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Z. I. Wang, L. F. Dell'Osso; Tenotomy Alleviates the "Slow to See" Phenomenon in Infantile Nystagmus Syndrome: Model Prediction and Patient Data. Invest. Ophthalmol. Vis. Sci. 2008;49(13):136. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Our purpose was to perform a systematic study of the post-tenotomy changes in target acquisition time by comparing predictions from the behavioral Ocular Motor System (OMS) model and data from Infantile Nystagmus Syndrome (INS) patients.
We studied five INS patients who underwent only tenotomy for their INS treatment. We measured their pre- and post-tenotomy target-acquisition changes using data from infrared reflection and high-speed digital video. Three key aspects were calculated and analyzed: the saccadic latency (Ls), the time to target acquisition after the target jump (Lt) and the normalized stimulus time within the cycle. Analyses were performed in MATLAB environment using OMLAB software (OMtools, downloadable from http://www.omlab.org). Model simulations were performed using MATLAB Simulink.
Consistent with the model prediction, improvement in Lt ranging from ~300 ms to ~500 ms, was documented in all 5 subjects post-tenotomy. This effect occurred simultaneously with the NAFX elevating and broadening improvements. The time window for these post-surgical changes was less than 1 week. The Lt improvement was not the result of a reduced Ls.
INS patients acquired step-target stimuli faster post-tenotomy. The improvement in target acquisition might be due to the elevated foveation quality resulting in less inherent variation in the input to the INS ocular motor control system. A refined OMS model, with "fast" and "slow" motor neuron pathways and a more physiological plant, successfully predicted this improved visual behavior and again demonstrated its utility in guiding ocular motor research.Figure:Foveation (NAFX vs. Gaze Angle curves, Left column) and target acquisition changes (Lt, right column) due to Tenotomy. Data are fitted by second-order polynomial functions.
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