Search results for "eye"
showing 10 items of 2511 documents
Drifts in real-time partial wavefront correction and how to avoid them
2017
In visual experiments that require real-time partial correction of wavefront aberrations, small errors occur that accumulate over time and lead to drifts in Zernike coefficients of the uncorrected aberrations. A simple algorithm that does not require the inclusion of an additional optical path to obtain independent measurements of the eye's aberrations is described here, and its effectiveness in preventing these drifts is demonstrated.
The tear film and the optical quality of the eye
2010
The stability of the tear film plays an important role in the optical quality of the eye. Various methods have been developed to quantify the contribution of the tear film to optical quality, including the double-pass optical method, Hartmann-Shack wavefront sensing, videokeratoscopy, retroillumination analysis, and interferometry. In addition to assessing the effect of tear film irregularities, these methods can aid in the diagnosis of dry-eye related conditions and the monitoring of therapy. This review describes the methodologies used to assess the relationship between the tear film and optical quality of the eye and summarizes the most important findings obtained with these methods with…
Efficient excitation of dielectric-loaded surface plasmon-polariton waveguide modes at telecommunication wavelengths
2008
International audience; The excitation of surface plasmon-polariton (SPP) waveguide modes in subwavelength dielectric ridges deposited on a thin gold film has been characterized and optimized at telecommunication wavelengths. The experimental data on the electromagnetic mode structure obtained using scanning near-field optical microscopy have been directly compared to full vectorial three-dimensional finite element method simulations. Two excitation geometries have been investigated where SPPs are excited outside or inside the dielectric tapered region adjoint to the waveguide. The dependence of the efficiency of the SPP guided mode excitation on the taper opening angle has been measured an…
Crystalline wax coverage of the imaginal cuticle inCalopteryx splendens(Odonata: Calopterygidae)
2009
Abstract In this study we use high resolution SEM to describe the diversity of wax crystals and their distribution on different morphological structures in male individuals of Calopteryx splendens. The entire cuticle surface of this damselfly, with the exception of ommatidia and ocelli, is covered with crystalline wax in dimensions from submicron to micron range. It is shown that shape - rod-like, plate like, filamentous, etc. -, size, and density of crystals vary on different surfaces and in individuals of different ages. Additionally, we demonstrate different types of damage to the crystalline wax layer: scratches, compressions, wear, and contamination. The primary function of the wax cry…
Pattern Dystrophy of the Macula in a Case of Steinert Disease
2013
<b><i>Introduction:</i></b> Myotonic dystrophies are typically associated with ocular complications like ptosis, weakness of the ocular muscle and cataracts, but also with less recognized retinal changes. <b><i>Case Report:</i></b> A 41-year-old female with type 1 myotonic dystrophy complained of progressive vision loss. Slit lamp examination revealed the presence of typical bilateral polychromatic cataract with posterior subcapsular component. Dilated fundus examination was remarkable for bilateral macular depigmented changes. Multimodal imaging analysis of the macula suggested the presence of a butterfly-shaped pattern dystrophy. <b>&l…
Device interchangeability on anterior chamber depth and white-to-white measurements: a thorough literature review
2016
We have reviewed a set of recently published studies that compared the anterior chamber depth (ACD) and/or white-to-white (WTW) distance obtained by means of different measuring devices. Since some of those studies reached contradictory conclusions regarding device interchangeability, this review was carried out in attempting to clarify which clinical devices can or cannot be considered as interchangeable in clinical practice to measure ACD and/or WTW distance, among these devices: A-scan, ultrasound biomicroscopy, Orbscan and Orbscan II (Bausch&Lomb Surgical Inc., San Dimas, California, USA), Pentacam and Pentacam HR (Oculus, Wetzlar, Germany), Galilei (Ziemer, Switzerland), Visante optica…
Did the three little pigs frighten the wolf? How deaf readers use lexical and syntactic cues to comprehend sentences
2020
Abstract Background The ways in which students with deafness process syntactic and semantic cues while reading sentences are unclear. While some studies have supported the preference for semantic cues, others have not. Aim To examine differences in the processing of syntactic versus semantic cues during sentence reading among students who are deaf or hard of hearing (DHH). Method Twenty DHH students (mean age = 12.48 years) and 20 chronologically age-matched students with typical hearing (TH) were asked to read sentences written in Spanish with different grammatical structures and to choose the picture that best matched the sentences’ meaning while their eye movements were being registered.…
Parasite resistance and avoidance behaviour in preventing eye fluke infections in fish.
2004
This paper examines the efficiency of acquired resistance in protecting the fish host, rainbow trout (Oncorhynchus mykiss), against the trematode parasite Diplostomum spathaceum, and the hypothesis that fish recognize areas where infective stages are aggregated and show avoidance behaviour. We found that when fish with a low level of infection were held in restricted cages in natural conditions they became infected and developed cataracts as a result of this infection. This suggests that acquired resistance is insufficient in protecting fish against the parasite or the deleterious effects of infection in conditions where fish could not avoid the parasite. Behavioural experiments in the labo…
Some optical methods for cutaneous diagnostic help - Focus on multispectral imaging
2010
International audience; Some optical methods for cutaneous diagnostic help - Focus on multispectral imaging
Conjugate and cut loci in averaged orbital transfer
2006
The objective of this Note is to describe the conjugate and cut loci associated with the averaged energy minimization problem in coplanar orbit transfer.