Analysis of retinal and optic nerve electrogenesis dynamics after vitrectomy for complicated catarct surgery

Background. The article presents impact results of vitrectomy for complicated cataract surgery on retinal and optic nerve electrogenesis. Materials and methods. 30 patients (30 eyes) with history of dropped nucleus (1st group) or intraocular lens dislocated into the vitreous cavity after phacoemulsification (2nd group) underwent electrophysiological examination before vitrectomy, and on Day 1, Day 3, Day 7, Day 14, Day 30, Day 60, and Day 180 after surgery. Results. In the 1st and 2nd groups, on the 1st day after vitrectomy, we observed a significant decrease in retinal and optic nerve electrogenesis in comparison to normal indices (p > 0.01); to Day 180, electrophysiologic indices returned to normal values. In the 1st group, baseline retinal and optic nerve electrogenesis was decreased in comparison to normal parameters. In the 1st and 2nd groups, the electrogenesis of photoreceptors recovered twice as rapidly, as that of bipolar cells; papillomacular bundle neurons were more resistant to vitrectomy. Conclusion. Thus, the presence of lens nucleus fragments in the vitreous cavity results in a reliable inhibition of the retinal and optic nerve electrogenesis due to phacotoxic effect. Vitrectomy causes a short-term depression of the retinal and optic nerve electrogenesis, followed by normalization of indices to Day 180. Photoreceptors have greater rehabilitation activity than bipolar cells. The neurons of axial topographic orientation have the highest resistance to vitrectomy impact.

Climatology of Anomalous Propagation Radar Echoes in a Coastal Area

Anomalous propagation (AP) of ground-based radar beam results in the detection of ground echoes beyond the horizon. One year of data gathered with an S-band meteorological radar located on the coast in southwest France is used to analyze the spatial distribution of AP ground echoes (APE). The APE distributions of duration and reflectivity in the radar-observed area are found to be strongly related to the main feature of the regional orography and topography up to the farthest distance (250 km) observed by the radar, notably the nature of the surface, the topographic orientation with respect to the radar beam direction, and the altitude. The distribution of APE in the studied area is found to be strongly anisotropic around the radar, with wide differences between land and sea. Rain accumulation equivalent to the APE is, in certain places, of the same order or higher than the real rain depth. The distribution of the ground surfaces, as calculated from a ground numerical model, compares qualitatively well with the APE radar reflectivity distribution.