Principles of Accommodation and Technology Update of Presbyopia Corrections using IR and UV Lasers

Purpose: To update and review the technology and principles of laser presbyopia reversal (LAPR) via sclera ablation and thermal shrinkage using infrared and UV lasers. Recent clinical data and new methods are also summarized. Study Design: LAPR using laser sclera ablation for increased accommodation of presbyopic eyes. Place and Duration of Study: New Taipei City, Taiwan, between June, 2021 and July, 2021. Methodology: Accommodation gain was obtained by laser scleral ablation of an eye using Er:YAG laser (at 2.94 um) using either line-pattern or dots-pattern outside the limbus in the oblique quadrants of an eye. The principles of accommodation and the key factors influencing the outcomes are discussed. The accommodation gain (AG) after the surgery is mainly due the change in anterior curvature and anterior shift of the lens. The effectiveness of ciliary body contraction for lens relaxation (or accommodation) may be influenced by the combined aging factors, including lens property changes (index, size, thickness and curvature), tissue elastic changes (in sclera and ciliary) and the zonular tension change. Classical theories of accommodation include Helmholtz and Schachar hypothesis. The key issues and new directions to overcome the drawbacks of the existing LAPR procedure (based on scleral ablation) are proposed. Clinical outcomes from two major groups, SurgiLight and Ace Vision, with two years follow are summarized. Results: Clinical outcomes during 2000 to 2020 are summarized showing an average Accommodation gain about 2.0 D, and postoperative egression about 0.25 D (after two years). Conclusion: Laser presbyopia reversal (LAPR) via sclera ablation using infrared laser is safe and effective, but suffers drawbacks of being invasive and procedures are too slow. New directions are required for improved outcomes.

Thermal and Manufacturing Design Considerations for Silicon-Based Embedded Microchannel Three-Dimensional-Manifold Coolers (EMMC)—Part 3: Addressing Challenges in Laser Micromachining-Based Manufacturing of Three-Dimensional-Manifolded Microcooler Devices

Laser machining is an inexpensive and fast alternative to conventional microfabrication techniques and has the capability to produce complicated three-dimensional (3D), hierarchical structures. It is especially important while performing rapid prototyping and quick design studies of extreme heat flux cooling devices. One of the major issues plaguing the use of laser micromachining to manufacture commercially usable devices, is the formation of debris during cutting and the difficulty in removing these debris efficiently after the machining process. For silicon substrates, this debris can interfere with surrounding components and cause problems during bonding with other substrates by preventing uniform conformal contact. This study delves deep into the challenges faced and methods to overcome them during laser micromachining-based manufacturing of such complicated 3D-manifolded microcooler structures. Specifically, this work summarizes several postprocess techniques that can be employed for complete debris removal during etching of silicon samples using an Nd/YVO4 ultraviolet (UV) laser, detailing the advantages and drawbacks of each approach. A method that was found to be particularly promising to achieve very smooth surfaces with almost complete debris removal was the use of polydimethylsiloxane (PDMS) as a high-rigidity protective coating. In the process, a novel technique to strip PDMS from silicon surface was also developed. The result of this study is valuable to the microfabrication industry where smooth and clean substrate surfaces are highly desirable and it will significantly improve the process of using UV lasers to create microstructures for commercial applications as well as in a research environment.

ESA’s Lidar Missions Aeolus and EarthCARE

ESAs Earth Explorer Aeolus was launched in August 2018. Aboard the first spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) was switched on in early September 2018 and demonstrated the capability to provide atmospheric wind profiles globally from particle and molecular backscatter. In doing so, it will contribute to the improvement in numerical weather prediction (NWP) and the understanding of global dynamics. At the same, it is a major step for powerful and frequency stabilized ultraviolet (UV) lasers for space applications. In parallel, ESA and its partners continue the development of this technology by setting up further ground tests based on Aeolus, and preparing the next milestone with ATLID (ATmospheric LIDar) for the Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission. ATLID is currently fully integrated and getting prepared for its on-ground testing.