Mydriatics

Anti- muscarinic: competitive acetylcholine antagonists

• acetylcholine has affinity for muscarinic receptors

• they block the muscarinic receptors

• sphincter pup dont constrict

Sympathomimetic: noradrenaline agonists

• noradrenaline has affinity for alpha receptors

  • dilator pup weaker than sphincter pup

• dilator pup function enhanced

It is paralysis of cil msc = loss of accom

anti-msc drugs cause significant cyclo

Atropine

• hot as a hare ( increase in body temp)

• mad as a hatter ( confusion)

• red as a beet ( flushed face/ tachycardia)

• dry as a bone ( thirsty)

• blind as a bat ( cycloplegia)

• if px wears soft CL- absorbs drug so reduces effect + stays there for longer

• px with symptoms of acute or chronic CAG ( red eyes, eye ache , blurred vision)

• px diagnosed with CAG

• px with narrow anterior chamber angles

• those using cyclopentolate ( anti msc same as atropine)

• in hyperopic pxs

• px over 60

• px with shallow AC depth

1. Tropicamide Hydrochloride (anti- msc) POM

   • dark irides are more resistant to pupillary dilation so instill more BUT take care not to OVERDOSE

   • stings on instillation BUT LESS than cyclo

   • provides mild cycloplegia

   • less toxicity than cyclopentolate so used more commonly

   • mydriasis takes 5-10 mins

2. Cyclopentolate Hydrochloride ( anti-msc) POM

   • stings in instillation

   • longer mydriasis than tropicamide so light relex fully abolished

     ( check reflex with pen torch, pupil should not constrict)

   • not commonly used due to unwanted cycloplegia

   • more toxic than tropicamide so MUST NOT OVERDOSE

3. Phenylephrine HCL ( sympathomimetic) P

   • minimal effect on accom so light reflex not fully abolished

   • may cause corneal clouding if instilled when corneal epi is damaged

   • may reverse action of hypertensives = FATAL

   • interacts w/ anti-despressants and quinidine ( used to treat irregular heartbeats)

   • protect from sunlight

   • mydriasis takes 30mins