Subs30

Hi Joni

Take a look at this see if helps---did u wear glasses prior to this junk hitting?

...."Visual System Problems

Just as unreliable or erroneous information from the vestibular system can cause sensory conflicts, unreliable visual information can also create conflicts. Along with dizziness, many patients with visual system problems complain about photophobia, motion sickness, inability to function in situations involving peripheral motion (e.g., moving down the aisle in a grocery store or library), reading difficulties, and anxiety.(43) Common causes of faulty visual information include abnormal eye movements, lack of image clarity, image size differences, binocular conflicts, and field reductions.

Eye Movements
When examining a patient complaining of dizziness, special care should be taken to check for nystagmus or failures of the normal visual/vestibular reflexes. In cases of gross vestibular reflex failure, patients can lose the ability to hold the visual world stable as they move their head and will complain that the world bounces up and down as they walk (oscillopsia).(25,44) Some patients also complain about blur, but, on closer questioning, it will be found that they are really experiencing shimmer or colored fringes on letters possibly because of small nystagmoid eye movements.

Image Clarity
Vision care specialists typically provide lenses that yield the maximum acuity for their patients. Most of the time this approach is successful, but occasionally patients will have trouble adapting to new lenses, especially if the retinal images created are considerably different in size or position as compared to the images produced by the old lenses. This is because the brain has adjusted its expectation to the images produced by the old lenses and the new images create conflicts with the expectation. Another source of conflict might involve conflicts that would occur when the information carried by the new images is compared to the information coming from the vestibular system.

Most patients adjust to their new lenses in a few days or weeks, but some will experience the vertigo, nausea, and discomfort associated with sensory conflict during this adaptation period. A few patients, especially those with vestibular or hyper-vigilance related psychological problems, will be unable to adapt to their new lenses and will be very willing to sacrifice acuity for a reduction in conflict symptoms.

Binocular Image Conflicts
Binocular image conflicts can occur because the images produced on the retinas are of unequal sizes, or because the eyes fail to align properly. Often an image size difference (aniseikonia) is created when lenses of significantly different powers are used to compensate for anisometropia.(45) The resulting difference in retinal image sizes makes it difficult for the brain to fuse the images into a single precept.

Other patients have aniseikonia that occurs without anisometropia; this condition can sometimes be quite difficult to detect. Treatment for aniseikonia can involve the prescription of contact lenses instead of spectacles to reduce the difference in magnification effects, or the use of "size lenses" that can change retinal image sizes.

Ocular alignment problems can involve potential misalignments that require constant effort by the patient to overcome, (e.g., high phorias or fixation disparities), or major problems in which the eyes are significantly misaligned, (e.g., strabismus). These misalignments can be in the horizontal or vertical directions, or they can involve rotation of the eye around the line of sight.

Detection of these problems ranges from simple observation of ocular postures in the case of strabismus, to the need for prolonged occlusion in the case of latent vertical deviations.(43) It is also possible for the misalignment to occur only intermittently (e.g., during periods of high stress), and perhaps only during specific tasks such as reading or when the eyes are in specific positions of gaze.

Patients with normal binocular alignment and those with gross misalignments are often relatively symptom free, whereas those with deviations that are intermittent, small enough to overcome with mental effort, or situation-specific experience the most symptoms. As an adaptive measure, the visual system can develop the ability to suppress a considerable portion of the information from a deviating eye if the deviation is large and constant.(45) However, if the deviation is not large and constant, the brain must work to "sort-out" the information from the two eyes prior to comparing it to the information arriving from the vestibular system. This process can produce symptoms of dizziness in many patients.

Treatment of ocular misalignment involves restoring alignment optically, surgically, or with vision therapy. Care must be taken, however, when attempting to restore binocular vision to patients who have adapted to their deviations by learning to suppress the image from the deviating eye. Often these patients experience an increase in symptoms before they feel better. In some cases, especially with elderly patients, faulty binocular vision can be intentionally disrupted with an occluding filter over one eye to remove a sensory conflict.

Reduction in Visual Fields
The brain uses information from the peripheral visual fields, along with vestibular and other sensory information, to maintain balance and a sense of position in the environment. Restricted fields can, therefore, cause many patients to experience disequilibrium, especially when the field loss is recent.(46) Skills associated with cognitive mapping, the ability to move about in a complex environment, and eye-hand coordination can also be affected by field restrictions.(46)

New Spectacles Can Cause Dizziness

When the head moves from side to side, the vestibular system detects this motion and sends a message to the eye muscle control systems causing the eyes to move counter to the head movement. This allows gaze to be held still as the head moves. The process is called the Vestibulo-Ocular Reflex (VOR). Failure of this mechanism can cause oscillopsia (bouncing vision) when a patient walks or otherwise moves the head.

To operate properly, the ratio (sometimes called the gain) of vestibular movement signals to the amount of compensating eye movements must be correct. If the eyes move too much or too little in response to a head movement, a sensory conflict results and the patient gets sick.

If there is a significant power change in the patient's new glasses, the image has been made larger or smaller on the retina so the VOR gain must be re-calculated by the brain. For some patients this is easy to do (a no-brainer), but for others it takes time - up to several weeks. And some never manage the task. This is why some patients experience transient dizziness caused by their new lenses.

Now consider the patient whose vestibular system is a little shaky to begin with and who needs bifocals or progressive addition lenses. In addition to the distortions on the periphery of the lenses, consider the range of VORs the brain has to calculate. A different one is needed for every spot on the lens because the powers are different at each spot.

CLINICAL PEARL. NEVER GIVE A PATIENT WITH A HISTORY OF DIZZINESS OR VESTIBULAR PROBLEMS A PROGRESSIVE ADDITION LENS. IN FACT DO NOT EVEN GIVE THEM A BIFOCAL. GIVE THEM SEPARATE NEAR AND DISTANCE LENSES SO THAT THE BRAIN HAS TIME TO RECALCULATE THE VOR AS THE PATIENT CHANGES GLASSES.

Vertical Imbalances as Causes of Dizziness

A frequently discussed source of sensory conflict problems is unresolved vertical imbalance. It is often said that vertical imbalances are like hyperopia in that a portion of the imbalance is manifest so that it can easily be detected during a normal examination, and another portion is latent which means that special techniques must be used to reveal it.

One of these techniques is prolonged monocular occlusion which was advocated by Raymond Roy, Sr.(43) Using the Roy technique, patients are monocularly occluded for 3 days per eye. This prolonged occlusion releases the latent vertical which can then be compensated with prism.

Roy developed a sign and symptom list that he believed suggested a latent vertical problem. These include:

- possible vertigo, but not always
- possible autonomic involvement
- chronic sea sickness
- mild nausea
- headache
- vision changes
- "blur", shimmer, jumping
- photophobia, dislike bright lights
- reading problems
- problems with flicker
- difficulty in conversation
- difficulty in crowds
- difficulty in grocery or library
- walk with head down
- driving problems
- problems with bridges, tunnels, multi-lane roads
- reduced ability to remember and to "think"
- lack of sense of closure or completion
- loss of self confidence
- clumsiness
- slurred speech
- poor handwriting
- chronic fatigue
- inability to divide attention
- reduced input channel capacity
- can't handle a lot of sensory or Intellectual information
- poor memory access
- loss of words in conversation
- can't recall names
- anxiety
- depression, possible suicide
- personality changes

Many of these problems are associated WITH sensory conflicts, but others suggest higher level involvement with cognitive processes.

Other problems suggest that peripheral retinal information is somehow causing the patient grief. Classic problems that sensory conflict patients report occur in environments with very busy peripheral information like aisles in grocery stores or libraries. Many patients will not enter these environments without a shopping cart or another person to hold onto for support. Problems with driving over bridges and through tunnels can also be understood as involving lack of a horizon to use for a reference when on top of the bridge or in the tunnel.".....