Future of contact lens usage

I was recently part of a small committee looking at higher qualifications in contact lens practice and the discussion turned to future technologies. There was mention of different materials and different applications of contact lenses. Drug delivery with contact lenses was discussed as this has been talked about in the literature for a while. The first paper I could find that talked about using contact lenses for drug delivery dates back over 40 years. There was a review paper in CLAE in 2008 that looked specifically at this too [1]. However, where are these products? Why are we not seeing them in the market place? Maybe the technology is not quite there yet, or maybe patents are prohibiting usage or maybe the market is not big enough to develop such products? We do have lenses on the market with slow release of lubricating agents but not therapeutic agents used for ocular or systemic conditions. Contact lenses with pathogen detectors may be part of our contact lens armoury of the future and again we can already see papers in the literature that have trialled this technology for glucose monitoring in diabetics or lactate concentration in the tear film. Future contact lenses may incorporate better optics based on aberration control and we see this starting to emerge with aspheric designs designed to minimise spherical aberration. Irregular corneas can be fitted with topography based designs and again this technology exists and is being used by some manufacturers in their designs already. Moreover, the topography based fitting of irregular corneas is certainly something we see a lot of today and CLAE has seen many articles related to this over the last decade or so. What about further into the future? Well one interesting area must the 3-dimensional contact lenses, or contact lenses with electronic devices built in that simulate a display screen. A little like the virtual display spectacles that are already sold by electronics companies. It does not take much of a stretch of the imagination to see a large electronic company taking this technology on and making it viable. Will we see people on the train watching movies on these electronic virtual reality contact lenses? I think we will, but when is harder to know.

Effectiveness of nonpharmacologic treatments for acute seasonal allergic conjunctivitis

Objective - To investigate whether artificial tears and cold compress alone or in combination provide a treatment benefit and whether they were as effective as or could enhance topical antiallergic medication. Design - Randomized, masked clinical trial. Participants - Eighteen subjects (mean age, 29.5±11.0 years) allergic to grass pollen. Intervention - Controlled exposure to grass pollen using an environmental chamber to stimulate an ocular allergic reaction followed by application of artificial tears (ATs), 5 minutes of cold compress (CC), ATs combined with CC, or no treatment applied at each separate visit in random order. A subset of 11 subjects also had epinastine hydrochloride (EH) applied alone and combined with CC in random order or instillation of a volume-matched saline control. Main Outcome Measures - Bulbar conjunctival hyperemia, ocular surface temperature, and ocular symptoms repeated before and every 10 minutes after treatment for 1 hour. Results - Bulbar conjunctival hyperemia and ocular symptoms decreased and temperature recovered to baseline faster with nonpharmaceutical treatments compared with no treatment (P?tears combined with CC reduced hyperemia more than other treatments (P?tear instillation alone or CC combined with ATs or EH significantly reduced the temperature (P??0.05). At all measurement intervals, symptoms were reduced for both EH and EH combined with CC than CC or ATs alone or in combination (P?

Anterior segment anomalies and effects on visual quality

The tear film, cornea and lens dictate the refractive power of the eye and the retinal image quality is principally defined by diffraction, whole eye wavefront error, scatter, and chromatic aberration. Diffraction and wave aberration are fundamentally pupil diameter dependent; however scatter can be induced by refractive surgery and in the normal ageing eye becomes an increasingly important factor defining retinal image quality. The component of visual quality most affected by the tear film, refractive surgery and multifocal contact and intraocular lenses is the wave aberration of the eye. This body of work demonstrates the effects of each of these anomalies on the visual quality of the eye. When assessing normal or borderline self-diagnosed dry eye subjects using aberrometry, combining lubricating eye drops and spray does not offer any benefit over individual products. However, subjects perceive a difference in comfort for all interventions after one hour. Total higher order aberrations increase after laser assisted sub-epithelial keratectomy performed using a solid-state laser on myopes, but this causes no significant decrease in contrast sensitivity or increase in glare disability. Mean sensitivity and reliability indices for perimetry were comparable to pre-surgery results. Multifocal contact lenses and intraocular lenses are designed to maximise vision when the patient is binocular, so any evaluation of the eyes individually is confounded by reduced individual visual acuity and visual quality. Different designs of aspheric multifocal contact lenses do not provide the same level of visual quality. Multifocal contact lenses adversely affect mean deviation values for perimetry and this should be considered when screening individuals with multifocal contact or intraocular lenses. Photographic image quality obtained through a multifocal contact or intraocular lens appears to be unchanged. Future work should evaluate the effect of these anomalies in combination; with the aim of providing the best visual quality possible and supplying normative data for screening purposes.

Effectiveness of nonpharmacologic treatments for acute seasonal allergic conjunctivitis

Objective To investigate whether artificial tears and cold compress alone or in combination provide a treatment benefit and whether they were as effective as or could enhance topical antiallergic medication. Design Randomized, masked clinical trial. Participants Eighteen subjects (mean age, 29.5±11.0 years) allergic to grass pollen. Intervention Controlled exposure to grass pollen using an environmental chamber to stimulate an ocular allergic reaction followed by application of artificial tears (ATs), 5 minutes of cold compress (CC), ATs combined with CC, or no treatment applied at each separate visit in random order. A subset of 11 subjects also had epinastine hydrochloride (EH) applied alone and combined with CC in random order or instillation of a volume-matched saline control. Main Outcome Measures Bulbar conjunctival hyperemia, ocular surface temperature, and ocular symptoms repeated before and every 10 minutes after treatment for 1 hour. Results Bulbar conjunctival hyperemia and ocular symptoms decreased and temperature recovered to baseline faster with nonpharmaceutical treatments compared with no treatment (P <0.05). Artificial tears combined with CC reduced hyperemia more than other treatments (P <0.05). The treatment effect of EH was enhanced by combining it with a CC (P <0.001). Cold compress combined with ATs or EH lowered the antigen-raised ocular surface temperature to less than the pre-exposure baseline. Artificial tear instillation alone or CC combined with ATs or EH significantly reduced the temperature (P <0.05). Cold compress combined with ATs or EH had a similar cooling effect (P > 0.05). At all measurement intervals, symptoms were reduced for both EH and EH combined with CC than CC or ATs alone or in combination (P <0.014). Conclusions After controlled exposure to grass pollen, CC and AT treatment showed a therapeutic effect on the signs and symptoms of allergic conjunctivitis. A CC enhanced the use of EH alone and was the only treatment to reduce symptoms to baseline within 1 hour of antigenic challenge. Signs of allergic conjunctivitis generally were reduced most by a combination of a CC in combination with ATs or EH. © 2014 by the American Academy of Ophthalmology.

Report of the inaugural meeting of the TFOS i2 = initiating innovation Series:targeting the unmet need for dry eye treatment

On March 21, 2015, a meeting was held in London, United Kingdom, to address the progress in targeting the unmet need for dry eye disease (DED) treatment. The meeting, which launched the i2 = initiating innovation series, was sponsored by the Tear Film & Ocular Surface Society (TFOS; www.TearFilm.org) and supported by Dompé. The TFOS i2 meeting was designed to review advances in the understanding of DED since publication of the 2007 TFOS International Dry Eye WorkShop (DEWS) report, and to help launch the highly anticipated sequel, DEWS II. The meeting was structured to discuss the scope of the DED problem, to review the clinical challenges of DED, and to consider the treatment challenges of DED. This article provides a synopsis of the presentations of this TFOS i2 meeting.

Management of allergic conjunctivitis and dry eye

Ocular allergy is a common eye condition encountered in clinical practice. However, little is known how seasonal allergic conjunctivitis (SAC), the most common subtype, is managed in clinical practice. Further, dry eye, another common eye condition, may be misdiagnosed as SAC and vice-versa as they share similar signs and symptoms. In addition, despite the frequent recommendation of non-pharmacological treatments for SAC, evidenceto support their use has not been identified in the scientific literature. The aim of this thesis was therefore to determine the actual diagnosis and management of SAC and dry eye in clinical practice and investigate the efficacy of non-pharmacological treatments for these conditions. The diagnostic and management strategies for SAC and dry eye employed by pharmacy staff are found to be inconsistent with current guidelines and scientific evidence based upon a mystery shopper design. Cluster analysis of tear film metrics in normal and dry eye patients identified several clinically relevant groups of patients that may allow for targeted treatment recommendations. Using a novel environmental chamber model of SAC, the use of artificial tears and cold compresses, either alone or combined is an effective treatment modality for acute and symptomatic SAC, on a par with topical anti-allergic medication, and has been demonstrated for the first time. In addition, eyelid warming therapy with a simple, readily available, seed filled device is an effective method of treating meibomian gland dysfunction (MGD) related evaporative dry eye, perhaps the most common dry eye subtype. A greater focus on ophthalmology must be implemented as part of the formal education and training of pharmacy staff, while greater professional communication between community pharmacists, optometrists and the population they serve is required. Artificial tears and cold compresses may be considered as front line agents for acute SAC by pharmacy staff and optometrists, to whom pharmacological treatment options are limited.

A review of non-pharmacological and pharmacological management of seasonal and perennial allergic conjunctivitis

Allergic eye disease encompasses a group of hypersensitivity disorders which primarily affect the conjunctiva and its prevalence is increasing. It is estimated to affect 8% of patients attending optometric practice but is poorly managed and rarely involves ophthalmic assessment. Seasonal allergic conjunctivitis (SAC) is the most common form of allergic eye disease (90%), followed by perennial allergic conjunctivitis (PAC; 5%). Both are type 1 IgE mediated hypersensitivity reactions where mast cells play an important role in pathophysiology. The signs and symptoms are similar but SAC occurs periodically whereas PAC occurs year round. Despite being a relatively mild condition, the effects on the quality of life can be profound and therefore they demand attention. Primary management of SAC and PAC involves avoidance strategies depending on the responsible allergen(s) to prevent the hypersensitivity reaction. Cooled tear supplements and cold compresses may help bring relief. Pharmacological agents may become necessary as it is not possible to completely avoid the allergen(s). There are a wide range of anti-allergic medications available, such as mast cell stabilisers, antihistamines and dual-action agents. Severe cases refractory to conventional treatment require anti-inflammatories, immunomodulators or immunotherapy. Additional qualifications are required to gain access to these medications, but entry-level optometrists must offer advice and supportive therapy. Based on current evidence, the efficacy of anti-allergic medications appears equivocal so prescribing should relate to patient preference, dosing and cost. More studies with standardised methodologies are necessary elicit the most effective anti-allergic medications but those with dual-actions are likely to be first line agents. © 2011 British Contact Lens Association.

Editorial

Welcome to the latest issue of Contact Lens and Anterior Eye. In this issue, Kuldeep Razaida provides a fascinating look at fitting prosthetic lenses to patients in India. I had the good fortune of visiting his clinic in August 2006 at the LV Prasad Eye Institute in Hyderabad, India and was humbled by the vast expertise within the one building. The institute started in 1987 and is the brainchild of the infamous Professor Rao. I think there are few such places in the world where the clinicians work so passionately in treating such interesting patients (for details regarding the LV Prasad Eye Institute see www.lvpei.org). I was in Hyderabad courtesy of IACLE (see issue 29:5 for an editorial by Judith Morris and Sonja Cronje about IACLE) and was able to share ideas with contact lens educators from across the world (for more information on IACLE see www.iacle.org). The issue contains some regular contact lens type papers too; with our aging population readers will be particularly interested in a paper by Mike Freeman and Neil Charman looking at modified monovision with diffractive bifocal lenses. There is an article looking at visual problems with video display terminal use and a study looking at the effects of surface treatment of silicone hydrogel contact lenses. There is an interesting piece from Dr Aisling Mann of Aston University looking at tear protein analysis; this article contains one CET point too for readers who complete the attached multiple choice questions before the relevant deadline. Also, congratulations to the BCLA members who successfully undertook the Fellowship of the BCLA at this year's BCLA conference in Manchester. If you are interested in undertaking the Fellowship please look at the details on the BCLA web page (http://www.bcla.org.uk/fellowship.asp). Amongst the case reports in this issue of CLAE you will notice one from Andrew Elder-Smith, this particular case report was presented as part of his successful Fellowship submission in 2006 and was thought to be of particular good quality by the examiners who asked Andrew to kindly submit it for publication to Contact Lens and Anterior Eye as an example for potential candidates. Finally, it is my sad duty to report the death of Howard Gee earlier this year, a past council member of the BCLA. Our thoughts and prayers are with his family and friends.

The relation between physical properties of the anterior eye and ocular surface temperature

PURPOSE. To examine the relation between ocular surface temperature (OST) assessed by dynamic thermal imaging and physical parameters of the anterior eye in normal subjects. METHODS. Dynamic ocular thermography (ThermoTracer 7102MX) was used to record body temperature and continuous ocular surface temperature for 8 s after a blink in the right eyes of 25 subjects. Corneal thickness, corneal curvature, and anterior chamber depth (ACD) were assessed using Orbscan II; noninvasive tear break-up time (NIBUT) was assessed using the tearscope; slit lamp photography was used to record tear meniscus height (TMH) and objective bulbar redness. RESULTS. Initial OST after a blink was significantly correlated only with body temperature (r = 0.80, p < 0.0005), NIBUT (r = -0.68, p < 0.005) and corneal curvature (r = -0.40, p = 0.05). A regression model containing all the variables accounted for 70% (p = 0.002) of the variance in OST, of which NIBUT (29%, p = 0.004), and body temperature (18%, p = 0.005) contributed significantly. CONCLUSIONS. The results support previous theoretical models that OST radiation is principally related to the tear film; and demonstrate that it is less related to other characteristics such as corneal thickness, corneal curvature, and anterior chamber depth. © 2007 American Academy of Optometry.

Anterior ophthalmic imaging

Improvements in imaging chips and computer processing power have brought major advances in imaging of the anterior eye. Digitally captured images can be visualised immediately and can be stored and retrieved easily. Anterior ocular imaging techniques using slitlamp biomicroscopy, corneal topography, confocal microscopy, optical coherence tomography (OCT), ultrasonic biomicroscopy, computerised tomography (CT) and magnetic resonance imaging (MRI) are reviewed. Conventional photographic imaging can be used to quantify corneal topography, corneal thickness and transparency, anterior chamber depth and lateral angle and crystalline lens position, curvature, thickness and transparency. Additionally, the effects of tumours, foreign bodies and trauma can be localised, the corneal layers can be examined and the tear film thickness assessed. © 2006 The Authors.

Clinical performance of daily disposable soft contact lenses using sustained release technology

Purpose: Polyvinyl alcohol (PVA) is a successful tear film stabiliser and is widely used in comfort drops and some soft contact lens materials. A PVA-containing lens, nelfilcon A has been modified to include additional (non-functional) PVA in order to provide improved comfort. This study aims to examine the clinical performance of this nelfilcon A lens with AquaRelease™ (AquaRelease). Methods: Two contralateral, investigator masked, open label, subjective and objective evaluations were conducted. The first examined the effect of adding increased molecular weight PVA to nelfilcon A (n = 5), and the second compared this AquaRelease lens to ocufilcon B (n = 34). The principal measures were non-invasive break-up time (NIBUT) and subjective comfort, which were assessed at the beginning and end of a week of daily wear, and three times throughout 1 day at 8, 12 and 16 h. Results: All subjects successfully completed the daily wearing schedule of 16 h. On initial insertion, subjective comfort and NIBUT improved for AquaRelease than original nelfilcon A lenses (p < 0.05). Initial comfort was better for AquaRelease compared to ocufilcon B lenses (p = 0.01); however, NIBUT was not statistically different (11.7 ± 15.6 s versus 8.4 ± 6.8 s; p = 0.26). Subjective comfort decreased with time (p < 0.001), but there was no significant difference between AquaRelease and ocufilcon B lenses (p = 0.16). NIBUT was not significantly affected by time (p = 0.56) or between lenses (p = 0.33). At the end of a weeks' wear, subjective initial, end-of-day, overall comfort and vision were rated significantly better with AquaRelease than ocufilcon B (p < 0.01). Conclusions: Release of additional non-functionalised PVA from the nelfilcon A lenses appears to enhance comfortable contact lens wear. © 2006 British Contact Lens Association.

Technological enhancements to optometric clinical tests

A sizeable amount of the testing in eye care, requires either the identification of targets such as letters to assess functional vision, or the subjective evaluation of imagery by an examiner. Computers can render a variety of different targets on their monitors and can be used to store and analyse ophthalmic images. However, existing computing hardware tends to be large, screen resolutions are often too low, and objective assessments of ophthalmic images unreliable. Recent advances in mobile computing hardware and computer-vision systems can be used to enhance clinical testing in optometry. High resolution touch screens embedded in mobile devices, can render targets at a wide variety of distances and can be used to record and respond to patient responses, automating testing methods. This has opened up new opportunities in computerised near vision testing. Equally, new image processing techniques can be used to increase the validity and reliability of objective computer vision systems. Three novel apps for assessing reading speed, contrast sensitivity and amplitude of accommodation were created by the author to demonstrate the potential of mobile computing to enhance clinical measurement. The reading speed app could present sentences effectively, control illumination and automate the testing procedure for reading speed assessment. Meanwhile the contrast sensitivity app made use of a bit stealing technique and swept frequency target, to rapidly assess a patient’s full contrast sensitivity function at both near and far distances. Finally, customised electronic hardware was created and interfaced to an app on a smartphone device to allow free space amplitude of accommodation measurement. A new geometrical model of the tear film and a ray tracing simulation of a Placido disc topographer were produced to provide insights on the effect of tear film breakdown on ophthalmic images. Furthermore, a new computer vision system, that used a novel eye-lash segmentation technique, was created to demonstrate the potential of computer vision systems for the clinical assessment of tear stability. Studies undertaken by the author to assess the validity and repeatability of the novel apps, found that their repeatability was comparable to, or better, than existing clinical methods for reading speed and contrast sensitivity assessment. Furthermore, the apps offered reduced examination times in comparison to their paper based equivalents. The reading speed and amplitude of accommodation apps correlated highly with existing methods of assessment supporting their validity. Their still remains questions over the validity of using a swept frequency sine-wave target to assess patient’s contrast sensitivity functions as no clinical test provides the range of spatial frequencies and contrasts, nor equivalent assessment at distance and near. A validation study of the new computer vision system found that the authors tear metric correlated better with existing subjective measures of tear film stability than those of a competing computer-vision system. However, repeatability was poor in comparison to the subjective measures due to eye lash interference. The new mobile apps, computer vision system, and studies outlined in this thesis provide further insight into the potential of applying mobile and image processing technology to enhance clinical testing by eye care professionals.

Metastable de-excitation spectroscopy and density functional theory study of the selective oxidation of crotyl alcohol over Pd(111)

The extremely surface sensitive technique of metastable de-excitation spectroscopy (MDS) has been utilized to probe the bonding and reactivity of crotyl alcohol over Pd(111) and provide insight into the selective oxidation pathway to crotonaldehyde. Auger de-excitation (AD) of metastable He (23S) atoms reveals distinct features associated with the molecular orbitals of the adsorbed alcohol, corresponding to emission from the hydrocarbon skeleton, the O n nonbonding, and C═C π states. The O n and C═C π states of the alcohol are reversed when compared to those of the aldehyde. Density functional theory (DFT) calculations of the alcohol show that an adsorption mode with both C═C and O bonds aligned somewhat parallel to the surface is energetically favored at a substrate temperature below 200 K. Density of states calculations for such configurations are in excellent agreement with experimental MDS measurements. MDS revealed oxidative dehydrogenation of crotyl alcohol to crotonaldehyde between 200 and 250 K, resulting in small peak shifts to higher binding energy. Intramolecular changes lead to the opposite assignment of the first two MOs in the alcohol versus the aldehyde, in accordance with DFT and UPS studies of the free molecules. Subsequent crotonaldehyde decarbonylation and associated propylidyne formation above 260 K could also be identified by MDS and complementary theoretical calculations as the origin of deactivation and selectivity loss. Combining MDS and DFT in this way represents a novel approach to elucidating surface catalyzed reaction pathways associated with a “real-world” practical chemical transformation, namely the selective oxidation of alcohols to aldehydes.

Why is it possible to detect doped regions of semiconductors in low voltage SEM:a review and update

There is an urgent need for fast, non-destructive and quantitative two-dimensional dopant profiling of modern and future ultra large-scale semiconductor devices. The low voltage scanning electron microscope (LVSEM) has emerged to satisfy this need, in part, whereby it is possible to detect different secondary electron yield values (brightness in the SEM signal) from the p-type to the n-type doped regions as well as different brightness levels from the same dopant type. The mechanism that gives rise to such a secondary electron (SE) contrast effect is not fully understood, however. A review of the different models that have been proposed to explain this SE contrast is given. We report on new experiments that support the proposal that this contrast is due to the establishment of metal-to-semiconductor surface contacts. Further experiments showing the effect of instrument parameters including the electron dose, the scan speeds and the electron beam energy on the SE contrast are also reported. Preliminary results on the dependence of the SE contrast on the existence of a surface structure featuring metal-oxide semiconductor (MOS) are also reported. Copyright © 2005 John Wiley & Sons, Ltd.

Synthesis and evaluation of nanoparticle-polymer composites

This thesis describes the synthesis of functionalised polymeric material by variety of free-radical mediated polymerisation techniques including dispersion emulsion, seeded emulsion, suspension and bulk polymerisation reactions. Organic fluorophores and nanoparticles such as quantum dots were incorporated within polymeric materials, in particular, thiol-functionalised polymer microspheres, which were fluorescently labelled either during synthesis or by covalent attachment post synthesis. The resultant fluorescent polymeric conjugates were then assessed for their utility in biological systems as an analytical tool for cells or biological structures. Quantum dot labelled, thiol-functionalised microspheres were assessed for their utility in the visualisation and tracking of red blood cells. Determination of the possible internalisation of fluorescent microspheres into red blood cells was required before successful tracking of red blood cells could take place. Initial work appeared to indicate the presence of fluorescent microspheres inside red blood cells by the process of beadfection. A range of parameters were also investigated in order to optimise beadfection. Thiol-functionalised microspheres labelled successfully with organic fluorophores were used to image the tear film of the eye. A description of problems encountered with the covalent attachment of hydrophilic, thiol-reactive fluorescent dyes to a variety of modified polymer microspheres is also included in this section. Results indicated large microspheres were particularly useful when tracking the movement of fluid along the tear meniscus. Functional bulk polymers were synthesised for assessment of their interaction with titanium dioxide nanoparticles. Thiol-functionalised polymethyl methacrylate and spincoated thiouronium-functionalised polystyrene appeared to facilitate the attachment of titanium dioxide nanoparticles. Interaction assays included the use of XPS analysis and processes such as centrifugation. Attempts to synthesise 4-vinyl catechol, a compound containing hydroxyl moieties with potential for coordination with titanium dioxide nanoparticles, were also carried out using 3,4-dihydroxybenzaldehyde as the starting material.