Dry Eyes

Question 1

What is the definition of dry eye disease?

Answer 1

a multifactorial disease of the ocular surface and tear film accompanied by increased osmolarity of the tear
film and inflammation of the ocular surface.

Question 2

What is the definition of keratoconjunctivitis sicca?

Answer 2

refers to any eye with some degree of dryness.

Question 3

What is the definition of Xerophthalmia?

Answer 3

describes a dry eye associated with vitamin A deficiency.

Question 4

What is the definition of Xerosis?

Answer 4

refers to the extreme ocular dryness and keratinization that occurs in eyes with severe conjunctival cicatrization.

Question 5

What is Sjogren syndrome?

Answer 5

an autoimmune inflammatory disease of which dry eyes is a feature.

Question 6

What are the layers of the tear film?

Answer 6

• Lipid layer secreted by the meibomian glands.
• Aqueous layer secreted by the lacrimal glands.
• Mucous layer secreted principally by conjunctival goblet cells.

Question 7

What is the composition of the outer lipid layer of tear film?

Answer 7

a polar phase containing phospholipids adjacent to the aqueous-mucin phase and a non-polar phase containing waxes, cholesterol esters and triglycerides.

Question 8

What is the function of the lipid layer of the tear film?

Answer 8

○ To prevent evaporation of the aqueous layer and maintain tear film thickness.
○ To act as a surfactant allowing spread of the tear film.
○ Deficiency results in evaporative dry eye.

Question 9

What % of aqueous do the lacrimal glands produce?

Answer 9

95%

Question 10

Where is the remaining 5% of aqueous produced?

Answer 10

Glands of Wolfring and Krause

Question 11

How is the reflex tearing mechanism mediated?

Answer 11

in response to corneal and conjunctival sensory stimulation, tear break-up an ocular inflammation and is mediated via the fifth cranial
nerve. It is reduced by topical anaesthesia and falls during sleep. Secretion can increase 500% in response to injury.

Question 12

What is the function of the aqueous layer?

Answer 12

○To provide atmospheric oxygen to the corneal epithelium.
○Antibacterial activity due to proteins such as IgA, lysozyme and lactoferrin.
○To wash away debris and noxious stimuli and facilitate the transport of leukocytes after injury.
○To optically enhance the corneal surface by abolishing minute irregularities.

Question 13

What is the composition of the mucous layer of tears?

Answer 13

○ Mucins are high molecular weight glycoproteins that may be transmembrane or secretory in type.
○ Secretory mucins are further classified as gel-forming or soluble. They are produced mainly by conjunctival goblet cells but also by the lacrimal glands.

Question 14

What is the function of the mucous layer of tear film?

Answer 14

○ To permit wetting by converting the corneal epithelium from a hydrophobic to a hydrophilic surface.
○Lubrication.
○Deficiency of the mucous layer may be a feature of both aqueous deficiency and evaporative states. Goblet cell loss occurs with cicatrizing conjunctivitis, vitamin A deficiency, chemical burns and toxicity from medications.

Question 15

What are the 4 core inter-related mechanisms postulated to be causing dry eye?

Answer 15

tear instability,
tear hyperosmolarity,
inflammation
ocular surface damage.

Question 16

What are the 2 types of Aqueous deficient dry eye?

Answer 16

*Sjögren syndrome dry eye (primary or secondary).
*Non-Sjögren syndrome dry eye.
○Lacrimal deficiency
○Lacrimal gland duct obstruction
○Reflex hyposecretion: sensory

Question 17

What are the 2 types of Evaporative dry eye?

Answer 17

Intrinsic
Extrinsic

Question 18

What are the causes for Non-Sjogren syndrome dry eyes?

Answer 18

○Lacrimal deficiency: primary (e.g. age-related dry eye, congenital alacrima, familial dysautonomia) or secondary (e.g. inflammatory and neoplastic lacrimal gland infiltration, acquired immunodeficiency syndrome (AIDS), graft-versus-host disease, lacrimal gland or nerve ablation).

○Lacrimal gland duct obstruction, e.g. trachoma, cicatricial pemphigoid, chemical injury, Stevens–Johnson syndrome.

○Reflex hyposecretion: sensory (e.g. contact lens wear, diabetes, refractive surgery, neurotrophic keratitis) or motor block (e.g. seventh cranial nerve damage, systemic drugs).

Question 19

What are the causes of Evaporative Intrinsic dry eyes?

Answer 19

○Meibomian gland deficiency, e.g. posterior blepharitis, rosacea.
○Disorders of lid aperture, e.g. excessive scleral show, lid retraction, proptosis, facial nerve palsy.
○Low blink rate, e.g. Parkinson disease, prolonged computer monitor use, reading, watching television.
○Drug action, e.g. antihistamines, beta-blockers, antispasmodics, diuretics.

Question 20

What are the causes of Evaporative extrinsic dry eyes?

Answer 20

○Vitamin A deficiency.
○Topical drugs including the effect of preservatives.
○Contact lens wear.
○Ocular surface disease such as allergic conjunctivitis.

Question 21

What is the pathophysiology of Sjogren Syndrome?

Answer 21

an autoimmune disorder characterized by lymphocytic inflammation and destruction of lacrimal and salivary glands and other exocrine organs. The classic clinical triad consists of dry eyes, dry mouth and parotid gland enlargement, but other features are common and
can affect all organ systems.

Question 22

What is the ACR criteria for Sjogren syndrome?

Answer 22

*Positivity for anti-SSA or anti-SSB antibodies, or positive rheumatoid factor together with significantly positive antinuclear antibody.
*Ocular surface staining above a certain grade.
*Focal lymphocytic sialadenitis to a specified extent on salivary gland biopsy

Question 23

What is keratoconjunctivitis sicca exacerbated by?

Answer 23

by exposure to wind, air-conditioning and central heating.

Question 24

What are some signs seen in patients with Sjogren syndrome?

Answer 24

*Posterior (seborrhoeic) blepharitis with meibomian gland dysfunction is often present

*Conjunctiva redness, stain with Rose Bengal and Lissamine green and conjunctivochalasis

*Reduced tear film meniscus <0.25mm

*Cornea shows PEE’s, filaments of mucus and debris staining well with Rose Bengal

*Epithelial breakdown, melting and perforation

Question 25

What tests can be used to assess the severity of dry eye disease?

Answer 25

*Stability of the tear film as related to its break-up time (BUT).
*Tear production (Schirmer, fluorescein clearance and tear
osmolarity).
*Ocular surface disease (corneal stains and impression cytology).

Question 26

How to measure TBUT?

Answer 26

*Fluorescein 2% is instilled into the lower fornix.
*The patient is asked to blink several times.
*The tear film is examined at the slit lamp with a broad beam using the cobalt blue filter
*The BUT is the interval between the last blink and the appearance of the first randomly distributed dry spot. A BUT of less than 10 seconds is suspicious.

Question 27

How is the Schirmer test performed?

Answer 27

*Excess tears are delicately dried.
*The filter paper is folded 5 mm from one end and inserted at the junction of the middle and outer third of the lower lid, taking care not to touch the cornea or lashes
*The patient is asked to keep the eyes gently closed.
*After 5 minutes the filter paper is removed and the amount of wetting from the fold measured.
*Less than 10 mm of wetting after 5 minutes without anaesthesia or less than 6 mm with anaesthesia is considered abnormal.

Question 28

What does fluorescein stain?

Answer 28

stains corneal and conjunctival epithelium where there is sufficient damage to allow the dye to enter the tissues.

Question 29

What does Rose Bengal and Lissamine green stain?

Answer 29

a dye that has an affinity for dead or devitalized epithelial cells that have a lost or altered mucous layer. Corneal filaments and plaques are also shown up more clearly by the dye and the use of a red-free filter may help visualization.

Question 30

What is seen on histology of Sjogren syndrome in the lacrimal gland?

Answer 30

Lymphocytic infiltration

Question 31

What does interpalpebral staining pattern tell us?

Answer 31

○ Interpalpebral staining of the cornea and conjunctiva is common in aqueous tear deficiency.

Question 32

What does superior stain pattern tell us?

Answer 32

may indicate superior limbic keratoconjunctivitis.

Question 33

What does inferior staining pattern tell us?

Answer 33

often present in patients with blepharitis or exposure

Question 34

What is the threshold value distinguishing between a healthy and dry eye in tear film osmolarity?

Answer 34

varies from 305 mOsm/l and
316 mOsm/l, depending on the degree of tear film instability.

A widely accepted threshold is 308 mOsm/l and a value of 316 mOsm/l appears to discriminate between mild and moderate/severe dry eye.

Question 35

What is the level 1 treatment for dry eyes?

Answer 35

*Education and environmental/dietary modifications
*Systemic medication review
*Artificial tear substitutes including gels and ointments
*Eyelid therapy. Warm compress and lid hygiene

Question 36

What is the level 2 treatment for dry eyes?

Answer 36

*Non-preserved tear substitutes
*Anti-inflammatory agents
*Tetracyclines (for meibomianitis, rosacea).
*Punctal plugs.
*Secretagogues, e.g. pilocarpine, cevimeline, rebamipide.
*Moisture chamber spectacles and spectacle side shields.

Question 37

What is the level 3 treatment for dry eyes?

Answer 37

*Serum eye drops. Autologous or umbilical cord serum.
*Contact lenses.
*Permanent punctal occlusion.

Question 38

What is the level 4 treatment for dry eyes?

Answer 38

*Systemic anti-inflammatory agents.
*Surgery
○Eyelid surgery, such as tarsorrhaphy.
○Salivary gland auto-transplantation.
○Mucous membrane or amniotic membrane transplantation for corneal complications.

Question 39

Types of tear film drops and gels?

Answer 39

○Cellulose derivatives (e.g. hypromellose, methylcellulose)
are appropriate for mild cases.

○Carbomer gels adhere to the ocular surface and so are longer-lasting, but some patients are troubled by slight
blurring.

○Other agents include polyvinyl alcohol (PVA), which increases the persistence of the tear film and is useful in mucin deficiency, sodium hyaluronate, povidone, glycerine, propylene glycol, polysorbate and others.

○Diquafosol is a newer agent that works as a topical secretagogue

Question 40

Types of tear film ointments?

Answer 40

Containing petrolatum (paraffin) mineral oil can be used at bedtime to supplement daytime drops or gel instillation; daytime use is precluded by marked blurring. Some practitioners do not prescribe these for long-term use.

Question 41

How are tear film eyelid sprays used?

Answer 41

Applied to the closed eye and typically
contain a liposome-based agent that may stabilize the tear film and reduce evaporation.

Question 42

How do mucolytic agents for dry eyes work?

Answer 42

Acetylcysteine 5% drops may be useful in patients with corneal filaments and mucous plaques, which
acetylcysteine dissolves; it may cause stinging on instillation. Acetylcysteine is malodorous and has a limited shelf-life. Manual debridement of filaments may also be useful

Question 43

When is punctal occlusion beneficial?

Answer 43

in patients with moderate–severe KCS who have not responded to frequent instillation of topical agents.

Question 44

What are some anti-inflammatory agents useful in dry eye syndrome?

Answer 44

*Topical steroids, generally low-intensity preparations such as
fluorometholone
*Omega fatty acid supplements (e.g. omega-3 fish oil, flax seed oil) can have a dramatic effect on symptoms and may facilitate the reduction of topical medication.
*Oral tetracyclines for an extended course, often 3 months at a relatively low dose, may control associated blepharitis
*Topical ciclosporin (usually 0.05%) reduces T-cell mediated inflammation of lacrimal tissue, resulting in an increase in the number of goblet cells and reversal of squamous metaplasia of the conjunctiva.