Heart by development originates from near the same spot , where the brain develop (Neuralcrest) .Hence there is no surprise to note, heart being a primary vascular organ still retain many neural connections with brain .Eyeballs with it’s extensive neural inputs can be considered as adirect extension of brain.
Oculo cardiac reflex .
When the eyeballs or the ocular muscles are manipulated or massaged slowing of heart rate can occur .This is due to a reflex called Oculo cardiac reflex mediated by vagal stimulation .This phenomenon is also referred to as Aschner phenomenon
- Afferent _Trigeminal branch of opthalmic nerve
- Center- Medulla : Trigeminal neural signal spill over signals to Vagal nucleus
- Efferent- Vagus -SA node
Biochemical mediator -Acetyl choline
- Adequate local anesthesia
- Retro bulbar block of ciliary ganglion
- Prompt Atropine injection
- Opthalmic surgery : Serious bradycardia even asystole can occur as a rare complication especially in elderly and very young (Cataract /Squint surgery) .
- Cardiac events and strokes are clustered around opthalmic surgery in many elderly for some unknown reason ( OCR triggered ?)
- OCR can unmask hidden sinus node dysfunction in elderly.Routine cardiac evaluation before eye surgery may be recommended .
- Orbital fracture especially Medial orbit can elicit dangerous bradycardia (BMJ Case Rep. 2014 Apr 15;2014.)
- Rarely sudden death has been reported (Smith R (1994). “Death and the occulocardiac reflex.”. Can J Anaesth 41 (8): 760. )
- OCR for termination of SVT/AVNRT : , One can use the eyeballs to stimulate the brain stem nucleus of vagus to terminate a rapid supraventricular tachycardia (Like carotid sinus message) .Cold water immersion of eye is effective way to stimulate the vagus.(Diving reflex -Mathews 1981)
Neural control of heart how Important it is ?
Many sudden cardiac deaths are now believed to be neurogenic in origin . Though, somatic nerve supply of heart is least important except over pericardium , extensive sympathetic and parasympathetic nerve supply is present . They can now be visualized by adrenergic receptor imaging . Neuro cardiology is distinct developing field. A hyperbole: Of course one could argue , these connection has less overall significance as a person can live with an entirely new donor heart with zero neural connection with brain.
1.Lang S, Lanigan D, van der Wal M (1991). “Trigeminocardiac reflexes: maxillary and mandibular variants of the occulocardiac reflex.”. Can J Anaesth 38 (6): 757–60
2.Mathew PK (January 1981). “Diving reflex. Another method of treating paroxysmal supraventricular tachycardia”. Arch. Intern. Med. 141 (1): 22–3.