Obituary - Rigid contact lenses

Scleral and corneal rigid lenses represented 100 per cent of the contact lens market immediately prior to the invention of soft lenses in the mid-1960s. In the United Kingdom today, rigid lenses comprise 2 per cent of all new lens fits. Low rates of rigid lens fitting are also apparent in 27 other countries which have recently been surveyed. Thus, the 1998 prediction of the author that rigid lenses – also referred to as ‘rigid gas permeable’ (RGP) lenses or ‘gas permeable’ (GP) lenses – would be obsolete by the year 2010 has essentially turned out to be correct. In this obituary, the author offers 10 reasons for the demise of rigid lens fitting: initial rigid lens discomfort; intractable rigid lens-induced corneal and lid pathology; extensive soft lens advertising; superior soft lens fitting logistics; lack of rigid lens training opportunities; redundancy of the rigid lens ‘problem solver’ function; improved soft toric and bifocal/varifocal lenses; limited uptake of orthokeratology; lack of investment in rigid lenses; and the emergence of aberration control soft lenses. Rigid lenses are now being fitted by a minority of practitioners with specialist skills/training. Certainly, rigid lenses can no longer be considered as a mainstream form of contact lens correction. May their dear souls (bulk properties) rest in peace.

In vivo performance of melimine as an antimicrobial coating for contact lenses in models of CLARE and CLPU

Purpose: One strategy to minimize bacteria-associated adverse responses such as microbial keratitis, contact lens–induced acute red eye (CLARE), and contact lens induced peripheral ulcers (CLPUs) that occur with contact lens wear is the development of an antimicrobial or antiadhesive contact lens. Cationic peptides represent a novel approach for the development of antimicrobial lenses.---------- Methods: A novel cationic peptide, melimine, was covalently incorporated into silicone hydrogel lenses. Confirmation tests to determine the presence of peptide and anti-microbial activity were performed. Cationic lenses were then tested for their ability to prevent CLPU in the Staphylococcus aureus rabbit model and CLARE in the Pseudomonas aeruginosa guinea pig model. ---------- Results: In the rabbit model of CLPU, melimine-coated lenses resulted in significant reductions in ocular symptom scores and in the extent of corneal infiltration (P < 0.05). Evaluation of the performance of melimine lenses in the CLARE model showed significant improvement in all ocular response parameters measured, including the percentage of eyes with corneal infiltrates, compared with those observed in the eyes fitted with the control lens (P ≤ 0.05). ---------- Conclusions: Cationic coating of contact lenses with the peptide melimine may represent a novel method of prevention of bacterial growth on contact lenses and consequently result in reduction of the incidence and severity of adverse responses due to Gram-positive and -negative bacteria during lens wear.

Pull-out strength of steel roof and wall cladding systems

When steel roof and wall cladding systems are subjected to wind uplift/suction forces, local pull-through/dimpling failures or pull-out failures occur prematurely at their screwed connections. During extreme wind events such as storms and hurricanes, these localized failures then lead to severe damage to buildings and their contents. An investigation was therefore carried out to study the failure that occurs when the screw fastener pulls out of the steel battens, purlins, or girts. Both two-span cladding tests and small-scale tests were conducted using a range of commonly used screw fasteners and steel battens, purlins, and girts. Experimental results showed that the current design formula may not be suitable unless a reduced capacity factor of 0.4 is used. Therefore, an improved design formula has been developed for pull-out failures in steel cladding systems. The formula takes into account thickness and ultimate tensile strength of steel, along with thread diameter and the pitch of screw fasteners, in order to model the pull-out behavior more accurately. This paper presents the details of this experimental investigation and its results.

The impact of community health professional contact postpartum on breastfeeding at 3 months : a cross-sectional retrospective study

This study investigated the effect of any health professional contact and the types of contact new mothers received in the first 10 days post-discharge on breastfeeding rates at 3 months. This cross-sectional retrospective self-report survey was distributed to women who birthed in Queensland, Australia between 1st February and 31st May 2010 at 4–5 months postpartum. Data were collected on pregnancy, birth, postpartum care and infant feeding. Logistic regression was used to assess the relationship between health professional contact and breastfeeding at 3 months. Data were analysed by birthing facility sector because of significant differences between sectors in health professional contact. The study cohort consisted of 6,852 women. Women in the public sector were more likely to be visited at home than women birthing in the private sector. Any health professional contact (AOR 1.65 99 % CI 0.98–2.76 public sector, AOR 0.78 99 % CI 0.59–1.03 private sector) and home visits (AOR 1.50 99 % CI 0.89–2.54 public sector, AOR 0.80 99 % CI 0.46–1.39 private sector) were not associated with breastfeeding at 3 months in either sector. A telephone call (AOR 2.07 99 % CI 1.06–4.03) or visit to a general practitioner (GP) (AOR 1.83 99 % CI 1.04–3.21) increased the odds of breastfeeding in public sector women. Health professional contact or home visiting in the first 10 days post-discharge did not have a significant impact on breastfeeding rates at 3 months. Post-discharge telephone contact for all women and opportunities for self-initiated clinic visits for women assessed to be at higher risk of ceasing breastfeeding may be the most effective care.

The TFOS International Workshop on Contact Lens Discomfort: report of the contact lens interactions with the ocular surface and adnexa subcommittee

The report of this subcommittee concerns the impact of contact lenses (CLs) on the ocular surface, with a particular emphasis on CL discomfort (CLD). We define the ocular surface, its regional anatomy, and the physiological responses of each region to CL wear.

The epidemiology of microbial keratitis with silicone hydrogel contact lenses

It was widely anticipated that after the introduction of silicone hydrogel lenses, the risk of microbial keratitis would be lower than with hydrogel lenses because of the reduction in hypoxic effects on the corneal epithelium. Large-scale epidemiological studies have confirmed that the absolute and relative risk of microbial keratitis is unchanged with overnight use of silicone hydrogel materials. The key findings include the following: (1) The risk of infection with 30 nights of silicone hydrogel use is equivalent to 6 nights of hydrogel extended wear; (2) Occasional overnight lens use is associated with a greater risk than daily lens use; (3) The rate of vision loss due to corneal infection with silicone hydrogel contact lenses is similar to that seen in hydrogel lenses; (4) The spectrum of causative organisms is similar to that seen in hydrogel lenses, and the material type does not impact the corneal location of presumed microbial keratitis; and (5) Modifiable risk factors for infection include overnight lens use, the degree of exposure, failing to wash hands before lens handling, and storage case hygiene practice. The lack of change in the absolute risk of disease would suggest that exposure to large number of pathogenic organisms can overcome any advantages obtained from eliminating the hypoxic effects of contact lenses. Epidemiological studies remain important in the assessment of new materials and modalities. Consideration of an early adopter effect with studies involving new materials and modalities and further investigation of the impact of second-generation silicone hydrogel materials is warranted.

The role of RGPs in modern practice

Has the 1998 prediction of a well-known contact lens researcher – that rigid contact lenses will be obsolete by the year 2010 – come to fruition? This Eulogy to RGPs will demonstrate why it has. A recent survey of international contact lens prescribing trends shows that rigid lenses constituted less than 5% of all contact lenses prescribed in 16 out of 27 nations surveyed. This compares with rigid lenses representing 100% of all lenses prescribed 1965 and about 40% in 1990). With the wide range of sophisticated soft lens materials available today, including super-permeable silicone hydrogels, and designs capable of correcting astigmatism and presbyopia, there is now no need to fit cosmetic patients with rigid lenses, with the associated intractable problems of rigid lens-induced ptosis, 3 and 9 o’clock, staining, lens binding, corneal warpage and adaptation discomfort. Orthokeratology is largely a fringe application of marginal efficacy, and the notion that rigid lenses arrest myopia progression is flawed. That last bastion of rigid lens practice – fitting patients with severely distorted corneas as in keratoconus – is about to crumble in view of a number of demonstrations by independent research groups of the efficacy of custom-designed wavefront-corrected soft contact lenses for the correction of keratoconus. It is concluded that rigid contact lenses now have no place in modern contact lens practice.

A call for better care: the impact of postnatal contact services on women’s parenting confidence and experiences of postpartum care in Queensland, Australia

Background Universal postnatal contact services are provided in several Australian states, but their impact on women’s postnatal care experience has not been evaluated. Furthermore, there is lack of evidence or consensus about the optimal type and amount of postpartum care after hospital discharge for maternal outcomes. This study aimed to assess the impact of providing Universal Postnatal Contact Service (UPNCS) funding to public birthing facilities in Queensland, Australia on women’s postnatal care experiences, and associations between amount and type (telephone or home visits) of contact on parenting confidence, and perceived sufficiency and quality of postnatal care. Methods Data collected via retrospective survey of postnatal women (N = 3,724) were used to compare women who birthed in UPNCS-funded and non-UPNCS-funded facilities on parenting confidence, sufficiency of postnatal care, and perceived quality of postnatal care. Associations between receiving telephone and home visits and the same outcomes, regardless of UPNCS funding, were also assessed. Results Women who birthed in an UPNCS-funded facility were more likely to receive postnatal contact, but UPNCS funding was not associated with parenting confidence, or perceived sufficiency or perceived quality of care. Telephone contact was not associated with parenting confidence but had a positive dose–response association with perceived sufficiency and quality. Home visits were negatively associated with parenting confidence when 3 or more were received, had a positive dose–response association with perceived sufficiency and were positively associated with perceived quality when at least 6 were received. Conclusions Funding for UPNCS is unlikely to improve population levels of maternal parenting confidence, perceived sufficiency or quality of postpartum care. Where only minimal contact can be provided, telephone may be more effective than home visits for improving women’s perceived sufficiency and quality of care. Additional service initiatives may be needed to improve women’s parenting confidence.

In response: Changes in ultraviolet transmittance of hydrogel and silicone hydrogel contact lenses induced by wear

We thank Dr Shedden and Dr Pall for their insightful comments and the opportunity to clarify a number of points from our work.1 The “protection factor” (PF) expressed as the inverse of the transmittance of contact lens (CL) material (1/Tλ), where T is the percentage transmittance of ultraviolet radiation (UVR) in a given waveband (UVC, UVB or UVA) of the UV spectrum for contact lenses is the standard method for reporting PF values and as such there should not be any controversy. We have calculated the PF for each wavelength across the entire UV spectrum (UVC, UVB, UVA) as presented in figure 3 of our previous publication.1 In that article, we were simply stating the observation when transmission in the UVC spectra band is considered especially because appreciable amounts of potentially carcinogenic short UV wavelengths was shown to be present in sunlight in our region three decades ago2 and these short wavelength photons are reported to be more biologically damaging to ocular tissues.3 In addition, the depletion of the Ozone layer is still continuing. Nevertheless, we understand the concern of the authors that the results of the PF might be confusing to those who are not familiar with the science of UVR and as such we have made some revisions to the findings of the calculated PF...

Assessment of fundamental movement skills in childhood cancer patients

Background The improved treatment protocols and subsequent improved survival rates amongst childhood cancer patients has shifted the focus towards the long-term consequences arising from cancer treatment. Children who have completed cancer treatment are at a greater risk of delayed development, diminished functioning, disability, compromised fundamental movement skill (FMS) attainment and long term chronic health conditions. The aim of the study was to compare FMS of childhood cancer patients with an aged matched healthy reference group. Methods Pediatric cancer patients aged 5-8 years of age (n=26; median age 6.91 years), who completed cancer treatment (<5 years) at the Sydney Children’s Hospital were assessed performing 7 key FMS; sprint, side-gallop, vertical-jump, catch, over-arm throw, kick and leap. Results were compared to the reference group (n=430; 6.56 years). Results Childhood cancer patients scored significantly lower on 3 out of 7 FMS tests when compared to the reference group. These results equated to a significantly lower overall score for FMS. Conclusion This study highlighted the significant deficits in FMS within pediatric patients having completed cancer treatment. In order to reduce the occurrence of significant FMS deficits in this population, FMS interventions maybe warranted to assist in recovery from childhood cancer, prevent late effects and improve the quality of life in survivors of childhood cancer.

Effect of different surface profile on wear of rail steel (AS1085.1) used in Australian heavy-haul railways

The extreme diversity of conditions acting on railways necessitates a variety of experimental approaches to study the critical wear mechanisms that present themselves at the contact interface. This work investigates the effects of contact pressure and geometry in rolling-contact wear tests by using discs with different radii of curvature to simulate the varying contact conditions that may be typically found in the field. It is commonly adapted to line contact interface as it has constant contact pressure. But practical scenario of the rail wheel interface, the contact area increase and contact pressure change as tracks worn off. The tests were conducted without any significant amount of traction, but micro slip was still observed due to contact deformation. Moreover, variation of contact pressure was observed due to contact patch elongation and diameter reduction. Rolling contact fatigue, adhesive and sliding wear were observed on the curved contact interface. The development of different wear regimes and material removal phenomena were analysed using microscopic images in order to broaden the understanding of the wear mechanisms occurring in the rail-wheel contact.

The effectiveness of interventions which promote self-management for people with End Stage Renal Disease undergoing haemodialysis

Review Objectives: This systematic review seeks to establish what best practice is for: Interventions which promote self-management for patients with End Stage Renal Disease (ERSD) undergoing Haemodialysis. Review questions: 1) Do education interventions improve self-management for patients with end stage renal disease? 2) Do psychosocial interventions such as Cognitive Behavioural Therapy, behavioural therapy or other counselling therapies and social support, improve self-management for patients with end stage renal disease? Criteria for considering studies for this review: Types of participants: This component of the review will consider studies with: • All adults over the age of 18 years • Patients with end stage renal disease • Undergoing haemodialysis Types of interventions/Phenomena of Interest: All studies evaluating the following interventions will be considered for inclusion in the review such as: Interventions which promote self management including: • Education interventions. • Psychosocial interventions such as cognitive behavioural therapy and other behavioural therapies, counselling and social support. Types of outcome measures/anticipated outcomes: This component of the review will consider studies that include the following outcomes: • Adherence with haemodialysis treatment, • Depression and/or anxiety, • Quality of life, • Carer burnout, • Social support • Patient satisfaction • Adverse events potentially attributable to the intervention or control treatment • Cost effectiveness of home haemodialysis Keywords chronic kidney failure; renal failure; end stage renal disease; chronic kidney disease

Experimental investigation of wear modes of hardened rail material used in Australian heavy-haul railways

This work investigates the effects of contact pressure and geometry in rolling-contact wear tests by using discs with different radii of curvature to simulate the varying contact conditions that may be typically found in the field. The tests were conducted without any significant amount of traction, but micro slip was still observed due to contact deformation. Moreover, variation of contact pressure was observed due to contact patch elongation and diameter reduction. Rolling contact fatigue, adhesive and sliding wear were observed on the curved contact interface. The development of different wear regimes and material removal phenomena were analyzed using microscopic images in order to broaden the understanding of the wear mechanisms occurring in the rail-wheel contact.

Fasteners in Composite Plates - Effects of Interfacial Friction

The effects of tangential friction at pin—hole interfaces are appropriately modelled for the analysis of fasteners in large composite (orthotropic) plate loaded along its edges. The pin—hole contact could be of interference, clearance or neat fit. When the plate load is monotonically increased, interference fits give rise to receding contact, whereas clearance fits result in advancing contact. In either case, the changing contact situations lead to non-linear moving boundary value problems. The neat fit comes out as a special case in which the contact and separation regions are invariant with the applied load level and so the problem remains linear. The description of boundary conditions in the presence of tangential friction, will depend on whether the problem is one of advancing or receding contact, advancing contact presenting a special problem. A model is developed for the limiting case of a rigid pin and an ideally rough interface (infinitely large friction coefficient). The non-linearity resulting from the continuously varying proportions of contact and separation at the interface, is handled by an “Inverse Formulation” which was successfully applied earlier by the authors for smooth (zero friction) interfacial conditions. The additional difficulty introduced by advancing contact is handled by adopting a “Marching Solution”. The modelling and the procedure are illustrated in respect of symmetric plate load cases. Numerical results are presented bringing out the effects of interfacial friction and plate orthotropy on load-contact relations and plate stresses.

Analysis of a finite composite plate with smooth rigid pin

A continuum method of analysis is presented in this paper for the problem of a smooth rigid pin in a finite composite plate subjected to uniaxial loading. The pin could be of interference, push or clearance fit. The plate is idealized to an orthotropic sheet. As the load on the plate is progressively increased, the contact along the pin-hole interface is partial above certain load levels in all three types of fit. In misfit pins (interference or clearance), such situations result in mixed boundary value problems with moving boundaries and in all of them the arc of contact and the stress and displacement fields vary nonlinearly with the applied load. In infinite domains similar problems were analysed earlier by ‘inverse formulation’ and, now, the same approach is selected for finite plates. Finite outer domains introduce analytical complexities in the satisfaction of boundary conditions. These problems are circumvented by adopting a method in which the successive integrals of boundary error functions are equated to zero. Numerical results are presented which bring out the effects of the rectangular geometry and the orthotropic property of the plate. The present solutions are the first step towards the development of special finite elements for fastener joints.