Comparison of image quality of corneal and retinal optical coherence tomography using sedation and general anesthesia protocols with or without retrobulbar anesthesia in horses.

This research evaluates the impact of different anesthesia methods on the quality and acquisition time of imaging in horses. The results suggest that retrobulbar blocks increase the effectiveness of imaging by reducing motion artifacts.

Objective of the Research

• This study aimed to compare image quality and acquisition time of two types of spectral domain optical coherence tomography (SD-OCT) imaging in horses—corneal and retinal—under three different anesthesia conditions.

Research Methodology

• Six middle-aged geldings free of ocular disease were selected for the study.
• In each horse, one eye was randomly selected and examined using SD-OCT under standing sedation without retrobulbar anesthetic block (RB), standing sedation with RB, and general anesthesia with RB.
• Five regions of interest within each horse’s eye were assessed— the axial and 12, 3, 6, and 9 o’clock positions in the cornea and the optic nerve head in the fundus.
• Three diagnostic scans of a predetermined quality were obtained per anatomical region.
• The time taken to acquire images and the total scans per site were also documented.
• The SD-OCT images obtained for both corneal and retinal were rated from 0 (nondiagnostic) to 4 (excellent) in terms of quality.

Findings of the Research

• The research data revealed that the mean values for total cornea scan attempts were lowest under general anesthesia (17), followed by standing sedation with RB (23) and without RB (24).
• Similarly, the total retina scan attempts were also found to be lowest under general anesthesia (19), tied with standing sedation with RB while highest for standing sedation without RB (23).
• Time taken for a total cornea scan was lowest under general anesthesia (9.2 minutes), followed by standing sedation with RB (13.2 minutes), and highest for standing sedation without RB (14.6 minutes).
• In case of total retina scan time, it was found to be lower under standing sedation with RB (9.2 minutes), higher under general anesthesia (13.0 minutes), and highest under standing sedation without RB (19.1 minutes).
• Both corneal and retinal image quality results showed improvement under general anesthesia and standing sedation with RB compared to standing sedation without RB.

Conclusions from the Research

• This research concluded that using retrobulbar blocks during SD-OCT examination helped in reducing eye movements and thus increased the percentage of scans fitting to region of interest, resulting in better imagining results.
• According to the research, retrobulbar blocks were beneficial in improving clinical image acquisition time and quality by reducing motion artifacts.