Basics

Question 1

Where are puncta

Answer 1

at the posterior edge of the lid margin, at the junction of the lash-bearing (opatrzony) lateral five-sixths (pars ciliaris) and the medial non-ciliated one-sixth (pars lacrimalis).

Question 2

Rosenmüller valve - where and what does

Answer 2

A small flap of mucosa (Rosenmüller valve) overhangs the junction of the common canaliculus and the lacrimal sac (the internal punctum) and prevents reflux of tears into the canaliculi

Question 3

ampullae - length

Answer 3

2 mm

Question 4

canaliculi horizontally - length

Answer 4

8 mm

Question 5

lacrimal sac - length

Answer 5

10–12 mm

Question 6

nasolacrimal duct - length

Answer 6

12–18 mm

Question 7

nasolacrimal duct - how does it go

Answer 7

slightly laterally and posteriorly to open into the inferior nasal meatus, lateral to and below the inferior turbinate. partially covered by a mucosal fold (valve of Hasner)

Question 8

mechanism of tears movement

Answer 8

• With each blink, the pretarsal orbicularis oculi muscle compresses the ampullae, shortens and compresses the horizontal canaliculi, and closes and moves the puncta medially, resisting reflux. Simultaneously, contraction of the lacrimal part of the orbicularis oculi creates a positive pressure that forces tears down the nasolacrimal duct and into the nose
• When the eyes open, the canaliculi and sac expand, creating negative pressure that draws tears from the canaliculi into the sac

Question 9

Causes of a watering eye

Answer 9

• Hypersecretion
• Defective drainage
○ Malposition (e.g. ectropion) of the lacrimal puncta.
○ Obstruction at any point along the drainage system, from the punctal region to the valve of Hasner.
○ Lacrimal pump failure, which may occur secondarily to lower lid laxity or weakness of the orbicularis muscle (e.g. facial nerve palsy).