A manual of the principles and practice of ophthalmic medicine and surgery /

Mode of access: Internet.

Principles and practice of ophthalmic medicine and surgery /

Mode of access: Internet.

National apprenticeship standards for ophthalmic finisher-dispenser.

Mode of access: Internet.

Ophthalmic review; a record of ophthalmic science.

Subtitle varies.

The ophthalmic test for glanders.

Mode of access: Internet.

The ophthalmic and intradermic tests for glanders /

Mode of access: Internet.

Synthetic polymers for ophthalmic applications

The contact lens represents a well-established important class of biomaterials. This thesis brings together the literature, mostly Japanese and American patents, concerned with an important group of polymers, `rigid gas permeable contact lens materials'. A comparison is made of similarities in the underlying chemical themes, centring on the use of variants of highly branched siloxy compounds with polymerizable methacrylate groups. There is a need for standard techniques to assess laboratory behaviour in relation to in vitro performance. A major part of the present work is dedicated to the establishment of such standardised techniques. It is apparent that property design requirements in this field (i.e. oxygen permeability, surface and mechanical properties) are to some extent conflicting. In principle, the structural approaches used to obtain high oxygen permeability lead to surface properties that are less than ideal in terms of compatibility with tears. PMMA is known to have uniquely good (but not perfect) surface properties in this respect; it has been used as a starting point in attempting to design new materials that possess a more acceptable compromise of transport and surface properties for ocular use. Initial examination of the oxygen permeabilities of relatively simple alkyl methacrylates, show that butyl methacrylate which has a permeability some fifty times greater than PMMA, represents an interesting and hitherto unexplored group of materials for ophthalmic applications. Consideration was similarly given to surface modification techniques that would produce materials having the ability to sustain coherent tear film in the eye without markedly impairing oxygen transport properties. Particular attention is paid to the use of oxygen plasma techniques in this respect. In conclusion, similar design considerations were applied to an extended wear hydrogel lens material in an attempt to overcome mechanical stability deficiencies which manifest themselves lq`in vivo' but not `in vitro'. A relatively simple structure modification, involving steric shielding of the amide substituent group, proved to be an effective solution to the problem.

Ocular and ophthalmic features of Alzheimer's disease

This article describes the ocular and ophthalmic features that have been dsecribed in AD and identifies those that may be the most characteristic of the disorder.

Comparative performance of analytical techniques for polyhexamethylene biguanide (PHMB) in ophthalmic solutions

Purpose: The use of PHMB as a disinfectant in contact lens multipurpose solutions has been at the centre of much debate in recent times, particularly in relation to the issue of solution induced corneal staining. Clinical studies have been carried out which suggest different effects with individual contact lens materials used in combination with specific PHMB containing care regimes. There does not appear to be, however, a reliable analytical technique that would detect and quantify with any degree of accuracy the specific levels of PHMB that are taken up and released from individual solutions by the various contact lens materials. Methods: PHMB is a mixture of positively charged polymer units of varying molecular weight that has maximum absorbance wavelength of 236 nm. On the basis of these properties a range of assays including capillary electrophoresis, HPLC, a nickelnioxime colorimetric technique, mass spectrophotometry, UV spectroscopy and ion chromatography were assessed paying particular attention to each of their constraints and detection levels. Particular interest was focused on the relative advantage of contactless conductivity compared to UV and mass spectrometry detection in capillary electrophoresis (CE). This study provides an overview of the comparative performance of these techniques. Results: The UV absorbance of PHMB solutions, ranging from 0.0625 to 50 ppm was measured at 236 nm. Within this range the calibration curve appears to be linear however, absorption values below 1 ppm (0.0001%) were extremely difficult to reproduce. The concentration of PHMB in solutions is in the range of 0.0002–0.00005% and our investigations suggest that levels of PHMB below 0.0001% (levels encountered in uptake and release studies) can not be accurately estimated, in particular when analysing complex lens care solutions which can contain competitively absorbing, and thus interfering, species in the solution. The use of separative methodologies, such as CE using UV detection alone is similarly limited. Alternative techniques including contactless conductivity detection offer greater discrimination in complex solutions together with the opportunity for dual channel detection. Preliminary results achieved by TraceDec1 contactless conductivity detection, (Gain 150%, Offset 150) in conjunction with the Agilent capillary electrophoresis system using a bare fused silica capillary (extended light path, 50 mid, total length 64.5 cm, effective length 56 cm) and a cationic buffer at pH 3.2, exhibit great potential with reproducible PHMB split peaks. Conclusions: PHMB-based solutions are commonly associated with the potential to invoke corneal staining in combination with certain contact lens materials. However this terminology ‘PHMBbased solution’ is used primarily because PHMB itself has yet to be adequately implicated as the causative agent of the staining and compromised corneal cell integrity. The lack of well characterised adequately sensitive assays, coupled with the range of additional components that characterise individual care solutions pose a major barrier to the investigation of PHMB interactions in the lenswearing eye.

Professionalisation and ophthalmic optics

This thesis is a sociological study of the ophthalmic optical profession in Britain. It includes a survey of the development of ophthalmic optics as an occupation and three questionnaire, surveys, one each of first and final year ophthalmic optics students, and one of practising opticians. The developmental survey showed that four themes have been important in the occupation's process of professionalisation - the actions of the opticians' leaders, the gradual unification of the bodies, representing segments of the profession, the struggle with medicine and the involvement of ophthalmic opticians in state-organised optical welfare schemes. The student surveys showed that the profession is now recruiting largely from middle class, state educated groups, and increasingly from women, who hold significantly different attitudes to income, independence and career commitment. In general, both first and final year students considered service to be rather more important than furthering knowledge. Practising opticians have been recruited increasingly, from middle class backgrounds, mostly from state selective secondary schools, but with a large minority from non-state schools. The self-recruitment rate of the profession (18.9%) is very similar to that for British medical students. Significant differences in concepts of professionalism were found among ophthalmic opticians of different ages, sexes and types of practice but few among those in different areas of practice. In general, ophthalmic opticians seemed to stress service more·than furthering knowledge. It is suggested that the leaders of the profession have 'negotiated' considerable autonomy for its members and that the possibilities for commercialism within the ophthalmic optician's professional role are intrinsically no greater than those in more 'established' professions.

Ophthalmic factors in dyslexia

Although the role of ophthalmic factors in dyslexia remains the subject of controversy, recent research has indicated that the correlates of dyslexia may include binocular dysfunction, unstable motor ocular dominance, a deficit of the transient visual subsystem, and an anomaly that can be treated with tinted lenses. These features, typically, have been studied in isolation and their inter-relationship has received little attention. The aim of the present research was to investigate ophthalmic factors in dyslexia, with a particular emphasis on the interaction between optometric variables. Further aims were to establish the most appropriate investigative techniques for optometric practice and to explore the relationship between optometric and psychometric variables. A pilot study was used to refine the experimental design for a subsequent detailed study of 39 children with a specific reading disability and 43 good readers, who were selected from 240 children. The groups were matched for age, sex, and performance IQ. The following factors emerged as correlates of dyslexia: slight impaired visual acuity; reduced vergence amplitudes; increased vergence instability; decreased accommodative amplitude; poor peformance at tests that were designed to assess the function of the transient visual system; and slightly slower performance at a non-verbal simulated reading visual search task. The `transient system deficit', as measured by reduced flicker sensitivity, was significantly associated with decreased accommodative and vergence amplitudes. This links the motor and sensory visual correlates of dyslexia. Although the binocular dysfunction was correlated with increased symptoms, the difference in the groups' simulated reading visual search task performance was largely attributable to psychometric variables. The results suggest tht optometric problems may be a contributory factor in dyslexia, but are unlikely to play a key causative role. Several optometric variables were confounded by psychometric parameters, and this interaction should be a priority for future investigation.

Ionic and neutral hydrogels for dermal and ophthalmic applications

This thesis is concerned with the use of ionic and neutral hydrogels in dermal and ocular applications with particular reference to controlled release applications. The work consists of three interconnected themes.The first area of study is the use of skin adhesive bioelectrode hydrogels as ground plate electrodes for ophthalmic iontophoresis applications. The work provides a basis of understanding the relative contributions made by ionic monomers (such as sodium s-(acrylamide)-2-methyl propane sulphonate and acrylic acid-bis-(3-sulfopropyl-ester, potassium salt) and neutral monomers (such as acryloymorpholine, N,N-dimethylacrylamide and N-vinyl pyrrolidone) to adhesion, rheology and impedance of bioelectrode gels. The general advantage of neutral monomers, which have been used to successfully replace ionic monomers, is that they enable more effective control of independent anion and cation species (for example potassium chloride and sodium chloride) unlike ionic monomers where polymerisation produces an immobile polyanion thus limiting cation mobility. Secondly, release from a completely neutral hydrogel under the influence of mechanical shaking was studied for the case of crosslinked polyvinyl alcohol (PVA) containing low concentration of linear soluble PVA in a contact lens application. The soluble PVA was observed to be eluting by reptation from the lens matrix due to the mechanical action of the eyelid. This process was studied in an in vitro model, which in this research was used as a basis for developing a lens made with enhanced release polymer. The third area of work is related to the factors that control drug release (in particular non-steroidal anti-inflammatory drugs) from a hydrogel matrix. This links both electrotherapy applications, such as transcutaneous electrical nerve stimulation, in which the passive diffusion from the gel could be used in conjunction with enhanced transmission across the dermal surface with passive diffusion from a contact lens matrix and the development of therapeutic contact lenses.

Ophthalmic lenses availability:the guide to spectacle lenses, coatings and tints available in the United Kingdom

The guide to spectacle lenses and coatings and tints available in the UK. The Ophthalmic Lenses Availability Guide aims to collate information from lens manufacturers in the UK enabling practitioners to rapidly locate lenses suitable for your patients. Twenty lens and coating manufacturers are represented in the Guide which consists of three sections; the availability index, manufacturer's data and lens data files. In the 2008 edition, the availability index has been updated; arranging lenses by type and then in ascending order of refractive index. Additionally, for progressive power lenses, the corridor length or fitting height is included allowing the practitioner to more rapidly identify a lens which meets the fitting requirements of a selected frame. Further technical information is provided for a selected by going to the appropriate page number in the manufacturer’s section. The lens data files contain additional information on the optical properties of materials, tints and coatings and a summary list of hidden markings on progressive power lenses enabling the practitioner to identify the lens a patient is currently wearing.