Equine ocular ultrasonography

A case study explaining the Indications, preparation and techniques required to effectively perform diagnostic equine ocular ultrasonography.


Any situation in which the view into the globe is obscured. For example:

  • Corneal oedema
  • Intra-ocular haemorrhage or pus (hypopyon)
  • Cataracts
  • Severe chemosis
  • Eye/eyelid trauma (resulting in eyelid swelling that obscures the globe).

horse eye


  • Sedation is almost always required as this is not well-tolerated in most unsedated horses.
  • Performance of an auriculopalpebral block (technique described elsewhere).
  • Application of topical local anaesthetic agent to the surface of the cornea.


  • Either via direct placement of the probe on to the cornea, or transpalpebrally.
  • Directly on to the cornea:
    • Better images of the posterior part of the globe, and of the orbit, but…
    • Near-field artifacts result in poor images of the anterior part of the globe.
    • Requires sterile K-Y jelly (or similar) as an acoustic gel.
  • Transpalpebral:
    • Better images of the anterior part of the globe.
    • Also preferred method in cases of corneal disease/injury (and post-surgery) and after ocular trauma.
  • Examine the eyes in two orthogonal planes – vertical (between 12 o’clock and 6 o’clock) and horizontal (between 3 o’clock and 9 o’clock), from the central axis.
  • Fan the probe dorsoventrally in the horizontal plane and rostrolaterally in the vertical plane to visualise the whole globe.
  • Examine the cornea, lens (anterior and posterior surfaces) and retina. (N.B. Strictly speaking you will see retina, choroid and sclera as one layer.)
  • Can also visualise the iris and ciliary body, corpora nigra, optic nerve and periorbital structures (fat and muscles).
  • N.B. the contralateral eye may be valuable as a normal for comparison.

horse scan

horse ultrasound

Posterior lens luxation with retinal detachment.

Glaucoma affecting the right eye.

All images kindly provided by Professor Derek Knottenbelt OBE BVM&S DVM&S DipECEIM MRCVS.

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