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Ophthalmic Nerve

The human eye is such a delicate tissue that it may get damaged by even a dust particle that causes irritation on the eye’s surface, i.e., the cornea of the eye. To avoid damage to the cornea, there are several mechanisms that nature has developed to perform this function, i.e., tears that lubricate the corneal surface. One such mechanism is unintentional blinking or closing of the eyes when something touches the cornea. This mechanism is so sensitive that even a small silk thread that sometimes cannot be seen with the naked eye, can provoke this blinking reflex. This blinking reflex is also known as the corneal reflex. The afferent pathway for this reflex is made up of the neurons of the ophthalmic division of the trigeminal nerve. In the following, we shall have a look at the origin, course, classification, and functional component(s) of the Ophthalmic nerve. We shall also discuss the branches, area of supply, and functions of the ophthalmic nerve and its role in reflexes like a corneal reflex. Last but not least, we shall have a look at the diseases caused by damage to the ophthalmic nerve.

Illustration showing the location and path of the ophthalmic nerve
Illustration showing the location and path of the ophthalmic nerve

Ophthalmic Nerve

The Head and neck region gets its nerve supply from the central nervous system through the cranial nerves that originate directly from the brain, especially from the brain stem. These cranial nerves are 24 in number in the form of 12 pairs. The fifth cranial nerve is the trigeminal nerve which is the chief sensory nerve of the area of the face, temple, and mucous surfaces of the paranasal sinuses, nasal cavity as well as oral cavity. As the name suggests, the trigeminal nerve is made up of three big divisions known as the ophthalmic division (CN V1), maxillary division (CN V2), and mandibular division (CN V3). The ophthalmic division is the smallest division of the trigeminal nerve, and it is purely sensory in function, like the maxillary division. The mandibular division also contains some motor fibers that supply the muscles with mastication.

Read more about the Optic Nerve

Classification and Functional Components

The trigeminal nerve is a mixed nerve and contains general somatic afferents and special visceral afferents. The first two divisions of the trigeminal nerve, i.e., ophthalmic and maxillary divisions, contain only general somatic afferent fibers; they are purely sensory in nature. They have general sensory afferents, so they do not carry special sensations like vision, hearing, olfaction or taste, etc.

Origin and Course of Ophthalmic Nerve

The trigeminal nerve, the parent nerve of the ophthalmic nerve, emerges from the brain at the anterior aspect of the pons in the posterior cranial fossa. It moves forwards in the middle cranial fossa lying over the petrous part of the temporal bone and ends in a crescent-shaped ganglion, called a trigeminal ganglion, present in the Meckel cave. Meckel cave is a pouch formed by the dura mater (the outermost brain covering). Arising from the trigeminal ganglion, the ophthalmic nerve passes forward and enters into the lateral wall of the cavernous sinus (a big paired sinus for venous drainage of the brain) in the middle cranial fossa, divides into several branches that leave the skull through the superior orbital fissure and enter into the orbital cavity. 

Branches of Ophthalmic Nerve

There are several branches of the ophthalmic nerve that innervate different structures. These branches include the frontal nerve, the Nasociliary nerve, and the lacrimal nerve. These are briefly discussed below: 489 657

Frontal Nerve

The frontal nerve is the largest branch of the ophthalmic nerve. It leaves the skull cavity and enters the orbital cavity via a superior orbital fissure. In orbit, it passes forward and continues over the levator palpebrae superioris, it divides into two branches; supraorbital and supratrochlear nerves.

The supraorbital nerve is the larger terminal branch of the frontal nerve. It leaves the orbital cavity through the supraorbital notch and becomes cutaneous. As the name shows, it supplies structures lying superiorly to the orbit, i.e., the mucous membrane of the frontal sinus, the skin of the forehead, the skin and conjunctiva of the upper eyelid, and the skin of the scalp.

The Supratrochlear is a smaller terminal branch of the frontal nerve. after its origin from the frontal nerve, it runs forward and continues over the trochlea for the superior oblique, it leaves the orbital cavity via the frontal notch. It supplies, along with the supraorbital nerve, the skin of the forehead, scalp, and upper eyelid, and also the conjunctiva of the upper eyelid. It also communicates with the infratrochlear nerve (a branch of the Nasociliary nerve) through a descending branch.  

Nasociliary Nerve

The nasociliary nerve enters the orbit through the common tendinous ring, crosses the optic nerve and ophthalmic artery, and runs to the medial wall of the orbit. It gives off several branches, including anterior and posterior ethmoidal nerves, infratrochlear nerves, and 2-3 long ciliary nerves. it also gives some twigs to the ciliary ganglion.

The anterior ethmoidal nerve leaves the orbital cavity through the anterior ethmoidal foramen, runs in the canal of the same name, and reenters the cranial cavity. It runs over the cribriform plate of the ethmoid plate, and through a slit-like opening, it again leaves the cranial cavity and enters into the nasal cavity. Here, it further divides into the medial and lateral internal nasal branches that supply the anterior part of the nasal septum, etc.

The posterior ethmoidal nerve leaves the orbital cavity via the posterior ethmoidal foramen and reaches the ethmoidal and sphenoidal sinuses, where it innervates the mucous membranes of these sinuses. 

The infratrochlear nerve, as the name shows, is present below the trochlea. It supplies the skin and conjunctiva of the upper eyelid, lacrimal sac, and side of the nose. As stated above, it also communicates with the supratrochlear nerve. 

Long ciliary nerves are 2-3 in number. They arise from the Nasociliary nerve in orbit, pierce the sclera and pass forward in between the sclera and the choroid and supply the ciliary body, cornea, and iris. They also contain postganglionic sympathetic fibers coming from the cervical sympathetic ganglion to the pupillary dilator muscles.

Lacrimal Nerve

The lacrimal nerve is the smallest of all the branches of the ophthalmic nerve. It enters into the orbital cavity via the superior orbital fissure and runs along the lateral orbital wall lying over the lateral rectus muscle. It pierces the lacrimal gland and supplies the lateral part of the skin and conjunctiva of the upper eyelid. 

Nuclei of CN III Related to its Ophthalmic Division

The nuclei of cranial nerves are the collection of cell bodies of axons forming that cranial nerve. There are four nuclei of the trigeminal nerve. These include the main sensory nucleus, mesencephalic nucleus, spinal nucleus, and motor nucleus of the trigeminal nerve. All four nuclei collectively constitute the trigeminal system. Out of these four nuclei, only two (main sensory nucleus and spinal nucleus) are concerned with ophthalmic nerve fibers. 

Main Sensory Nucleus

This nucleus is present in the pons. The sensations of touch and pressure carried by the ophthalmic nerve are relayed here. The fibers coming here from the periphery have their cell bodies in the trigeminal ganglion. This nucleus also receives touch and pressure sensations from other divisions of the trigeminal nerve.

Spinal Nucleus

It is in the form of a column extending from the main sensory nucleus present in the pons, continuing through the medulla to the upper part of the spinal cord as far as the second cervical segment of the cord. The sensations of pain and temperature coming through the ophthalmic nerve fibers are relayed here. Pain and temperature sensations coming through the other divisions of the trigeminal nerve, i.e., maxillary and mandibular nerves, are also received here. 

Ophthalmic Sensory Pathway and Trigeminal Lemniscus

General afferent fibers carry sensations from the area supplied by the ophthalmic nerve to the trigeminal nuclei present in the brainstem. Carrier neurons at this step are the first-order neurons. From the main sensory nucleus, the spinal nucleus, and the mesencephalic nucleus, the axons of the second-order neurons ascend upward in the form of a neuronal band or bundle named trigeminal or spinal lemniscus and reach the thalamus. Thalamus is the main sensory collection center of the brain. From the thalamus, sensory information is directed to the cerebral cortex. Axons of the third-order neurons reach the somatosensory area located in the post-central gyrus of the cerebral hemisphere, where all the general sensory information from the body is received, integrated, and used for making an appropriate and proper response by the motor cortex and also used for decision making and thinking process of the brain. 

Functions of the Ophthalmic Nerve

The ophthalmic nerve carries general sensations from the structures which have embryonic origin from the frontonasal prominence of the head. These include the skin of the forehead and scalp, skin and conjunctiva of the upper eyelid, the mucous lining of the frontal, ethmoidal and sphenoidal sinuses, part of the nasal cavity, and part of the skin of the side of the nose, etc. The sensations carried by the ophthalmic nerve are pain, temperature (both warmth and cold), pressure, touch (light and crude), vibratory stimulus (vibrations, etc.), and two-point discrimination, etc.  

Corneal Reflex

The corneal reflex is characterized by the spontaneous blinking of the eye when the surface of the cornea is touched or when excess light is thrown into the eye. When the stimulus touches the cornea or conjunctiva of the eye, it causes closure of the orbicularis oculi muscle resulting in a blinking response of the eye. The afferent information is carried by the general sensory afferent fibers of the ophthalmic division of the trigeminal nerve to its sensory nucleus. From the sensory nucleus, information is passed onto the nuclei of the facial nerve via the medial longitudinal fasciculus. Motor or efferent signals through the facial nerve cause contraction of the orbicularis oculi muscles, which close the eyes. The corneal reflex prevents any damage to the sensitive and delicate corneal membrane. 

Diseases Related to Ophthalmic Nerve and Their Management

There are many diseases that affect the nervous system. Some of them are systemic, which affect the nervous system as a whole, and some are localized to particular nerves. We will limit our discussion to the trigeminal nerve, more specifically, its ophthalmic division along with its branches.

Trigeminal/Ophthalmic Nerve Palsy

Injury to the trigeminal nerve may result in sensory loss from a large part of the face and mucous membranes of the nose, paranasal sinuses, and mouth. In addition, muscles of mastication are paralyzed, resulting in problems with chewing and grinding the food. If the damage to the trigeminal nerve involves only its ophthalmic division, it can be called ophthalmic nerve palsy.

Causes of trigeminal/ophthalmic nerve palsy are diabetic neuropathy, aneurysm or tumor pressing the nerve, stenosis of the foramen from where the branches of the nerve leave the skull, inflammation (neuritis), multiple sclerosis or vascular diseases resulting in ischemia, etc. Trauma to the head can result in crush injury of the nerve. This can occur especially to the ophthalmic nerve due to road traffic accidents or falls resulting in orbital fractures.

Different methods can clinically test the ophthalmic nerve. One such method uses a cotton whisp. A piece of cotton is gently applied at the side of the cornea. If the nerve is intact, it will result in the blinking of the eye (intact corneal reflex). Lesions of the ophthalmic nerve result in loss of this reflex (absent corneal reflex). A blunt end pin can also be used to check pain sensations from the forehead area.   

Trigeminal Neuralgia

Acute severe stabbing or burning pain on the face in the area supplied by the trigeminal nerve. Frequently, the maxillary and mandibular divisions are involved. The ophthalmic division may participate in some severe conditions, but this is rare and uncommon. Trigeminal neuralgia is also known as tic douloureux. The pain is episodic and completely subsides when the acute attack is over. There is no facial muscle dysfunction. Usually, the pain is unilateral. The cause of trigeminal neuralgia is unknown yet. Pain can be triggered by talking, chewing, or even by a light touch on the face. Tic douloureux is one of the most painful conditions in which pain occurs. Treatment of trigeminal neuralgia involves the resection of one or more divisions of the trigeminal nerve. Pharmacological interventions include the use of NSAIDs and other analgesics. 

Trigeminal Nerve Block

Nerve block means anesthetizing a nerve. This block is performed for the treatment of trigeminal neuralgia or other conditions in which suppression of pain from the area of supply of the trigeminal nerve is required. Usually, one or two divisions of the trigeminal nerve are anesthetized. The most common trigeminal block is done for its maxillary division but less often done for ophthalmic and mandibular divisions.  This results in local anesthesia and analgesia in that area. In extremely painful conditions, a trigeminal nerve block can be performed to relieve that pain, but this is a temporary remedy, and treatment of the underlying cause is required for the complete dissolution of the pain. 

Summary

The ophthalmic nerve (CN V3) is the 3rd division of the trigeminal nerve, which is the third cranial nerve. It is purely a sensory nerve and contains general somatic efferent fibers as its functional components. The parent nerve, the Trigeminal nerve, emerges from the mid-brain at its anterior aspect at the level of the pons. It passes forward in the posterior cranial fossa, rests on the petrous temporal bone in the middle cranial fossa, and ends at a crescent-shaped ganglion, the trigeminal ganglion, located in the Meckel cave. Here, it divides into three divisions; 1) Ophthalmic nerve (CN V1), 2) Maxillary nerve (CN V2), and 3) Mandibular division (CN V3). 

The ophthalmic nerve runs through the lateral wall of the cavernous sinus and divides into several branches. These branches leave the cranial cavity via the superior orbital fissure and enter into the orbital cavity. Branches of the ophthalmic nerve include the frontal nerve, the Nasociliary nerve, and the lacrimal nerve. The frontal nerve is further divided into supraorbital and supratrochlear nerves. Branches of the Nasociliary nerve include anterior and posterior ethmoidal nerves, infratrochlear nerve, and 2-3 long ciliary nerves. 

There are two out of four trigeminal nuclei are involved in the sensory pathway of the ophthalmic nerve, the main sensory nucleus, and the spinal nucleus. 

The ophthalmic nerve supplies the skin of the forehead and scalp, the mucous lining of the frontal, ethmoidal and sphenoidal sinuses, the side of the nose, and part of the nasal septum, etc. Sensations carried by the ophthalmic nerve include pain, touch, pressure, temperature, proprioception, etc. The ophthalmic nerve also forms the afferent pathway of the corneal reflex.

Diseases related to the Ophthalmic nerve include trigeminal/ophthalmic nerve palsy and trigeminal neuralgia (most commonly, the maxillary and mandibular divisions are involved, but rarely ophthalmic division may get involved). Damage can be caused by neuritis, pressure due to tumor, ischemic or traumatic injury, exposure to toxins or drugs, and demyelinating diseases like multiple sclerosis, diabetic neuropathy, etc. Lesions of the midbrain involving the spinal lemniscus may result in the same signs and symptoms. Treatment involves the solution of the underlying cause by using either medications or surgical interventions. Trigeminal nerve block is also used in trigeminal neuralgia.

References

Blumenfeld H. Neuroanatomy Through Clinical Cases. Sinauer Associates, 2002

Brodal A. Neurological Anatomy in Relation to Clinical Medicine, 3rd ed. Oxford University Press, 1981

Brodal P. The Central Nervous System, 3rded. Oxford University Press, 2004

Butler AB, Hodos W. Comparative Vertebrate Neuroanatomy, 2nd ed. Wiley-Interscience, 2005

Carpenter MB. Core Text of Neuroanatomy, 4th ed. Williams & Wilkins, 1991

Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science, 4th ed. McGraw-Hill, 2000

Martin JH. Neuroanatomy Text and Atlas, 3rd ed. McGraw-Hill, 2003

Patten J. Neurological Differential Diagnosis, 2nd ed. Springer, 1996

Ropper, AH, Brown RH. Victor’s Principles of Neurology, 8th ed. McGraw-Hill, 2005

Standring S (ed.) Gray’s Anatomy, 39th edition. Elsevier Churchill Livingstone, 2005Image Source: Ophthalmic Nerve