Which path accounts for more than half of outflow in horses?

Which path accounts for more than half of outflow in horses?

• A. Uveoscleral outflow (non-conventional)
• B. Trabecular meshwork
• C. Lacrimal drainage
• D. Retinal outflow

Answer: (A)

Aqueous humor exits the eye mainly through two routes: the conventional pathway through the trabecular meshwork into Schlemm’s canal, and the unconventional uveoscleral pathway through the ciliary body and sclera into the choroidal spaces. In horses, the uveoscleral (non-conventional) route carries more than half of the drainage. This reflects equine ocular anatomy where a substantial portion of outflow occurs by passing through the ciliary muscle and scleral tissues into supraciliary and suprachoroidal spaces, making this route the dominant one. The conventional trabecular pathway remains important but is not the primary route in horses. Lacrimal drainage pertains to tear film drainage, not intraocular aqueous humor, and retinal outflow is not a recognized pathway for aqueous humor drainage.

Aqueous humor exits the eye mainly through two routes: the conventional pathway through the trabecular meshwork into Schlemm’s canal, and the unconventional uveoscleral pathway through the ciliary body and sclera into the choroidal spaces. In horses, the uveoscleral (non-conventional) route carries more than half of the drainage. This reflects equine ocular anatomy where a substantial portion of outflow occurs by passing through the ciliary muscle and scleral tissues into supraciliary and suprachoroidal spaces, making this route the dominant one. The conventional trabecular pathway remains important but is not the primary route in horses. Lacrimal drainage pertains to tear film drainage, not intraocular aqueous humor, and retinal outflow is not a recognized pathway for aqueous humor drainage.