[Panretinal laser photocoagulation with reduced pulse duration--first experience with linear multispot cascades]

BACKGROUND

VISULAS 532 s VITE is a 532 nm laser device which allows semi-automated photocoagulation in fast cascades with short pulse durations in addition to conventional retinal single-spot coagulation.

METHODS

In a prospective randomised study 101 peripheral laser treatments for retinopathy of various origins were divided into two groups: control group A (n = 35) coagulation in conventional single-spot modus and study group B (n = 66) coagulation with the new semiautomated VITE-function of VISULAS 532 s. Spot diameter was the same in both groups (300 µm at the retina). Patients were asked about pain immediately after therapy on a scale ranging from 0 ( = no pain) up to 10 ( = maximum pain). From video recording, treatment times were measured. After each treatment, a photo-documentation followed to control the laser effects. The shorter laser pulses in group B were offset by higher laser power to achieve similar moderate effects.

RESULTS

In group A 509 (462-609) effects were set with a pulse duration of 100-150 ms and power of 157 (70-380) mW. 46.0% of the patients complained of pain at an intensity of 4.4 (2-8). The treatment time was 73.4 (61.6 to 103.7) s per 100 effects. In group B 555 (120-600) effects were set with pulse duration of 20 ms and a power of 286 (120-600) mW. 1.3% of the patients complained of pain at an intensity of 3 and 4. The treatment time was 49.4 (24.0-97.5) s per 100 effects. None of the groups experienced complications.

CONCLUSION

The semiautomated function of the laser using a 20 ms pulse duration allows almost painless coagulation of the retina. The treatment times can be reduced by one third. This leads to improved patient compliance. Long-term results regarding the regression of proliferative changes are still lacking.

Solid and liquid spectroscopic analysis (SALSA)--a soft x-ray spectroscopy endstation with a novel flow-through liquid cell

We present a novel synchrotron endstation with a flow-through liquid cell designed to study the electronic structure of liquids using soft x-ray spectroscopies. In this cell, the liquid under study is separated from the vacuum by a thin window membrane, such that the sample liquid can be investigated at ambient pressure. The temperature of the probing volume can be varied in a broad range and with a fast temperature response. The optimized design of the cell significantly reduces the amount of required sample liquid and allows the use of different window membrane types necessary to cover a broad energy range. The liquid cell is integrated into the solid and liquid spectroscopic analysis (SALSA) endstation that includes a high-resolution, high-transmission x-ray spectrometer and a state-of-the-art electron analyzer. The modular design of SALSA also allows the measurement of solid-state samples. The capabilities of the liquid cell and the x-ray spectrometer are demonstrated using a resonant inelastic x-ray scattering map of a 25 wt % NaOD solution.

High-resolution, high-transmission soft x-ray spectrometer for the study of biological samples

We present a variable line-space grating spectrometer for soft x-rays that covers the photon energy range between 130 and 650 eV. The optical design is based on the Hettrick-Underwood principle and tailored to synchrotron-based studies of radiation-sensitive biological samples. The spectrometer is able to record the entire spectral range in one shot, i.e., without any mechanical motion, at a resolving power of 1200 or better. Despite its slitless design, such a resolving power can be achieved for a source spot as large as (30 x 3000) microm2, which is important for keeping beam damage effects in radiation-sensitive samples low. The high spectrometer efficiency allows recording of comprehensive two-dimensional resonant inelastic soft x-ray scattering (RIXS) maps with good statistics within several minutes. This is exemplarily demonstrated for a RIXS map of highly oriented pyrolytic graphite, which was taken within 10 min.

[Influence of two different cameras on the spectrometric measurement of oxygen saturation]

OBJECTIVES

Oxygen saturation in retinal vessels can be measured by spectrometry. However, there are no studies on the influence of different camera chips on these measurements. The presented study reports the effect of two different camera chips ("1-CCD" vs. "3-CCD") on the spectrometric measurements in the same patients.

METHODS

61 eyes of 61 patients were included in this study. The study was approved by the local ethics commission. Patients were separated in 3 groups: the first group contained healthy volunteers, the second group patients with diabetes mellitus but without previous laser treatment, the third group included patients with diabetes mellitus and previous laser coagulation treatment. The oxygen saturation was calculated from the difference between wavelengths on and right next to the retinal vessel. This methodology uses the different absorption spectra of oxy- and deoxyhaemoglobin.

RESULTS

All 3 groups demonstrated valid outcomes of the retinal oxygen saturation in arterial and venous vessels. No significant differences we found in the arterial-venous oxygen difference between the two different camera chips (group 1 p = 0.063, group 2 p = 0.204, group 3 p = 0.059).

CONCLUSION

As no significant differences could be found between the two camera chips, the less expensive system should be used if the spectrometric measurement of oxygen saturation is added to an analysis system already established on the market.