Vision Challenges with Vestibular Disorders by the Vestibular Disorders Association

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Vision Challenges with Vestibular Disorders By the Vestibular Disorders Association

A common complaint for people with held steady by the photographer (the vestibular disorders is that they have VOR) in order to produce clear pictures. difficulty with their vision. They have However, if the photographer is unable problems focusing on an object or to hold the camera steady, the resulting perceive that objects are moving from pictures will be blurry or perhaps have side to side or revolving around them double exposures, even though the (vertigo). They may see their visual field camera itself is in perfect working order. jiggle or bounce (oscillopsia) or have A malfunctioning vestibular system double vision (diplopia). When they hold changes the once skilled photographer their heads still, the problems disappear. into an unskilled one. People with a The optometrist, who conducts eye chronic vestibular disorder must learn to exams while a patient’s head is securely adapt to this newly unpredictable visual braced against a head rest, is often world—a challenge that only increases in unaware that a vestibular problem complexity if they also require glasses or exists. When the optometrist then other visual correction. explains the normal results of the exam, such patients may become disgruntled or How does the vestibulo-ocular reflex frustrated because the test results don’t work? reflect the symptoms that they When the head is motionless, the experience in the course of daily life. number of impulses transmitted from the vestibular organs on the right side is Why do vestibular disorders affect equal to the number of impulses from the vision? left side. When the head turns toward The vestibular system sends motor the right, the number of impulses control signals via the nervous system to transmitted through the nervous system the muscles of the eyes with an from the right ear increases and the automatic function called the vestibulo- number from the left ear decreases. The ocular reflex (VOR). The VOR is a crucial difference in impulses sent from each part of maintaining balance and clear side controls eye movements to stabilize vision, controlling eye positions so that the gaze during active head motions. when the head moves, gaze remains stable. Another way of explaining this is There is a predictable ratio between the to compare the vision system to photo- amount of head movement and the graphy. The camera (the eyes) must be amount of eye movement required for a

stable gaze. When the head rotates at a frequent head movements are required, certain angle and speed, the eyes rotate such as when a person converses with at the same speed (gain) but in the others at work or at a social gathering. opposite direction (phase). The sensory information provided by both ears is Reading text on a printed page presents normally symmetrical. Signals coming a special challenge for people with an from the left ear correspond with the impaired VOR. The bouncing and shifting information provided by the right ear. words and letters require more effort to Thus, if the vestibular organs in one or process (see Figure 1), which is why both ears are not working properly, the children with an undiagnosed vestibular brain receives conflicting signals about disorder are sometimes mistakenly movement, resulting in the sensation of thought to be dyslexic. vertigo.

Impacts of a disrupted vestibulo- Try to read this ocular reflex May appear like this: A disrupted or impaired VOR can result Try to read thiis in abnormal nystagmus, an excessive Try to read this to-and-fro movement of the eyes, and oscillopsia, where objects appear to Figure 1. For people with oscillopsia, tracking printed words on a page can require bounce because they do not remain a great deal of effort because of the fixed on the same point on the retina. distortion produced by even small head A person with a vestibular disorder may movements. also experience photosensitivity (discomfort with bright light) and other Reading text on a computer monitor can vision problems such as: intense be even more problematic because of a discomfort with flickering lights, heightened sensitivity to screen flickering particularly fluorescent, sodium, or or scrolling pages of text. Many people mercury vapor lights; moving objects; with an impaired VOR resort to manually rows of similar objects, such as in bracing their head to reduce reading grocery store aisles or lines of text on a problems, such as by cupping their chin page; or busy, high contrast patterns, in their hand, in an effort to prevent tiny such as polka dots or sunlight filtering movements—even those as small as are through mini-blinds. Environments with produced by a pulse. a combination of fluorescent lighting and busy patterns or moving objects are People with vestibular disorders face especially problematic which is why particular challenges with peripheral shopping in large stores may be very vision, which works to integrate visual difficult. Even environments with information with vestibular functions and subdued décor can be fatiguing if is vital for maintaining a sense of balance

and orientation. A damaged VOR may called visual dependence, where the result in peripheral visual flickers that brain suppresses vestibular input and may be mistakenly perceived as becomes extremely reliant on vision to movement, such as the illusion of a bird maintain balance. However, because of flying quickly past. In addition, the impaired VOR, disorientation and nystagmus is more pronounced when a symptoms of panic can occur in person looks to the far right or left, so situations where movement of objects actions such as looking over the shoulder near the person may be mistaken for while backing up a car can be especially self-movement. These symptoms may uncomfortable. also occur when a person’s visual field is overwhelmed (e.g., in a room wallpaper- Peripheral vision distortions are especially ed with busy patterns) or lacks a point of problematic for a person who wears fixation (e.g., in intense darkness, wide glasses and has adapted to a vestibular open spaces, or as experienced with disorder by minimizing head movements snow blindness). and relying instead on moving the eyes. Although eyeglasses produce clear and Evaluation consistent vision straight ahead, lens The diagnosis of a vestibular disorder aberrations such as visual field curvature relies on a combination of careful and distortion reduce vision clarity when inspection of the history of the problem, a person looks through the side of a lens physical examination, and tests. Because (Figure 2). Thus, if a person with glasses vision is so closely linked to the vestibular moves the eyes rather than the head to system, many of these diagnostic tests scan, objects viewed to the side will involve evaluation of the gain, phase, appear to distort and move. Certain and symmetry of eye movements that shapes of windshields in cars or vans occur with vestibular stimulation. may cause similar peripheral distortion at their edges. Figure 2 (below). Projection of a flat object (A) onto a curved surface causes straight Ironically, a person with a vestibular lines to appear curved (B) as the power disorder may experience a phenomenon (curvature) of a lens increases, so does the

A B C D

correct farsightedness cause pincushion-type disorder is to treat the vestibular distortion (C) and glasses that correct disorder. Depending on the specific nearsightedness cause a barrel-like distortion vestibular disorder diagnosis, treatment (D). may involve surgery, physical therapy, medication, or other strategies. When a For example, electronystagmography chronic vestibular disorder does not (ENG) tests measure nystagmus that resolve with treatment, specialized occurs when the head is positioned in vestibular rehabilitation exercises may certain ways while a person tracks a still be useful in helping with the related moving object, or when the ear on one impacts on vision. Vestibular side is stimulated with warm or cold rehabilitation is an exercise-based water or air (the caloric test). During program that includes coordinating eye these tests, eye movements are recorded and head movements, stimulating the using small electrodes placed on the skin symptoms of dizziness in order to around the eyes or with an infrared video desensitize the vestibular system, camera mounted on goggles (known as improving balance and walking ability, videonystagmography or VNG). Rotation and improving fitness. testing employs the same electrodes or goggles to measure the relationship Optometric therapies may also be part between the speed of head movement of treatment—especially if an underlying and eye movements while the head is focusing, ocular alignment, visual acuity, rotated. or visual processing problem is suspected in addition to the VOR It is important to note that these and problem caused by the vestibular other tests employed to evaluate vision disorder. Such optometric rehabilitation and vestibular disorders must be treatment may involve the use of administered and interpreted by trained corrective lenses, including prisms and 1 specialists. Factors such as age, spectacles, phototherapy (light therapy), 2(p. 51) medications, or systemic processes and therapy to help sharpen vision skills 3 4 such as depression, migraine, or sleep or develop the eye muscles involved in 5,6 deprivation can modify the VOR. Such focusing, such as exercises that have a factors must be incorporated into the person cover one eye while reading. testing process and interpretation of the results by physicians such as otolaryn- Glasses and contact lenses gologists/ENTs, otologists, neurotologists, With glasses, the type of vision otoneurologists, and ophthalmologists. correction alters the size of the visual world, growing larger for farsighted Treatment people and shrinking for nearsighted The first approach to resolving vision people. This change forces the brain to problems resulting from a vestibular recalculate the ratio between head and

eye movement, which is a fairly simple Coping strategies adjustment to make with lenses that To facilitate the adaptation process, have only one optical power. If a person a person can adopt certain strategies needs correction for both distance and to improve tolerating problematic reading, using bifocals, trifocals, or environments: When outside, wearing progressive lenses will create extra work high quality sunglasses can help a for a brain already overtaxed by person tolerate glare from sunshine. negotiating a vestibular disorder because To minimize visual distractions in their multiple levels of magnification in the peripheral vision, some people find it same lens require the brain to calculate helpful to use glacier glasses (sun- and adjust to multiple eye-head glasses with side visors). Other adapta- movement ratios. Such a person may tions may include fixing attention on a want to consider having two pairs of large object a short distance away while single-vision glasses—one for each task. walking toward it, using a cane to Regardless, even with a single power increase touch cues, and ensuring that lens, adjustment will be more difficult if home or office lighting is consistent the glasses are not fit properly such that from room to room and doesn’t use they tend to slide down the nose and unshielded bulbs and fluorescent lights. cause the distance between the eye and If fluorescent lighting is unavoidable at the lens to vary. work, using a small incandescent desk light may help disguise some of the A person with a vestibular disorder who fluorescent light’s flickering. wears glasses may also consider switching to lenses with a small lens diameter Home décor can be modified to to reduce visual aberrations, thus eliminate patterns wherever possible. helping to reduce vertigo and dizziness. This might include replacing wallpaper Another possibly helpful alternative is that has a busy pattern, substituting switching from glasses to contact lenses. light-filtering curtains for mini-blinds, Unlike glasses, where the distance and replacing or removing highly between the eye and the lens can vary, patterned carpets, which can trick the contacts are worn directly on the cornea eye into believing that there is a of the eye, allowing objects to appear depression or elevation in the floor without distortion and in the correct size where none exists. and position. In some cases, contact lenses may also help dampen the Although it may be tempting for nystagmus associated with a vestibular people with VOR disturbances to cope disorder. However, a disadvantage of by staying at home and avoiding visual contact lenses is that they can increase a stimulation, this can undermine the person’s sensitivity to light. ability to adapt in the long term.

Additional resources patients complaining of dizziness. Some helpful documents available from J Anxiety Disord. 2003;17(4): VEDA: 369–388. . The Human Balance System: A 4. Cha Y-H, Lee H, Santell LS, Baloh Complex Coordination of Central RW. Association of benign and Peripheral Systems (Pub. S-7) recurrent vertigo and migraine in . Vestibular Rehabilitation: An 208 patients [published online Effective, Evidence-Based ahead of print January 16, 2009]. Treatment (Pub. F-7) Cephalalgia. Accessed April 9, . Computer Monitors and Digital 2009. Televisions (Pub. F-30) 5. Fransson PA, Patel M, Magnusson . Vestibular Injury: Compensation, M, Berg S, Almbladh P, Gomez S. Decompensation, and Failure to Effects of 24-hour and 36-hour Compensate (Pub. F-26) sleep deprivation on smooth pursuit and saccadic eye References movements. J Vestibular Res. 1. Fife TD, Tusa RJ, Furman JM, 2008;18:209–222. Zee DS, Frohman E, Baloh RW, 6. Quarck G, Ventre J, Etard O, Denise Hain T, Goebel J, Demer J, Eviatar P. Total sleep deprivation can L. Vestibular testing techniques in increase vestibulo-ocular responses. adults and children: report of the J Sleep Res. 2006;15(4):369–375. therapeutics and technology subcommittee of the American © 2009 Vestibular Disorders Association Academy of Neurology. Neurol. VEDA’s publications are protected under 2009;55:1431–1441. copyright. For more information, see our 2. Desmond A. Vestibular Function: permissions guide at www.vestibular.org. Evaluation and Treatment. New This document is not intended as a substitute York: Thieme; 2004. for professional health care. 3. Eckhardt-Henn A, Breuerb P, Thomalskec C, Hoffmann SO, Hopf HC. Anxiety disorders and other psychiatric subgroups in

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