The Oculocardiac Reflex: An Overview

Euan MacInnes

I can recall the first time being taught about the oculocardiac reflex (OCR) and being in disbelief that simple manipulation of the globe or extraocular muscles could lead to cardiac arrest. The body has many distinct reflexes such as the gastrocolic reflex or deep tendon reflexes that make anatomically and physiological sense but try to understand the purpose of the OCR, I could not.

Introduction

The OCR, also known as the Aschner reflex or trigeminovagal reflex, results in bradycardia, and sometimes more significant arrythmias such as asystole, when pressure is applied to the globe or traction to the extra-ocular muscles. Typical manifestations occur during paediatric strabismus cases, with a reported prevalence of around 10% in such cases (1). Other occurrences reported in the literature include during retinopathy of prematurity examinations (2), and during maxillofacial trauma reconstructive cases (3).

Anatomy and pathophysiology

The OCR is a Trigeminal (CN V) – Vagal (CN X) reflex. The long and short ciliary nerves, (branches of the ophthalmic division of CN V), detect sensory information from the eye and orbit. These nerves then travel to the ciliary ganglion and continue as the ophthalmic division of trigeminal nerve to the trigeminal ganglion. From there the afferent pathway travels to the primary sensory nucleus of the trigeminal nerve, situated in the pons. From there, the efferent pathway synapse with the visceral motor nucleus of the vagus nerve in medulla oblongata. From there, the efferent pathway travels to the myocardium to activate the vagus response at the SA node, resulting in bradycardia (4).

Management

The most important step in the management of the OCR is to remove the offending stimulus. Prompt resolution of symptoms occurs in majority of cases (5). Several pre-operative considerations can be made. For example, the use of pre-operative anticholinergics such as glycopyrrolate has been shown to reduce the incidence of OCR (4). Furthermore, the administration of retrobulbar blocks has also been shown to reduce the risk of OCR, but these are not routinely used in children as they have been known to elicit the OCR. Sub-tenon blocks have been shown to reduce the incidence and severity of the OCR (6). Although most cases result in spontaneous resolution of symptoms, an estimated 1 in 3500 cases of OCR related arrythmia results in death (7), highlighting the importance of being able to recognise and manage this phenomenon.

Summary

The OCR is an intriguing phenomenon that occurs not infrequently during ophthalmic surgery. The condition most commonly manifests as a bradycardia but can extend to asystole and cardiac arrest in rare scenarios. Commonly caused by manipulation of the extra ocular muscles and the globe, mainstay of treatment is with cessation of causative stimuli. Although most cases resolve spontaneously, more serious sequalae can occur. As an ophthalmologist, being aware of this reflex and its management is of utmost importance to ensure patient safety.

References

  1. Arnold RW. The oculocardiac reflex: a review. Clinical Ophthalmology. 2021 Jun 24:2693-725.
  2. Schumacher AC, Ball ML, Arnold AW, Grendahl RL, Winkle RK, Arnold RW. Oculocardiac reflex during ROP exams. Clinical Ophthalmology. 2020 Dec 4:4263-9.
  3. Kharia A, Rao SJ, Dubey V, Bhatt S, Bhatt D, Baig F. Oculocardiac Reflex in a Patient With Maxillofacial Trauma: A Case Study and Literature Review. Cureus. 2024 May 2;16(5).
  4. Oculocardiac Reflex – EyeWiki [Internet]. Eyewiki.org. 2024. Available from: https://eyewiki.org/Oculocardiac_Reflex
  5. Juan I, Lin M, Greenberg M, Robbins SL. Surgical and anesthetic influences of the oculocardiac reflex in adults and children during strabismus surgery. Survey of Ophthalmology. 2023 Sep 1;68(5):977-84.
  6. Talebnejad MR, Khademi S, Ghani M, Khalili MR, Nowroozzadeh MH. The Effect of Sub-Tenon’s Bupivacaine on Oculocardiac Reflex during Strabismus Surgery and Postoperative Pain: A Randomized Clinical Trial. J Ophthalmic Vis Res. 2017 Jul-Sep;12(3):296-300. doi: 10.4103/jovr.jovr_66_16.
  7. Mendelblatt, Frank I., Ralph E. Kirsch, and Louis Lemberg. “A study comparing methods of preventing the oculocardiac reflex.” American Journal of Ophthalmology 53.3 (1962): 506-512.

Leave a Reply