Small incision lenticule extraction (SMILE) techniques: patient selection and perspectives

Jeewan S Titiyal, Manpreet Kaur, Farin Shaikh, Meghal Gagrani, Anand Singh Brar, Anubha Rathi Cornea, Cataract and Refractive Surgery Services, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India Abstract: Refractive lenticule extraction is becoming the procedure of choice for the management of myopia and myopic astigmatism owing to its precision, biomechanical stability, and better ocular surface. It has similar safety, efficacy, and predictability as femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and is associated with better patient satisfaction. The conventional technique of small incision lenticule extraction (SMILE) involves docking, femtosecond laser application, lenticule dissection from the surrounding stroma, and extraction. It has a steep learning curve compared to conventional flap-based corneal ablative procedures, and the surgical technique may be challenging especially for a novice surgeon. As SMILE is gaining worldwide acceptance among refractive surgeons, different modifications of the surgical technique have been described to ease the process of lenticule extraction and minimize complications. Good patient selection is essential to ensure optimal patient satisfaction, and novice surgeons should avoid cases with low myopia (thin refractive lenticules), difficult orbital anatomy, high astigmatism, or uncooperative, anxious patients to minimize complications. A comprehensive MEDLINE search was performed using “small incision lenticule extraction,” “SMILE,” and “refractive lenticule extraction” as keywords, and we herein review the patient selection for SMILE and various surgical techniques of SMILE with their pros and cons. With increasing surgeon experience, a standard technique is expected to evolve that may be performed in all types of cases with optimal outcomes and minimal adverse effects. Keywords: refractive lenticule extraction, femtosecond-laser assisted lenticule extraction, SMILE techniques, refractive surger

Electrically programmable solid-state metasurfaces via flash localised heating

In the last decades, metasurfaces have attracted much attention because of their extraordinary light-scattering properties. However, their inherently static geometry is an obstacle to many applications where dynamic tunability in their optical behaviour is required. Currently, there is a quest to enable dynamic tuning of metasurface properties, particularly with fast tuning rate, large modulation by small electrical signals, solid state and programmable across multiple pixels. Here, we demonstrate electrically tunable metasurfaces driven by thermo-optic effect and flash-heating in silicon. We show a 9-fold change in transmission by <5 V biasing voltage and the modulation rise-time of <625 µs. Our device consists of a silicon hole array metasurface encapsulated by transparent conducting oxide as a localised heater. It allows for video frame rate optical switching over multiple pixels that can be electrically programmed. Some of the advantages of the proposed tuning method compared with other methods are the possibility to apply it for modulation in the visible and near-infrared region, large modulation depth, working at transmission regime, exhibiting low optical loss, low input voltage requirement, and operating with higher than video-rate switching speed. The device is furthermore compatible with modern electronic display technologies and could be ideal for personal electronic devices such as flat displays, virtual reality holography and light detection and ranging, where fast, solid-state and transparent optical switches are required

Polypoidal choroidal vasculopathy: a comprehensive clinical update

Polypoidal choroidal vasculopathy as a disease is yet to be comprehended completely. The clinical features consisting of huge serosanguineous retinal pigment epithelial and neurosensory layer detachments, although unique may closely mimick neovascular age-related macular degeneration and other counterparts. The investigative modalities starting from indocyanine angiography to optical coherence tomography angiography provide diagnostic challenges. The management strategies based on the available therapies are plenty and not vivid. A detailed review with clarifying images has been compiled with an aim to help the readers in getting a better understanding of the disease

Imprints of local lightcone projection effects on the galaxy bispectrum. II

General relativistic imprints on the galaxy bispectrum arise from observational (or projection) effects. The lightcone projection effects include local contributions from Doppler and gravitational potential terms, as well as lensing and other integrated contributions. We recently presented for the first time, the correction to the galaxy bispectrum from all local lightcone projection effects up to second order in perturbations. Here we provide the details underlying this correction, together with further results and illustrations. For moderately squeezed shapes, the correction to the Newtonian prediction is ~30% on equality scales at z ~ 1. We generalise our recent results to include the contribution, up to second order, of magnification bias (which affects some of the local terms) and evolution bias.Comment: 23 pages, 10 figures. Accompanies arXiv:1610.03351. v4 matches published versio