NAVLE Special Senses

Equine Nasolacrimal Duct Obstruction and Dacryocystitis Study Guide

Nasolacrimal duct (NLD) obstruction and dacryocystitis are frequently encountered conditions in equine ophthalmology.

Overview and Clinical Importance

Nasolacrimal duct (NLD) obstruction and dacryocystitis are frequently encountered conditions in equine ophthalmology. The nasolacrimal system functions to drain tears from the eye to the nasal cavity, and any obstruction leads to epiphora (overflow of tears), ocular discharge, and secondary infection. These conditions may be congenital or acquired and represent an important differential diagnosis for horses presenting with chronic ocular discharge.

Understanding the anatomy of the equine nasolacrimal system is essential for accurate diagnosis and successful treatment. The equine NLD is approximately 24-30 cm long in adult horses, making it one of the longest nasolacrimal ducts among domestic animals and prone to obstruction at multiple sites along its course.

Structure Clinical Details
Lacrimal Puncta Two oval openings (approximately 2 mm diameter) located 8-9 mm lateral to the medial canthus on superior and inferior eyelids
Lacrimal Canaliculi 3-4 mm diameter tubes connecting puncta to the lacrimal sac
Lacrimal Sac Funnel-shaped structure located in the bony fossa of the lacrimal bone; much less developed in horses compared to humans
Nasolacrimal Duct Total length: 24-30 cm. Three segments: (1) Caudal osseous segment through lacrimal canal (6-7 mm diameter narrowing to 3-4 mm), (2) Middle membranous segment, (3) Rostral cartilaginous segment
Nasal Orifice (NLO) 3-4 mm oval opening on the ventral floor of the nasal vestibule at the mucocutaneous junction; accessory openings common

Anatomy of the Equine Nasolacrimal System

The equine nasolacrimal system consists of both secretory and excretory components. The lacrimal gland is located at the dorsolateral aspect of the orbit within the lacrimal fossa, beneath the supraorbital process of the frontal bone.

You've been studying hard

Create a free account to keep reading

Free accounts get 5 articles/day + daily practice question

Join 14,000+ vet students already studying with NavleExam.

No credit card needed — free account takes 30 seconds.

Create Free Account — Keep Reading Already have an account? Log in
or skip signup — just get daily questions

No spam. One question per day. Unsubscribe anytime.

NAVLE Exam Prep Platform

Everything you need to pass the NAVLE

10,000+ Practice Questions
Exam-style with full explanations
Past Exam Papers
Real previous exam questions
Flashcard Mode
Species & topic quick review
High-Yield Study Guides
What's actually on the exam
Start Free Trial → See Plans & Pricing No credit card required to start