Optical Coherence Tomography Angiography in the Thirteen-Lined Ground Squirrel

Area of Science:

• Ophthalmology
• Comparative Physiology
• Biomedical Imaging

Background:

• Hypoperfusion is a critical factor in various retinal diseases.
• The thirteen-lined ground squirrel (13-LGS) offers a natural model for studying hypoperfusion due to its hibernation cycle.
• Optical coherence tomography-angiography (OCT-A) is a key imaging modality for retinal vasculature assessment.

Purpose of the Study:

• To evaluate the performance of two spectral-domain OCT-A systems in the natural hypoperfusion model of the hibernating 13-LGS.
• To assess the impact of hibernation on retinal microvasculature imaging using OCT-A.

Main Methods:

• Retinal imaging of 13-LGS was performed using a high-speed (HS-OCT-A) and a commercial (BE-OCT-A) system throughout the hibernation cycle.
• Custom software extracted retinal capillary plexuses (SCP, MCP, DCP).
• Adaptive optics scanning light ophthalmoscopy (AOSLO) and correlative histology were used for validation.

Main Results:

• Vessel density measurements showed minimal differences between systems during euthermia, except for the deep capillary plexus (DCP).
• Apparent capillary dropout was observed during torpor, particularly with HS-OCT-A, but resolved upon arousal.
• AOSLO measurements indicated that extending OCT-A scan duration by ~1000x could mitigate this artifact.

Conclusions:

• The HS-OCT-A system, while efficient, may be more prone to artifactual capillary dropout due to shorter interscan intervals.
• Differentiating between transient capillary dropout artifact and actual ischemia is crucial for managing retinal diseases.
• The hibernating 13-LGS serves as a valuable model for studying OCT-A utility in conditions of altered blood flow.