Sem1 - 1 - Mydriatics + Miotics Flashcards
Indications for mydriatics? (9 total)
- Sudden VA loss
- Unexplained VA diff.
- Flashes, floaters (RD)
- History of RD
- Cataract (can’t assess retina otherwise)
- New high myope Px
- Diabetes
- Headache (increased ICP)
- Metastatic cancer
Contraindications for mydriatics?
- Narrow angle
- Some types of pseudophakia
- Allergy
- Corneal diease
- Systemic drug not compatible
Two types of mydriatics?
- What kind of drugs are they?
- Examples?
- DIfferences?
Parasympathetic antagonist (relaxes sphincter)
- Competitively blocks muscarinic receptors
- e.g. Tropicamide, cyclopentolate, atropine…
- Light reflex gone.
Sympathetic agonists (contracts dilator)
- e.g. Phenylephrine
- Light reflex fine
Sympathetic pathway
Efferent:
- Posterior hypothalamus at brainstem to Ciliospinal centre of budge (C8 – T2 near neck)
- Past/near lung apex, to Superior cervical ganglion
- Surround ICA, past cavernous sinus, beccomes ophthalmic division of CNV
- Innervates dilator pupillae
Parasympathetic pathway
Afferent:
- Retina -> Optic nerve -> chiasm -> tract -> midbrain at level of superior colliculus
Interneuron:
- Pretectal nuclei of SC -> Edinger-Westphal nuclei
Efferent:
- EW –(Ocular motor nerve 3)–> Ciliary ganglion -> Sphincter pupillae + cilliary muscle.
Pre-mydriatic checks?
- History? (Previous reaction, family history of glaucoma?)
- Tonometry (pre + post-mydriatics)
- AC angle (is it less than 0.2?)
Depends on risk-benefit analysis
Tropicamide
- What drug is it?
- Concentration?
- Time scale
- Side effects and/or contraindications?
- Competitively blocks muscuranic ACh receptors
- 0.5% just as good as 1.0%
- 15min, 30min, 4-6hrs (onset, max, recovery)
- Low systemic + ocular side effects, but ocular allergy possible
Avoid in: - Brain damaged children
- Downs’ syndrome
- Tropicamide allergy
- Narrow AC angle
Phenylephrine
- What drug is it?
- Concentration?
- Time scale
- Side effects and/or contraindications?
- Other notes?
- Directly agonistic. Binds reveresibly to alpha 1 receptors of dilator pupillae muscle, conjunctival vasculature, and Muller’s muscle
- 2.5%
-10min, 60-90min, 5-7hrs
_____________________
Side effects: - Pain
- Lacrimation
- Keratitis (rare)
- Iris pigment release
- Endothelial changes in compromised corneas
______________________
Contraindication: - Insulin-dependent diabetics (super sensitive to adrenergic agonists)
- Thyroid overactivity
- Monoamine oxidase inhibitors (MAOIs) (vasopressor effect exacerbated)
______________________ - Reversed w/ Dipiprazole
- Pupillary dilation (can be combined w/ tropicamide for increased effect)
- Blanching of conjunctiva
- Upper eyelid elevation
- NOT cycloplegia
- NOT pupillary light reflex abolishment
- In older ppl, can release iris pigment
- Vasopressure -> raise BP
Management of acute closed-angle glaucoma
- Check for signs and symptoms (pain, vomiting, blurred vision, hazy cornea)
- Unless inflammatory glaucoma, 1 drop of pilocarpine 2% BE, every 10 min for affected eye for up to ½ hr.
- If pressure still >40mmHg, oral diamox (CAI) needed.
- If inflammatory glaucoma, avoid pilocarpine due to increasing inflammation, iris bombe + psoterior synechiae risk.
Purpose of miotics
- Improve outflow in glaucoma (particullary closed-angle glaucoma)
- Reduce chances of posteriorly luxated lens from entering AC.
- Reversing mydriasis
Two types of miotics
- Examples
Muscuranic agonists (parasympathomimetic)
- Direct acting = pilocarpine
- Indirect acting = physostigmine, neostigmine (inhibit AChE)
Adrenergic antagonists (sympatholytics)
- Block alpha receptors = dapiprazole, thymoxamine
Describe pilocarpine
- What drug is it?
- Concentration?
- Side effects and/or contraindications?
- Directing acting muscuranic agonist
- 0.25 - 10%
Adverse reactions: - Hyperaemia
- Ciliary muscle spasm (in young)
- Lacrimation
- Salivation
- GI tract contractions
Physotigmine, neostigmine
- What drug is it?
- Medical + Ophthalmic uses?
- Systemic effects?
- Inhibit ACh Esterase
Medical use: - Myasthenia gravis (autoimmunity of ACh receptor)
- Anticholinergic toxicity (caused by antihistamines, antidepressants)
Ophalmic use: - Glaucoma treatment via intense, long lasting miosis (longitudinal muscle opens up TM)
Systemic effects: - Cardiovascular
- GI tract increased motility, bronchial secretions
- Exocrine increased secretions.
Warnings for cholinergic agonist users
- Ciliary spasm
- Conjunctival hyperaemia
- Hx, ocular pain
- Re-dilation possible if reversing mydriasis when mydriatics last longer
- Pupillary block if
– narrow angle
– Advancing cataract - Bronchoconstriction (bad for asthma)
Thymoxamine + Dapiprazle
Not in NZ. Otherwise, used for miosis and both are effective at reversing mydriasis
