Experimental comparison of dynamic tracking performance of iGPS and laser tracker

External metrology systems are increasingly being integrated with traditional industrial articulated robots, especially in the aerospace industries, to improve their absolute accuracy for precision operations such as drilling, machining and jigless assembly. While currently most of the metrology assisted robotics control systems are limited in their position update rate, such that the robot has to be stopped in order to receive a metrology coordinate update, some recent efforts are addressed toward controlling robots using real-time metrology data. The indoor GPS is one of the metrology systems that may be used to provide real-time 6DOF data to a robot controller. Even if there is a noteworthy literature dealing with the evaluation of iGPS performance, there is, however, a lack of literature on how well the iGPS performs under dynamic conditions. This paper presents an experimental evaluation of the dynamic measurement performance of the iGPS, tracking the trajectories of an industrial robot. The same experiment is also repeated using a laser tracker. Besides the experiment results presented, this paper also proposes a novel method for dynamic repeatability comparisons of tracking instruments. © 2011 Springer-Verlag London Limited.

Congenital prosopagnosia in a child:neuropsychological assessment, eye movement recordings and training

Here we report the assessment and treatment of a 6-year-old boy (L.G.) who was referred to us for congenital prosopagnosia (CP). We investigated his performance using a test battery and eye movement recordings pre- and post-training. L.G. showed deficits in recognising relatives and learning new faces, and misrecognition of unfamiliar people. Eye movement recordings showed that L.G. focused on the lower part of stimuli in naming tasks based on familiar or unfamiliar incomplete or complete faces. The training focused on improving his ability to explore internal features of faces, to discriminate specific facial features of familiar and unfamiliar faces, and to provide his family with strategies to use in the future. At the end of the training programme L.G. no longer failed to recognise close and distant relatives and classmates and did not falsely recognise unknown people.

Medical management of diabetic retinopathy:fenofibrate and ACCORD eye studies

The approach of all ophthalmologists, diabetologists and general practitioners seeing patients with diabetic retinopathy should be that good control of blood glucose, blood pressure and plasma lipids are all essential components of modern medical management. The more recent data on the use of fenofibrate in the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) and The Action to Control Cardiovascular Risk in Diabetes (ACCORD) Eye studies is reviewed. In FIELD, fenofibrate (200 mg/day) reduced the requirements for laser therapy and prevented disease progression in patients with pre-existing diabetic retinopathy. In ACCORD Eye, fenofibrate (160 mg daily) with simvastatin resulted in a 40% reduction in the odds of retinopathy progressing over 4 years, compared with simvastatin alone. This occurred with an increase in HDL-cholesterol and a decrease in the serum triglyceride level in the fenofibrate group, as compared with the placebo group, and was independent of glycaemic control. We believe fenofibrate is effective in preventing progression of established diabetic retinopathy in type 2 diabetes and should be considered for patients with pre-proliferative diabetic retinopathy and/or diabetic maculopathy, particularly in those with macular oedema requiring laser. © 2011 Macmillan Publishers Limited All rights reserved.

Diagnosis of retinopathy in children younger than 12 years of age:implications for the diabetic eye screening guidelines in the UK

Aim: To assess whether the current starting age of 12 is suitable for diabetic retinopathy (DR) screening and whether diabetes duration should be taken into account when deciding at what age to start screening patients. Materials and methods: A retrospective analysis of 143 patients aged 12 years or younger who attended diabetic eye screening for the first time in the Birmingham, Solihull and Black Country Diabetic Eye Screening Programme was performed. Results: The mean age of the patients was 10.7 (7-12) years with 73 out of 143 aged below 12 years and 70 were 12 years of age. 98% had type 1 diabetes and mean diabetes duration was 5 (1 month-11 years) years. For those younger than 12 years, 7/73 (9.6%) had background DR (BDR), of these mean diabetes duration was 7 years (6-8). The youngest patient to present with DR was aged 8 years. In those aged 12 years, 5/70 (7.1%) had BDR; of these mean diabetes duration was 8 years (6-11). No patient developed DR before 6 years duration in either group. Conclusions: The results show that no patient younger than the age of 12 had sight-threatening DR (STDR), but BDR was identified. Based on the current mission statement of the Diabetic Eye Screening Programme to identify STDR, 12 years of age is confirmed as the right age to start screening, but if it is important to diabetic management to identify first development of DR, then screening should begin after 6 years of diabetes diagnosis.

Eye-related photophobia

This article provides an overview of the various eye-related causes of photophobia and the likely mechanisms responsible. Photophobia is an experience of discomfort affecting the eyes due to exposure to light. It has a variety of causes including the result of eye or brain disease, or it can be a side effect of various drugs or laser surgery. Photophobia can also be a symptom of a more serious disorder such as meningitis and therefore, requires appropriate investigation, diagnosis, and treatment. Trauma or disease affecting several structures of the eye are a common cause of photophobia and can be associated with: (1) the ocular adnexia, such as blepharitis and blepharospasm, (2) the cornea, including abrasion, ulcerative keratitis, and corneal dystrophy, (3) problems in eye development, such as aniridia, buphthalmos, coloboma, and aphakia, (4) various eye inflammations, including uveitis, and (5) retinal disorders, such as achromatopsia, retinal detachment, and retinal dystrophy. There may be two main explanations for eye-related photophobia: (1) direct stimulation of the trigeminal nerve due to damage, disease, or excessive light entering the eye and (2) overstimulation of the retina including a specific population of light-sensitive ganglion cells.

Clinical characteristics and benefit of cataract intervention amongst UK domiciliary eye care recipients

Purpose: Given the ageing UK population and the high prevalence of activity-limiting illness and disability in the over 65s, the demand for domiciliary eye care services is set to grow significantly. Over 400,000 NHS domiciliary eye examinations are conducted each year, yet minimal research attention has been directed to this mode of practice or patient needs amongst this group. The study aimed to compare clinical characteristics and benefits of cataract surgery between conventional in-practice patients and domiciliary service users. Methods: Clinical characteristics were compared between patients in North-West England receiving NHS domiciliary eye care services (n = 197; median age 76.5 years), and an age-matched group of conventional in-practice patients (n = 107; median age 74.6 years). Data including reason for visit; logMAR uncorrected and best corrected distance (UDVA and CDVA) and near acuities (UNVA and CNVA); presence of ocular pathology and examination outcome were documented retrospectively. To compare the benefit of cataract surgery in terms of functional capacity between the patient groups, individuals undergoing routine referral for first-eye surgery completed the VF-14 questionnaire pre-operatively, and at 6 weeks post-operatively. Results: UDVA was similar between the two groups (median 0.48 and 0.50 logMAR in the domiciliary and practice groups, P = 0.916); CDVA was significantly worse in the domiciliary group (median 0.18 vs 0.08 logMAR, P<0.001), who were more likely to have clinically-significant cataract. Both groups showed similar improvements in VF-14 scores following cataract surgery (mean gains 24.4 ± 11.7, and 31.5 ± 14.7 points in the in-practice and domiciliary groups, respectively. P = 0.312). Conclusions: Patients receiving domiciliary eye care services are more likely to have poorer corrected vision than in-practice patients of a similar age, partly due to a higher prevalence of significant cataract. Despite limitations in their activities due to illness and disability, domiciliary patients experience similar gains in self-reported functional capacity following cataract surgery

Comparative performance between two photogrammetric systems and a reference laser tracker network for large-volume industrial measurement

This paper determines the capability of two photogrammetric systems in terms of their measurement uncertainty in an industrial context. The first system – V-STARS inca3 from Geodetic Systems Inc. – is a commercially available measurement solution. The second system comprises an off-the-shelf Nikon D700 digital camera fitted with a 28 mm Nikkor lens and the research-based Vision Measurement Software (VMS). The uncertainty estimate of these two systems is determined with reference to a calibrated constellation of points determined by a Leica AT401 laser tracker. The calibrated points have an average associated standard uncertainty of 12·4 μm, spanning a maximum distance of approximately 14·5 m. Subsequently, the two systems’ uncertainty was determined. V-STARS inca3 had an estimated standard uncertainty of 43·1 μm, thus outperforming its manufacturer's specification; the D700/VMS combination achieved a standard uncertainty of 187 μm.

The framework of the virtual laser tracker - A systematic approach to the assessment of error sources and uncertainty in laser tracker measurement

Laser trackers have been widely used in many industries to meet increasingly high accuracy requirements. In laser tracker measurement, it is complex and difficult to perform an accurate error analysis and uncertainty evaluation. This paper firstly reviews the working principle of single beam laser trackers and state-of- The- Art of key technologies from both industrial and academic efforts, followed by a comprehensive analysis of uncertainty sources. A generic laser tracker modelling method is formulated and the framework of the virtual tracker is proposed. The VLS can be used for measurement planning, measurement accuracy optimization and uncertainty evaluation. The completed virtual laser tracking system should take all the uncertainty sources affecting coordinate measurement into consideration and establish an uncertainty model which will behave in an identical way to the real system. © Springer-Verlag Berlin Heidelberg 2010.

Verification of the indoor gps system by comparison with points calibrated using a network of laser tracker measurements

This paper details a method of determining the uncertainty of dimensional measurement for a three dimensional coordinate measurement machine. An experimental procedure was developed to compare three dimensional coordinate measurements with calibrated reference points. The reference standard used to calibrate these reference points was a fringe counting interferometer with the multilateration technique employed to establish three dimensional coordinates. This is an extension of the established technique of comparing measured lengths with calibrated lengths. Specifically a distributed coordinate measurement device was tested which consisted of a network of Rotary-Laser Automatic Theodolites (R-LATs), this system is known commercially as indoor GPS (iGPS). The method was found to be practical and able to establish that the expanded uncertainty of the basic iGPS system was approximately 1 mm at a 95% confidence level. © Springer-Verlag Berlin Heidelberg 2010.

Parsing mathematical constructs:results from a preliminary eye tracking study

The semantic model described in this paper is based on ones developed for arithmetic (e.g. McCloskey et al. 1985, Cohene and Dehaene 1995), natural language processing (Fodor 1975, Chomsky 1981) and work by the author on how learners parse mathematical structures. The semantic model highlights the importance of the parsing process and the relationship between this process and the mathematical lexicon/grammar. It concludes by demonstrating that for a learner to become an efficient, competent mathematician a process of top-down parsing is essential.

Exploring business models to provide a foundation for enhanced eye care services in high street optometric practice

High street optometric practices are for-profit businesses. They mostly provide sight testing and eye examination services and sell optical products, such as spectacles and contact lenses. The sight testing services are often sold at a vastly reduced price and profits are generated primarily through high margin spectacle sales, in a loss leading strategy. Published literature highlights weaknesses in this strategy as it forms a barrier to widening the scope of services provided within optometric practices. This includes specialist non-refraction based services, such as shared care. In addition this business strategy discourages investment in advanced diagnostic equipment and higher professional qualifications. The aim of this thesis was to develop a greater understanding of the traditional loss-leading strategy. The thesis also aimed to assess the plausibility of alternative business models to support the development of specialist non-refraction services within high street optometric practice. This research was based on a single independent optometric practice that specialises in advanced retinal imaging and offers a broad range of shared care services. Specialist non-refraction based services were found to be poor generators of spectacle sales likely due to patient needs and presenting concerns. Alternative business strategies to support these services included charging more realistic professional fees via cost-based pricing and monthly payment plans. These strategies enabled specialist services to be more self-sustainable with less reliance on cross-subsidy from spectacle sales. Furthermore, improving operational efficiency can increase stand-alone profits for specialist services.Practice managers may be reluctant to increase professional fees due to market pressures and confidence. However, this thesis found that patients were accepting of increased professional fees. Practice managers can implement alternative business models to enhance eye care provision in high street optometric practices. These alternative business models also improve revenues and profits generated via clinical services and improve patient loyalty.