Dry eye Flashcards
What keeps healthy eye comfortable and wet
tear film
- > lipid, aqueous and mucus layer
- > dry eye disease sees breakdown of squaeous and lipid layers
what is the prevalence of DED
- exact prevalence not know because of difficulty defining DED & no single diagnostic test
- 7.8-33.7% of population
- close to 3/4 of a million Canadians have dry eye disease
- prevalence is expected to increase as population of developed countries continues to age
what are the risk factors for DED
- ocular surgery
- Age > 40 years
- female gender
- medications: can decrease # of aq tears produced
- systemic diseases: diabetes, hypertension, rheumatoid arthritis, Sjogren’s syndrome, thyroid disorders etc)
- smoking
- computer vision syndrome
- environmental factors (humidity, air current/drafts, air conitioning)
- contact lens wear
what is the impact of dry eye disease on quality of life
- significantly decreased vision related quality of life, w/ inc anxiety and depression
- significantly dec funcional visual acuity
- discontinuation of contract lens wear in 1/3 of patients
- high prevalent digital eye strain syndrome
what is current definition of dry eye disease
- multifactorial disease of the ocular surface
- characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms -> tear film instability and hyperosmolarity, ocular surface inflammation and damage
- >neurosensory abnormalities play etiological roles.”
what is the main unit that is disrupted in dry eye disease
- lacrimal functional unit
what are the parts of the lacrimal functional unit
- lacrimal glands -> aqueous layer of tear film
meibomian glands -> lipid layer of tear film
ocular surface (cornea and conjunctiva) -> mucus layer of tear film
sensory and motor nerves
eye lids
*breakdown of any part of the lacrimal unit can cause dry eye disease
what is the role of tear film
- nutrition O2
- Blink
- imp for contact lens wear
- lubrication
- vision
- lid margin (inflammation here will cause there to be inadequate secretion of lipid layer
what are teh four components of the vicious circle of dry eye disease
- Tear film hyper osmolarity: environmental factors associated with dry eye
*ow humidity, wind, heat, inadequate blinking, smoking cigs
- tear film instability: factors ass with evaporative dry eye
*meibomian gland dysfunction, blepharitis, unstable tear film lipid layer, vit A deficiency, ocular allergy, contact lens wear
- Surface damage (cellular level)
- Inflammatory mediators: factors assocaited with aq deficient dry eye
*aging, low androgens, autoimmune reposnse, lactimal obsturction
*management of dry eye targets there 4 components
What are the main types of dry eye diseae classification
- aqueous deficient vs eaproative
- Evaporative
- most prevalent
- lack of quality tears (usually lipid component)
- leads to quick evaproation of tears on ocular surface
- usually due to meibomian gland dysfunction
- Aqueous deficient dy eye
- uncommon to have without overlapping signs of evaporative disease
- aqueous defiicent defined by lack of aqueous tear production by lacrimal gland
- common causes: Sjogrens syndrome, aging, systemic drugs
what are the symptoms of dry eye disease
– Foreign body sensation
– Sandy / scratchy feeling
– Burning
– Itching
– Tired eyes
– Feeling of dryness
– Increased tearing
– Vision related problems (intermittent blur, particularly later in the day)
*Symptoms tend to worsen over the course of the day, except with evaporative dry eye which is worse in the morning
how is the sevarity fo dry eye graded
Mild: good secretions
Moderate: plugging of gland, vascularization of eyelid margins
Severe: blocked meibomian ducts (thick secretions)
the msot common form of dry eye disease is
evaporative
what are goals of therapy for dry eye disease
- improve patients ocular comfort and quality of life
- return ocular surface and tear film to normal homeostatic state
what are the types of maintenance treatment for dry eye disease
- tear suplement composition: polymer/lubricant, viscoity, lipid supplements, electrolytes/buffers, osmolarity, preservaties
- evironmental: ambient humidity, air movement, computer use
peronal (ocular): hot compress/lid hydiene, moisture chambers
- personal (non-ocular): systemic medications, alcohol smoking, hormonal status, sleep apnea
what are the types of maintenance treatment for chronic (inflammatory) dry eye
Short term: topical steroid (trial)
Long term: essental Fatty acids, topical cyclosporine
Adjunctive: oral tetracyclines/macrolides, topical azithromycin
Supportive: Episodic treatments + tear preservation (lacrimal occulaion), tear film stimulation (secretagogues), meibomian gland expression (in office, lipiflow)
primary self care for evaproative or mixed DED
- tear suplements or lubricants
ocular considerations; apply hot compress, lid hygience, modifications to contact lens wear
Non-ocular considerations: environemntal modification, dietary suplments, alcohol use, smoking , hormonal status, sleep apnea
what makes a good artificial tear
Drops should:
- Reduce burning
- improve reading speed and comprehension
- Normalize blink pattern and frequency
what are the difficulties encountered with artificial tears
- Do not address the underlying inflammation causing Dry Eye
- Do not contain the complex mixture of proteins, mucins or other factors found in healthy tears (just a supprtive mechanism)
- temporary palliative relief
- does not restore normal tear composition
- does not reverse damage to ocualr surface
impoartant factors of artiifical tears
- Preservatives
- Electrolyte composition
- Osmolarity
- Viscosity
artificial tears, solutions:
- most contain hyaluronate: naturally occuring polysaccardie in body found in vitreous/ aqueous humour
- adds viscoelasticity: increased tear stability, reduction fo tear removal, protective effects on corneal epithelium
aritificial tears, gels and ointments
- typically mineral oil and petrolatum
- some have lanolin -> can be irritating
- ointments do not support bacterial growth so they dont require preservatives
- Gels are less viscous then ointments but provide increased retention time
- disadvantage: blurring
lipid based emulsions for artifical tears
- lipid oil-in-water nano-emulsions have been shown to have a long residence time on the tear film,
- reduce the tear evaporation rate
- have a positive effect on the lipid layer
- Nano-emulsions also improve ocular bioavailability of lipophilic or poorly water-soluble drugs
Examples: Systane Balance, Soothe XP, Refresh Optive Advance
preservative vs preservative free artificial tears
- Preservative
- have antimicrobial activity, prolong shelf like by preventing decomposition of active drug
- may be toxic to cornea
- not recommended for extremly dry eye
- Non preservative
- usually more $
- eliminates risk of toxic side effects
- occasionally patient may react to buffer in solution
- come in uni dose vials, multi dose may be mroe difficult to use
- much better for severe dry eye but will get $$
