A novel ultrasonographic approach for evaluating the optic nerve in dogs

Increased intracranial pressure (ICP) can cause hypoxia in the central nervous system, leading to permanent neurological sequelae or even death. Ultrasonography (US) of the optic nerve may serve as an alternative for monitoring this increase, since the diameter of the nerve enlarges in response to elevated ICP. Currently, two ultrasonographic techniques are used to evaluate the eye, transpalpebral and corneal, both providing an axial view. The aim of this study was to describe a novel ultrasonographic technique for visualizing the optic nerve in dogs using a coronal view. Our hypothesis is that measuring the optic nerve in dogs using the coronal view is both feasible and reliable. A total of 157 dogs were included in the study, comprising 80 females and 77 males, with no neurological, ophthalmic, or cranial conformational disorders. Three measurements of the optic nerve diameter (OND) were obtained from each eye (coronal plane). When comparing the three OND measurements for each eye, with a 95% confidence interval, no statistically significant differences were observed, nor were there differences between the left and right eyes of the same patient. We conclude that ultrasonographic measurement of the normal optic nerve diameter (OND) in dogs is feasible using the coronal view.