Exploring Ophthalmic Nerve Injuries - Guardian of Vision

Introduction

The trigeminal nerve consists of three branches, namely, ophthalmic, maxillary, and mandibular nerve. Thus, the ophthalmic nerve is the branch of the trigeminal nerve, and it is the smallest of all three branches. It arises from the anteromedial part of the trigeminal ganglion. The ophthalmic nerve supplies the structures of the eyes, cornea, ciliary body, lacrimal gland, and conjunctiva. It also supplies eyelids, eyebrows, forehead, and nose skin. This nerve allows one to blink quickly when some foreign object enters the eye. Damage to the ophthalmic nerve causes loss of sensations to all the structures supplied by the ophthalmic nerve. The corneal reflex is also lost when an injury to the ophthalmic nerve occurs.

What Is the Anatomy of the Ophthalmic Nerve?

The ophthalmic nerve is purely sensory and has no motor function. It begins at the lateral wall of the cavernous sinus (cavity present between the front and the middle of the skull). Along the pathway, the ophthalmic nerve gives several lateral branches, and the most important of them is the recurrent tentorial nerve, which innervates the tentorium cerebelli. The ophthalmic nerve lies below the oculomotor and trochlear nerve and thus divides into terminal branches: frontal, nasociliary, and lacrimal. Then these nerves enter the orbital socket through the superior orbital fissure and supply the mucus membrane of the skin, eyes, head, and nose.

1. The frontal nerve is the ophthalmic nerve's middle and largest branch. Branches of the frontal nerve are supratrochlear nerves that supply sensory innervations to the upper eyelid, conjunctiva, and forehead, and supraorbital nerves supply sensory innervations to the upper eyelid, conjunctiva, and scalp.

2. The lacrimal nerve is the smallest and thinnest branch of all three branches. It supplies the sensory innervations to the lacrimal gland, upper eyelid, and conjunctiva.

3. The nasociliary nerve is the medial terminal branch of the ophthalmic nerve. The branches of the nerve are the posterior ethmoid nerve that supplies sensory innervations to the sphenoid sinus; the infratrochlear nerve that supplies the sensory innervations to the nose, upper eyelid, and conjunctiva and long ciliary nerves that supply sensory innervations to the cornea and the iris.

What Are the Functions of the Ophthalmic Nerve?

The ophthalmic nerve provides sensory innervation to the following structures: forehead, scalp, frontal, ethmoid, and sphenoid sinus, dorsum of the nose, upper eyelid, cornea, and conjunctiva.

What Are the Injuries Associated With Ophthalmic Nerve?

The ophthalmic nerve can be associated with the following injuries:

• Damage to the ophthalmic nerve can cause symptoms related to sensory dysfunction. Ophthalmic nerve injury can cause supraorbital neuralgia. The supraorbital nerve arises from the frontal nerve fibers, the largest branch of the ophthalmic nerve. Supraorbital fibers send sensory nerve fibers to the scalp and provide sensory innervation to the scalp, upper eyelid, and forehead. Supraorbital neuralgia can cause persistent pain in the head and can cause sudden burning or prickling sensation to the structures supplied by ophthalmic nerves. A supraorbital nerve block can be given to achieve local anesthesia of the face. The target structure is the supraorbital nerve, a branch of the frontal nerve, again a branch of an ophthalmic nerve. It is an easy way to prevent the distortion of tissue and uncomfortable sensations for the patient while doing surgical procedures in the forehead region.

• Herpes zoster virus (shingles) can cause painful sensations along the path of the trigeminal nerve and mainly affect those areas supplied by the ophthalmic nerve. This infection can lead to loss of sensations in the affected areas.

• Trigeminal neuralgia can occur, and it can cause an electric shock-like pain. Triggering factors include brushing the teeth, applying makeup, or cold air can provoke excruciating pain. Initially, there can be small bouts of attacks, and it can progress to long attacks with spasms of muscles. It is generally seen on one side of the face and becomes intense over some time.

• The corneal reflex is an involuntary blinking of the eyelids that is stimulated by the tactile, painful stimulus of the cornea. The ophthalmic nerve is a part of the corneal reflex. Lack of corneal reflex indicates damage to an ophthalmic nerve or facial nerve.

• Bell's palsy usually affects the branches of the facial nerve. Dysfunctions of the facial nerve are also linked with the dysfunctions of the ophthalmic nerve. Bell's palsy affects the structures supplied by the facial nerve, but sometimes sensory structures innervated by trigeminal nerves are also affected. This condition causes nerve inflammation and is mainly caused by the herpes simplex virus, herpes zoster virus, and human immunodeficiency virus.

How to Diagnose Ophthalmic Nerve Injury?

A diagnosis of ophthalmic nerve injury can be made through a combination of medical history, physical examination, and diagnostic tests. Following are some steps that a healthcare provider might take to diagnose ophthalmic nerve injury:

• Medical History: The healthcare provider will take a detailed history of the patient's symptoms and any other medical conditions they may have. They will ask about any recent trauma, infections, or surgeries that could have caused the nerve injury.

• Physical Examination: The healthcare provider will perform a thorough physical examination, including a neurological examination of the eyes and surrounding areas. They will look for any signs of inflammation, swelling, or discoloration and assess the patient's vision, eye movements, and reflexes.

• Diagnostic Tests: There are several diagnostic tests that can help confirm a diagnosis of ophthalmic nerve injury, including:

1. Imaging Tests: Magnetic resonance imaging (MRI) and computed tomography (CT) scans can help visualize the structures around the eye and identify any abnormalities or lesions.

2. Electromyography (EMG): This test measures the electrical activity of the muscles around the eye and can help determine if there is any damage to the ophthalmic nerve.

3. Pupil Reflex Test: This test evaluates how the pupil responds to light and can help identify any problems with the ophthalmic nerve.

4. Visual Field Test: This test measures the patient's peripheral vision and can help identify any abnormalities that could be caused by ophthalmic nerve damage.

How to Treat Ophthalmic Nerve Injury?

Treatment of ophthalmic nerve injury mainly depends on the underlying medical condition. If the cause is herpes zoster, then antiviral treatment is started. Anticonvulsants and muscle relaxants are given to treat the pain associated with neuralgias. In severe cases, surgery is indicated. Microvascular decompression is a surgical procedure done to treat neuralgias. In this procedure, rerouting of blood vessels is done that is pressing the trigeminal nerve. In certain conditions, nerves are excised, so pain signals are stopped. Trigeminal plasticity can also be done to treat neuralgias. In this procedure, adjacent nerves may develop the leading nerve role and cover the affected nerve areas. It allows some time to rehabilitate the nerve function after the non-surgical nerve damage.

Conclusion

Injury to the ophthalmic nerve is rare. However, careful examination of patients should be done with proper history, symptoms, type, the intensity of pain, course of episodes, and red flags. Anticonvulsants and painkillers are advised to treat pain and spasms in the muscles. If the symptoms persist even after the medical treatment, the patient is referred to neurosurgery or neurology.