Preclinical imaging of iridocorneal angle and fundus using a modified integrated flexible handheld probe

Abstract

A flexible handheld imaging probe consisting of a [Formula: see text] charge-coupled device camera, light-emitting diode light sources, and near-infrared laser source is designed and developed. The imaging probe is designed with specifications to capture the iridocorneal angle images and posterior segment images. Light propagation from the anterior chamber of the eye to the exterior is considered analytically using Snell's law. Imaging of the iridocorneal angle region and fundus is performed on ex vivo porcine samples and subsequently on small laboratory animals, such as the New Zealand white rabbit and nonhuman primate, in vivo. The integrated flexible handheld probe demonstrates high repeatability in iridocorneal angle and fundus documentation. The proposed concept and methodology are expected to find potential application in the diagnosis, prognosis, and management of glaucoma.

Keywords: fundus imaging; imaging systems; iridocorneal angle imaging; medical imaging; ophthalmology.

Fig. 1

Schematic illustration of light transmission from iridocorneal angle to air.

Fig. 2

Imaging scheme for (a) iridocorneal angle imaging and (b) fundus imaging (inset: side and top view of the distal end of the imaging probe showing the illumination conduits and $3\mathrm{mm}\times 3\mathrm{mm}$ CCD conduit).

Fig. 3

Iridocorneal angle images of (a) porcine sample, (b) New Zealand white rabbit, and (c) nonhuman primate. The white arrows indicate the iridocorneal angle regions.

Fig. 4

Superior quadrant of the New Zealand white rabbit using (a) white LEDs and (b) near-infrared LED and laser source. The white arrows indicate the iridocorneal angle regions.

Fig. 5

Fundus images of the (a) porcine sample and (b) New Zealand white rabbit.

Fig. 6

Images acquired using the integrated flexible handheld probe. (a) An open angle where the iris processes are seen reaching toward the scleral spur. (b) The indentation examination of the same eye where the iris is flattened as the cornea is indented. (c) A closed angle of the same eye after deliberately injecting fluids into the vitreous chamber. The increase in pressure caused the iris to close up toward the cornea, narrowing and occluding the iridocorneal angle. (d) The indentation examination of the eye after injection. Part of the iris root is adhered to the cornea.