Outreach Programs
www.tsbvi.edu |512-454-8631 | 1100 W. 45th St. | Austin, Texas 78756
2012-13 Texas Focus
Nystagmus in Children:
Causes, Effects and Strategies
March 31, 2013
8:30-10:00 AM or
Presented by
Dr. Ana Perez, OD, FAAO
Low Vision Rehabilitation Michael E. DeBakey VAMC
Developed for
Texas School for the Blind & Visually Impaired
Outreach Programs
1
Nystagmus in Children: Causes, Effects, and Strategies
Ana M. Perez, OD, FAAO
Low Vision Rehabilitation, Michael E. DeBakey VAMC,
University of Houston College of Optometry
Objectives
- Participants will discover the causes and treatments for nystagmus.
- Participants will review how nystagmus affects visual performance in both near and distance visual activities, as well as ways to improve visual performance.
Nystagmus
Condition in which the eyes make repetitive, uncontrolled movements, often resulting in reduced vision
Types of movement
· Side to side: horizontal nystagmus
· Up and down: vertical nystagmus
· Rotary: torsional nystagmus
Nystagmus is a sign of a problem
Ocular structure
Pathways that connect the eye to the parts of the brain that deal with eye movement
It is not really a condition in its own right!
Two main types of nystagmus
Congenital nystagmus or early onset nystagmus
· It appears in the first months of life
Acquired nystagmus
· Develops later in life
Nystagmus affects one in 1500 people
Causes of Nystagmus
Physiological nystagmus – normal part of how our eyes work
· If you watch someone’s eyes as they are watching a train passing, their eyes follow the train then flick back to a starting point; this is repeated over and over
· OKN drum
Pathological nystagmus –
· If the eye or the visual pathway (where visual information is processed) are damaged
Idiopathic nystagmus – condition starts early in life and the cause is unknown
Congenital Nystagmus
Occurs in the first couple of years of life
Caused by two things:
- A problem with the eye structure
- A problem with the visual pathway from the eye to the brain
New born babies
All children are born with a visual system that is not fully developed
Vision continues to develop in the first few years of life as a result of the eye and brain being stimulated
Eye conditions affecting vision
· Congenital cataracts – lack of good stimulation to the retina
· Congenital glaucoma – damaged optic nerve
· Optic nerve hypoplasia – under developed optic nerve
· Albinism – under developed macula
Visual system will not develop normally
Severity of the congenital nystagmus
· Depends on the severity of the sight loss caused by the underlying condition
· Vision tends to worsen when:
o The eye movements of the nystagmus increases
§ Not being at the null point
o Patient is stress and/or fatigue
o There is occlusion of an eye
Congenital Nystagmus
· It is not painful
· It does not lead to progressive vision loss
· For the most part, patient do not see the world jumping
· Typically, vision tend to improve until it stabilizes at age five or six.
Giving children plenty of visual stimulation in the early years leads to best use of visual function
Acquired Nystagmus
Typically, develops in adulthood
Causes
· Multiple sclerosis
· Brain tumor/ brain injury
· Effects of a drug: Dilantin (anti-seizure med)
· Thiamine or Vit B12 deficiency
Patients are aware of the movement: Oscillopsia. Typically, very disabling
Drug Induced Nystagmus
· Dilantin (phenytoin) – an anti-seizure medication
· Excessive alcohol
· Sedating medications
Classifying Nystagmus
Describing eye movements
· Jerk nystagmus: movement is quick in one direction and slow in another
· Pendular: the speed of movement is equal in both directions
Direction of the nystagmus
· Vertical
· Horizontal
· Circular/tortional
Jerk and Pendular Nystagmus
Video Clip
Null Point
A particular head position that results in the slowest eye movement
Reductions in the movement (amplitude) of the nystagmus usually means the vision is at its best
Visual acuity is variable
· 20/30 to 20/200
Null point
Video clip
Nystagmus Treatment
· Nystagmus cannot be cured
· Muscle surgery
o Reduces the amount of head turn needed to reach the null point
o Cosmetic/Postural
· Medication: Botox (baclofen)
o Temporary effect
· Biofeedback training
o Making patients aware of the movement thru visual and audio signals
Pharmacologic, Optical, and Surgical Treatments
Choice of treatment depends on the characteristics of the nystagmus and the severity of the associated visual symptoms
Electro-optical devices are currently being developed (optical stabilizer)
Different meds for different types of nystagmus
· Downbeat nystagmus
o 4-aminopyridine, 3,4-diaminopyridine or clonazepam
· Upbeat nystagmus
o Memantine, 4-aminopyridine or baclofen
· Torsional nystagmus
o gabapentin
· Acquired pendular nystagmus
o In multiple sclerosis: partially suppressed by gabapentin or mematine
o In oculopalatal tremor: gabapentin, memantine or trihexyphenidyl
· Infantile nystagmus nystagmus
o Gabapentin, memanine, acetazolamide, contact lenses, prisms, or surgery.
Maximizing Visual Function with Nystagmus
Early intervention
· Visual stimulation with engagement of the environment
Because of the variability in patients with congenital nystagmus (with or without pathology) it is difficult to predict best VA
Intervention: Active looking, searching, & selecting
· Visual curiosity
o Visual
o Tactile
· Explore environment
o Mobility
DISTANCE
Video Clip
Extending Visual Reach
· Having a desire/need to look at a distance
o Typically, distance is of little consequence to a young child with visual impairments
· Creating curiosity for exploration
· Creating skills for safety
· Creating independence
How do we make it interesting?
· Incorporating navigational skills
o The child should learn landmarks and give directions
o This is to be done without the use of optical devices which provide detail information like telescopes
· Use a “big wheel” and place cones to navigate a path
Implications for Distance
The use of telescopes (TS) in cases of congenital nystagmus is not contraindicated
Patients with nystagmus generally perform very well with the use of TS
Telescopes for distance
Provide magnification by creating a larger image and placing it on the retina
If the magnification is 4x, then the image movement through the TS is 4x faster
If the patient has congenital nystagmus, they will NOT see the image jumping
Recommendations for Distance
· Modified seating placement
o Specific distance in meters or feet
· Introduction to the use of HHTS
o Localization/Copying skills
o TS power for in- classroom activities
o TS power for outside activities (may be different)
NEAR/READING
Video Clip
Reading with Congenital Nystagmus
Visual acuity is typically reduced
It is not possible to predict with any amount of certainty the visual acuity by the amplitude/frequency of the nystagmus
The null point is the position of least eye movement and best resolution
The words on a page are NOT jumping when reading
Foveation Periods
Intervals in the CN waveform when the eye velocity is relatively slow and the target is imaged on or near the fovea.
Initially, it was thought that patients with CN “sample” their environment only during foveation and suppressed visual input thru out the rest of the CN waveform; and in this way they do not have the perception of oscillopsia. Evidence has been found against this hypothesis.
Jin YH, Goldstein HP, Reinecke RD. Absence of visual sampling in infantile nystagmus. Korean J Ophthalmology 1989
Implications for Reading Research-based information
· Patients with CN have equal maximum reading speeds when comparing rapid serial visual presentation (RSVP) and continuous text (CT)
o 449 and 448 words/minute
· Patients with CN can read at rates faster than the frequency of nystagmus
o This suggest that they are able to read during non-foveation periods.
Woo S, Bedell H. Beating the Beat: Reading can be faster than the frequency of the eye movements in persons with congenital nystagmus. Optometry and Vision Science. Aug 2008
What does this mean for our visually impaired students…?
Patients with congenital nystagmus need to have a reading reserve… They should not be reading at their threshold!
Make sure that this has been address for each student
Providing Reading Reserve
Low Vision Optometrist can provide
· Print size recommendation
· Reading glasses/bifocals
· Incorporation of magnifiers
· Use of CCTV: with an enlargement recommendation
LV Rehab Optometrist need to know…
· What is the patient‘s reading level?
o Does it correlate with their grade level?
· What is the reading demand?
o Size of textbook print: science/social studies
o Size of math print
o Is patient reading paperback books
o Is patient reading off the computer screen
Implications for School
Best correction in place
Allow patient’s prefer head position, so as to reach their null point à which in turn provides best visual resolution
There is no way of predicting visual acuity in patients with nystagmus
Congenital nystagmus is not a progressive condition
Patients with congenital nystagmus do not see the world moving
Patients with nystagmus respond very well to the implementation of optical devices
Texas School for the Blind & Visually Impaired
Outreach Programs
Figure 24 TSBVI logo.
"This project is supported by the U.S. Department of Education, Office of Special Education Programs (OSEP). Opinions expressed herein are those of the authors and do not necessarily represent the position of the U.S. Department of Education.
Figure 25 IDEA logo
Nystagmus in Children: Causes, Effects and Strategies – Perez, 2012 – 2012 Texas Focus Conference 9