UG MBBS Phase II Practical EP

1. Effect of Unknown
Drugs on Rabbit Eye
Dr Shivankan Kakkar, MBBS,MD

2. Drugs in Question
• Pilocarpine
• Physostigmine
• Atropine
• Phenyl ephrine
• Lignocaine
• Cocaine

3. Parameters in Question
• Pupil size
• Corneal reflex
• Light reflex
• Colour of conjunctiva

4. Parameters analysed
• Pupil size: Increased in sympathetic stimulation
(fear) and decreased in parasympathetic
stimulation
• Corneal reflex: Absent for LA
• Light reflex: Absent with use of parasympatholytics
• Colour of conjunctiva: Red only for directly acting
parasympathomimetics

5. Muscarinic stimulation
Miosis

6. Muscarinic stimulation
Accommodation (Near Vision)

7. Muscarinic
Stimulation Vs Antagonism

8. Muscarinic Agonists
• Pilocarpine (Directly acting)
Decreased pupil size, corneal reflex +, light reflex +,
colour of conjunctiva: red
• Physostigmine (Indirectly acting) ~ AchE Inhibitor
Decreased pupil size, corneal reflex +, light reflex +,
colour of conjunctiva: normal

9. Muscarinic Antagonists
• Atropine
Increased pupil size, corneal reflex +, light reflex: absent,
colour of conjunctiva: normal

10. Alpha 1 stimulation
Mydriasis

11. Alpha 1
Stimulation - only mydriasis, no cycloplegia

12. Alpha 1 Agonist
• Phenyl ephrine
Increased pupil size, corneal reflex +, light reflex +, colour
of conjunctiva: normal

13. Local Anaesthetic
• Lignocaine
pupil size: normal, corneal reflex: absent, light reflex +,
colour of conjunctiva: normal

14. Local Anaesthetic and
Sympathomimetic
• Cocaine
Increased pupil size, corneal reflex: absent, light reflex +,
colour of conjunctiva: normal