1. Lacrimal Disorders Flashcards
Describe the development of the secretory apparatus of the lacrimal system
Secretory Apparatus: Lacrimal gland
Develops from multiple solid ectodermal “buds” at the anterio-superior-lateral orbit
The buds branch and canalize forming ducts and alveoli
Why do newborns not produce tears when crying?
Lacrimal glands not fully functional until ~6 weeks after birth
Describe the development of the excretory apparatus of the lacrimal system
At end of gestational week 5, nasolacrimal groove forms between nasal and maxillary prominence
In the groove, a linear thickening of the ectoderm extends as a solid cord, which sinks into the mesenchyme and canalizes, forming NLD and lacrimal sac
Where does the nasolacrimal duct exit to?
Inferior Meatus
What is Congenital NLDO?
What is the prevalence?
Failure of caudal end of duct to completely canalize —> causes an obstruction at the distal end
Present in 5% of infants at birth; 20% in pts with mid facial abnormalities
How do you manage Congenital NLDO?
Self-limiting, most of the time
(Patency usually occurs spontaneous within first few months to a year)
If not, digital massage usually successful
What is the Valve of Rosenmuller?
A fold between the canaliculi and lacrimal sac, that prevents tear reflex from the sac from getting back into the canaliculi
How long is the nasolacrimal duct (in mm)?
~12 mm
The nasolacrimal duct opens into the nose via _____ called the _____, located under the ______
The nasolacrimal duct opens into the nose via ostium (cavity) called the inferior meatus, located under the inferior turbinate (bone structure in the nose)
What is the valve of Hasner
Mucosal fold/membrane at the distal end of the NLD that prevents reflux from the nasal cavity
What is the difference between a simple and a complex congenital NLDO?
Simple — involves the valve of Hasner
Complex — diffuse compression or bony obstruction (more challenging to treat)
What is a conjunctiva-dacryocystorhinostomy?
A surgical bypass of the lacrimal system
Atresia of puncta
No puncta visible at exam
Epiphora
Overflow of tears, to the point of running down cheeks
What are 5 (general) causes of epiphora?
- Paresis of orbicularis muscle
- Obstruction of lacrimal passage
- Overproduction of tears
- Faulty apposition of puncta in lacrimal lake (usually 2º/ ectropion in geriatric pts)
- Scarring of puncta
Describe the cell lining of the canaliculi
Non-keratinized, non-mucin-producing, stratified squamous epithelium
Length of vertical canaliculi
2 mm
Length of horizontal canaliculi
8-10 mm
Evaporation rate for young patients
10%
Evaporation rates for elderly patients
20%
What muscle is responsible for the majority of tear flow, being pumped from the tear lake?
Orbicularis
In a patient with Bell’s Palsy, is epiphora more common in a LMN lesion or UMN lesion?
Explain why.
More common with LMN bc both upper and lower half of the face is paralyzed (in UMN, only the lower face is affected.
A defect in CN 7, which innervates the OO m., would cause a weakened blink, leading to epiphora
“Tearing patients can be loosely divided into 2 groups…”
- Hypersecretion of tears
- Drainage impairment
Case History: what are some characteristics of the patients complaint (epiphora) that should be asked? (3)
- Constant vs Intermittent/Periods of Remission
- Unilateral vs Bilateral
- Associated ocular surface discomfort
