Fabrication and performance evaluation of a design for an extended depth-of-focus intraocular lens based on an improved sinusoidal profile.

This study presents the fabrication and evaluation of a sinusoidal extended depth-of-focus (EDoF) intraocular lens (IOL) based on our previously proposed design approach. The power, through-focus MTF, and surface profile were measured using commercial instruments. Through-focus images of a United States Air Force (USAF) 1951 resolution target formed by the fabricated IOL were compared with Symfony and AR40E under monochromatic and polychromatic light using optical bench testing. Simulations assessed visual acuity (VA) of a pseudophakic model eye with the EDoF IOL, including evaluation of tilt and decentration effects. Results indicate that the base power, add power, and the through-focus MTF@50 lp/mm of the fabricated IOL at a 3 mm pupil size align with the design specifications. The extended-depth-of-focus and imaging performance for the far vision of the fabricated IOL under both monochromatic and polychromatic light conditions at a 3.0 mm pupil diameter is comparable to that of Symfony. In addition, the fabricated IOL exhibits a similar extended-depth-of-focus for three discrete wavelengths. The pseudophakic model eye with the designed EDoF IOL demonstrates a VA exceeding 0.1 logMAR within a defocus range of 2.44 D. The VA is tolerant to both IOL tilt and decentration. These findings demonstrate the promising potential of the sinusoidal EDoF IOL design for future applications in cataract surgery.

A Multi-market Comparison of the Intraday Lead-Lag Relations Among Stock Index-Based Spot, Futures and Options.

Using 1-min data, we explore the dynamic variation of the intraday lead-lag relations between stock indices and their derivatives through a comprehensive study with broader coverage of research objectives and methodologies. This paper provides explicit evidence that the futures and options exhibit price leadership over the spot market, and the options is ahead of the futures on most trading days in all three markets. This paper also reports a new finding that the relation between the derivative and its underlying index reverses when the index return has a significantly larger mean value, and the reversal phenomenon is also observed in the relations between the futures and the options, which enriches the empirical results of intraday lead-lag relations. Moreover, these conclusions still hold under the impact of extreme events, e.g., the outbreak of the Covid-19. Finally, we construct a pair trading strategy based on the intraday lead-lag relationships, which can get better performance than the corresponding spot index. Our findings can potentially help regulators understand the price discovery process between the index and its derivatives, and also be of great value for timely adjustment of investors intraday trading strategies.