Dry eye preparations Flashcards
1
Q
what are ocuar lubricants
A
- the term artifical tears ia a misnomer because they dont mimic the composition of human tears
- most function as lubricants, although some formulations attempt to mimic the electrolyte composition of human tears
- ocular lubricants in the form of eye drops, gels and ointments are used to treat the discomfort associated with conditions in which the tear film is reduced or unstable
- lubricating eye ointments are also used in treatment of recurrent corneal erosions - happen following an abrasion where epi hasnt healed properly - epithelial doesnt anchor the stroma properly
2
Q
ocular lubricant preparations
A
- majority of preparations are available over the counter (mostly CE marked products) and can therefore be sold and supplied by optoms
- the first lubricants were classed as P medicines
- increasingly available as CE marked products
- these are ‘medical devices’, similar to cl solution and so not regulated by medicines act
- may limit their availability on nhs prescriptions
3
Q
management of dry eye (step 1)
A
- education regarding the condition
- modify local enviro
- nutritional advice - including oral essential fatty acid consumption
- modification/ elimination of systemic and topical mediciations
- ocular lubricants
- lid hygiene and warm compresses
4
Q
management of dry eye (step 2)
A
- non preserved lubricans
- tear conseration eg punctal plugs
- non medicated ointment at night
- topical antibiotics for ant bleph (if present)
- oral antibiotics eg tetracyclines
- topical immunomodulatory drugs eg ciclosporin
5
Q
ocular lubricants for dry eye objectives
A
- improve the ocular comfort and quality of life, - return the ocular surface and tear film to the normal homeostatic state
- although symptoms can rarely be eliminated, they can often be improved with ocular lubricants, leading to an improvement in quality of life
6
Q
limitations of using lubricants for dry eye
A
- formulation cant replace complexity of natural tears
- administered intermittently rather than continuously as with natural tears - so formulated to increase their contact time eg mucoadhesive polymers
- choice of therapy is determined by severity of condition taking into account the lifestyle and dexterity of the px
- presence of preservatives in artifical tears can compromise the ocular surface following prolonged use
7
Q
tear replacement approaches
A
- aqueous substitutes - viscosity enhancers
- biological tear substitutes
- other agents - to stimulate lipid or mucus production
8
Q
aqueous substitution
A
- cellulose esters
- carbomers
- polyvinyl alcohol
- sodium hyaluronate
- hydroxypropyl (HP) guar
9
Q
ocular lubricants: mucoadhesive properties
A
increased contact time with ocular surface
- mucoadhesive viscous gels
- associated with side effects eg blurring, sticky lids
10
Q
tear viscosity in relation to blinking
A
- tear fluid displays non newtonian behaviour - when shear rate (force applied across surface) is low, viscosity is high eg when eye is open
11
Q
aqueous substitution - cellulose esters
A
- good retention time on ocular surface
- viscoelastic polysaccharides
- can cause blurred vision and crusting of eyelids mimicking bleph
- eg hydroxypropyl methyl cellulose (hypromellose) - most commonly used, methylcellulose, carboxymethylcellulose (carmellose)
12
Q
aqueous substitution - carbomer
A
- carbomer 980 or carbomer 940
- synthetic polymer
- good retention time on ocular surface
- good viscosity when eyes open shear thin during blinking (non newtonian shear thinning)
- tend to blur vision
eg gel tears
13
Q
aqueous substitution - polyvinyl alcohol
A
- synthetic polymer
- low viscosity - doesnt impact vision
- beneficial in mucin or lipid deficiency
- short retention time
- eg liquifilm tears
14
Q
aqueous substitution - sodium hyaluronate
A
- naturally occurring polymer in body
- mucopolysaccharide
- viscous formulation
- good retention time on ocular surface
- exhibits non newtonian shear thinning properties
- tends to blur vision
15
Q
aqueous substitution - HP guar - SYSTANE
A
- systane contains HP guar, which increases in viscosity after contacting the ocular surface
- this change is based on pH value
- systane is a liquid in the bottle at a pH of 7.0 but when placed on the eye (pH 7.4) , a chemical reaction happens
- HP guar binds to the ocular surface and simultaneously crosslinks with borate ions in the solutino, forming a network with a gel like consistency
16
Q
ocular lubricants and preservatives
A
- used to avoid microbial contamination when solution is exposed to atmosphere
- if you had a px taking preservative drops for dry eye and glaucoma, there may be an increase in toxicity
17
Q
preservative free eyedrops
A
preservative free is indicated
- preservative sensitivity
- immediately after invasive surgery
- if frequency of use raises concerns regarding cumulative exposure (>3/12 treatment, >6 times per day)
- ocular surface disease
- contact lenses
18
Q
preservatives and contact lenses
A
- benzylkonium chloride is avidly taken up by SCLs and is released slowly, exceeding upper safety limits
- high water content lenses absorb greater quantities than low water content
- hard contact lenses take up a very small amount of benzalkonium, with a release that approaches the upper limit of safety
- tear film conc of benzalkonium, such as after eye drop use in the presence of SCL could result in adverse effects on the ocular surface
19
Q
newer opthalmic preservatives
A
newer preservatives have been developed with reduced ocular toxicity eg:
- purite: stabilised oxychloro complex dissipates into water and sodium chloride on exposure to light
- sodium perborate: converts into water and oxygen on instillation
- sofzia: modified into harmless elements on instillation
- polyquatemium: less toxic than BAK - common in multidose CL care products
20
Q
multi dose preservative free systems
A
- hycosan: 0.1% hyaluronate
- hycosan extra 0.2%: hyaluronate
- hylotear 0.1% hyaluronate
- hyloforte 0.2% hyaluronate
- hyabak 0.15% hyaluronate
21
Q
lubricating eye ointments
A
opthalmic lubricating ointments
- useful adjunct to other artifical tears when used at night
- liquid paraffin/ wool alcohols
- high viscosity
- contribute to rebuild the lipid layer
- melt at the temp of ocular tissues
- long retention time
- blurred vision
- used in recurrent corneal erosions
- eg larilube, Vit A Pos (contains retinol)
22
Q
tear modification
A
mucolytic in filamentary keratitis
- acetylcysteine 5-10% eg ilube (POM)
- stinging sensation on instillation into eye
- dissolves mucous filaments by breaking disulphide bonds
23
Q
lipid supplementation: liposomal sprays
A
- an aqueous suspension of phospholipid containing liposomes containing hydrogrenated phosphatidylcholine has been shown to be beneficial in evaporative dry eye
- the formulation is sprayed onto the closed eyelids
- works its way onto lid margins then spreads across tears
24
Q
immunosuppressants/ immunomodulators
A
- current understanding of the pathogenesis of dry eye disease has recognised of inflam as a key pathogenic mechanism
- ikervis, 1mg/mL ciclosporin (santen) has recently received marketing approval in the EU for ‘treatment of severe keratitis in adult pxs with DED, which has not improved despite treatment with tear substiturtes
25
Q
autologous serum
A
- used in extreme cases
1) procure 40ml of blood through veripuncture
2) centrifuge for 5 mins at 1500rpm
3) centrifuging will divide the blood into 2 components - blood and serum
4) place 1cc of serum in each bottle
5) add 4cc of saline to make a con of 20% serum eye drops
- needs to be refrigerated, v short shelf life
26
Q
tear stimulation approaches
A
- several topical pharmacological agents that stimulate aqueous, mucin and/or lipid secretion are commercially available in some countries or under development
- aqueous secretalogues eg diquafosol tetrasodium
- mucin secretalogues eg rebamipide
- lipid secretalogues eg IGF-1, androgens
27
Q
prescribing guidance
A
mild dry eye
- hypromellose 0.3% eye drops
- carbomer 980 0.2% gel
- carmellose 0.5% eyedrops
moderate dry eye
- carbomer 980 0.2% gel
- carmellose 0.5% SDU
- multi dose preservative free eg 0.1% sodium hyaluronate eyedrops
severe dry eye
- opthalmic lubricating ointments
- multidose preservative free eg 0.1% sodium hyaluronate eydrops
- multidose preservative free eg 0.2% sodium hyaluronate eyedrops
- use preservative free if they use >6 times a day
