Dry Eyes Flashcards
What is the definition of dry eye disease?
a multifactorial disease of the ocular surface and tear film accompanied by increased osmolarity of the tear
film and inflammation of the ocular surface.
What is the definition of keratoconjunctivitis sicca?
refers to any eye with some degree of dryness.
What is the definition of Xerophthalmia?
describes a dry eye associated with vitamin A deficiency.
What is the definition of Xerosis?
refers to the extreme ocular dryness and keratinization that occurs in eyes with severe conjunctival cicatrization.
What is Sjogren syndrome?
an autoimmune inflammatory disease of which dry eyes is a feature.
What are the layers of the tear film?
- Lipid layer secreted by the meibomian glands.
- Aqueous layer secreted by the lacrimal glands.
- Mucous layer secreted principally by conjunctival goblet cells.
What is the composition of the outer lipid layer of tear film?
a polar phase containing phospholipids adjacent to the aqueous-mucin phase and a non-polar phase containing waxes, cholesterol esters and triglycerides.
What is the function of the lipid layer of the tear film?
○ 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.
What % of aqueous do the lacrimal glands produce?
95%
Where is the remaining 5% of aqueous produced?
Glands of Wolfring and Krause
How is the reflex tearing mechanism mediated?
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.
What is the function of the aqueous layer?
○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.
What is the composition of the mucous layer of tears?
○ 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.
What is the function of the mucous layer of tear film?
○ 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.
What are the 4 core inter-related mechanisms postulated to be causing dry eye?
tear instability,
tear hyperosmolarity,
inflammation
ocular surface damage.
What are the 2 types of Aqueous deficient dry eye?
*Sjögren syndrome dry eye (primary or secondary).
*Non-Sjögren syndrome dry eye.
○Lacrimal deficiency
○Lacrimal gland duct obstruction
○Reflex hyposecretion: sensory
What are the 2 types of Evaporative dry eye?
Intrinsic
Extrinsic
What are the causes for Non-Sjogren syndrome dry eyes?
○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).
What are the causes of Evaporative Intrinsic dry eyes?
○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.
What are the causes of Evaporative extrinsic dry eyes?
○Vitamin A deficiency.
○Topical drugs including the effect of preservatives.
○Contact lens wear.
○Ocular surface disease such as allergic conjunctivitis.
What is the pathophysiology of Sjogren Syndrome?
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.
What is the ACR criteria for Sjogren syndrome?
*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
What is keratoconjunctivitis sicca exacerbated by?
by exposure to wind, air-conditioning and central heating.
What are some signs seen in patients with Sjogren syndrome?
*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
What tests can be used to assess the severity of dry eye disease?
*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).
How to measure TBUT?
*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.
How is the Schirmer test performed?
*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.
What does fluorescein stain?
stains corneal and conjunctival epithelium where there is sufficient damage to allow the dye to enter the tissues.
What does Rose Bengal and Lissamine green stain?
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.
What is seen on histology of Sjogren syndrome in the lacrimal gland?
Lymphocytic infiltration
What does interpalpebral staining pattern tell us?
○ Interpalpebral staining of the cornea and conjunctiva is common in aqueous tear deficiency.
What does superior stain pattern tell us?
may indicate superior limbic keratoconjunctivitis.
What does inferior staining pattern tell us?
often present in patients with blepharitis or exposure
What is the threshold value distinguishing between a healthy and dry eye in tear film osmolarity?
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.
What is the level 1 treatment for dry eyes?
*Education and environmental/dietary modifications
*Systemic medication review
*Artificial tear substitutes including gels and ointments
*Eyelid therapy. Warm compress and lid hygiene
What is the level 2 treatment for dry eyes?
*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.
What is the level 3 treatment for dry eyes?
*Serum eye drops. Autologous or umbilical cord serum.
*Contact lenses.
*Permanent punctal occlusion.
What is the level 4 treatment for dry eyes?
*Systemic anti-inflammatory agents.
*Surgery
○Eyelid surgery, such as tarsorrhaphy.
○Salivary gland auto-transplantation.
○Mucous membrane or amniotic membrane transplantation for corneal complications.
Types of tear film drops and gels?
○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
Types of tear film ointments?
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.
How are tear film eyelid sprays used?
Applied to the closed eye and typically
contain a liposome-based agent that may stabilize the tear film and reduce evaporation.
How do mucolytic agents for dry eyes work?
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
When is punctal occlusion beneficial?
in patients with moderate–severe KCS who have not responded to frequent instillation of topical agents.
What are some anti-inflammatory agents useful in dry eye syndrome?
*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.
