Morphologic features of the aqueous humor drainage pathways in horses.

In simpler terms, this study investigated the structural features of the eye structures involved in the drainage of the aqueous humor in horses.

Morphology of the Iridocorneal Angle

In this research, the authors studied the iridocorneal angle in horses, which is the area where the cornea meets the iris. They found that:

• This angle was lined with a pectinate ligament.
• The ligament contained multiple layers of vertically oriented beams made from collagen, which were interjected with spaces filled with extracellular matrix.

Characteristics of the Anterior Chamber Angle

The anterior chamber angle had the following features:

• A large portion of it was made up of a uveal trabecular meshwork, which was notably composed of thick and widely-spaced trabeculae.
• These trabeculae connected to the extensions of the ciliary body musculature at the back and the prominent pectinate ligament at the front.

Study of the Corneoscleral Trabecular Meshwork

The authors examined the corneoscleral trabecular meshwork as well and found that:

• It was hemiobovate (meaning half-oval) in shape and formed the external boundary of the iridocorneal angle.
• The spaces in this area were found to be smaller and more evenly-distributed relative to those in the uveal trabecular meshwork.
• The trabecular beams, which were mainly composed of collagen and elastin covered by several layers of a basement membrane-like material, were enveloped by trabecular cells.

Examination of the Anterior Narrow Zone and Angular Aqueous Plexus

The researchers also described:

• An anterior narrow zone filled with wide corneoscleral trabeculae composed of elastin-collagen cores surrounded by circular bundles of long-spacing collagen.
• The extensive angular aqueous plexus which formed most of the external border of the outer corneoscleral trabecular meshwork.

Study of the Supraciliary Trabecular Meshwork

The study further detailed the supraciliary trabecular meshwork. The researchers found that it connected the iridocorneal angle and a band of trabeculae located between the ciliary body musculature and the underlying sclera, and suggests that this region might be integral for the outflow of aqueous humor in the equine eye. This observation highlights the importance of these structures in maintaining proper intra-ocular pressure and thus, their potential involvement in certain eye conditions.