Lacrimal Apparatus Flashcards
Tera Film
Structure
3 layers
1) mucin layer (innermost)
- consists of mucin
- secreted by the conjunctival goblet cells and glands of manz
- converts the corneal surface from hydrophobic to hydrophilic
2) aqueous layer (middle layer)
- secreted by main and accessory lacrimal glands
- tears mainly composed of water, sodium, urea, sugar and proteins (therefore, alkaline and salty)
lyzozyme, beta lysin, lactoferrin, iga, igg, igm
3) lipid / oily layer (outermost thinnest)
- secreted by meibomian glands, zeis glands and glands of moll
- prevents evaporation, overflow and lubricates the eyelids
functions
- keeps the cornea and conjunctiva moist
- creates uniform corneal surface
- provides oxygen to the corneal epi
- antibacterial properties
- washes away debris
- facilitates movement of eyelids
secretion of tears
- main (reflex) and accessory (basal) lacrimal glands
- hyperlacrimation occurs due to irritative sensations from the cornea and conjunctiva
elimination of tears
- either by evaporation or drained through the canaliculi
- 70% through inf canaliculi and 30% via superior canaliculi by an active lacrimal pump mechanism
- drained into the inferior meatus through the NLD
Dry eye (classification)
multifactorial disease of the ocular surface characterized by loss of homeostasis of the tear film, and accompanied by ocular symptoms in which tear film instability and hyperosmolarity, ocular surface inflammation and damage and neurosensory abnormalities play etiological roles
etiological classification
1) aqueous deficiency dry eye (adde)
2) evaporative dry eye
adde / keratoconjunctivitis sicca (kcs)
a) sjogren’s syndrome - 1° / 2°
b) non sjogren’s kcs
• lacrimal deficiency
- primary age related hyposecretion (mcc)
- congenital alacrima, infiltrations of lg eg. sarcoidosis, tumours
• lacrimal gland obstruction - old trachoma, chemical burns, cicatricial pemphigoid and SJS
• hyposecretory state - parkinsons ds, 7th nerve damage, reduced corneal sensations, familial dysautonomia
• other disorders - meige syndrome, dm
evaporative dry eye
• meibomian gland diseases
- meibomian gland dysfunction
- congenital absence of mg
- chronic post blepharitis
- age related changes
• lid aperture congruity and blink dynamics
- lagophthalmos (facial nerve palsy, severe proptosis)
- defective blinking (parkinsonism, prolonged computer users)
• ocular surface related
- allergic, vit a deficiency, contact lens, topical drugs
clinical features of dry eye
symptoms:
- irritation
- foreign body sensation
- feeling of dryness
- itching
- non specific ocular discomfort
- chronic sore eyes
signs
tear film changes -
- presence of stingy mucous and particulate matter
- marginal tear strip is reduced / absent
- froth
conjunctival signs
- lustreless,
- mildly congested,
- conjunctival xerosis
- keratinization
corneal signs
- punctate epi erosions
- mucus plagues
- loose lustre
signs of causative disease
complications - vision threatening (epi breakdown, corneal ulceration, and even perforation)
tear film tests
if any two positive, diagnosis is confirmed
1) TBUT - tear film break up time
- interval between a complete blink and the appearance of the first dry spot on cornea.
- a drop of fluorescein dye
- cobalt blue light of a slit lamp
- normal - 10-35 seconds
- < 10 seconds - unstable tear film
- if at same place - corneal disease
2) schirmer - I test
- measures total tear secretions
- whatman filter paper no 41 (5x35 mm)
- folded at 5 mm and kept in the fornix at junction of lateral 1/3 and medial 2/3
- wait for 5 minutes
- measured from the bent end
- if >15 mm - normal
- 5-10 mm - moderate to mild
- <5 mm - severe
3) rose bengal staining
- 3 patterns seen
C: mild / early with fine punctate stains in the interpalpebral area
B : moderate with excessive staining
A : severe with confluent staining of conjunctiva and cornea
Treatment
Grading
level 1 : mild ded
level 2 : moderate ded
level 3 : severe ded
level 4 : very severe ded
treatment
level 1
1) education and supportive measures
- importance of blinking
- avoidance of medications and use of preservative free topical medications
- environmental review and modifications
2) supplementation with tear substitutes : artificial tear drops / ointments / slow release inserts
contain cellulose derivatives (methyl cellulose and hypromellose) or polyvinyl alcohol (1.4%)
3) rx of causative disease
- vit a for deficiency
- systemic tetracyclines and lid hygiene for chronic post blepharitis
- rx of lagophthalmos
level 2
4) anti inflammatory agents
• low potency topical steroids fluorometholone
• topical cyclosporine - reduces the cell mediated inflammation of lacrimal tissue
• chloroquine eyedrops
• omega fatty acid supplements
5) secretagogues - oral cholinergic agonists (pilocarpine and cevimeline)
6) mucolytics - 5% acetylcysteine 4x a day help in decreasing tear viscosity
7) preservation of existing tears by reducing evaporation and decreasing drainage
- use of moist chambers and protective glasses
- punctal occlusion
- permanent lateral tarsorrhaphy
8) mgd associated ded
a) relieve mg obstruction - hot compression, digital massage, infra red rays application
b) improve quality of mg oily secretion - fish oil supp, syst tetracyclines or macrolides
c) eyelid hygiene
level 3
9) serum eye drops
10) contact lens - producing a fluid reservoir
level 4
11) topical steroids
12) systemic anti inflammatory
13) surgical
- permanent punctal occulsion
- tarsorrhaphy
- mucous membrane / amniotic membrane transplantation
- submandibular gland transplantation
