This is usually a sign of a serious cerebellar disorder. MSO is a disorder where the eye makes saccades back and forth about a target. It is best seen with the ophthalmoscope in the hands of an experienced clinician, or a high-resolution eye movement recording device such as a scleral eye coil (see figure above). Microsaccadic oscillation cannot be recorded with EOG or VNG because it is too small and too fast. It is generally benign although it can obscure vision. Microsaccadic oscillation denotes a tiny (0.2 deg) back-back saccadic oscillation. Zee, M.D., recording method - scleral search coil) Microsaccadic oscillation (image courtesy of D. In our experience, infrared recording methods including commercial video ENG systems will not reproduce this nystagmus because of their limited spatial and temporal resolution, but systems including optics that produces an iris image that nearly fills the screen work acceptably.ĭo not rely upon commercial VENG systems to capture saccadic nystagmus. Our advice is to either directly record the nystagmus with a fast video gogggle system (not so easy to locate) or use a high-performance recording system such as a scleral eye coil. Many systems use tiny eye-images, shown at low resolution and infrequently updated on a computer monitor.Microsaccadic oscillation may only be 0.2 deg in amplitude - impossible to resolve with EOG or most IR systems. Saccadic nystagmus may be too small to resolve (as well as too fast).Rapid back-back saccades appear similar to noise and may be replaced by a flat line by some EOG systems. Blink rejection algorithms that consider saccadic nystagmus as noise.A 20 hz recording will not be able to capture a 10 hz. Saccadic nystagmus may exceed the bandwidth of the recording system.This failure of many contemporary ENG clinical systems to work for this disorder is related to a combination of factors: Rather than seeing back-back saccades, saccadic nystagmus looks like square wave jerks (see below). Practically, we have failed to register obvious saccadic nystagmus on numerous occasions with an infrared VENG system from Micromedical Technologies. Recording saccadic nystagmus isn't easy:Īlthough one might think that recording of a very fast eye movement would be very easy, as it is easy to spot with the naked eye, eye movement recording systems often fail to register saccadic nystagmus. With saccades, most disorders consist of either instability (oscillation, flutter and opsoclonus), or inability to inhibit saccades (square wave jerks, saccadic intrusions). Things that happen very quickly often have a tendency to get out of control. Accordingly, saccades typically move at speeds between 200 and 600 degrees/sec - for 300 deg/sec, to move gaze 90 degrees, it takes 1/3 second (which still seems like a rather long time not to see). As one does not see during a saccade, it is best to get them over as quickly as possible. Saccades are used to bring the eye rapidly from one point of regard to another.