Evaluation of equine corneal disease using spectral domain optical coherence tomography (SD-OCT)

Purpose: The purpose of this case series is to evaluate the use of spectral domain optical coherence tomography (SD-OCT) imaging in equine corneal disease to demonstrate the feasibility, diagnostic effectiveness, and limitations of this imaging modality.

Methods: Retrospective study: Handheld SD-OCT (Envisu, Bioptigen Inc, Morrisville, NC) was used for high-resolution imaging of horses with corneal disease presenting to the North Carolina State University Equine Ophthalmology Service from 2013 to 2018.

Results: Fourteen horses were included in this study, including six horses with corneal ulceration, three with stromal abscesses (SA), three with immune-mediated keratitis (IMMK), and two with ocular neoplasms. High-resolution images of the cornea were obtained using handheld SD-OCT in standing horses; however, acquiring images was time-consuming due to the inherent movement of the examiner and horse. Despite this, in horses with corneal ulcers, SA, and IMMK, SD-OCT assisted with determining location of disease in the cornea (eg, superficial, mid-stromal, endothelial) and if disruption of Descemet's membrane was present. In horses with neoplasia, the SD-OCT helped to determine whether the cornea had neoplastic invasion from anterior chamber masses.

Conclusions: Results from this retrospective study suggest that handheld SD-OCT for imaging the cornea of horses is feasible and may be helpful in determining depth and extent of lesions in the cornea.