Upside-down vision: a systematic review of the literature

BackgroundReversal of vision metamorphopsia (RVM) is a rarely reported disorder characterised by rotation of vision, 180 degrees in the coronal plane. A systematic review and analysis of all available reports of RVM was undertaken to identify the clinical picture, underlying aetiology and proposed pathophysiology and to define anatomical localisation.MethodsWe followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and used Scopus, Web of Science, Ovid, Medline, Embase, PubMed and CINAHL databases to search for articles about RVM. The available articles were published from 1974 to 2022. We summarised the evidence, analysed the data and represented anatomical localisation to provide information on the clinical patterns for diagnostics and management.ResultsTwenty-eight articles fulfilled the selection criteria, providing 52 cases of reported RVM. Reports focused on the clinical picture and evaluation of neurological signs and symptoms. The most common underlying aetiology was a posterior circulation stroke or interruption of the vestibular system. In the analysis, we demonstrated statistically significant differences between ischaemic and vestibular aetiology in the duration of episodes (p=0.03, Z=2.13) and vomiting (p=0.02, Z=2.28) subgroups. Insults present on brain imaging have been mapped via two-dimensional graphical representations (n=16).ConclusionsThis review intends to raise awareness of this unusual phenomenon. Swift recognition of this disorder is paramount and appropriate management should be tailored to the individual aetiology. Brain mapping and analysis of cases may elucidate the anatomical localisation of the central integrator of visuospatial orientation. We suggest that sensory information may be synthesised by a multinucleated visuospatial system to form a visual representation of extrapersonal verticality.