Purpose: To evaluate the changes in the optical quality of corneas of hyperopic patients operated using central multifocal presbyLASIK treatment through the study of light patterns around the retinal plane. Methods: This study included eight hyperopic eyes that underwent central presbyLASIK surgery with Presby-one software using an H. Eye Tech Technovision excimer laser platform. Mean patient age was 57 years. Mean preoperative spherical equivalent refraction was 1.28±0.87 diopters (D). Mean distance decimal visual acuity with correction was 1.02±0.13 and without correction was 0.37±0.15. The optical quality was characterized by the Strehl ratio, the spot size on the retina, and objective decimal visual acuity calculated based on measured corneal topography using Fresnel propagation algorithm based on a realistic eye model. Results: The postoperative spherical equivalent refraction was −0.55±0.48 D. The distance decimal visual acuity with correction was 0.94 and without correction was 0.70. The pseudoaccommodation range was 1.60±0.40 D. A good Pearson correlation coefficient was obtained (r ² =0.86) for the linear fit between the real and calculated decimal visual acuity for the eight eyes. The Strehl ratio value on the retinal plane increased after the surgery by a mean factor of 4.7. Conclusions: With a complete characterization of the eye and a complete propagation algorithm (that takes into account all refractive surfaces in the eye at the same time), it is possible to evaluate the optical quality in eyes of patients who have undergone central presbyLASIK treatment. [ J Refract Surg . 2007;23:39–44.]

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Object tracking with subpixel accuracy is of fundamental importance in many fields since it provides optimal performance at relatively low cost. Although there are many theoretical proposals that lead to resolution increments of several orders of magnitude, in practice this resolution is limited by the imaging systems. In this paper we propose and demonstrate through simple numerical models a realistic limit for subpixel accuracy. The final result is that maximum achievable resolution enhancement is connected with the dynamic range of the image, i.e., the detection limit is $1/2^{\wedge }(\mathrm{nr}.\mathrm{bits})$. The results here presented may aid in proper design of superresolution experiments in microscopy, surveillance, defense, and other fields.

The evaluation of eye blinking has been used for the diagnosis of neurological disorders and fatigue. Despite the extensive literature, no objective method has been found to analyze its kinematic and dynamic behavior. A non-contact technique based on the high-speed recording of the light reflected by the eyelid in the blinking process and the off-line processing of the sequence is presented. It allows for objectively determining the start and end of a blink, besides obtaining different physical magnitudes: position, speed, eyelid acceleration as well as the power, work and mechanical impulse developed by the muscles involved in the physiological process. The parameters derived from these magnitudes provide a unique set of features that can be used to biometric authentication. This possibility has been tested with a limited number of subjects with a correct identification rate of up to 99.7%, thus showing the potential application of the method.