OOA (Old Order Amish)

Inheritance: x-linked
autosomal recessive
autosomal dominant
Genes: FRMD7

Nystagmus
Abnormal eye movements
Head nodding
Head turn
Poor vision

Nystagmus 1
Infantile nystagmus
Congenital motor nystagmus 1
Idiopathic infantile nystagmus

Congenital Nystagmus

Clinical Characteristics

General description (for patients):

Congenital nystagmus (CN) is used to describe a diverse group of abnormal eye movements which are identified at birth or shortly after when no other ocular abnormalities are present. Congenital nystagmus typically involves horizontal eye movements, but vertical and rotary eye movements have also been reported.  If the nystagmus is horizontal, the eye movement is usually “to-and-fro”.  In general, as the patient gets older, the amplitude of the nystagmus decreases and the frequency of the nystagmus increase, particularly when the patient tries to fixate or look directly at an object. This nystagmus can increase in size and frequency when the patient is tired, sick, or fatigued.  Some very young patients are noted to have head nodding or head shaking, but these usually disappear over time. Vision is reduced and varies through the day.  Balance may also be affected. Many suffers have a “null point” where the eye movement is reduced and vision is improved. They will often turn their head to one side to make the best use of their vision.

Medical descriptions:  

True congenital nystagmus can only be diagnosed in patients who do not have other obvious ocular or systemic disease such as albinism, optic nerve disease, congenital cataracts, or retinal disease.  An ophthalmologic examination is mandatory. Patients with congenital nystagmus often spontaneously find a “null” point in a direction of gaze that will decrease the oscillations and improve their vision which may result in unusual head positions, especially for near vision tasks.  Head nodding and/or head shaking in some young patients may also be compensatory resulting in improved vision.

Genetics:

Different heritable patterns of congenital nystagmus including X-linked, dominant, and recessive have been found.  A number of genes associated with X-linked congenital nystagmus have been reported on the short arm of the X chromosome including Xp11.4-p11.3 and  Xq26-q27.  A variety of mutations in the FRMD7 gene (containing 12 exons) located in the latter region have been identified.  A dominant congenital nystagmus gene has been linked to chromosomal region 6p12.  No specific mutation has been identified among plain people but the disease has been seen in the Amish.

Treatment:  

Nystagmus cannot be cured.  However, there are several treatments that can help.  Glasses and contact lenses, and, occasionally, surgery to alter the insertions of the extraocular muscles may be helpful.  The latter should be considered especially when patients adopt a consistent head postion for best vision.  This avoids long-term secondary changes in neck muscles and many improve two or more lines in visual acuity.

Prognosis: 

Reduced vision to the 20/60 to 20/100 range is common. In the absence of other ocular abnormalities, it is a non-progressive condition. There is no systemic disease in idiopathic congenital nystagmus.

Ancillary treatments and support:

Low vision evaluations with the use of appropriate visual aids can be enabling and are strongly recommended.

Specialists and speciality centers:

Pediatrician, neurologist and ophthalmologist.

References:

Abel, L.A.: Infantile nystagmus: current concepts in diagnosis and management.  Clin. Exp. Optom. 89: 57-65, 2006. PubMed ID: 16494607

Self, J., and Lotery, A.: The molecular genetics of congenital idiopathic nystagmus.  Semin. Ophthalmol.  21: 87-90, 2006. PubMed ID: 16702075

Tarpey, P., Thomas, S., Sarvananthan, N., Mallya, U., Lisgo, S., Talbot, C.J., Roberts, E.O., Awan, M., Surendran, M., McLean, R.J., Reinecke, R.D., Langmann, A., et al.: Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus.  Nature Genet. 38: 1242-1244, 2006.  PubMed ID: 17013395

Resources:

American Nystagmus Network
Nystagmus-a guide