Medical Care
The treatment of these patients should begin with correction of any refractive error. Amblyopia should be addressed as well.
Contact lens wear has been noted to diminish infantile nystagmus, presumably by a trigeminal efferent pathway. This may also increase foveation time by avoiding induced spectacle distortion with ocular movement in patients with high degrees of ametropia.
Refractive errors, even low plus, should be prescribed, as this has been shown to improve visual acuity. An optical system with high plus spectacles and high minus contact lenses has also been shown to improve visual acuity in some patients.
Base-out prisms (eg,7 prism diopters) may be combined with -1.00 D myopic overcorrection for convergence damping in patients with binocular vision. [4]
Pharmacologically useful agents for patients with nystagmus are primarily GABA agonists or inhibitors of the excitatory neurotransmitter system. The only drug found to be of benefit in adult patients with a history of idiopathic infantile nystagmus is baclofen. This drug has not been approved for use in children. Baclofen has been effective in treating the periodic alternating nystagmus (PAN) subtype.
Recent case reports have shown gabapentin to be beneficial in congenital nystagmus, with an improvement in foveation time and vision and a decrease in amplitude and frequency of the nystagmus.
McLean et al investigated treatment of congenital nystagmus with memantine or gabapentin in a randomized, double-blind, placebo-controlled trial of 48 patients. [8] Improvement in mean visual acuity was noted in both treatment groups (F=6.2; p=0.004, analysis of variance). Patients with afferent visual defects showed poorer improvements in visual acuity to medication than those with apparently normal visual systems. However, nystagmus intensity (F=7.7; p=0.001) and foveation (F=8.7; p=0.0007) improved in both nystagmus forms as shown on eye movement recordings. Patients in both treatment groups reported vision improvement more often than patients in the placebo group (p=0.03). McLean et al concluded that memantine and gabapentin can improve visual acuity, reduce nystagmus intensity, and improve foveation in congenital nystagmus.
More study is needed to determine the role of oral and topical carbonic anhydrase inhibitors. [4]
Treatment for aquired nystagmus may be useful in cases of congential nystagmus as well. Low force magnets may be one such option. Pankhurst et al implanted paired magnets in the orbital floor and extraocular muscles of subjects with acquired nystagmus. The force applied in voluntary eye movements is much greater than the force involved in nystagmus. This allowed the magnets to dampen the oscillation at the point of fixation, with out hindering gaze shifts at other times. [9]
Alternative measures, such as biofeedback, acupuncture, or cutaneous head and neck stimulation, have been reported to decrease nystagmus in select (adult) patients with a history of infantile nystagmus.
Surgical Care
Retrobulbar or intramuscular injection of botulinum toxin
Retrobulbar or intramuscular injection of botulinum toxin (BOTOX®) has been demonstrated to abolish nystagmus temporarily, but patient satisfaction has been poor due to adverse effects, such as ptosis or diplopia, and the need for reinjection.
Strabismus surgery
Strabismus surgery is used in patients with certain forms of nystagmus with varying degrees of success.
Anderson or Kestenbaum procedures are used to move the eyes into the null zone to diminish an anomalous head position in the setting of idiopathic infantile nystagmus.
Recession or simple tenotomy of all 4 horizontal rectus muscles has been advocated; however, preliminary results have been mixed. A pilot study has been completed that showed some improvement, but the definitive study is still pending. [10]
Surgery occasionally is used in the treatment of superior oblique myokymia.
Hertle et al conducted a prospective interventional case study to determine the effects of early eye muscle surgery on 19 patients younger than 24 months who had infantile nystagmus syndrome. [11] Outcome measures included acuity, head position, strabismic deviation, and eye movement recordings, including waveform types and a nystagmus optimal foveation fraction (NOFF). Improvements were noted in all outcomes measured. Hertle et al concluded that early eye muscle surgery in patients with oculographically infantile nystagmus syndrome improves the oscillation and visual functions. Increases in foveation periods and the NOFF were measureable.
Consultations
Pediatric neurology consultation can be helpful in patients suspected of harboring CNS disease and in evaluating nystagmus for localizing a CNS lesion.
Pediatric endocrinology consultation may be useful in patients with optic nerve hypoplasia to assist in evaluation of pituitary function.
Pediatric metabolic disease specialists can offer assistance in patients with congenital cataracts or optic atrophy who are thought to have an underlying metabolic abnormality.
Pediatric geneticists play an increasing role in the diagnosis and management of patients with nystagmus whose diagnosis is uncertain or who have dysmorphic features.
Pediatric neuroradiologists are of considerable value in evaluating the infant brain for abnormalities uncovered with neuroimaging.
Complications
Strabismus surgery carries anesthesia risks, as well as the risk for vision loss. This consideration becomes more important when potential benefits are less certain.
Alternative therapy probably is harmless at worst but should not delay diagnosis or treatment of an underlying disorder.
