Vision and Osteopathy in the Cranial Field
Visual problems are very common in today's society and take many forms. A good number of these go undiagnosed or untreated, but are amenable to osteopathic treatment.
Functional Eye Problems
involving pressure or tension on nerves controlling the muscles of the eyes, such as strabismus, have responded well to treatment. Certain types phorias and binocularity problems, that is, inability of the eyes to work together properly, respond well also.
Slight pressure on the areas of the brain that coordinate or control the eye muscles can interfere with or scramble the signals causing either the eyes to function improperly or the signals to be interpreted by the brain incorrectly.
There is a particular geometric relationship of the eyes and orbits (bony container around the eye) with respect to the rest of the head. This mechanical relationship must be maintained in order for the eyes to work properly.
Pressure on the nerves involved in the visual pathways can affect the ability to see properly. Some problems require concomitant treatment with an eye doctor and the use of vision therapy.
A number of years ago an osteopathic colleague, Dr. James Jealous, found that some of his patients who were slow to respond to treatment used corrective lenses. On further investigation he discovered that while checking patients’ heads, strains were actually increased or generated in many patients while they were wearing glasses or contact lenses. When these patients were referred to a developmental optometrist and new corrective lenses prescribed, the strains in these patients would noticeably decrease.
One of his students, Dr. Joe Field, took this a step further and spent much time working with this optometrist, Dr. James Mancini, in an attempt to figure out this phenomenon. He worked with the concept that most patients’ glasses altered the patterns that an osteopath could sense in the patient’s body, sometimes to a profound degree. After much study he found that, starting at the point of refraction for correct central vision, he could fit patients with lenses. When this was done correctly, it reduced the strains on the head (and thus the whole body) and many patients with difficult to treat problems improved.
Another colleague, Dr. Paul Dart, studied with Dr. Fields and took this one step further, simplifying the approach and using a system that was easier to understand and reproduce. In addition he added many aspects of dealing with binocular vision problems and proper use of prismatic correction. Since there was much interest, Dr. Dart began to show his colleagues this approach and is constantly working to refine it. He coined the term “visual somatic dysfunction” which describes the structural problems produced in the body through compensation in the eyes.
This whole phenomenon can be easily understood by looking at the anatomy of the eye. The retina, in the back of the eye, is sensitive to incoming light focused on it by the lens and cornea. The retina has many cells in it that respond to light.
|Figure 1. The eye, showing the retina and fovea.|
The most highly concentrated area of these cells in the middle of the retina is called the fovea. The fovea is the area that allows us to have highly discriminatory central vision, vision that can distinguish detail to a great degree. Most of the remainder of the retina is referred to as the periphery, and this is the area that allows us to have peripheral vision. Incoming light is focused on the whole retina including the fovea and this forms an image, which is then transmitted to the brain and discerned as a visual image.
The eye is filled with a gelatinous, light transmitting substance with orderly rows of protein molecules that give it slight “contractile” properties. We believe this allows the eye to somewhat change shape in response to the proper stimulus. The shape of the eye is also subject to tension in the connective tissue surrounding it to some degree.
The fovea is in a depression almost 1/2 a millimeter behind the surface of the retina so it has a different plane of focus than the rest of the eye. That is, when an object is in focus on the periphery, it is not in perfect focus on the fovea and visa versa. To get the very best visual acuity possible, the light can be made to focus on the fovea as opposed to the rest of the retina. Glasses are usually fit to enhance visual acuity to its maximum amount.
Production of Visual Strain
The problem occurs due to the fact that the body prefers the image to be in focus on the periphery, not the fovea. In other words, it appears that evolution has favored peripheral vision over central vision, as this may have been a survival mechanism. When the image is focused centrally, the eye tries to compensate for this, producing a physical strain as it attempts to slightly change its configuration such that light will be focused more on the periphery. This can be felt by anyone with the proper training.
Exam for Visual Somatic Dysfunction
The procedure to do this is very simple, but balancing the strain with corrective lenses can sometimes be time consuming.
To screen a patient the physician usually monitors the head of the patient according to standard procedure in OCF. This is done with no light entering the eyes and carefully compared to the findings with light entering the eye. This can be done with the patient looking at a distance and then closely, with the patient reading printed material. This screening exam allows us to determine if visual somatic dysfunction is present.
Treatment of Visual Strains
The physician usually inquires about a recent refraction. The patient may be referred to an eye doctor for an eye exam if this not recent. In addition, the eye doctor can uncover any unusual problems. The refraction is the starting point in determining treatment.
Balancing the strain
The osteopathic prescription to treat a visual strain should be close to the refraction, but is rarely the same.
The physician checks the physical strain patterns by monitoring the motion in the patient’s head while fitting different lenses over the eyes, comparing what he finds with the eyes closed and as opposed to being open. If there is no change between the two, no strain is produced by light entering the eyes; this is a balanced prescription. If a strain is produced when the eyes are open (by the eye compensating when light enters it), then a problem still exists and the prescription needs to be adjusted accordingly. Keep in mind that this is a stepwise process repeated with different types and combinations of lenses.
Effects of Treatment
Remember, the proper prescription will produce the least effect on the body’s normal motion and will add no new strain patterns with light coming through the eyes. As the body is one continuous unit, this balanced prescription will not only reduce the physical strain on the head, but also on the neck, shoulders, back and in fact, the whole body. Reducing the stress load on the body increases the level of health and thus, the ability of the body to help itself. Along with osteopathic treatment, this will help resolve chronic strains in the body, which contribute to health problems.
Since the use of corrective lenses is aimed at optimally reducing the strain on the body, as compared with increasing visual acuity, the prescription needs to be checked every 1-2 months and adjusted accordingly over time as the body balances itself out. Some patients can progress to the point where no correction is needed to balance the body.
As the strength of the prescription is usually being reduced over time, this can have the side effect of increasing the ability to see clearly without glasses.
Occasionally nearsighted individuals may notice that their distance vision (acuity) is not quite as good with a balanced prescription as with a traditional prescription, though it should still be acceptable. Very rarely a patient will notice that their visual acuity is significantly different with a balanced prescription. This is usually a temporary condition and tends to decrease with time. These patients, as in most, should notice a difference in their other problems, such as a decrease in headaches or musculoskeletal pain.
In conditions such as mild dysphorias and amblyopia, prism correction may be required. An eye doctor is consulted before working with this type of problem, as there may be certain cautions or difficulties if central suppression is present.
Many advances in corrective lenses have been made in recent years and there are now a large number of choices in types of hardware.
Glasses have been around for several centuries and have been highly refined over that period of time. They are usually the answer for most common types of visual strains. The strong point of glasses is that they are easy to fit, relatively inexpensive and the lenses can be manufactured quickly. In addition, glasses with wire frames (which are the ones recommended) can be easily adjusted for slight binocularity problems.
Contact lenses are very useful for strong prescriptions, as there tends to be less distortion than glasses. They are also lighter and more acceptable cosmetically. Recently they have come down in price and are very affordable. Contacts can be used to correct visual strains, but this requires an extra step of seeing an eye doctor to convert the required correction to a form suited for contacts and to make sure the proper contacts are fitted for the shape of the patient’s eyes. Contacts are not the perfect solution for precisely balancing astigmatisms as the weighted contacts that are used still move around to a degree. Also, not all people can wear contacts due to individual idiosyncrasies.
Monovision is used in patients needing correction for both reading and distance. It is the practice of prescribing a corrective prescription for one eye for distant vision and the other eye for near vision. The idea is that a person will always be able to see both near and far.
Unfortunately, acuity is only one aspect of vision. The eyes need to work together to produce a 3-dimensional image in the brain. On using this type of correction, you disrupt this ability and interfere with depth perception. Since one eye is corrected for near and one for far, one eye will always be in visual somatic dysfunction, causing very large and noticeable visual strains. These strains will eventually manifest as other symptoms.
One of the recent advances in optics was the use of computer aided lens grinding machines. With this came software to make a type of bifocal lens without the line or abrupt transition that many people dislike cosmetically.
|Figure 2. Schematic of progressive lens demonstrating different zones of focus.|
This type of lens has the advantage of having an intermediate zone of focus for near objects that are not quite at reading distance. There is a progressive change from the distance to the reading prescription, rather than an abrupt one.
Unfortunately, these are not very useful in reducing visual strains. The problem is that there is a large area for distance vision and a small area for near vision; the area for near vision is too small to properly incorporate the periphery. The zone of focus from the area for central vision to the area for peripheral vision constantly changes (progressive zone). In addition, due to the way these lenses are made, the cylinder or astigmatism correction is different at the periphery than at the central area, again causing visual strain.
Laser Eye Surgery
This type of eye surgery has been successful for correcting visual acuity in many individuals, but is unfortunately not useful in eliminating visual strain. The problem is that with these techniques, only the middle of the cornea is reshaped. This does improve central vision, but then leaves more of a disparity between central and peripheral vision, increasing the strain. The procedure may be done on an eye that has a great deal of strain in or on it, which will make it much more difficult to treat later, especially since it was probably originally contributing to the problem with visual acuity. In addition, the changes are permanent.
This type of surgery is still relatively new and will be refined over the years. Perhaps a new method will be developed which is compatible with reducing visual somatic dysfunction.
Monovision contacts, monovision lens implants, bifocal contacts, bifocal lens implants and aspheric lenses (usually in pre-made reading glasses) all will create significant visual strains.
This type of exam does not check for most diseases of the eye and should be used in conjunction with normal eye care, not as a replacement for periodic eye exams. Remember, this approach uses corrective lenses as a biomechanical device to treat visual somatic dysfunction. The treatment goal is not to get the absolute best visual acuity possible. The goal is to reduce strains on the body that are being generated from the body’s response to light stimulus in order to increase the overall level of health as much as possible.
1. Dart, Paul, M.D., Ophthalmologic Principles And Their Relationship To Osteopathy In The Cranial Field, Second Edition, privately published, Eugene, Oregon, 2002.
2. Dart, Paul, M.D., The Use of Optometric Lenses to Reduce Visual Strain, privately published, Eugene, Oregon, 2001.