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YR 3 Eye Disease and Therapeutics > Dry eye preparations > Flashcards

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
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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
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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
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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
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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
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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
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7
Q

tear replacement approaches

A
  • aqueous substitutes - viscosity enhancers
  • biological tear substitutes
  • other agents - to stimulate lipid or mucus production
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8
Q

aqueous substitution

A
  • cellulose esters
  • carbomers
  • polyvinyl alcohol
  • sodium hyaluronate
  • hydroxypropyl (HP) guar
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9
Q

ocular lubricants: mucoadhesive properties

A

increased contact time with ocular surface

  • mucoadhesive viscous gels
  • associated with side effects eg blurring, sticky lids
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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
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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)
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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
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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
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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
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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
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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

YR 3 Eye Disease and Therapeutics (9 decks)

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