method: A scoping review based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines (PRISMA-ScR). The search was conducted in PubMed and Scopus databases using a combination of the MeSH terms: "attention deficit and hyperactivity disorder" OR “ADHD” OR “attention deficit disorder” AND “vision” OR “visual function” AND “psychostimulants” OR “stimulants”.

Results: Our review yielded 8 clinical studies on the effects of stimulants in several aspects of the visual function. Most studies were comparative cross-sectional studies (n=7) with one prospective observational follow-up study, involving a total of 234 patients and 253 healthy controls. Only one study found no significant differences between groups. Results obtained demonstrated that refractive errors were higher in unmedicated patients (compared with medicated and even control patients), contrast sensitivity improved with treatment as well as visual processing speed and inhibitory oculomotor control. One study measured general visual function and visual acuity, finding that medicated ADHD patients performed better in both parameters. In terms of structural changes, one study focused on retinal ganglion cell layer (GCL) thickness, demonstrating that medicated ADHD patients had higher GCL thickness when compared with unmedicated patients.

Discussion & Conclusions: This scoping review suggests that psychostimulant treatment in ADHD may be associated with measurable improvements in several domains of visual function, including contrast sensitivity, visual processing speed, oculomotor inhibitory control, and, in some studies, general visual performance and acuity. Structural findings, such as increased retinal ganglion cell layer thickness in medicated patients, further support the hypothesis that visual alterations in ADHD may reflect underlying neurobiological mechanisms, potentially modulated by dopaminergic pathways.
Overall, the available evidence supports the concept of ADHD as a systemic neurodevelopmental condition extending beyond core cognitive and behavioural symptoms, with visual function representing a relevant non-cognitive domain affected by the disorder and responsive to treatment. However, the evidence base remains limited by small sample sizes, heterogeneous methodologies, and predominantly cross-sectional designs. Future longitudinal and controlled studies using standardised visual outcome measures are needed to clarify causal relationships, treatment effects, and the potential clinical relevance of visual function as a biomarker or therapeutic outcome in ADHD.