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zhenghao yang, Norihiko Yokoi, Georgi Asenov Georgiev, Mengxi Niu, Hiroaki Kato, Noriko Koizumi, Shigeru Kinoshita; Assessment of the Impact of Saccade on Corneal Topography Using Video-Topographer. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):359. doi: https://doi.org/.
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We recently reported use of video-interferometry and video-slit-lamp microscopy, to observe, respectively, the tear film lipid layer (TFLL) and mucoaqueous subphase (MAS) of the tear film. We found that the precorneal tear film (PTF), comprising TFLL and MAS, behaves like a “Fluid Shell”, integrated as one body, moving with the cornea during horizontal saccades (Ocul Surf, 2014). However, changes are imposed on the PTF during vertical, downward saccades that result in decreased TF stability. We used a video-topographer to assess the impact of saccades on corneal topography.
17 subjects without ocular surface disease [8 males and 9 females, age: 31.4 ±8.4 (SD) years], were enrolled and the left eye studied. A custom-made video-topographer was used to assess the impact of temporal (T), upward (U) and downward (D) saccades, followed by a return saccade, on corneal topography, based on the occurrence of distortion of a placido ring. A pause for 1 or 3 sec was imposed at the end of each primary saccade. To evaluate disturbance of topography, the corneal area was divided into 5 zones, (upper, lower, temporal, nasal and central) and a score 0 or 1 was recorded for absence or presence of distortion in each zone.
The total score for D-1 sec was significantly less than for D-3 sec (p=.002). However, for U or T, there were no significant differences according to pause time. For 1 sec pausing, the total score for D was significantly greater than that for T or U (p<.003). A similar trend was seen for the 3 sec pausing.
The present study demonstrated a greater impact of the downward and return saccades on corneal topography than T or U saccades. This could imply that downward saccades have a greater impact on the quality of vision such as when working at the visual display terminal.
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