Lacrimal System

Schematic Diagram of the Lacrimal system

Function of the lacrimal system?

• Main aqueous producer for the tear film - aided by accessory glands Krause and Wolfring

• Contain 6-12 ducts - originating in orbital lobe and ending in the superior conjunctival fornix

What is the lacrimal system innervated by?

• Ophthalmic division of the trigeminal nerve 

  • Emotional response - tearing - lacrimal system receives afferent fibres from hypothalamus

  • Facial nerve also has some control over lacrimal gland in Bell’s Palsy = dry eye

What is Bell’s Palsy?

• 7th nerve palsy 

• Inability to close the eye - DRY EYE

• Inability to smile

• Inability to puff cheeks

What is dacryoadenitis?

• Rare inflammatory condition of lacrimal gland - sx of swelling and blurred vision, dry eyes + watery eye

• Acute form can be bacterial (staphylococcus/gonococcus) or viral (mumps/herpes simplex)

• Chronic - due to non-infectious inflammatory disorders e.g sarcoid, thyroid eye disease

What is a lacrimal gland tumour?

• From epithelial cells that line the lacrimal gland

• 50% Benign, 50% Malignant

• Commonly present in 3rd decade or teenage years

• Very rare

Sx of lacrimal gland tumour?

• Proptosis - eyes bulge from natural position 

• Dipl + distorted vision

• Pain

Function of the TF?

• Lubricates the globe

• Provides smooth pre-corneal refracting surface

• Removes Debris from ocular surface

• Provides Microbial Defence

• Helps regulate temperature of globe

Size and function of Mucin layer

• Innermost layer - 0.5 micrometres in thickness

• Wets the microvilli of of corneal epithelium

• Helps prevent pathogen adhesion to epithelium

• Contributes to regulation of epithelial growth

Size and function of Lipid layer

• Outermost layer 

• 0.2 to 0.9 micrometres in thickness

• Inhibits aqueous evaporation 

• Hydrophobic barrier - prevents overspill of tears

Size and function of Aqueous layer

• Middle layer - 6.5 to 7.5 micrometres in thickness

• Provides nourishment of avascular cornea 

• Microbial defence and washes away foreign bodies/debris

IMG of the TF layers

Modern day thoughts about the aqueous and mucin layers?

• Now considered a single layer of mucoaqueous gel 

• Decreasing mucin concentration towards the lipid layer

What is the Mucin layer produced by?

• Conjunctival goblet cells

• Crypts of Henle 

• Glands of Manz

What is the Aqueous layer produced by? 

• Lacrimal gland

• Accessory glands of Krause and Wolfring - serve as backup

What is the lipid layer produced by 

• Meibomian glands, 

• Glands of Zeiss and Moll

Where are the accessory glands of Krause and Wolfring located?

• Krause - superior fornix

• Wolfring - Tarsal conjunctiva - above the top edge of the tarsal plate

What does the Aqueous layer contain to provide microbial defence?

• Lysozyme - enzyme which destroys gram +ve bacterial cell wall e.g Staphylococcus, Streptococcus

• Immunoglobulins - IgA is the main immunoglobulin - Act as an antibody by binding onto pathogens and neutralising

• Lactoferrin - mops up iron which leads to bacterial death

• Beta-Lysin - protein that destroys whole bacterial cell

What happens to microbial defence in ADDE?

Defence proteins are decreased = eye more vulnerable to infection

Where are the meibomian glands located and how do they secrete lipids?

• Located within tarsal plate

• 25 upper lid, 20 lower eyelid

• Secrete lipid via duct and orifice

What are Glands of Zeiss and Moll?

• Backup to meibomian glands in lipid secretion

  • ZEISS - Discharge into each eyelash follicle

  • Moll - discharge via duct to surface of eyelid

What is the tear volume?

• 7-10 microliters 

• Majority is the in the upper and lower marginal tear strips e.g tear meniscus height (5-6 microliters)

What does Tear Meniscus height show?

• Reliable predictor of tear volume insufficiency

• Normal height around 0.45mm

• Dry eye around 0.24mm

Definition of Dry eye

• Loss of homeostasis of the TF leading to;

  • TF instability

  • Hyperosmolarity

  • Ocular surface inflammation 

  • Damage

What is hyperosmolarity and what is the threshold between normal and Dry eyes?

• Osmolarity is an objective measurement of salt concentration in Px’s tears

• Hyperosmolarity is indicative of reduced aqueous levels 

• 308mOsm/L is the threshold

Diagram linked ADDE and EDE

ADDE

• Insufficient secretion rate from lacrimal gland - tear drainage exceeds production

• Leads to keratoconjunctivitis sicca

• Can be caused by;

  • Atrophy of lacrimal glands (Age related or pathology)

  • Reduced neural input to gland (Rx surgery)

  • Poor tear retention due to eyelid abnormality

EDE

• Deficient Lipid layer - MGD

• Deficient Mucin layer

• Contamination of the tear film by environmental factors; airborne pollution, irritants/chemicals

Why does MGD lead to EDE?

• Reduced rate of lipid secretion due to an increase in viscosity (orifices) 

• Without lipids in TF, evaporation is not prevented

• 70% of chronic DE due to MGD

Why might MGD occur?

• Hormonal changes - change in oestrogen levels lead to thickening of the oils

• Change in oestrogen levels also increase the amount of staphylococcal bacteria resulting in MG inflammation

• Blepharitis

What has recent research shown regarding MGD?

• Hormone Androgen involvement - control MG secretion - precursor to Oestrogen 

• Deficient androgens = loss of lipid layer due to thicker, more viscous secretions

• Px taking antiandrogenic therapy e.g has prostate disease results in DED

What happens if MG is lost?

Irreversible changes once atrophied

What causes MG dropout?

• Radiation therapy / Chemotherapy

Cases of ADDE?

• Taking systemic drugs

• Refractive surgery

• Ageing

• CL Wear

Cases of EDE?

• Vitamin A deficiency

• Ocular Allergy

• Preservatives

• CL Wear

What are the similarities and differences between ADDE and EDE?

• ADDE and EDE exist continuously and are part of a cycle

• ADDE - lacrimal function issues - not enough production of tears

• EDE - lid related (MGD, blink rate) and ocular surface (mucin production and CL wear)

Cause of Dry eye?

• Deficient tear volume (ADDE)

• Deficient tear quality (EDE)

• Abnormal eyelid function - (ADDE)

• Systemic disease / Medication

• Environmental factors e.g humidity 

• Refractive surgery

Treatment for MGD

• Hot compress - Eye bag / rice bag

• Massage lids after heating

• Treat any blepharitis - lid wipes/cotton buds

• Flaxseed oil

What is an Internal Hordeolum?

• Tender inflamed swelling within the tarsal plate

• Bacterial infection (usually staphylococcal) of Meibomian gland 

• More painful than stye

• May point anteriorly through the skin

What is a Chalazion (Meibomian Cyst)?

• Cessation of lipid secretion due to total blockage of MG ducts leading to a stagnation of meibomian gland contents

• Focal, hard, painless nodule

• Non-infectious, granulomatous inflammation of meibomian gland

• May develop from retention of gland secretions

Why might a Deficient Mucin layer occur?

• 20 mucin synthesizing genes - defect in these genes may be a factor in DE

• Loss of Goblet cells

• Vitamin A deficiency

What can cause Loss of Goblet Cells?

• Steven-Johnson syndrome 

• Pemphigoid

• Burns

• Trachoma

What is Steven-Johnson syndrome and RF?

• Disorder of the immune system caused by an adverse reaction to drugs and viruses e.g herpes simplex

• Hypersensitivity of mucous membranes and skin - MUCIN DEFICIENCY 

• Males more susceptible (2:1)

• Signs of;

  • Papillary conjunctivitis

  • Dry eye 

  • Epiphora following lacrimal drainage obstruction

What is Pemphigoid and its RF?

• Systemic autoimmune inflammatory disease - ‘blister’

• Usually bilateral

• Females - mainly in the 7th decade - females more prone to autoimmune conditions - rule!!

What is Trachoma?

• Caused by the bacterium Chlamydia trachomatis 

• Spread by direct contact with eye, nose and throat secretions from affected individuals or items they have used

• Also spread by flies

Vitamin A deficiency

• Leads to build up of Keratin Debris - common in children in developing world

• Bitot’s Spots

• Interpalpebral conjunctival foamy looking patches

Can eventually lead to corneal ulceration

What does Abnormal eyelid function lead to?

• Poor post-blink redistribution of TF

• Poor tear pump mechanism 

• Large palpebral aperture e.g in ectropion / thyroid eye disease - elevated tear evaporation due to greater exposed ocular surface - resulting in DED and epiphora 

• Elevated tear secretion rate e.g entropion = corneal irritation leading to reflex lacrimation - resulting in epiphora

What systemic diseases cause Aqueous deficiency?

• Sjogren’s Syndrome

• Systemic lupus erythematosus

What is Sjogren’s syndrome?

• Autoimmune disorder affecting primarily salivary and lacrimal glands - DRY EYE; AQUEOUS DEFICIENCY

• Joints and muscles affected by mild arthritis 

• Females 90% of cases, onset most commonly in 40s

What is Systemic Lupus Erythematosus?

• Autoimmune disorder can affect multiple organ systems such as heart, skin, joints and nervous system

• May have butterfly rash on forehead and cheeks 

• DRY EYE; AQUEOUS DEFICIENCY 

• Can only treat sx, no cure

• Females 90%

What is Rheumatoid Arthritis and its Ocular issues?

• When the body's immune system targets affected joints which leads to pain and swelling - AUTOIMMUNE

• Females 3x more affected

• Ocular manifestations occur in 25% of cases

  • Keratoconjunctivitis sicca in 15-25% cases

  • Episcleritis 0.17%

  • Scleritis 0.67%

• No correlation between DED and RA

Management of Px with DED and RA?

• Ocular lubricants - if not responsive to treatment - mild topical steroid 2-4x daily

What is hyperthyroidism?

• Overactive thyroid gland

• Swelling of EOM

• Proptosis - eye bulges out 

• Inadequate globe coverage by eyelids = incomplete blink

What environmental factors lead to DED?

• VDU use 

• Air Conditioned offices and cars - reduced humidity

• Pollution - increase tear debris + reflex lacrimation = epiphora

• Wind

Medicines causing dry eyes?

What is the link between Rx surgery and dry eyes?

• Reduction in rate of tear secretion - anterior corneal nerve plexus damaged during surgery = reflex lacrimation rate reduced 

• Damage to corneal epithelium = mucin layer disrupted = localised reduction in corneal wetting

Sx of Wet eye?

• Excessive tearing

• Itching

• Soreness of skin below eye

Wet eye Sx can be worsened by?

• Wind

• Cold conditions

What tests can you use to evaluate the tear volume?

• Schirmer test

• Color Bar test

• Phenol red thread test

• Tear meniscus 

• Ocular surface assessment (staining agents)

Schirmer test 1 without anaesthesia:

• Measure of basal and reflex tear secretion

• Fold schirmer strip at notch and hook over temporal part of lower eyelid

• Leave in place for 5 mins - encourage normal blinking 

• Greater than 10mm of wetting = normal

• 5-10mm of wetting = borderline dry eye

• 5mm or less = dry eye

Schrimer test 1 with Anesthesia:

• Measure basal lacrimation only

• Instil one drop of 0.5% proxymetacaine HCL 

• Expect lower level of secretion compared to without anaesthesia 

• 5mm or less in 5 mins = borderline dry eye

Schrimer test 2:

• Direct measure of reflex lacrimation

• Instil 1 drop of 0.5% proxymetacaine 

• Stimulate nasal mucosa with cotton bud for 15-20 seconds

• Measure tear secretion after 2 mins 

• Normal if greater than 15mm of tear secretion in 2 mins

What is the Phenol Red Thread test?

• 70mm thread impregnated with phenol red

• Yellow when dry, red once wetted by tears

• Hook over lower eyelid such as Schrimer test for 15 seconds

• Less than 9mm of wetting = dry eye

Less than 5 seconds TBUT is indicative of?

• KCS

How do the different staining agents work?

• Fluorescein - stains damaged cells

• Rose Bengal - stains dead cells, mucus and mucin-deficient tissues - shows devitalized epithelial and conjunctival cells - incomplete blinking - stings but gold standard for detection of ocular damage due to dry eye

• Lissamine Green - stains damaged cells, dead cells and mucus - much more comfortable than RB and also gold standard

How should you use lissamine green?

• Staining fades quickly so assess one eye at a time

• Assess 1-4 mins after instillation 

• Use a Wratten 25 filter

Signs of Keratoconjunctivitis Sicca;

• Bulbar conjunctiva stains first 

• Temporal and inferior cornea stain as disease progresses

Signs of Bacterial Keratoconjunctivitis sicca?

Diffuse punctate staining

Management of tear dysfunction?

• Increasing tear volume and ocular lubrication - Artificial tears, Dietary changes

• Reducing rate of tear fluid loss from conjunctival sac - Punctual occlusion, alter environment/eye shield

• Improvement of tear quality /consistency - Lipid layer deficiency - use hot compress, lid massage

• Improvement of lacrimal drainage in cases of epiphora

Formulation of artificial tear substitutes?

• pH 7.4 

• Tonicity 0.9% sodium chloride 

• Viscolizing agent - substitute for mucin 

• Preservatives - prevent bacterial colonisation once opened

Examples of artificial tears

• Systane Polyquad - preservatives (can cause irritation) - contain Polyethylene Glycol - can get on the NHS 

• Hycosan - sodium hyaluronate 0.1%

• Hyabak - sodium hyaluronate 0.15%

• Artelac - Hypromellose 0.32%

What Dietary changes can we advise?

• Omega-3 fatty acids - soften secretions from MG

• Increase water intake

• Flaxseed oil

• Fish oil

• Oily fish - tuna, salmon, sardines

What are the 2 types of silicone punctal plugs?

• Freeman type

• Herick type

Reducing rate of tear evaporation; Changing temperature/surgery/optical

• Use of room humidifiers

• Reduce room temp

• Computer breaks!

• Reduce palpebral aperture area - lateral tarsorrhaphy

• Everest-Harris specs - side shields reduce evaporative effect of wind

Where do tears drain from?

70% drain via inferior canaliculus - gravity

How to investigate the drainage system?

• Dilation and irrigation

  • lacrimal syringing

  • lacrimal lavage

  • can also have therapeutic value - dislodge mucus 

• Jones Dye test - 1 and 2

Interpretation of Dilation and Irrigation?

• Px feels saline in throat - drainage system is fine - D&I has cleared obstruction

• if fluid regurgitates through upper punctum - blockage exists in/beyond the common canaliculus

• IF fluid regurgitates through Lower Punctum - blockage exists between inferior punctum and common canaliculus

Jones Dye Tests

• Used in cases of suspected obstruction of lacrimal drainage system 

• Carried out after dilation and irrigation procedure

Results Jones Dye Test 1

• Dye detected initially after 5 mins = normal drainage

• Dye detected after massage and nose blow = partial obstruction of nasolacrimal duct

• If no dye present carry out Jones Dye Test 2

Results of Jones Dye Test 2

• Dye present in collected fluid = functional blockage of nasolacrimal duct - fluid flow only under high pressure

• Fluid present but no dye = functional blockage of nasolacrimal duct = site of blockage is close to punctum 

What happens if Dilation + Irrigation doesn’t work?

• Dacryocystorhinostomy

  • Hole drilled into nasal cavity - silicone tube inserted to maintain drainage

What is canaliculitis?

• Inflammation of the canaliculi - relatively rare 

• Px over 50s 

• Signs include - chronic unilateral red eye with epiphora - mucopurulent discharge, more likely to be inferiorly 

Can get dacryoliths building up - form pockets and block drainage

What is Dacryocystitis?

• Bacterial infection within the nasolacrimal sac

• Rare - occurs when nasolacrimal duct is blocked

• Acute - painful swelling at medial canthus, sac full of pus - treated with antibiotics, warm compress and dacryocystorhinostomy 

• Chronic - conjunctivitis with epiphora, sac filled with mucoid material - treated with dacryocystorhinostomy

What is a Nasolacrimal Sac tumour?

• Interferes with tear drainage - epiphora

• Rare 

• Needs complete excision followed by radiation 

• Congenital occlusion common - often spontaneously resolves - 70% by 3/12, 90% 12/12