Pathway to lacrimal gland via pterygopalatine ganglion
- Valve of Hasner
- Congenital dacrocystitis
- Dacryocystectomy is the treatment for lacrimal sac fibrosis.
- Dacryocystorhinostomy (DCR)
- For nasolacrimal duct obstruction and chronic Dacrocystitis in adults
- Procedure
- bypass the blocked duct.
- The lacrimal sac is connected to the middle meatus of the nose.
- Allows tears to drain properly.
Most common tumor: Pleomorphic adenoma
Most common carcinoma: Adenoid cystic carcinoma
Dry Eye
Mnemonic:
- MALl → going to Mall make u tearful
Disorders
ㅤ | Deficiency Type | AKA | Examples |
Corneal epithelium | Has microvilli | ㅤ | ㅤ |
Inner → Goblet cells | Mucin deficiency | – | Vit A deficiency |
Middle → Lacrimal | Aqueous deficiency | keratoconjunctivitis sicca | Eg. Sjögren syndrome |
Outer → Meibomian gland | Lipid deficiency | Prevents evaporation of aqueous | Eg. meibomian gland disease Contact lens wearer |
Tests for Dry Eyes
1. Schirmer test
- Demonstrates function of 7th cranial nerve.
- Quantifies tear production.
- Uses whatman's filter paper No. 41.
- Procedure:
- Inserted in lower fornix
- After 5 mins
- Measure Length of wet strip
- Interpretation:
- >15 mm → Normal
- <10 mm → Dry eye / Keratoconjunctivitis sicca
2. TBUT (Tear Film Break-up Time)
- Procedure:
- 2% Fluorescein instilled in conjunctival sac → Illuminated with blue light.
- Interval between a blink and appearance of 1" spot of dryness on cornea.
- Interpretation:
- <10 sec → mucin deficiency
- Dry spot at a particular location → Corneal disease
3. Phenol red thread test
- Thread impregnated with phenol red dye which is Yellow in colour → placed in lower fornix.
- Phenol red dye + tears → Red in colour.
- Interpretation:
- < 6 mm → Dry eye
- >15 mm → Normal
Eye related anasthesia and N supply
Route | Target Space | Complications |
Retrobulbar | Intraconal | More complications |
Peribulbar | Extraconal | Fewer complications |
- SET CEI
Nasociliary Nerve
- Courses along medial wall of the orbit.
- Branches
- Posterior ethmoidal nerve
- Anterior ethmoidal nerve
- Infratrochlear nerve
Innervation
- Lacrimal sac
- Inner canthus
- Lateral aspect of nose
Anterior Ethmoidal Nerve Block
- Branch of nasociliary nerve.
- Blocks distal external nasal branch.
- Clinical Use
- Provides pain relief during procedures involving:
- Lacrimal sac
- Inner canthus
- Lateral nose
- Infratrochlear Nerve Block Used in
- Dacryocystorhinostomy (DCR)
Infraorbital nerve block :
Sphenopalatine ganglion block :
- Anaesthesia of internal nose.
- Via nose
- Via greater palatine foramen (Medial to 3rd molar)
NOTE:
- Biopsy above VC → anesthetize ILN at thyrohyoid membrane
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