INTRODUCTION LASIK surgery is currently the preferred procedure to correct low to moderate myopia. The aim of this study was to determine the orientation of the steepest meridian of regular astigmatism in order to determine the relative incidence of vertical, horizontal, and oblique regular astigmatism among highly myopic Egyptian patients seeking non-ablative surgical correction of the refract...

Many animals move using lateral undulations, but snakes are noteworthy for using this type of locomotion in an unusual diversity of environments, including trees in which both the spacing and orientation of branches vary considerably. Despite branches providing discrete locations for snakes to generate propulsive forces during lateral undulation, the consequences of branch spacing for the locom...

Particle concentration banding has been studied by experiments in the flow driven by the inner cylinder of a partially filled concentric cylinder, or Couette, device. In this geometry, alternating bands of relatively concentrated and dilute particle fraction are observed along the axis. A small ratio of the inner to outer radius was used, with Ri /Ro50.29, and Ri50.64 cm, resulting in concentra...

Suggestions that peripheral imagery may affect the development of refractive error have led to interest in the variation in refraction and aberration across the visual field. It is shown that, if the optical system of the eye is rotationally symmetric about an optical axis which does not coincide with the visual axis, measurements of refraction and aberration made along the horizontal and verti...