Each eye is innervated by several cranial nerves, each carrying variously visual information from the retina, control of the extrinsic and intrinsic muscles of the eye, and autonomic innervation. The six cranial nerves that innervate the eye are:
All of the nerves innervating the eye and its container are cranial nerves, each of which arises from the brain stem. All cranial nerves exit the brain case through apertures in the cranial base. Some cranial nerves exit the brain case through a single port. Other cranial nerves branch extensively within the brain case, with some of their individual branches exiting the brain case through each of several ports. Some whole or branches of cranial nerves share a port with other cranial nerves. Some branches of cranial nerves innervate structures within the cranium including the meninges (see Figure 1).
Several cranial nerves travel from the brain case to the orbit, all of them entering the orbit through three closely adjacent apertures in the posterior surface of the orbit. Once in the orbit these nerves fan out to innervate the several parts of the eye and its musculature. Given the more
or less cone fan-shape of nerves from a small area in the back of the orbit to the several parts of the eye and its muscles, each movement of the eye will slack nerves toward one side of the eye and add tension to nerves on the opposite side. Therapeutically, we can utilize slow small movement of the eye to assess tension in these nerves, and to apply therapeutic load to nerves which may be too tight. How to do this is detailed below.
The eye is housed in the bony orbit. The shape of the orbit resembles an elongated four-sided pyramid with a flattened top. The four sides of the orbit – left, right, superior, and inferior – are relatively flat, more or less trapezoidal surfaces, converging posteriorly toward the back of the orbit where they are capped by a rhombic planar surface that lies in an approximately coronal plane.
The inner surface of the orbit has sensory innervation from the trigeminal nerve. This is different from the branch of the trigeminal nerve that provides sensory innervation to the eye itself. A method is described below to apply therapeutic levels of tension to the trigeminal branches supplying the surface of the orbit.
The eyelids have motor innervation by branches of both CN VII, the facial nerve, and CN III, the oculomotor nerve. Eyelid sensory innervation is from the trigeminal nerve, CN V1. The ‘1’ after V designates the ophthalmic branch, the most superior of three branches of the trigeminal nerve which exit the braincase separately.
As a step to understanding the assessment and treatment methods provided in this article, here is descriptive information about the structure of nerves in general.
Each nerve cell is an elongate single cell, having a wider body and a thin, elongated axon that may be up to 1m in length. The diameter of axons is variable but in human nerves the dimension of their diameter clusters around one micrometer, or 1/1,000mm. The largest diameter axon might be seen with a strong magnifying glass, but most axons require a microscope for visualization. In contrast to the individual axons, macroscopic nerves are easy to see with the naked eye and to feel with the hand. For example, the optic nerve is about 5mm in diameter. The largest nerve in the body, the sciatic nerve, is about the diameter of the person’s thumb.
How do individual axons with a diameter of .001mm relate to macroscopic nerves of 1mm, 5mm, or 2cm in diameter? Each macroscopic nerve contains many individual axons bundled together as a multiconductor cable, resembling a telephone cable with many individual
wires in it carrying separate conversations. Within each macroscopic nerve, each individual nerve axon is insulated so that the nerve cells do not cross-talk with each other. The insulating material is connective tissue, part of the interstitium. In addition to the insulating material, macroscopic nerves also contain additional connective tissue for structural strength. While each macroscopic nerve is made up of many axons, the composition of each nerve is 50%-90% connective tissue. Like any other connective tissue, the connective- tissue components of nerves can, and frequently do, become fibrosed. That is to say, the repair process overshoots, adding too much fiber and shifting the fiber balance toward more collagen and proportionately less elastin. Fibrosity of the connective- tissue components of a nerve reduces its elasticity. Elasticity of nerves is necessary to accommodate movement.
A common way for nerves innervating the eye to become fibrosed is acceleration injuries. If while walking or running I run into something, my body is abruptly stopped while my eyes continue forward, ballistically stretching the nerves to the eye. Nerves also fibrose as they heal from other insults including infection or injury due to chemical exposure.
When a nerve to an eye is fibrosed it cannot adequately elongate as the eye moves in its socket. This movement limitation can lead to the person either positioning the head more or less off center, and/or making routine asymmetrical movements with the head as a whole in order to position the eyes. Over time these adaptations have large effects on the person’s neck and, from there, the rest of the body.
The methods described below restore the elasticity of the nerves to the eyes.
is felt, you may make the tissue feel less tense at this time, but you are tipping into tissue damage that will be followed in the weeks ahead by new fibrosis in the area. Rather than continuing with treatment of this tissue at this time, note what was accomplished, then at a future treatment two weeks or more in the future, re-assess the area. You will likely find the tissue to be better than you left it. Further treatment may be desirable at this later date. This caution and process is important for all tissue. Given the vulnerability of the eye, this cautious process is mandatory.
The general first-barrier method above describes first slacking the tissue and then springing out to and perhaps eventually beyond the resting equilibrium of the tissue as the tension in the tissue incrementally decreases. For the eye this is done in a special way utilizing movement by the client.
It is possible to work on one eye at a time, by using a one-handed hold on the ipsilateral side of the cranial base for the eye being worked on. The second hand can then very gently contact the eye through the eye lid. The practitioner then moves the eyeball. While this can be effective, there are drawbacks. The unilateral hold on the cranial base is less certain than a bilateral contact, and there is some risk to the client from directly contacting the eye (for example, if the person has glaucoma, the added pressure on the eye can be damaging). In contrast, having the person move their own eye engages them in the process and gives them agency.
Motor and sensory innervation of the eyelid is achieved by CN VII (the facial nerve), CN III (the oculomotor nerve), and sympathetic nerve fibers. The facial nerve innervates the orbicularis oculi, frontalis, procerus, and corrugator supercilii muscles and supports eyelid protraction. A treatment method similar to that described for the innervation of the eye can be used. For the eyelid, however, it is practical for the therapist to contact and manipulate the eyelid itself. It is best to treat one eyelid at a time.
– one on the eyelid and the other on the ipsilateral cranial base. Unlike for the eye itself, the client’s movements are not used.
The innervation of the lining of the eye socket is by the trigeminal nerve and is purely sensory. As with the nerves serving the eye, these trigeminal branches to the lining of the socket emerge from a port in the posterior surface of the eye socket.
A mechanism of injury for the nerves innervating the eye was described in which the forward motion of the body is suddenly stopped, while the eyes continue forward ballistically stretching the nerves to the eye. For the trigeminal branches innervating the lining of the eye socket, the related mechanism is somewhat different but also related to concussion. If the brain is ballistically accelerated within the braincase, this jerks on cranial nerves. This mechanism of injury can
apply to any cranial nerve. The trigeminal nerves innervating the lining of the socket are relatively fixed in their positions. If the brain is quickly accelerated within the braincase, this motion sharply pulls on the nerve branches to the orbit, injuring them.
To apply a first-barrier stretch to the trigeminal branches to the lining of the orbit we make use of the elasticity of bone. Living bone has about the same elasticity as a piece of nylon of the same size and contour. Our general understanding of bone has been led astray by handling dead, dry bone, which has the same relationship to living bone as beef jerky does to living muscle tissue. It takes surprisingly little force to bend bone. For the method described here be gentle.
The innervation of the eye and its adnexa is complex and fascinating. While it is not necessary to know all of the details of anatomy to perform the assessments and treatments described in this article, knowing more detail is likely to increase the practitioner’s sensitivity. Details of the innervation are readily available in anatomy books and on-line.
In closing I want to emphasize safety. Before beginning, ask your client about any known eye-related pathology. In response to what you hear, err on the side of caution. If you decide to proceed, describe what you want to do with your client. Get their agreement. Work gently and at a slow to moderate pace. Keep up the conversation with your client. Describe what you are doing and why. Ask the client about their awareness as you work. Stop if there is any discomfort.
Jeffrey Burch was born in Eugene, Oregon in 1949. He grew up there except for part of his teen years lived in Munich, Germany. Jeffrey received bachelor’s degrees in biology and psychology, and a master’s degree in counseling from the University of Oregon. He was certified as a Rolfer in 1977 and completed his advanced Rolfing® Structural Integration certification in 1990. Jeffrey studied cranial manipulation in three different schools, including with French etiopath Alain Gehin. Starting in 1998 he began studying visceral manipulation with Jean-Pierre Barral and his associates, completing the apprenticeship to teach visceral manipulation. Although no longer associated with the Barral Institute, Jeffrey has Barral’s permission to teach visceral
manipulation. Having learned assessment and treatment methods in several osteopathically derived schools, he then developed several new assessment and treatment methods that he now teaches, along with established methods. In recent years he has developed original methods for assessing and releasing fibrosities in joint capsules, bursas, and tendon sheathes, which he is also beginning to teach. Jeffery is the founding editor of the IASI Yearbook to which he contributes regularly, as well as to other journals. He served for many years as a member of the Rolf Institute® Ethics Committee. For more information visit www.jeffreyburch.com.
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