Contact Lens & Anterior Eye - Articles in Press

Abstracts of the 34th BCLA Annual Clinical Conference, Birmingham, 2010 - Corrected Proof

2010-08-19

Void volume variations in contact lens polymers - Corrected Proof

P. Sane, F. Tuomisto, J.M. Holopainen — 2010-07-20

Abstract: Aim: In this study, void size and free volume properties in different contact lens materials have been investigated in their hydrated state using positron annihilation lifetime spectroscopy (PALS).Methods: PALS is used to characterize the void size distributions inside the lens materials. Three different types of contact lenses were used (Balafilcon A, Hilafilcon B and Polymacon).Results: Measurements on different contact lenses reveal significant differences between the materials, up to ∼100% difference in void volume was observed between Hilafilcon B and Balafilcon A, the latter having larger voids. As oxygen diffusion is strongly correlated with the void sizes, the results are in good agreement with the usage recommendations of the specific lens types (daily disposable lenses or 1 month continuous use lenses). The void sizes in monthly lenses (Balafilcon A) were found to decrease 25% under artificial aqueous tear (albumin–water solution) exposure in 4 weeks leading to a significant decrease in the oxygen permeation rate through the contact lens. Yet, the voids were still significantly larger than in disposable or semi-disposable lenses.Conclusions: We have showed that PALS is a viable method to probe the microstructure of biotechnologically relevant polymers and can be used to quantify the void properties in different types of contact lenses. Usage recommendations correlate well with measured void sizes and the median void size decreases during the incubation of albumin solution as a function of time. We anticipate the use of PALS for any polymer-based intracorneal/intraocular device in which diffusivity plays a crucial role.

Global trends in prescribing contact lenses for extended wear - Corrected Proof

2010-07-14

Abstract: Extended wear has long been the ‘holy grail’ of contact lenses by virtue of the increased convenience and freedom of lifestyle which they accord; however, this modality enjoyed only limited market success during the last quarter of the 20th century. The introduction of silicone hydrogel materials into the market at the beginning of this century heralded the promise of successful extended wear due to the superior oxygen performance of this lens type. To assess patterns of contact lens fitting, including extended wear, over the past decade, up to 1000 survey forms were sent to contact lens fitters in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA each year between 2000 and 2009. Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Analysis of returned forms revealed that, averaged over this period, 9% of all soft lenses prescribed were for extended wear, with national figures ranging from 2% in Japan to 17% in Norway. The trend over the past decade has been for an increase from about 5% of all soft lens fits in 2000 to a peak of between 9 and 12% between 2002 and 2007, followed by a decline to around 7% in 2009. A person receiving extended wear lenses is likely to be an older female who is being refitted with silicone hydrogel lenses for full-time wear. Although extended wear has yet again failed to fulfil the promise of being the dominant contact lens wearing modality, it is still a viable option for many people.

Keratoconus: A review - Corrected Proof

Miguel Romero-Jiménez, Jacinto Santodomingo-Rubido, James S. Wolffsohn — 2010-06-01

Abstract: Keratoconus is the most common primary ectasia. It usually occurs in the second decade of life and affects both genders and all ethnicities. The estimated prevalence in the general population is 54 per 100,000.Ocular signs and symptoms vary depending on disease severity. Early forms normally go unnoticed unless corneal topography is performed. Disease progression is manifested with a loss of visual acuity which cannot be compensated for with spectacles. Corneal thinning frequently precedes ectasia. In moderate and advance cases, a hemosiderin arc or circle line, known as Fleischer's ring, is frequently seen around the cone base. Vogt's striaes, which are fine vertical lines produced by Descemet's membrane compression, is another characteristic sign. Most patients eventually develop corneal scarring. Munson's sign, a V-shape deformation of the lower eyelid in downward position; Rizzuti's sign, a bright reflection from the nasal area of the limbus when light is directed to the limbus temporal area; and breakages in Descemet's membrane causing acute stromal oedema, known as hydrops, are observed in advanced stages.Classifications based on morphology, disease evolution, ocular signs and index-based systems of keratoconus have been proposed. Theories into the genetic, biomechanical and biochemical causes of keratoconus have been suggested. Management varies depending on disease severity. Incipient cases are managed with spectacles, mild to moderate cases with contact lenses and severe cases can be treated with keratoplasty. This article provides a review on the definition, epidemiology, clinical features, classification, histopathology, aetiology and pathogenesis, and management and treatment strategies for keratoconus.

Evaluation of the microstructure of cornea by in vivo confocal microscopy in contact lens wearing and non-contact lens wearing keratoconus patients - Corrected Proof

Baris Yeniad, Senay Yilmaz, Lale Kozer Bilgin — 2010-05-24

Abstract: Purpose: To compare the microstructure of the central keratoconic cornea in contact lens wearing and non-contact lens wearing keratoconus subjects.Methods: One hundred and one eyes of 56 keratoconic subjects were compared with control patients who wear contact lenses (22 subjects) and controls who do not wear contact lenses (40 subjects). The keratoconic subjects were assessed in 2 groups: the contact lens wearing keratoconus group (37 patients, 64 eyes, 20 female and 17 male; Group 1) and the keratoconus group comprising subjects who do not wear contact lenses (19 patients, 37 eyes, 9 female, 10 male; Group 2).Results: The mean age was 33±12 years in the contact lens wearer keratoconus group, 31±12 years in the non-contact lens wearer keratoconus group, 34±12 years in the non-contact lens wearing control group and 29±10 years in the contact lens wearing control group. Mean basal epithelial cell density was significantly lower in the contact lens wearer keratoconus group (p<0.001) and in the non-contact lens wearer keratoconus group (p<0.001) in comparison with controls. The anterior, intermediate and posterior keratocyte densities were significantly lower in both contact lens wearer keratoconic subjects (p<0.001, p<0.001, p<0.001) and non-contact lens wearer keratoconic subjects (p<0.001, p<0.001, p=0.004) as compared to controls. Endothelial cell density was not altered in keratoconic patients.Discussion: The decrease in basal epithelial cell density and in keratocyte density may highlight the role of apoptosis in keratoconus. Endothelial cell density does not change in keratoconus, but extensive variability in endothelial cell size and shape may be encountered.

Tear film evaporation—Effect of age and gender - Corrected Proof

Michel Guillon, Cécile Maïssa — 2010-04-12

Abstract: Purpose: Dry eye is more prevalent in older patients and among them more marked in women than men. The increase in dry eye with aging is traditionally thought to be associated with a decrease in tear production enhanced by hormonal changes. Clinical evidence of an abnormal lipid production system in older patients, in particular women is established. It is therefore postulated that the greater prevalence of dry eye problems in an older population has an evaporative component.Methods: Tear film evaporation was measured with the Oregon Health Sciences University Evaporimeter at 30% and 40% humidity.Results: 160 subjects less than 45 years old and 57 subjects aged 45 years or more formed the study population. The results revealed a significant effect of age (p<0.001), gender (p<0.001) and their interaction (p<0.001): (i) the rate of evaporation was higher in the older age group at both humidities; (ii) the rate of evaporation was overall higher for women; and (iii) the synergic effect of age and gender was very marked: the rate of evaporation of older women was 34–80% higher than that of older men and 36–69% than younger women.Conclusions: Aging of the tear film includes a significant evaporative component characterised by higher tear film evaporation for the over 45 compared to younger people. Further, in the over 45 years of age, a significantly greater tear film evaporation was recorded in women than men. The findings have significant implications for the management of presbyopic dry eye sufferers.

Onset time course of solution induced corneal staining - Corrected Proof

2010-03-16

Abstract: Purpose: To evaluate the early phase time course of solution induced corneal staining.Methods and materials: A double masked, single centred, prospective clinical trial was conducted. Twenty-five participants, either experienced or new contact lens wearers, participated in the study. Corneal staining response to short term use of ReNu MultiPlus® Multipurpose Solution and PureVision™ silicon hydrogel contact lens with fluorescein was observed using standard techniques after 15, 30, 45, 60 and 120min of lens wear and graded according to the IER scale. Measurements were carried out on separate days for each time point, in random order.Results: Mean extent of staining was greater in test than in control eyes at all time points except baseline. In test eyes, the degree of staining increased successively at each time point after insertion, up to, but not beyond, 60min. For those participants presenting with staining, maximum severity and frequency were both observed at 60min and were significantly greater (p<0.05) than at 15, 30, and 45min.Conclusion: Solution induced corneal staining gradually increased after lens insertion to a maximum at 1h. This level was maintained until at least 2h post-insertion.

Contact lens user profile, attitudes and level of compliance to lens care - Corrected Proof

Yvonne Wu, Nicole Carnt, Fiona Stapleton — 2010-03-15

Abstract: Purpose: To identify the demographics profile of lens wearers, and to evaluate the scope and level of noncompliant, behaviours in lens wearers.Methods: 210 contact lens wearers who attended an optometry clinic at an education and research institute, were surveyed using a self-administered questionnaire. The questionnaire was constructed to gather information regarding contact lens wearer demographics, contact lens hygiene behaviours and, attitudes toward lens care. Multivariate testing between lens wearers’ demographic, hygiene, behaviours and attitude to aftercare visit were analysed.Results: One hundred and eleven (62%) of participants responded, with a mean age of 33.8±12 years. 55% of the respondents were female. Major non-compliance aspects identified were poor hand hygiene (11%), inadequate cleaning of lenses (13%) and lens storage cases (61%), and wearers not remembering how often they were advised to return for an aftercare (50%). Lens wearers who purchased contact lenses, from the internet were 3.8 times more likely to forget their aftercare schedule than those who purchased contact lenses from the optometrists (95% CI=1.2–12.2, p=0.024).Conclusion: Poor hand hygiene, inadequate lens care, and not remembering when to come back for aftercares are the common non-compliant behaviours in lens wearers. Purchase of lenses via the internet was associated with lack of awareness of aftercare visit.

Metallic intraocular foreign body retained for four years—An unusual presentation - Corrected Proof

Usha K. Raina, Vinod Kumar, Vasu Kumar, Rouli Sud, Neha Goel, Basudeb Ghosh — 2010-03-11

Abstract: Intraocular foreign bodies present a great threat to both sight and the globe of the patient especially if they are metallic and of long duration. We report a case of a metallic intraocular foreign body that presented four years after the initial trauma. The case was successfully managed by a simple technique and the role of ultrasound biomicroscopy (UBM) is highlighted.

Clinical performance of different care systems with silicone hydrogel contact lenses - Corrected Proof

Nancy Keir, Craig A. Woods, Kathryn Dumbleton, Lyndon Jones — 2010-03-04

Abstract: Purpose: To assess the clinical and subjective performance of a one-step hydrogen peroxide (H2O2) lens care system compared to a multi-purpose disinfecting system (MPDS) when used with silicone hydrogel (SiH) lenses.Methods: This was an eight-week, contralateral (lens type) clinical trial with a randomized, cross-over (care system) design. The H2O2 system was Clear Care ((AO Sept Plus) CIBA VISION) and the MPDS was OPTI-FREE RepleniSH (Alcon) and the SiH materials were lotrafilcon B (Air Optix; CIBA VISION) and senofilcon A (Acuvue OASYS, Johnson & Johnson Vision Care). Investigators and subjects were masked to lens care and lens type, respectively. Clinical variables and ocular health assessments were conducted at a baseline, two-week and four-week visit for each cross-over phase. Comfort, dryness and vision were rated on 0–100 scales. Wearing times and comfortable wearing times were also recorded.Results: Twenty-six subjects were enrolled: nine male, 17 female, mean age (±standard deviation) 31±12 years (range 17–59 years) and 24 subjects completed the study. Clinical variables showed no difference between solutions (all p>0.05), however one subject exhibited solution-induced corneal staining with both lens materials and the MPDS. There was no difference between solutions in subjective overall ratings of comfort, dryness or vision (p>0.05). The H2O2 resulted in longer reported comfortable wearing times than the MPDS (10.93±1.71 vs 9.84±1.47h; repeated measures ANOVA, p<0.01).Conclusions: While both lens care systems performed well with the SiH lenses used, the H2O2 resulted in a longer reported comfortable wearing time then the MPDS.

Tear film dynamics and lipid layer characteristics—Effect of age and gender - Corrected Proof

Cécile Maïssa, Michel Guillon — 2010-03-04

Abstract: Purpose: Dry eye disease is significantly more prevalent in older subjects and among them more marked in women than men. Further, it is established that the tear film dynamics of dry eye sufferers is different to that of normal. It is therefore postulated that the greater prevalence of dry eye problems with advancing age is at least in part related to poorer tear film dynamics.Methods: Tear film dynamics (non-invasive break up time) and lipid characteristics (lipid layer thickness and contamination) were assessed using the Tearscope lighting system.Results: 160 Subjects less than 45 years old and 58 subjects aged 45 years or more formed the study populations. The tear film stability was mostly influenced by age; the break up time was statistically significantly shorter for the older age group (p<0.001). The lipid layer was also significantly thinner (p=0.013) for the subjects aged 45 years or older with a very marked synergic effect of age and gender. The lipid layer of older women was significantly thinner and more contaminated than that of younger women (p=0.002 and <0.001) and of older men (p=0.034 and 0.004).Conclusions: Aging of the tear film is characterised by its destabilisation associated with significant changes in the tear lipid layer producing less protection from evaporation in the older population; the observed changes are more marked in women than in men. The findings have significant implications for the management of presbyopic dry eye sufferers, for whom decreasing evaporative problems is essential.

Twenty first century trends in silicone hydrogel contact lens fitting: An international perspective - Corrected Proof

2010-01-07

Abstract: Silicone hydrogel contact lenses were introduced into the market in 1999. To assess prescribing trends of this lens type since then, up to 1000 survey forms were sent to contact lens fitters in Australia, Canada, Japan, the Netherlands, Norway, the UK and the USA each year between 2000 and 2008. Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Analysis of returned forms revealed a rapid increase in the prescribing of silicone hydrogel lenses over the survey period. In 2008, silicone hydrogel lenses represented 36% of all soft lenses prescribed. The categorization of the majority of lenses prescribed as ‘refits’ is primarily attributed to the mass conversion of lens wearers from hydrogel to silicone hydrogel lenses. Silicone hydrogels may soon represent the majority of soft contact lenses prescribed.