An international survey of daily disposable contact lens prescribing

Purpose The aim was to determine the extent of daily disposable contact lens prescribing worldwide and to characterise the associated demographics and fitting patterns. Methods Up to 1,000 survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for five consecutive years (2007 to 2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected since 1996 were also analysed for seven nations to assess daily disposable lens fitting trends since that time. Results Data were collected in relation to 97,289 soft lens fits, of which 23,445 (24.1 per cent) were with daily disposable lenses and 73,170 (75.9 per cent) were with reusable lenses. Daily disposable lens prescribing ranged from 0.6 per cent of all soft lenses in Nepal to 66.2 per cent in Qatar. Compared with reusable lens fittings, daily disposable lens fittings can be characterised as follows: older age (30.0 ± 12.5 versus 29.3 ± 12.3 years for reusable lenses); males are over-represented; a greater proportion of new fits versus refits; 85.9 per cent hydrogel; lower proportion of toric and presbyopia designs and a higher proportion of part-time wear. There has been a continuous increase in daily disposable lens prescribing between 1996 and 2011. The proportion of daily disposable lens fits (as a function of all soft lens fits) is positively related to the gross domestic product at purchasing power parity per capita (r2 = 0.55, F = 46.8, p < 0.0001). Conclusions The greater convenience and other benefits of daily disposable lenses have resulted in this modality capturing significant market share. The contact lens field appears to be heading toward a true single-use-only, disposable lens market.

International survey of rigid contact lens fitting

Purpose To determine the extent of rigid contact lens fitting worldwide and to characterize the associated demographics and fitting patterns. Methods Survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for five consecutive years (2007 to 2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected between 1996 and 2011 were also analyzed to assess rigid lens fitting trends in seven nations during this period. Results Data were obtained for 12,230 rigid and 100,670 soft lens fits between 2007 and 2011. Overall, rigid lenses represented 10.8% of all contact lens fits, ranging from 0.2% in Lithuania to 37% in Malaysia. Compared with soft lens fits, rigid lens fits can be characterized as follows: older age (rigid, 37.3 ± 15.0 years; soft, 29.8 ± 12.4 years); fewer spherical and toric fits; more bifocal/multifocal fits; less frequent replacement (rigid, 7%; soft, 85%); and less part-time wear (rigid, 4%; soft, 10%). High-Dk (contact lens oxygen permeability) (36%) and mid-Dk (42%) materials are predominantly used for rigid lens fitting. Orthokeratology represents 11.5% of rigid contact lens fits. There has been a steady decline in rigid lens fitting between 1996 and 2011. Conclusions Rigid contact lens prescribing is in decline but still represents approximately 10% of all contact lenses fitted worldwide. It is likely that rigid lenses will remain as a viable, albeit increasingly specialized, form of vision correction.

Cataract surgery in eyes with low corneal astigmatism : implantation of the AcrySof IQ Toric SN6AT2 intraocular lens

Purpose The aim of this study is to assess the refractive and visual outcomes following cataract surgery and implantation of the AcrySof IQ Toric SN6AT2 intraolcular lens (IOL) (Alcon Laboratories, Inc) in patients with low corneal astigmatism. Materials and Methods A retrospective, consecutive, single surgeon series of ninety-eight eyes of 88 patients following cataract surgery and implantation of the AcrySof IQ Toric SN6AT2 IOL in eyes with low preoperative corneal astigmatism. Postoperative measurements were obtained at one month post surgery. Main outcome measures were monocular distance visual acuity and residual refractive astigmatism. Results The mean preoperative corneal astigmatic power vector (APV) was 0.38 ± 0.09 D. Following surgery and implantation of the toric IOL, mean postoperative refractive APV was 0.13 ± 0.10 D. Mean postoperative distance uncorrected visual acuity (UCVA) was 0.08 ± 0.09 logMAR. Postoperative spherical equivalent refraction (SER) resulted in a mean of - 0.23 ± 0.22 D, with 96% of eyes falling within 0.50 D of the target SER. Conclusions The AcrySof IQ Toric SN6AT2 IOL is a safe and effective option for eyes undergoing cataract surgery with low amounts of preoperative corneal astigmatism.

Myopic anisometropia : ocular characteristics and aetiological considerations

Anisometropia represents a unique example of ocular development, where the two eyes of an individual, with an identical genetic background and seemingly subject to identical environmental influences, can grow asymmetrically to produce significantly different refractive errors. This review provides an overview of the research examining myopic anisometropia, the ocular characteristics underlying the condition and the potential aetiological factors involved. Various mechanical factors are discussed, including corneal structure, intraocular pressure and forces generated during near work that may contribute to development of anisomyopia. Potential visually guided mechanisms of unequal ocular growth are also explored, including the influence of astigmatism, accommodation, higher-order aberrations and the choroidal response to altered visual experience. The association between binocular vision, ocular dominance and asymmetric refraction is also considered, along with a review of the genetic contribution to the aetiology of myopic anisometropia. Despite a significant amount of research into the biomechanical, structural and optical characteristics of anisometropic eyes, there is still no unifying theory, which adequately explains how two eyes within the same visual system grow to different endpoints.

The visual and functional impacts of astigmatism and its clinical management

Purpose: To provide a comprehensive overview of research examining the impact of astigmatism on clinical and functional measures of vision, the short and longer term adaptations to astigmatism that occur in the visual system, and the currently available clinical options for the management of patients with astigmatism. Recent findings: The presence of astigmatism can lead to substantial reductions in visual performance in a variety of clinical vision measures and functional visual tasks. Recent evidence demonstrates that astigmatic blur results in short-term adaptations in the visual system that appear to reduce the perceived impact of astigmatism on vision. In the longer term, uncorrected astigmatism in childhood can also significantly impact on visual development, resulting in amblyopia. Astigmatism is also associated with the development of spherical refractive errors. Although the clinical correction of small magnitudes of astigmatism is relatively straightforward, the precise, reliable correction of astigmatism (particularly high astigmatism) can be challenging. A wide variety of refractive corrections are now available for the patient with astigmatism, including spectacle, contact lens and surgical options. Conclusion: Astigmatism is one of the most common refractive errors managed in clinical ophthalmic practice. The significant visual and functional impacts of astigmatism emphasise the importance of its reliable clinical management. With continued improvements in ocular measurement techniques and developments in a range of different refractive correction technologies, the future promises the potential for more precise and comprehensive correction options for astigmatic patients.

Macular retinal layer thickness in childhood

Purpose To examine macular retinal thickness and retinal layer thickness with spectral domain optical coherence tomography (OCT) in a population of children with normal ocular health and minimal refractive errors. Methods High resolution macular OCT scans from 196 children aged from 4 to 12 years (mean age 8 ± 2 years) were analysed to determine total retinal thickness and the thickness of 6 different retinal layers across the central 5 mm of the posterior pole. Automated segmentation with manual correction was used to derive retinal thickness values. Results The mean total retinal thickness in the central 1 mm foveal zone was 255 ± 16 μm, and this increased significantly with age (mean increase of 1.8 microns per year) in childhood (p<0.001). Age-related increases in thickness of some retinal layers were also observed, with changes of highest statistical significance found in the outer retinal layers in the central foveal region (p<0.01). Significant topographical variations in thickness of each of the retinal layers were also observed (p<0.001). Conclusions Small magnitude, statistically significant increases in total retinal thickness and retinal layer thickness occur from early childhood to adolescence. The most prominent changes appear to occur in the outer retinal layers of the central fovea.

Peripapillary choroidal thickness in childhood

Changes in the thickness of the invivo peripapillary choroid have been documented in a range of ocular conditions in adults; however, choroidal thickness in the peripapillary region of children has not been examined in detail. This study therefore aimed to investigate the thickness of the peripapillary choroid and the overlying retinal nerve fibre layer (RNFL) in a population of normal children with a range of refractive errors. Ninety-three children (37 myopes and 56 non-myopes) aged between 11 and 16 years, had measurements of peripapillary choroidal and RNFL thickness derived from enhanced depth imaging optical coherence tomography images (EDI-OCT, Heidelberg Spectralis). The average thickness was determined in a series of five 0.25 mm width concentric annuli (each divided into 8 equal sized 45° sectors) centred on the optic nerve head boundary, accounting for individual ocular magnification factors and the disc-fovea angle. Significant variations in peripapillary choroidal thickness were found to occur with both annulus location (p<0.001) and sector position (p<0.001) in this population of children. The innermost annulus (closest to the edge of the optic disc) exhibited the thinnest choroid (mean 77 ± 16 μm) and the outermost annulus, the thickest choroid (191 ± 52 μm). The choroid was thinnest inferior to the optic nerve head (139 ± 38 μm) and was thickest in the superior temporal sector (157 ± 40 μm). Significant differences in the distribution of choroidal thickness were also associated with myopia, with myopic children having significantly thinner choroids in the inner and outer annuli of the nasal and temporal sectors respectively (p<0.001). RNFL thickness also varied significantly with annulus location and sector (p<0.001), and showed differences in thickness distribution associated with refractive error. This study establishes the normal variations in the thickness of the peripapillary choroid with radial distance and azimuthal angle from the optic nerve head boundary. A significant thinning of the peripapillary choroid associated with myopia in childhood was also observed in both nasal and temporal regions. The changes in peripapillary RNFL and choroidal thickness associated with refractive error are consistent with a redistribution of these tissues occurring with myopic axial elongation in childhood.

Blur, eye movements and performance on a driving visual recognition slide test

Purpose Optical blur and ageing are known to affect driving performance but their effects on drivers' eye movements are poorly understood. This study examined the effects of optical blur and age on eye movement patterns and performance on the DriveSafe slide recognition test which is purported to predict fitness to drive. Methods Twenty young (27.1 ± 4.6 years) and 20 older (73.3 ± 5.7 years) visually normal drivers performed the DriveSafe under two visual conditions: best-corrected vision and with +2.00 DS blur. The DriveSafe is a Visual Recognition Slide Test that consists of brief presentations of static, real-world driving scenes containing different road users (pedestrians, bicycles and vehicles). Participants reported the types, relative positions and direction of travel of the road users in each image; the score was the number of correctly reported items (maximum score of 128). Eye movements were recorded while participants performed the DriveSafe test using a Tobii TX300 eye tracking system. Results There was a significant main effect of blur on DriveSafe scores (best-corrected: 114.9 vs blur: 93.2; p < 0.001). There was also a significant age and blur interaction on the DriveSafe scores (p < 0.001) such that the young drivers were more negatively affected by blur than the older drivers (reductions of 22% and 13% respectively; p < 0.001): with best-corrected vision, the young drivers performed better than the older drivers (DriveSafe scores: 118.4 vs 111.5; p = 0.001), while with blur, the young drivers performed worse than the older drivers (88.6 vs 95.9; p = 0.009). For the eye movement patterns, blur significantly reduced the number of fixations on road users (best-corrected: 5.1 vs blur: 4.5; p < 0.001), fixation duration on road users (2.0 s vs 1.8 s; p < 0.001) and saccade amplitudes (7.4° vs 6.7°; p < 0.001). A main effect of age on eye movements was also found where older drivers made smaller saccades than the young drivers (6.7° vs 7.4°; p < 0.001). Conclusions Blur reduced DriveSafe scores for both age groups and this effect was greater for the young drivers. The decrease in number of fixations and fixation duration on road users, as well as the reduction in saccade amplitudes under the blurred condition, highlight the difficulty experienced in performing the task in the presence of optical blur, which suggests that uncorrected refractive errors may have a detrimental impact on aspects of driving performance.

Future switching technology: bacterial protein-based programmable all-optical switch for integrated optics applications?

We report on the bacterial protein-based all-optical switches which operate at low laser power, high speed and fulfil most of the requirements to be an ideal all-optical switch without any moving parts involved. This consists of conventional optical waveguides coated with bacteriorhodopsin films at switching locations. The principle of operation of the switch is based on the light-induced refractive index change of bacteriorhodopsin. This approach opens the possibility of realizing proteinbased all-optical switches for communication network, integrated optics and optical computers.

Longitudinal changes in choroidal thickness and eye growth in childhood

PURPOSE To examine longitudinal changes in choroidal thickness and axial length in a population of children with a range of refractive errors. METHODS One hundred and one children (41 myopes and 60 nonmyopes) aged 10 to 15 years participated in this prospective, observational longitudinal study. For each child, 6-month measures of choroidal thickness (using enhanced depth imaging optical coherence tomography) and axial ocular biometry were collected four times over an 18-month period. Linear mixed-models were used to examine the longitudinal changes in choroidal thickness and the relationship between changes in choroidal thickness and axial eye growth over the study period. RESULTS A significant group mean increase in subfoveal choroidal thickness was observed over 18 months (mean increase 13 6 22 lm, P < 0.001). Myopic children exhibited significantly thinner choroids compared with nonmyopic children (P < 0.001), although there was no significant time by refractive group interaction (P ¼ 0.46), indicating similar changes in choroidal thickness over time in myopes and nonmyopes. However, a significant association between the change in choroidal thickness and the change in axial length over time was found (P < 0.001, β = −0.14). Children showing faster axial eye growth exhibited significantly less choroidal thickening over time compared with children showing slower axial eye growth. CONCLUSIONS A significant increase in choroidal thickness occurs over an 18-month period in normal 10- to 15-year-old children. Children undergoing faster axial eye growth exhibited less thickening and, in some cases, a thinning of the choroid. These findings support a potential role for the choroid in the mechanisms regulating eye growth in childhood.

Longitudinal changes in choroidal thickness in childhood

• Evidence from cross-sectional studies1,2 suggests that choroidal thickness (ChT) varies with age and refractive error in childhood. However, to date there have been no longitudinal studies examining changes in pediatric ChT. • In this prospective study, the longitudinal changes in ChT and its relationship with eye growth were examined in a population of normal children with a range of refractive errors.

Analysis of a Novel MOEM Race Track Resontor based Vibration Sensor

In this paper we analyze a novel Micro Opto Electro Mechanical Systems (MOEMS) race track resonator based vibration sensor. In this vibration sensor the straight portion of a race track resonator is located at the foot of the cantilever beam with proof mass. As the beam deflects due to vibration, stress induced refractive change in the waveguide located over the beam lead to the wavelength shift providing the measure of vibration. A wavelength shift of 3.19 pm/g in the range of 280 g for a cantilever beam of 1750μm×450m×20μmhas been obtained. The maximum acceleration (breakdown) for these dimensions is 2900g when a safety factor of 2 is taken into account. Since the wavelength of operation is around 1.55μm hybrid integration of source and detector is possible on the same substrate. Also it is less amenable to noise as wavelength shift provides the sensor signal. This type of sensors can be used for aerospace application and other harsh environments with suitable design.

锯齿形板条抽运结构的热效应数值比较

激光二极管抽运的全固态激光器中,除了激光介质的温度分布和热透镜效应以外,抽运、冷却结构对获得高光束质量、高功率激光输出至关重要。基于热传导方程,在相同的抽运功率和传导冷却边界条件下,对单侧面抽运锯齿形(zigzag)板条、单侧面键合锯齿形板条、部分抽运板条三种不同抽运结构的温度分布、热致应力、温度导致的折射率变化进行了详细的分析,并通过光线追迹方法,比较了光束在锯齿形面内和垂直于锯齿形面内的光程差,由光程差曲线分析了激光束的热透镜效应。对三种抽运结构的端面温度、端面变形和端面变形导致的光程差也进行了对比分

飞秒激光与晶体和玻璃的相互作用

总结了飞秒激光与晶体和玻璃相互作用产生的新现象，如光致折射率改变、光致晶体相变、光还原稀土离子及光致发光等。并分析了它们可能的应用。同时简要的介绍了各种现象产生的机理，展望了飞秒激光与其它物质相互作用可能的研究方向及可能出现的新现象。指出了进行这些研究时可能采用的新方法。

Environmental tobacco smoke exposure and eye disease

Aim: To undertake a systematic review of the literature on the effect of environmental tobacco smoke (ETS) and eye disease. Methods: Medline (1950-January Week 2 2007), EMBASE (1980 to 2007 Week 07), SCOPUS and Science Direct were searched on ETS exposure and eye disease using various combinations of the following terms: passive smoking, environmental tobacco smoke, sidestream smoke, involuntary smoking, secondhand smoke; with eye, conjunctiva, sclera, episclera, cornea, lens, iris, retina, choroid, uvea, optic nerve, uveitis, iritis, blindness, visual loss, cataract, thyroid eye disease, conjunctivitis, age-related macular degeneration, dry eye, tears. The above terms were also used to search abstracts published on The Association for Research in Vision and Ophthalmology Annual Meeting abstracts, from 1995 to 2006, and the grey literature, including PhD and MSc theses/dissertations. A search was further conducted specifically on eye diseases where active smoking has been proposed to be a risk factor, including age-related macular degeneration, Graves ophthalmology, glaucoma, uveitis, refractive errors, strabismus, tobacco-alcohol amblyopia, non-arteritic ischaemic optic neuropathy, Leber optic neuropathy and diabetic retinopathy. Given the scarce number of studies found through the above search, all articles found on ETS and eye disease were included in this review. Results: Seven studies evaluated the possible relationship between ETS and an eye disease. These studies referred to refractive errors in children (n = 2), cataract (n = 1), age-related macular degeneration (n = 3) and Grave ophthalmopathy (n = 1). The data available were insufficient to establish conclusive relationships between ETS and these eye diseases. Conclusion: Very scarce data exist in the literature on the effect of ETS on diseases of the eye. It seems appropriate that ETS should be included in future studies addressing the effect of smoking on eye disease.