Many multiply{imaged quasars have been found over the years, but none so far with image separation in excess of 8 00. The absence of such large splittings has been used as a test of cosmological models: the standard Cold Dark Matter model has been excluded on the basis that it predicts far too many large{separation double images. These studies assume that the lensing structure has the mass proo...

BACKGROUND The aim of this study was to describe the design, methods, and baseline characteristics of children enrolled in the Personalized Addition lenses Clinical Trial (PACT). PACT aims to test the myopia control efficacy of progressive addition lenses (PALs) with personalized addition values compared with standard (+2.00 D) addition PALs and single vision lenses (SVLs). METHODS PACT is a ...

There are many different types of lenses, but largely they fall into the three classes of the title: set-based, delta-based and edit-based lenses. This paper develops some of the general relationships between those classes. The main results are that a category of set-based lenses is a full subcategory of a category of delta-based lenses determined by sending sets to codiscrete categories; that ...

in view of the rapid expansion of contact lens amongst the users, new dimensions have been added to the domain of ophthalmology: giant papillay conjunctivitis, a disease caused by different kinds of contact lens, appears weeks or months after they are used, although some patients are struck years later. the predominant symptoms are increased awareness of lenses, ocular itching, blurred vision a...

purpose: to compare the effect of different deviation measurement techniques and different lens powers on gradient accommodative convergence to accommodation (ac/a) ratio. methods: we randomly selected 78 eligible students of different majors from zahedan university of medical sciences. following retinoscopy for refractive errors, alternate prism cover test, von graefe and maddox rod without ad...

In order to increase the water content and the oxygen permeability of hydrogels used in themanufacture of contact lenses, the polar monomer Silicon Hydrogel Contact Lenses (SHCL), and 2-hydroxyethyl methacrylate (HEMA) were copolymerized with the hydrogels. Due to the presence ofpolar monomers in the conventional contact lenses, the major component of the human tear,lysozyme is extensively adso...

This paper elaborates on analysis of progressive spectacle lenses, to correct presbyopia, which are nowadays offered at the market. The paper describes different types of progressive lenses, their parameters, length and width of their progressive segments. It also describes degressive spectacles lenses--progressive lenses on middle and near distance. The main part of the paper is a comparison o...

Six glycosidases were determined in: (1) lenses of alloxan-diabetic rats; (2) rabbit lenses incubated in high-glucose media in vitro; and (3) human senile cataracts, diabetic senile cataracts, and autopsy lenses. In diabetic rat lenses, the activities of /3-glucosaminidase, fi-galactosidase, and P-fucosidase increased with cataract progression as compared to control lenses. Glycosidase activiti...

this study compared tear function tests and cytologic changes on the conjunctival surface in asymptomatic patients wearing contact lens of different materials. included in this study were 40 eyes wearing daily wear 4 week replacement hydrogel (h) lenses, 32 eyes wearing silicone hydrogel (sih) lenses, 18 eyes wearing rigid gas-permeable (rgp) lenses, and 21 healthy eyes (no lenses) as the contr...