Improved accuracy and robustness of electron density profiles from JET's X-mode frequency-modulated continuous-wave reflectometers.

JET's frequency-modulated continuous wave (FMCW) reflectometers have been operating well with the current design since 2005, and density profiles have been automatically calculated intershot since then. However, the calculated profiles had long suffered from several shortcomings: poor agreement with other diagnostics, sometimes inappropriately moving radially by several centimeters, elevated levels of radial jitter, and persistent wriggles (strong unphysical oscillations). In this research, several techniques are applied to the reflectometry data analysis, and the shortcomings are significantly improved. Starting with improving the equilibrium reconstruction that estimates the background magnetic field, adding a ripple correction in the reconstructed magnetic field profile, and adding new inner-wall reflection positions estimated through ray-tracing, these changes not only improve the agreement of reconstructed profiles to other diagnostics but also solve density profile wriggles that were present during band transitions. Other smaller but also persistent wriggles were also suppressed by applying a localized correction to the measured beat frequency where persistent oscillations are present. Finally, the burst analysis method, as introduced by Varela et al. [Nucl. Fusion 46 S693 (2006)], has been implemented to extract the beat frequency from stacked spectrograms. Due to the strong suppression of spurious reflections, the radial jitter that sometimes would span several centimeters has been strongly reduced. The stacking of spectrograms has also been shown to be very useful for stacking recurring events, like small gas puff modulations, and extracting transport coefficients that would otherwise be below the noise level.

Histologic localization of indocyanine green dye in aging primate and human ocular tissues with clinical angiographic correlation.

OBJECTIVE: This study aimed to histologically localize indocyanine green (ICG) dye in the geriatric primate and human eye and to correlate these findings with clinical ICG angiography. DESIGN: The study design was a clinicopathologic correlation. PARTICIPANTS: Six eyes of three geriatric monkeys (Maccaca mulatta) with macular drusen, 19 to 29 years of age, housed at the California Primate Research Center and an enucleated human eye from a 66-year-old patient with choroidal melanoma were examined. INTERVENTION: All six monkey eyes and the human eye underwent clinical ICG angiography. Five monkey eyes were enucleated at varying intervals after intravenous ICG dye injection for histologic examination. One monkey eye was removed without prior ICG injection as an age-matched control. The human eye was enucleated after intravenous injection of ICG dye. MAIN OUTCOME MEASURES: Infrared fluorescence microscopy of freeze-dried tissue sections was performed to detect ICG fluorescence. Histologic sections were stimulated with an 810-nm diode laser, and the fluorescence emitted was detected with a Hamamatsu infrared camera. The images were digitally recorded. The distribution of fluorescence on histologic examination was correlated with the fluorescence of the clinical ICG angiogram. RESULTS: Infrared fluorescence microscopy of monkey sections localized fluorescence within retinal and choroidal vessels early after injection of ICG dye. The ICG fluorescence was seen in the extravascular choroidal stroma within 10 minutes after injection. The stromal fluorescence persisted in sections obtained 50 minutes after injection of ICG. The retinal pigment epithelium (RPE)-Bruch's membrane complex was brightly fluorescent in the middle- and late-stage histologic sections. Drusen deposits were brightly fluorescent at all timepoints examined. Similar findings were observed in freeze-dried tissue sections of the human eye. The fluorescence detected on histologic sections correlated closely with the fluorescence of the clinical ICG angiograms for the same interval. CONCLUSIONS: The ICG dye does not remain solely within the choroidal intravascular space but extravasates into the choroidal stroma and accumulates within the RPE. Extravascular ICG binds to drusen material. These findings will enhance the interpretation of clinical ICG angiography.

Corneal perforation associated with argon laser photocoagulation for a retinal tear.

PURPOSE: To report a corneal perforation during argon laser photocoagulation around a retinal tear following pneumatic retinopexy. METHODS: The patient was examined and found to have a corneal perforation with pigment in the base of the wound. To help explain this phenomenon, we evaluated the ability of argon blue-green laser to create a corneal perforation in a cadaver eye. RESULTS: In a cadaver eye, we induced a corneal perforation with argon laser only when a pigmented substance was present on the corneal surface. CONCLUSIONS: We hypothesize that pigmented material such as an eyelash or mascara caught between the cornea and contact lens interface may have facilitated this rare complication. Clinicians should be wary of any pigmented substance on the surface of the cornea or ophthalmoscopic lens when performing argon laser photocoagulation.

New stroboscopic light source for intraoperative retinal fluorescein angiography.

We tested a new stroboscopic light source for intraoperative fluorescein angiography. A pulsed xenon light source and narrow-band interference filters are coupled to a 20-gauge endoilluminator and a 35-mm camera mounted on a surgical microscope. The system was tested with good success in a patient undergoing penetrating keratoplasty. An 18- to 22-microJ flash of 2 milliseconds' duration is achieved, which is well below the safety threshold level. This new stroboscopic light source provides a flash of sufficient light intensity to perform high-resolution, high-contrast fluorescein angiography during operations for the removal of opacified media.