Consensus on recording of gas permeable contact lens fit

Purpose: To develop a new schematic scheme for efficiently recording the key parameters of gas permeable contact lens (GP) fits based on current consensus. Methods: Over 100 established GP fitters and educators met to discuss the parameters proposed in educational material for evaluating GP fit and concluded on the key parameters that should be recorded. The accuracy and variability of evaluating the fluorescein pattern of GP fit was determined by having 35 experienced contact lens practitioners from across the world, grading 5 images of a range of fits and the topographer simulation of the same fits, in random, order using the proposed scheme. The accuracy of the grading was compared to objective image analysis of the fluorescein intensity of the same images. Results: The key information to record to adequately describe the fit of an GP was agreed as: the manufacturer, brand and lens parameters; settling time; comfort on a 5 point scale; centration; movement on blink on a ±2 scale; and the Primary Fluorescein Pattern in the central, mid-peripheral and edge regions of the lens averaged along the horizontal and vertical lens axes, on a ±2 scale. On average 50-60% of practitioners selected the median grade when subjectively rating fluorescein intensity and this was correlated to objective quantification (r= 0.602, p< 0.001). Objective grading suggesting horizontal median fluorescein intensity was generally symmetrical, as was the vertical meridian, but this was not the case for subjective grading. Simulated fluorescein patterns were subjectively and objectively graded as being less intense than real photographs (p< 0.01). Conclusion: GP fit recording can be standardised and simplified to enhance GP practice. © 2013 British Contact Lens Association

Simulated Optical Performance of Custom Wavefront Soft Contact Lenses for Keratoconus

ABSTRACT: Purpose. Outstanding improvements in vision can theoretically be expected using contact lenses that correct monochromatic aberrations of the eye. Imperfections in such correction inherent to contact lenses are lens flexure, translation, rotation, and tear layer effects. The effects of pupil size and accommodation on ocular aberration may cause further difficulties. The purpose of this study was to evaluate whether nonaxisymmetric soft contact lenses could efficiently compensate for highe

Comparison of central corneal thickness and anterior chamber depth measurements using three imaging technologies in normal eyes and after phakic intraocular lens implantation

Contains fulltext : 81835.pdf (Publisher’s version ) (Open Access)BACKGROUND: The repeatability and interchangeability of imaging devices measuring central corneal thickness (CCT) and anterior chamber depth (ACD) are important in the assessment of patients considering refractive surgery. The purpose of this study was to investigate the agreement of CCT and ACD measurements using three imaging technologies in healthy eyes and in eyes after phakic intraocular lens implantation (pIOL). METHODS: In this comparative study, CCT and ACD were measured using anterior segment optical coherence tomography (AS-OCT), Orbscan II, and Pentacam in 33 healthy volunteers (66 eyes) and 22 patients (42 eyes) after pIOL implantation. Intraobserver repeatability was evaluated for all three devices in the healthy volunteer group. RESULTS: Pairwise comparison of CCT measurements showed significant differences between all devices (P < 0.001), except for the AS-OCT and Orbscan II in the healthy volunteer group (P = 0.422) and the Orbscan II and Pentacam in the pIOL group (P = 0.214). ACD measurements demonstrated significant differences between all pairwise comparisons in both groups (P < or = 0.001). Intraobserver reliability was high for CCT and ACD measurements in the healthy volunteer group, with coefficients of variation ranging from 0.6% to 1.2% and 0.4% to 0.5% respectively. CONCLUSIONS: CCT and ACD measurements using AS-OCT, Orbscan II, and Pentacam demonstrated high intraobserver reliability. However, these devices should not be used interchangeably for measurements of CCT and ACD in healthy subject and patients after pIOL implantation

Rifamycin Biosynthetic Congeners: Isolation and Total Synthesis of Rifsaliniketal and Total Synthesis of Salinisporamycin and Saliniketals A and B

We describe the isolation, structure elucidation, and total synthesis of the novel marine natural product rifsaliniketal and the total synthesis of the structurally related variants salinisporamycin and saliniketals A and B. Rifsaliniketal was previously proposed, but not observed, as a diverted metabolite from a biosynthetic precursor to rifamycin S. Decarboxylation of rifamycin provides salinisporamycin, which upon truncation with loss of the naphthoquinone ring leads to saliniketals. Our synthetic strategy hinged upon a Pt­(II)-catalyzed cycloisomerization of an alkynediol to set the dioxabicyclo[3.2.1]­octane ring system and a fragmentation of an intermediate dihydropyranone to forge a stereochemically defined (<i>E</i>,<i>Z</i>)-dienamide unit. Multiple routes were explored to assemble fragments with high stereocontrol, an exercise that provided additional insights into acyclic stereocontrol during stereochemically complex fragment-assembly processes. The resulting 11–14 step synthesis of saliniketals then enabled us to explore strategies for the synthesis and coupling of highly substituted naphthoquinones or the corresponding naphthalene fragments. Whereas direct coupling with naphthoquinone fragments proved unsuccessful, both amidation and C–N bond formation tactics with the more electron-rich naphthalene congeners provided an efficient means to complete the first total synthesis of rifsaliniketal and salinisporamycin

Dark-field illumination in conjunction with confocal Raman spectroscopy for real-time noninvasive aqueous humor investigation

To obtain a real-time noninvasive analysis of the content of the aqueous humor (AH) in the eye, a confocal dark-field ophthalmic probe was designed and optimized by ray-tracing software. The confocal technique allows Raman spectrometric sampling of the AH with suppressing signals from the surrounding tissues. Dark-field illumination prevents the excitation light to reach the vulnerable retinal tissue directly. In order to evaluate the optical performance and safety of this method, a functional prototyped eye contact probe has been designed and tested on ex vivo rabbit eyes

Baerveldt drainage tube motility in the anterior chamber

Purpose: To investigate the stability in position of the Baerveldt glaucoma drainage tube over time and to study movement of the drainage tube in the anterior chamber (AC) under varying light conditions. Methods: This prospective study included 70 eyes with implantation of a Baerveldt glaucoma drainage tube in the anterior chamber. Anterior segment optical coherence tomography (AS-OCT) images were made preoperatively to quantify AC depth. AS-OCT images were made twice under photopic and twice under scotopic conditions, in the angle parallel to the Baerveldt tube to quantify drainage tube position, at 3, 6, 12, and 24 months postoperatively. Tube-corneal (T-C) and tube-iris (T-I) distances were measured. Additionally, the central AC depth and the peripheral angle opening (AOD 500) were determined. Two subgroups were distinguished according to tube position: free in the AC (group 1, n = 48) and transiridal (group 2, n = 22). Results: After 24 months of follow-up, the drainage tube was found to move statistically significantly closer (0.12 mm) to the corneal endothelium in group 1 (p <0.01). There was no statistically significant difference in T-C distance over time in group 2. The T-C distance did not differ under photopic versus scotopic circumstances (p = 0.32). In both groups, the T-I distance was larger under scotopic conditions, a result of pupil dilation. Conclusions: The Baerveldt glaucoma drainage tube remained in a stable position when a transiridal implantation was performed, whereas the tube moved closer to the endothelium when placed free into the AC. Transiridal implantation of the Baerveldt tube seems a safe alternative for tube implantation with respect to tube motilit

Evaluation of the Comparability and Repeatability of Four Wavefront Aberrometers Visual Psychophysics and Physiological Optics

PURPOSE. To compare total ocular aberrations and corneal aberrations identified with four different aberrometers and to determine the repeatability and interobserver variability. METHODS. In this prospective comparative study, 23 healthy subjects underwent bilateral examination with four aberrometers: the Irx3 (Hartmann-Shack; Imagine Eyes, Orsay, France), Keratron (Hartmann-Shack; Optikon, Rome Italy), iTrace (raytracing; Tracey Technologies, Houston, TX), and OPD-Scan (Automated Retinoscopy; Nidek, Gamagori, Japan). Six images per eye were obtained. Second-, third-and fourth-order spherical aberrations were exported for 5.0-mm pupils. RESULTS. Significant differences in measurements were found for several total ocular aberrations (defocus 1-4 Wavefront analysis may be performed to design an ideal refractive correction, which corrects not only lower-order aberrations (sphere and cylinder), but also higher-order aberrations. In addition, it may be used to evaluate eyes with abnormal optics due to ageing or corneal disorders, such as keratoconus and pellucid marginal degeneration. Three different wavefront measuring principles are available to measure aberrations: (1) Hartmann-Shack, (2) Tscherning or ray tracing, and (3) automated retinoscopy. A HartmannShack aberrometer is an outgoing wavefront aberrometer. It measures the shape of the wavefront that is reflected out of the eye from a point source on the fovea. An array of microlenslets is used to subdivide the outgoing wavefront into multiple beams which produce spot images on a video sensor. The displacement of each spot from the corresponding nonaberrated reference position is used to determine the shape of the wavefront. 5,6 A Tscherning, or ray-tracing, aberrometer is an ingoing instrument. It projects a thin laser beam into the eye, parallel to the visual axis and determines the location of the beam on the retina by using a photodetector. Once the position of the first light spot on the retina is determined, the laser beam is moved to a new position, and the location of the second light spot on the retina is determined. Aberrations in the optical system cause a shift in the location of the light spot on the retina. METHODS In this prospective comparative study, 23 healthy volunteers were recruited from the Department of Ophthalmology, University Hospital Maastricht. Informed consent was obtained from all subjects after the nature of the experiment had been explained. The study adhered to the tenets of the Declaration of Helsinki. None of the subjects had a history of ocular surgery or ocular disease. All subjects were measured bilaterally with four different aberrometers. Per eye, six consecutive good-quality images were obtained: three by an expert and three by a nonexpert. An expert was defined as a person who had performed a minimum of 25 measurements with each aberrometer. Nonexperts were medical students with only basic knowledge of ophthalmology and no previous experience with any of the aberrometers. They received an oral instruction an