Citation: Kakiuchi N, Terasaki H, Sonoda S, et al. Regional differences of choroidal structure determined by wide-field optical coherence tomography. Invest Ophthalmol Vis Sci. 2019;60:2614-2622. https://doi.org/ 10.1167 PURPOSE. To compare the submacular to the perimacular choroidal structure in images obtained by wide-field optical coherence tomography (OCT).METHODS. Thirty eyes of 30 healthy volunteers (15 men) were studied. Twelve wide-field radial circumferential scans were recorded with enhanced depth imaging OCT from the macular and perimacular zones. The sizes of the luminal and stromal areas of the choroid were determined. The two zones were subdivided into the superior, inferior, nasal, and temporal sectors. The total choroidal area, the luminal and stromal areas, and the luminal ratio of each sector were compared. RESULTS.All of the choroidal structural parameters analyzed in the present study were largest in the superior sector followed by the temporal, inferior, and nasal sectors. The coefficients of variation were larger in the perimacular zone than in the macular zone: The luminal ratio in the macular zone varied by 1.2%, and that in perimacular zone varied by 4.2%.CONCLUSIONS. The variations in the ratios of the luminal areas of the choroid in the wide-field OCT images are slight in the macular zone but considerable in the perimacular zone.

Next-generation lithography will require an extreme-ultraviolet (EUV) light source that ensures high radiation intensities at a wavelength of around 13.5 nm. The characteristics of pinch dynamics and emission in this spectral range were studied experimentally for xenon capillary Z-pinch plasma driven by different dI=dt discharge current pulses. The pinch dynamics of the capillary Z-pinch plasma were examined by employing a high-speed camera, and the spectral emission from plasma was inspected using an EUV photodiode, a mini calorimeter and spectrometers. Our results confirm that high-dI=dt discharge current has better performance in comparison with the low one in terms of plasma dynamics, EUV power output and debris generation.

A pinhole camera has been employed to study the performance of a xenon capillary Z-pinch extreme ultraviolet (EUV) lithography light source driven by different dI/dt discharge current pulses. The performance of the EUV source in terms of dimension, intensity, collection efficiency and stability was specifically investigated by varying the experimental conditions such as the supplying gas pressure and dI/dt of the discharge current. Specific features, such as ring shape (annular profile) pinhole images and symmetrical and stable emission in the high dI/dt discharge current, have been observed or confirmed experimentally. Our results support the fact that the high dI/dt and short discharge currents have better EUV emission characteristics for EUV lithography compared with the low dI/dt discharge current.

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