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Monocular Blind Vision
This boy was not recognized to have nystagmus until he accidentally discovered that he had blurred vision in one eye while pulling a sweater off over his head and blocking the vision of one eye.
An ophthalmologist saw him and diagnosed latent nystagmus. He had no strabismus or any other ophthalmological disorder.
Cogan described latent nystagmus in his book, Neurology of the Ocular Muscles, 2nd Edition, Charles C. Thomas Publisher, 1956, as follows:
Latent nystagmus is a jerk type of nystagmus that is brought out by covering one eye. When both eyes are open and a clear image is present in both eyes, no nystagmus is present but covering one eye, blurring the image of one eye, or reducing the image brightness in one eye results in a conjugate nystagmus made up of a slow drift of the eyes toward the side of the covered eye, with a fast corrective phase toward the side of the open eye. The nystagmus is least when the gaze is directed toward the side of the covered eye and greatest when the gaze is directed toward the side of the open eye. It is usually present bilaterally, but cases have been reported in which it is elicited on the covering of one eye only.
Contrary to the general impression, it is not the disruption
of binocular fixation that gives rise to the nystagmus, since
it is frequently seen in patients with strabismus and a 15 degree prism placed before one eye so as to produce
vertical diplopia does not necessarily cause nystagmus.
Furthermore, the nystagmus may be brought out merely
by shining a bright light in one eye, and the resultant nystagmus is in the same direction as though the eye were being covered.
Thus, it appears that latent nystagmus is brought about by making the image brightness or distinctness in the two eyes unequal rather than simply by disrupting binocular fixation.
Latent nystagmus is typically horizontal and is usually not accompanied by other abnormalities, although strabismus, monocular amblyopia, and so-called alternating hyperphoria have been reported with it.
Loss of one eye in patients with latent nystagmus results in nystagmus of the other eye either permanent or with periodic spontaneous recurrences.
Latent nystagmus is one form of Fusional Maldevelopment Nystagmus Syndrome (FMNS).
Affected patients usually have:
• Strabismus, typically esotropia
• Amblyopia is frequent
• Normal stereopsis is rare
Occasionally, congenital nystagmus (INS) and latent nystagmus co-exist. (ID 907-2)
Latent nystagmus can be induced experimentally in monkeys either by depriving them of binocular vision early in life or by surgically creating strabismus.
Latent nystagmus occurs in some, but not all patients, who have congenital uni-ocular visual loss, suggesting that additional factors beyond visual deprivation are responsible for the development of nystagmus.
This case is a very good example of true latent nystagmus with a jerk nystagmus that is absent when both eyes are viewing but appears when one eye is covered; quick phases of both eyes beat away from the covered eye.
True latent nystagmus is rare, and, in most patients nystagmus (which may be of low amplitude) is present when both eyes are uncovered, termed manifest latent nystagmus.
1. Abadi RV, Scallan CJ. Waveform characteristics of manifest latent nystagmus. Invest Ophthalmol Vis Sci 2000;41:3805-3817.
2. Abel, L.A., Wang, Z.I. and Dell'Osso, L.F.: Wavelet Analysis in Infantile Nystagmus Syndrome: Limitations and Abilities. Invest. Ophthalmol. Vis. Sci. 2008. (In Press).
3. Classification of Eye Movement Abnormalities and Strabismus (CEMAS) Working Group. http://www.nei.nih.gove/news/statements/cemas 2003.
4. Cogan D. Neurology of the Ocular Muscles, 2nd Edition. Charles C. Thomas Publisher, Springfield, Ill. 1956.
5. Dell’Osso LF, Traccis S, Abel LA. Strabismus: a necessary condition for latent and manifest latent nystagmus. Neuroophthalmol 1983;3:247-257.
6. Gresty MA, Metcalfe T, Timms C, Elston J, Lee J, Liu C. Neurology of latent nystagmus. Brain 1992;115:1303-1321. http://www.ncbi.nlm.nih.gov/pubmed/1422790
7. Kushner BJ. Infantile uniocular blindness with bilateral nystagmus. A syndrome. Arch Ophthalmol 1995;113:1298-1300. http://www.ncbi.nlm.nih.gov/pubmed/7575263
8. Leigh RJ, Zee DS. Diagnosis of Nystagmus and Saccadic Instrusions. Chp 10:475-558. In: The Neurology of Eye Movements. 4th Ed. Oxford University Press, New York 2006.
9. Tusa RJ, Mustari MJ, Das VE, Boothe RG. Animal models for visual deprivation-induced strabismus and nystagmus. Ann NY Acad Sci 2002;956:346-360. http://www.ncbi.nlm.nih.gov/pubmed/11960818