SAQ Flashcards
Trans corneal diffusion
- Ratio of charged and uncharged drug has to be preserved on both sides
- Uncharged can pass through the epithelium into stroma
- Charged molecules left behind become uncharged to maintain ratio and pass through to the storma until all the drug passed through epithelium
- Inside stroma, some of drug becomes charged and passes through stroma
- Charged molecules become uncharged on the other end to preserve ratio and pass through endothelium
- Uncharged molecules become charged in endothelium
How to choose administration routes
Target tissue Speed of action Stability of drug Duration of action Solubility in water Physiology of patient Comorbidities Age, compliance
Legal classification
GSL - general sales list
P - pharmacy medicine
POM - prescription only medicine
Pharmacological classification
Mode of action
Chemical composition
Effect of drug
Pupil pathway
Autonomic nervous system:
- sympathetic
- parasympathetic
Sympathetic
- Stimulates
- adrenergic stimulation and blockers
Ocular uses of adrenergic stimulation in sympathetic
- dilation
- testing for oculosympathetic lesions eg horners syndrome
- constrict conjunctival vessels
- relief of minor allergic reactions
Ocular uses of adrenergic blocking in sympathetic
- beta blockers: control IOP
- alpha blockers: reverse dilation
- for pupil miosis
Parasympathtic nervous system
- cholinergic blocking:
Prevents miosis of pupil causing dilation
Paralyses accommodation
Sympathetic
Carotid artery - 6th cranial nerve - ophthalmic division of 5th CN - ciliary ganglion - long ciliary nerve - IRIS DILATOR MUSCLE AND MUELLERS MUSCLE
Parasympathetic
Edding westphal nucleus - 3rd nerve - ciliary ganglion - IRIS SPHINCTER
Indications for mydriasis (dilation)
- flashes floaters
- sudden vision loss
- progressive cataracts/ other media opacities
- small pupils
- ocular surgery
- imaging
- px with risk of retinal diseases
- high myopes
Mode of action for mydriatics
- SYMPA: DIRECT AGONIST: alpha and beta receptors stimulate contraction of IRIS DILATOR MUSCLE
- PARA: DIRECT ANTAGONIST: block SPHINCTER MUSCLE
Tropicamide
- muscarinic antagonist (blocks sphincter muscle - para)
- anticholinergic
- POM
Ocular side effects TROPICAMIDE
- transient stinging
- elevation of IOP
- photophobia
- blurred vision
Systemic side effects of TROPICAMIDE
- less severe than cyclopentolate and atropine
- safest
- ask px to bring sunglasses
- px not drive or operate machinery
Phenyephrine
- sympathimimetix amine
- stimulates iris dilator muscle via alpha receptors
- POM
Ocular side effects:
- pain
- teary
- keratitis
- pigmented aqueous floaters
- rebound miosis
- rebound conjunctival congestion
- conjunctival hypoxia
Systemic side effects
- hypertension
- occipital headache
- subarachnoid haemorrhage
- ventricular arrhythmia
- tachycardia
- blanching of skin
- reflex bradycardia
Cautions when using mydriatics
- allergies
- angle closure or narrow angles
- iris mounted IOLs
- new born babies
Tropicamide: angle closure glaucoma
Phenylephrine: hyperthyroidism, asthma, diabetes, stroke, other meds
Mode of action for Miotics (constrict)
- DIRECT CHOLINERGIC AGONIST
- indirect cholinergic agonist
- adrenergic antagonist
Pilocarpine POM
- 1,2,4 % minims
- pupil miosis
- spasm of accommodation
- reduce IOP
Contraindications of pilocarpine
- known sensitivity
- uveitis/ iritis
- iris mounted iol
- fragile iris
- retinal detachment
- exfoliation syndrome
Cyclopegics
- relax accommodation
- block acetylcholine at iris sphincter muscle and ciliary body
- use for: strabismus, children and infants, young hyperopia
Which one is most potent (powerful)
- AHCT
- atropine (most)
- homatropine
- cyclopentalate
- tropicamide (least)
Atropine
- available to optoms with additional supply or independent prescriber
- complete paralysis of accommodation
- amblyopia
Cyclopentalate
- optoms use in practice
- dark skin and iris can resist cyclopegia
- light eyes: 0.5% -20mins
- brown eyes: 1% -30/40 mins
- children: 1%
Cyclopentalate ocular effect
Irritation Lacrimation Conjunctival hyperaemia Allergic blepharo-conjunctivitis Elevated IOP
Cyclopentalate systemic effect
Drowsiness Ataxia Disorientation Incoherent speech Restlessness Visual hallucinations
Sodium fluorescein
- not true dye
- max absorption : 493nm
- emits at 520nm
- 1 %, 2%,
- 0.25% with 4% lidocaine
- use before any topical anaesthetics
Uses of fluorescein
RGP fitting Tear film assessment Corneal observations Foreign bodies/stray CLs Corneal staining Contact Tonometry Angiography Assess nasolacrimal drainage system Jones dye test Seidel rest
Rose Bengal
True stain Stains dead cells Maybe causes cell damage Not available in uk Stings Viewed with white light Instil and then wash away excess with saline Stings more than lissamine green Bind to unprotected corneal epithelial cells
Uses of rose Bengal
- Diagnose dry
- Evaluate corneal and conjunctival lesions
- differentiate between HSV and HZV
Lisaamine green
True dye Conjunctival staining for dry eye Good at identifying Marx line Impregnated strip with 1.5mg of dye Into lower fornix Viewed with white light Bind to unprotected corneal epithelial cells
Dry eyes assessment
S ubjective
O bjective
A ction
P lan
Artificial tears legal classification
P, POM, GSL
Hypromellose (P)
4 times a day
Thin watery
Low viscousity
Used preserved
Factors affecting eye drop bioavailability
Drug dosage Drug formulation and design Corneal integrity Topical anaesthetics used? Iris pigmentation Physiological features of px
Compare and contrast delivery modes of ocular drugs
Eye drops and eye ointments
See pictures
Anaesthetics actions
It’s an antagonist - blocks sodium channels
Nerve fibres:
Pain - touch - temperature - pressure
Softens cornea (affect IOP)
Reduce blink rate
Delay cell regeneration
Uses for anaesthetics
Contact tonometry Foreign body removal Punctual plugs Eye impression Diagnostic procedures Irrigation of the eye
Contraindications for anaesthetics
Known hypersensitivity Premature babies Global penetrating injuries Pregnancy and breastfeeding Where wound healing would be compromised
Which ones stings least
POLT
Proxymetacaine (least)
Oxybuprocaine
Lidocaine
Tetracaine (most)
Proxymetacaine (0.5%)
- less punctate staining than tetracaine
- stings least
- more potent than tetracaine
- stored in fridge
Uses: Tonometry Deep anaesthesia Removal of sutures Remove foreign bodies
Oxybuprocaine 0.4%
- produces less punctate staining than tetracaine
- stored room temperature
Use:
Tonometry/CLs
Foreign body removal
Lidocaine 4% with fluorescein 0.25%
Useful:
- contact Tonometry
- if pc has adverse reaction to any Esther anaesthetic group
Tetracaine (0.5% and 1%)
Above 1% can damage cornea
Not used on pc with known hypersensitivity
Analgesia - painkillers
Non-opioid:
- paracetamol
- aspirin
- ibuprofen
Opioid:
- morphine
- methadone
- tramadol
- codeine
Nonsteriodals anti inflammatory (NSAID)
Ocular painkiller
Selection of drop for glaucoma
HReduction of IOP Duration of effect Preservation of visual field Maintenance of effect Compatibility with other medication Lack of topical side effects Lack of systemic side effects Patient compliance
