Aim 30 years ago, Cullen1 (a neuro-ophthalmologist) developed and validated a simple paper chart for evaluation of the central 25 degrees of the visual field. We re-developed this concept in digital form (as a smartphone application) and sought to assess its sensitivity and specificity in detecting field loss, through comparison with formal machine-based perimetry. Method A case series pilot study was performed to test the app-based Cullen chart for concordance with formal machine-based perimetry (Humphrey and Octopus). 18 patients with a range of sellar/parasellar tumours (pituitary adenoma, craniopharyngioma, and meningioma) being managed in a single neurosurgical centre were involved in this study. Patients underwent formal visual field perimetry as part of standard care. They also underwent assessment using the smartphone-based Cullen chart as part of routine outpatient assessment. 37 eye episodes were assessed, incorporating pre- and post- treatment assessment for a range of potentially compressive pathologies. Results The digital Cullen chart had a sensitivity of 75% and specificity of 98% compared with machine-based perimeters. The positive predictive value was 93% and negative predictive value was 92%. Conclusions In the context of visual field assessment for patients with sellar/parasellar tumours, this smartphone-based chart shows strong concordance with machine-based perimeters. It is therefore an accessible visual field screening and monitoring tool for clinicians. With further study, there is also potential for approval as a remote patient-led visual field monitoring method.