During ocular surgery, when eye surgeon touches the medial rectus, he asked to assistant to measure heart rate because of
**Core Concept**
The oculocardiac reflex is a physiological response that occurs when there is compression or traction on the extraocular muscles, particularly the medial rectus, leading to a decrease in heart rate. This reflex is mediated by the autonomic nervous system, specifically through the stimulation of the vagus nerve.
**Why the Correct Answer is Right**
When the eye surgeon touches the medial rectus muscle during ocular surgery, it can lead to the compression of the ophthalmic branch of the trigeminal nerve, which is responsible for transmitting sensory information from the eye to the brain. This compression can stimulate the afferent fibers of the oculocardiac reflex, which then activate the efferent fibers of the vagus nerve, resulting in a decrease in heart rate. The vagus nerve releases acetylcholine, a neurotransmitter that slows the heart rate by decreasing the conduction velocity of the sinoatrial node.
**Why Each Wrong Option is Incorrect**
**Option B:** The occulocephalic reflex is a reflex that is responsible for the movement of the eyes in response to head movements. It is not related to changes in heart rate.
**Option C:** The occulovagal reflex is not a recognized reflex in medical literature. The oculocardiac reflex is mediated by the vagus nerve, but it is not referred to as the occulovagal reflex.
**Option D:** This option is incorrect because the oculocardiac reflex is a well-documented physiological response that can occur during ocular surgery.
**Clinical Pearl / High-Yield Fact**
It is essential for anesthesiologists and eye surgeons to be aware of the oculocardiac reflex and take necessary precautions to prevent its occurrence during ocular surgery. This includes avoiding compression or traction on the extraocular muscles, especially the medial rectus, and monitoring the patient's heart rate closely.
**✓ Correct Answer: A. Occulocardiac reflex**