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The article provides information on the prevalence of nystagmus in the Russian Federation and the world. However, the lack of standards for data collection and the very understanding of the definition of optical nystagmus is the reason for the variation in prevalence values in different sources. Additionally, the article presents various classifications of nystagmus. Currently, there are many different classifications, and the most commonly used examples are given. The classification of eye movement disorders and strabismus, adopted by the working group in 2001 (Classification of Eye Movement Abnormalities and Strabismus CEMAS), is used worldwide. In our country, the most popular was the classification proposed by E.S. Avetisov (2001). Various sources have suggested quite contradictory data on the nature of the onset and the mechanism of development of nystagmus. Recently, the issues related to the pathogenesis of nystagmus have been revised. The theories that existed at the end of the last century were not substantiated in modern works. The pathogenesis of optic nystagmus remains less studied due to its complexity and ambiguity. The investigations continue to find the relationship between the pathology of the central nervous system and functional disorders of visual functions. The question of the relationship between visual acuity and nystagmus remains unclear. Does a decrease in vision cause nystagmus? How do oscillatory movements in nystagmus affect visual functions? This article encompasses the main areas of this issue. However, despite a significant step in understanding the causes of the development of nystagmus, this pathology remains insufficiently studied. This prompts many researchers and practicing doctors to study its pathogenesis further

The use of the botulinum toxin A can be the method of choice for the treatment of oculomotor pathology. In certain cases of strabismus, this technique provides the sole correct and justified tool for the management of this condition. There are numerous publication concerning this issue in the foreign literature, but they do not permit to develop the well defined criteria for the application of the botulinum toxin A in the ophthalmological practice Specifically, such issues as the timing and dosages of botulinum toxin A administration remain to be addressed and solved. Of special interest is the application of the botulinum toxin A for the treatment of nystagmus. The expediency of the application of the botulinum toxin A for the treatment of oculomotor pathology should be estimated on an individual basis.

Optical nystagmus is an involuntary oscillatory movement. Nystagmus can occur as an isolated nosology and lead to decreased visual functions in combination with other pathologies. A decreased visual function, including visual acuity, is observed in many patients with optic nystagmus. Patients with optical nystagmus were noted by ophthalmologists with a significant difference in the acuity of monocular and binocular vision, which is much higher in the second case. As a rule, a difference is observed in visual acuity in the straight and forced position of the head. Frequently, nystagmus is combined with refractive errors. Some authors consider astigmatism the most common form of ametropia in nystagmus, and nystagmus itself, a predisposing factor for the presence of astigmatism. An important task in diagnostics is the quantitative eye movement assessments since the tactics of treatment and the prognosis of the course of the disease depend on this. One of the problems in the examination of patients with nystagmus is the assessment of the fundal condition. Modern optical coherence tomographs are helpful in the objective diagnostics of retinal structures of the posterior pole of the eye, as well as improved software, such as the Eye Tracking system, and an increased scanning speed allowed reliable studies even with spontaneous oscillatory eye movements and a significantly decreased visual acuity. With nystagmic relative amblyopia, both photosensitivity and fixation were violated, which may indicate the presence of organic changes in the central parts of the retina and a primary fixation violation.