Multifocal optical coherence tomography of the mouse eye to image the vitreoretinal vasculature in full depth

In vivo optical coherence tomography (OCT) of the mouse vitreoretinal vasculature in full depth is technically challenging. Conventional OCT techniques employ axial confocal gating, which induces signal drop-off and limits spatial resolution outside the Rayleigh range.

Our aim is to develop a multifocal OCT imaging approach using a tunable lens and a registration method that allows the generation of a composite image of the vitreoretinal vasculature while preserving high and uniform lateral spatial resolution, signal intensity, and image contrast in full depth.

A calibration target was developed to characterize the multifocal optical system and quantify the signal intensity, contrast, and resolution. These optical specifications were used to image mice at postnatal day 14. Intra- and inter-volume registration methods were necessary to correct for motion and generate a composite image from single-focus images using weighted averaging.

In the calibration target, signal intensity and contrast were 20 dB higher in the composite compared with single-focus images. Lateral resolution remained uniform (4 to $6\mu m$ ). In animals, signal intensity and contrast were 10 to 15 dB higher in the composite compared with single-focus images and highest in the hyaloid vasculature.

This technique is promising in studying the mouse vitreoretinal vasculature during eye development and disease.