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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

  1. Participants will discover the causes and treatments for nystagmus.
  2. 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:

  1. A problem with the eye structure
  2. 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:
  • The eye movements of the nystagmus increases
  • Not being at the null point
  • Patient is stress and/or fatigue
  • 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
  • Reduces the amount of head turn needed to reach the null point
  • Cosmetic/Postural
  • Medication: Botox (baclofen)
  • Temporary effect
  • Biofeedback training
  • 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
  • 4-aminopyridine, 3,4-diaminopyridine or clonazepam
  • Upbeat nystagmus
  • Memantine, 4-aminopyridine or baclofen
  • Torsional nystagmus
  • gabapentin
  • Acquired pendular nystagmus
  • In multiple sclerosis: partially suppressed by gabapentin or mematine
  • In oculopalatal tremor: gabapentin, memantine or trihexyphenidyl
  • Infantile nystagmus nystagmus
  • 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
  • Visual
  • Tactile
  • Explore environment
  • Mobility

DISTANCE

Video Clip

Extending Visual Reach

  • Having a desire/need to look at a distance
  • 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
  • The child should learn landmarks and give directions
  • 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
  • Specific distance in meters or feet
  • Introduction to the use of HHTS
  • Localization/Copying skills
  • TS power for in- classroom activities
  • 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)
  • 449 and 448 words/minute
  • Patients with CN can read at rates faster than the frequency of nystagmus
  • 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?
  • Does it correlate with their grade level?
  • What is the reading demand?
  • Size of textbook print: science/social studies
  • Size of math print
  • Is patient reading paperback books
  • 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  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 Conference1