Fig. 6. Examples of abnormal eye movements and their effect on vision. A: A pendular type of congenital nystagmus waveform with superimposed quick phases. Note that following each quick phase, foveation periods (indicated by arrows) occur, at which time the eye is close to desired fixation point (0 deg) and eye velocity is low (i.e., the image is on the fovea and image slip is low). This patient experienced no oscillopsia. B: A pendular type of acquired nystagmus in a patient with multiple sclerosis who complained of blurred vision and oscillopsia. Note the presence of both horizontal (HOR) and vetical (VER) components, and the absence of foveation periods. C: An example of saccadic intrusions (square waves) that repeatedly moved the image of regard off the fovea; the patient had progressive supranuclear palsy. D: Sustained saccadic oscillations that interfere with clear vision. The amplitudes of the horizontal and vertical components of this diagonal microsaccadic flutter are small, but the high frequency of these oscillations impaired vision in the patient, who was otherwise well. Clinically, these oscillations could only be discerned with an ophthalmoscope. E: Macrosaccadic oscillations in a patient with brainstem and cerebellar abnormalities. Note how the predominatly horizontal component oscillates across the fixation point. Upward deflections indicate rightward or upward eye movements. (Modified from Leigh RJ, Zee DS: The Neurology of Eye Movements, 3rd ed. New York: Oxford University Press, 1999)