We describe a novel scheme for obtaining a superhigh numerical aperture gradient-index (SHNA GRIN) lens from multiple thin layers of two or more materials with large refractive-index contrast. Design procedures for the lens are described, including variation of the layer thickness to achieve focusing and of the thickness limit to reduce scattering loss. We use an exact numerical solution by the...

In this paper we propose a method to convert the local variations of refractive index into local changes of one surface of the lens, which then can then be described as a free-form surface, easy to introduce in conventional simulation tools. The proposed method tries to provide an equivalent model of the lens with refractive index variations where the index changes have been replaced for local ...

PURPOSE Accommodation is a dioptric change in power of the crystalline lens resulting from ciliary muscle contraction that leads to an increase in lens surface curvatures and thickness and changes in the position of lens surfaces. Previous studies have used A-scan ultrasound to measure changes in the position of lens surfaces with voluntary accommodation, but have not simultaneously measured th...

The purpose of this study was to study the age-dependence of the optomechanical properties of human lenses during simulated disaccommodation in a mechanical lens stretcher, designed to determine accommodative forces as a function of stretch distance, to compare the results with in vivo disaccommodation and to examine whether differences exist between eyes harvested in the USA and India. Postmor...

Purpose. To determine the dynamic pre- and postlens tear film (PLTF and PoLTF) thicknesses by using optical coherence tomography (OCT). Methods. Ultrahigh-resolution OCT was used to image the tear film of 22 subjects before and after contact lens wear. A soft lens with 1 drop of artificial tears on its concave surface was inserted onto one randomly selected eye. OCT images were taken before ins...

Our purpose is to correct digital CCD-recorded Scheimpflug photographs, imaging both the anterior and posterior corneal surface, the anterior chamber, and the anterior eye lens surface for optical distortions. In a ray-tracing algorithm the imaging of the posterior corneal surface in a given Scheimpflug photograph is corrected by applying Snell's law on parallel incident rays entering through t...

Thirty-seven consecutive patients (41 eyes) diagnosed with primary angle closure glaucoma (PACG) attending the Glaucoma Clinic in University Malaya Medical Centre, over a period of 6 months were categorized into acute, subacute and chronic PACG from their clinical presentation. Each case was subjected to automated refraction, A-scan biometry for anterior chamber depth, axial length and lens thi...

PURPOSE Recently, the authors presented a technique that allows corneal thickness measurements along any meridian from optical sections obtained using a rotary scanning system. This paper presents three-dimensional mapping of the corneal thickness and topography of both corneal surfaces, obtained with the rotary system. METHOD Corneal thickness and topography are computed from optical section...

We propose a new fiber lens structure for large distance measurement in which a polymer layer is added to a conventional fiber lens. The proposed fiber lens can adjust the working distance by properly choosing the refractive index and thickness of the polymer layer. In our numerical analysis for the fiber lens radius of 120 μm, the working distance of the proposed fiber lens is about 10 mm whic...

PURPOSE To investigate changes in corneal topography and morphology in human eyes wearing orthokeratology (OK) lenses for overnight and over a 5-year period. MATERIALS AND METHODS Fifty-six adults with moderate myopia were assigned to 2 groups based on age matching: 5-year lens wear (n = 26, 51 eyes) and 1-night lens wear (n = 30, 60 eyes). All subjects wore reverse-geometry OK lenses with th...