The menace response and pupillary light reflex in neonatal foals

Age‐associated changes in the equine flash visual evoked potential

“…Menace responses were inconsistent in newborn foals in accordance with what has been described in normal foals during the first weeks of life. [21][22][23] Two positive wavelets (P2 and P4) and two negative wavelets (N1 and N2) were identified in all FVEP recordings, while additional wavelets (P1, N2a, P3, and P5) were observed in some recordings in accordance with what was seen in our previous study. 19 There were no specific differences when comparing tracings between age groups in this aspect.…”

“…Most foals move their heads away from a threatening gesture indicating that they can perceive the stimulus, although the quality of vision is difficult to assess . However, a normal menace response is often not seen until up to 2 weeks postpartum, whereas subcortical reflexes, such as the pupillary light and dazzle reflexes, are present at birth in the foal . We found that all newborn foals included in the study lacked normal menace responses, although their FVEP waveforms appeared mature‐like.…”

“…32 However, a normal menace response is often not seen until up to 2 weeks postpartum, whereas subcortical reflexes, such as the pupillary light and dazzle reflexes, are present at birth in the foal. [21][22][23] We found that all newborn foals included in the study lacked normal menace responses, although their FVEP waveforms appeared mature-like. It is known that the efferent pathway of the menace response is conveyed through cerebellum and facial neurons in the brainstem, 33 and the lack of menace response may also depend on the immature cerebellum in the newborn foal rather than an immature input to or processing in the visual cortex alone.…”

Electroretinographic changes after intravenous lipid emulsion therapy in a dog and a foal with ivermectin toxicosis

“…The menace response is present in dogs and cats at 10–12 weeks of age . In foals, the menace response develops by 5–9 days of age and can therefore be normally absent or incomplete during that time . The menace response may also not develop symmetrically OU .…”

Equine ophthalmic examination: Routine diagnostic techniques

“…The appropriated response is the closure of the ipsilateral eyelids and possible globe retraction or an avoidance head movement (Gilger and Stoppini ; Featherstone and Heinrich ). This is a protective learned response and, in the foal, is not complete until 2–3 weeks post natally (Adams and Mayhew ; Enzerink ). For detection of a visual deficit in one field, the menacing gesture is directed, separately, toward the nasal visual fields and then toward the temporal visual fields (George ).…”