PubMed · 7629523
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S Shaunak, E O'Sullivan, C Kennard. 1995. Eye movements.. https://doi.org/10.1136/jnnp.59.2.115
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Objective assessment of visual acuity (VA) is necessary in cases of malingering or poor cooperation in subjective VA evaluation. Based on Ohm's idea of the suppression of experimentally evoked optokinetic nystagmus (OKN), a new objective visual acuity test is presented. A commercially available system for monitoring eye movement (OBER2) allows the test to be performed on a standard PC with a minimum amount of time. A grating pattern moving horizontally on the screen evokes OKN, which is recorded by infrared nystagmography. Superimposed black optotypes of increasing size (brake marks) suppress OKN as soon as they are recognized. Eighty-two normal eyes with VA artificially reduced by different Bangerter dispersion foils (VA 0.04-1.6) and 152 eyes with visual disturbances (VA 0.04-1.0) of various etiologies were examined. The test allowed estimation of the least VA in steps of > or = 1.0, > or = 0.25, > or = 0.1, > or = 0.05. None of the eyes examined had a VA below these values when the OKN was suppressed by the referring brake mark.
The value of Head-Shaking maneuver has brought scientific controversies regarding its role as a clinical tool. In the following publication, we explain the discrepancies between the different studies and find out the role of such a maneuver for clinical evaluation during the pre and post operative period. We showed the influence of the diagnosis and the importance of time interval in the post Head-Shaking responses.
A computer-controlled system for the automatic induction, registration, and analysis of optokinetic nystagmus is presented. On a high-resolution computer video monitor, a horizontally moving pattern of vertical stripes of equal size and distance is displayed. Stimulus size, velocity, and direction of movement are computer-controlled and variable. Exposure to this display induces horizontal optokinetic nystagmus in the patient. The patient's eye movements are registered by an infrared non-contact limbus-tracker system and transferred to the computer in a digitized format. With a specifically developed computer program the pursuit eye movements are detected and analyzed for amplitude, duration, and velocity and may be displayed on a second monitor. Simultaneously, the congruence of the direction of the stimulus and of the direction of the eye movement are automatically supervised and quantified by an "acceptance coefficient." The first clinical studies with healthy experimentees showed that for each stimulus size a certain stimulus velocity exists that provides maximal nystagmus provocation. Smaller stimulus sizes require slower stimulus velocities. Future developments of the system will allow applications in other fields of nystagmus research and in the accessment of objective visual acuity.