bluuebunny/crossref_metadata_2025_split huggingface dataset:
Form deprivation myopia: elastic properties of sclera
Authors: Phillips J. R. , McBrien N. A. 
Published: July 2002

SummaryThinning of the posterior sclera may imply that stretching and/or weakening of the sclera plays a role in axial elongation of myopic eyes. We investigated the elastic stress‐strain properties of sclera from developing tree shrew eyes made myopic by monocular deprivation (MD) of form vision. Five days of MD induced a relative myopia (mean ± SEM) of −5.6 D ± 0.6 D (retinoscopy) and a vitreous chamber elongation (deprived minus control) of 106 ± 14 μm, n = 10 (ultrasonography). Posterior scleral test samples (2 mm wide) cut from myopic eyes were significantly thinner than their contralateral eye controls (149 ± 4 μm versus 164 ± 4 μm, n = 10, P < 0.01) when measured with a force‐controlled micrometer. However, posterior sclera from control eyes was significantly thicker than that from age‐matched normal eyes (164 ± 4 μm versus 149 ± 3μm, n = 10, P < 0.01). Under uniaxial tension, posterior scleral samples from myopic eyes failed at 18% lower load (162 g versus 198 g) and extended approximately 25% more than controls at a load corresponding to 20 mm Hg intraocular pressure. These differences were largely accounted for by the differences in scleral thickness. Finite element modelling of tree shrew eyes using the material properties summarised above, implies that simple elastic stretching of the sclera accounts for less than 20% of the observed difference in axial length between myopic and contralateral control eyes.
The Bristol Shared Care Glaucoma Study: study design
Authors: Spencer I. C. , Spry P. G. D. , Gray S. F. , Baker I. A. , Menage M. J. , Easty D. L. , Sparrow J. M. 
Published: July 2002

SummaryThe purpose of this study was the evaluation of community based optometric monitoring of stable glaucoma patients and glaucoma suspects compared to the routine Hospital Eye Services (HES) monitoring. Four hundred and five subjects were recruited from routine outpatient clinics at the Bristol Eye Hospital. All eligible participants were seen in the routine hospital clinic and then within two months were given a ‘Gold Standard Assessment’ (GSA) by an independent research team. Participants then visited one of 12 glaucoma‐trained optometrists, for a standard battery of tests. Randomisation resulted in 204 subjects being allocated to community care, with reviews on a six monthly basis, with 201 who remained a control group within the hospital. Referral criteria were established to enable optometric detection of apparent glaucomatous progression. A questionnaire was used to assess patient satisfaction with both care types. Additionally a cost analysis exercise was performed.
Surface wettability and hydrophilicity of soft contact lens materials, before and after wear
Authors: Shirafkan Abbas , Woodward E. Geoffrey , Port Michael J. A. , Hull Christopher C. 
Published: July 2002

SummarySurface wettability and hydrophilicity of pHEMA soft contact lenses were investigated utilising adherent liquid/laser method (ALLM) and adherent liquid/balance method (ALBM). The measurements were carried out before and after periods of 15 min to 2 h contact lens wear. Following the lens removal, the wetting angle of the contact lens of the left eyes and hydrophilicity (maximum force) of the contact lens of the right eyes of the five subjects were immediately measured, respectively, without cleaning (one value for pre‐lens wear and eight values for post‐lens wear). The wettability of soft contact lenses significantly increased after 15 min of wearing and stabilised at a maximum level after 30 min in vivo. Contact lens hydrophilicity was found to decrease as the lens was worn. The reduction continued for up to 1.5 h of wearing, for male cases, and for the female cases, the reduction continued until the end of the experiment.
Different uses of chromatic signals in patients with congenital and acquired colour vision deficiencies
Authors: Cole V. A. 
Published: July 2002

SummaryChromatic signals can be used to generate perceived colour and also to detect spatially structured objects defined only by chromatic differences. These two attributes have previously been investigated in dichromats and cerebral achromatopsic patients using a new colour vision test developed at City University that makes possible the isolation of pure chromatic signals (Barbur et al. Proc. R. Soc. LondonB 258, 327–334, 19941). We have investigated acquired colour vision changes in a 69‐year‐old patient, after conventional colour vision tests gave ambiguous results. His ability to detect an object using chromatic signals was impaired more than his ability to detect a colour change, and this impairment was greater in the right eye than in the left eye. This dissociation suggests parallel pathways may be involved in the two processes of coding chromatic signals. Recent neurological testing on the same patient has indicated the onset of multiple sclerosis. Our much earlier finding based on colour vision testing may therefore have useful diagnostic implications.
The use of coherence functions in the study of ocular mechanisms
Authors: Eadie A. S. , Pugh J. R. , Winn B. 
Published: July 2002

SummaryThe study of ocular mechanisms is often concerned with the possible interaction of two systems. Spectral analysis has been used previously by many investigators as a tool to investigate the interrelationships in the behaviour of two or more systems. This note demonstrates the value of computing coherence functions following spectral analysis to obtain a more rigorous tool for the investigation of synergy between two systems.
Is there a visual deficit in dyslexia resulting from a lesion of the right posterior parietal lobe?
Authors: Polikoff B. R. , Evans B. J. W. , Legg C. R. 
Published: July 2002

SummaryDyslexia has conventionally been attributed to a left hemisphere deficit affecting language skills. However, it has recently been suggested that two‐thirds of dyslexic people have a lesion of the right posterior parietal lobe (RPPL) resulting in poor oculo‐motor control. It has been reported that neurological patients with RPPL lesions commonly manifest a neglect of the left side of space and this has also been described in clinical observations of ‘visual dyslexics’. We investigated this hypothesis with a sample of 53 dyslexic children and 53 controls using a line‐bisection task. In the horizontal test condition both groups tended to transect slightly to the left of the midpoint (mean displacement 0.14 mm for controls; 0.4 mm for dyslexics). The result suggests a small right side neglect which, contrary to one report in the literature, is found here in developmental dyslexics as well as controls, and leads to the conclusion that RPPL lesion is unlikely to be a common feature of dyslexia.
Elimination and minimization of the spherical aberration of intraocular lenses in high myopia
Authors: González Concepción , Pascual Inmaculada , Bacete Angeles , Fimia Antonio 
Published: July 2002

SummaryBy applying Seidel aberration theory we have studied the spherical aberration of intraocular lenses in place (SIL), and the total spherical aberration of pseudophakic eyes (SIT). The optimum lens shapes for zero SIL and SIT or for minimum SIL and SIT of 12 schematic, highly myopic eyes were investigated. When the power required for emmetropization is positive, the total Seidel spherical aberration of the whole eye cannot be zero but can only be minimized. If the power of the intraocular lens is negative, the total Seidel spherical aberration of the whole eye can be made zero, and one of the optimum lens shapes would be meniscus with the convex surface towards the retina. In addition to improving the quality of the image, the lens has advantages from the physiological point of view, since it helps to maintain the structure of the eye.
Prevalence of spectacle and contact lens wear in the UK fire service
Authors: Margrain Thomas H. , Owen Christopher G. , Woodward E. Geoffrey 
Published: July 2002

SummaryDespite the fact that firefighting has been shown to be a visually demanding occupation, the present visual standards for firefighters prohibit the use of spectacles or contact lenses operationally. To determine the proportion of the UK fire service currently using spectacles and contact lenses, and how many may benefit from optical correction, a questionnaire was distributed. This contained 30 questions and was sent to 1550 firefighters. The data from 1064 returned questionnaires have been analysed. The results show that approximately 20% of those serving in the fire service have used an optical correction at some time in their lives. When not working, approximately 6% of firefighters wear spectacles for distance vision and 15% wear them for reading. Only 0.4% of firefighters use contact lenses. Half of this contact lens wearing group use their lenses while on operational duty. In total, approximately 2% of firefighters use an optical correction for operational duties. The results indicate that a high visual standard at the time of entry into an occupation cannot guarantee good vision throughout an individual's career. In addition, an estimated 11 000 firefighters in the UK, who have spectacles or contact lenses, do not use them for operational duties. The present visual standards prevent this group of firefighters from obtaining their optimal visual performance at work.
An evaluation of the keratoconic cornea using computerised corneal mapping and ultrasonic measurements of corneal thickness
Authors: Owens Helen , Watters Grant A. 
Published: July 2002

SummaryReports indicate the presence of up to three independent cone shapes in keratoconus (round/oval/global) but the preponderance of one cone over another is unclear. This work evaluates keratoconic corneal topography and corneal thickness using videokeratoscopy and ultrasound pachometry, respectively. An EyeSys™ videokeratoscope (VKS) (EyeSys Laboratories, Houston, TX, USA) was used to assess the topography of 54 keratoconic eyes (27 subjects) and 27 age‐matched normals. In addition, ultrasonic pachometry measurements were made over 14 known areas in normal and keratoconic eyes. Corneal thinning was significant for all keratoconic areas measured except for the far temporal cornea. A correlation between corneal radius and thickness was evident. Analysis of cone shape revealed a potential fourth variety: the asymmetric bow‐tie cone. Further topographic evaluation of this cone entity using the VKS revealed its dependence on gaze direction which may account for apparent differences in progression patterns between round and bow‐tie cones.
Determination of the radius of curvature of the anterior lens surface from the Purkinje images
Authors: Smith George , Garner Leon F. 
Published: July 2002

SummaryA new method for calculating the radius of curvature of the anterior surface of the crystalline lens from the measured heights of the Purkinje image PI and PIII is given. Equations are developed for determination of the radius of curvature of the equivalent mirror for three configurations commonly used in phakometry. The method can be applied to targets at any distance from the corneal vertex, for both a stationary target mounted independently of the camera, and for a mobile source attached to the camera where the distance of the target to the corneal vertex will change as the camera is refocused from image PI to PIII. The situation where only one recording is made of images PI and PIII, where the camera is focused on image PI, and the height of the defocused image of PIII is measured is also considered. The errors in calculating the anterior lens radius with the equivalent mirror method if no allowance is made for an object at a finite distance is examined. The new method described is an alternative to collimating targets to overcome the errors in phakometry that occur with targets at finite distances.
Optimal photographic imaging of the bulbar conjunctival vasculature
Authors: Palmer J. R. , Owen C. G. , Ford A. M. , Jacobson R. E. , Woodward E. G. 
Published: July 2002

SummaryA method for imaging the conjunctiva to yield greater contrast between the vasculature and the scleral background, by optimisation of the imaging system, is described. A simple modification to the image capture system, based on first principles calculations, is shown to give images with much improved information content. This will enhance the assessment of hyperaemic changes induced by foreign materials, indicating the degree of biocompatibility, e.g. with contact lenses and ophthalmic medications. Observation of vascular abnormalities associated with pathological conditions may assist in their diagnosis and monitor progressive changes.
Reliability of visual acuity in children with reduced vision
Authors: Kheterpal Sundeep , Jones Helen S. , Auld Rosemary , Moseley Merrick J. 
Published: July 2002

SummaryWe examined the test‐‐retest reliability of visual acuity in 18 children referred to the Hospital Eye Service with reduced vision. Unaided distance acuities were recorded, using logarithmically scaled letter charts, on two occasions separated by an interval of one week during which no clinical intervention took place. Coefficients of repeatability were found to be ±0.25 and ±0.21 log units in left and right eyes, respectively. A further analysis of 14 subjects' data each of whom had one eye with consistently poorer acuity in both test sessions yielded coefficients of repeatability of ±0.15 and ±0.22 log units in, respectively, the better and poorer eyes. The reliability of visual acuity recorded in the better eye closely approximates to that previously found in normal adults, whilst that of the poorer eye appears more comparable to that of adult clinical populations.
Effects of continuous light on experimental refractive errors in chicks
Authors: Guo S. S. , Sivak J. G. , Callender M. G. , Herbert K. L. 
Published: July 2002

SummaryIt is possible to induce ametropias in young chicks either by depriving the developing eye of clear form vision with a translucent goggle or by defocusing the retinal image with convex or concave lenses. The refractive properties of the developing chick eye are also altered by raising young birds in a continuous light environment. The effects of superimposing form deprivation or defocus treatments on chicks raised in continuous light are unclear. Newly hatched (n = 31) chicks were raised for 2 weeks under continuous light while wearing either translucent goggles or + 10 or − 10 diopter (D) lenses over one eye. Refractive states, corneal curvature and intraocular dimensions were measured periodically by retinoscopy, keratometry and A‐scan ultrasound. The birds were sacrificed after 2 weeks and the eyes removed and measured with calipers. Under continuous light, all eyes treated with translucent goggle and − 10D lens developed moderate myopia (− 2.6 ± 0.5 D and − 1.4 ± 0.3 D, respectively) by day 4. The eyes treated with a + 10 D lens developed moderate hyperopia (+ 4.8 ± 0.5 D) at day 4. Corneal curvatures of all treated eyes were slightly, but significantly, larger than contralateral control eyes by day 4. After 2 weeks of goggle or lens application, all the treated eyes were hyperopic due to corneal flattening. But the eyes treated with a goggle or a − 10 D lens still showed relative myopia compared to the fellow eyes (treated minus untreated = − 3.8 ± 0.4 D and − 2.8 ± 0.4 D, respectively), and the eyes treated with a + 10 D lens showed more hyperopia than fellow eyes (treated minus untreated = + 5.1 ± 0.6 D). Compared with the control eyes, the axial length (mainly vitreous chamber depth) was slightly, but significantly, increased in the eyes treated with a goggle or a − 10 D lens, and the axial length decreased slightly in the eyes treated with + 10 D lens. The results suggest that form deprivation and retinal defocus (induced by ± 10 D lenses) could still induce experimental refractive errors (myopia and hyperopia) in chicks kept under continuous light, but the effects of form deprivation and retinal defocus were partially suppressed by continuous light.
Night myopia and driving
Authors: Charman W. N. 
Published: July 2002

SummaryCurrent knowledge of the refractive shifts (twilight myopia, night myopia, dark focus) that occur as the luminance is progressively lowered from photopic levels is reviewed. In complete darkness, myopic changes of the order of 1 dioptre are typical in young adult subjects. These gradually diminish as presbyopia is approached. The possible role of these refractive changes in causing visual difficulties for young drivers on the road at night is considered. It is concluded that high mesopic levels (about 1 cd/m2) of road luminance produced by street and vehicle lighting are normally too great to allow significant refractive shifts to occur, although acuity will be reduced due to light‐dependent neural changes. Under these circumstances it appears unlikely that specific night‐driving prescriptions will be beneficial: the accurate correction of normal refractive errors is, however, more important during night than day driving due to the greater blur associated with the larger night‐time pupil. Suggestions are made for further experimental work in this area.
Therapeutic contact lenses
Authors: Weed Kathryn H. 
Published: July 2002

Therapeutic contact lenses are a rewarding area of optometric practice. Within Sunderland Eye Infirmary a diversity of ocular conditions present, creating a wide range of challenges. A variety of case histories will be discussed.A prosthetic scleral shell was made for a chemical burn injury which presented with symblepharon. A traumatic cataract (caused by a flying contact lens lid) was extracted and an aphakic hydrogel contact lens with an opaque iris print and clear pupil was required to maintain vision and decrease symptoms of glare. Two cases of perforating injury resulting in opaque corneas are shown. In one case the lens was ordered from a trial set, the other prosthetic contact lens was hand‐painted to match a photograph sent to the manufacturer. A hydrogel occlusive pupil contact lens was used to cover a dense white inoperable cataract caused by recurrent chronic uveitis in rheumatoid arthritis. This type of contact lens is also used for diplopia therapy.
Accuracy of a calibrated retinoscope
Authors: Smythe K. L. 
Published: July 2002

Aim: It is not always possible in clinical practice to use a trial frame. We have therefore attempted to compare the accuracy of cylinder axis determination using standard retinoscopy versus a calibrated retinoscope.Methods: We have designed a scale, fitted to a standard retinoscope, which indicates the axis of cylinder. A single experienced retinoscopist determined, in a blind manner, the axis of cylinder using the new calibrated retinoscope and a traditional instrument with a trial frame distant from the eye. Retinoscopy was performed on a model eye using each retinoscope first in a random fashion. The axis of cylinder was set randomly at 5° intervals between 5° and 180°, retinoscopy being performed using each instrument three times at each interval.Results: On χ2 statistical analysis we found the calibrated retinoscope was significantly more accurate to within 5° of the true cylinder axis.Conclusions: The accuracy of the cylinder determination, when refracting without using a trial frame, can be significantly improved to within 5°C of the true axis when using a calibrated retinoscope.
Demonstration of the sodium‐hydrogen exchanger NHE‐1 in corneal endothelial cells
Authors: Rimmer Sharon J. , Wigham Chris G. , Hodson Stuart A. 
Published: July 2002

Purpose: Maintenance of corneal hydration and transparency requires the presence of many membrane transporter proteins in the corneal endothelium, including, it is suggested, a sodium‐hydrogen (Na+/H+) exchanger. This study investigates the presence of the Na+/H+ exchanger (NHE) in bovine and sheep corneal endothelium.Methods: A polyclonal antibody, specific for type 1 Na+/H+ exchanger (NHE‐1), was used to screen bovine and sheep corneal endothelial cells for the presence of NHE activity by the Western blotting technique. Using immunoassay quantification techniques (ELISA), the quantity of NHE‐1 present was measured.Results: Western blot analysis, using the NHE‐1 antibody, recognized proteins with a mass of 70 kDa and 56 kDa in bovine and sheep corneal endothelial cells respectively. From the measured activity of NHE‐1 detected using ELISA and the previously measured cell density, an estimate of the number of NHE‐1 molecules present in each corneal endothelial cell was calculated to be 40 000 per cell.Conclusion: Bovine and sheep corneal endothelium contain type I Na+/H+ exchanger (NHE‐1). Future immunochemical studies will confirm its precise membrane location. This data provides direct evidence of its existence and the quantitative estimate of its concentration in the membrane provides further opportunity to resolve its role in transendothelial bicarbonate ion transport.Acknowledgement: The polyclonal antibody was a generous gift from Prof. L. Fliegel, Department of Biochemistry and Pediatrics, University of Alberta.
Infant emmetropization
Authors: Ehrlich D. L. , Anker S. , Atkinson J. , Braddick O. J. , Weeks F. , Wade J. 
Published: July 2002

Aim: The Cambridge vision screening programme allows the emmetropization process to be described in a large infant population (n = 278 infants). Cycloplegic retinoscopy refraction change between 9 and 20 months of age is described for various refractive components.Methods: Following videorefractive VPR‐1 screening at 75 cm, of over 5000 infants, groups of infants with large lags (>2.8 D) and normal lags (<2.8 D) of accommodation were longitudinally followed‐up. All were non‐strabismic. 1% cyclopentolate retinoscopy results (sphero‐cyl lens neutralized ± 0.5 D) were analysed.Results: For all components, the emmetropization rate significantly correlated with the initial powers (difference v mean correlation R).The relationship of hyperopia and astigmatism reduction will be discussed. Emmetropization in a subgroup of infants wearing spectacles will also be presented.Conclusion: Analysis of infant emmetropization shows the refractive components emmetropize with their rate of reduction related to initial power.Acknowledgement: Supported by Medical Research Council Grant G7908507.
Lectin analysis of endothelial glycoconjugates in the retina of the rat
Authors: Hayes A. J. , Lawrenson J. G. , Allt G. 
Published: July 2002

The vascular endothelial glycocalyx has many important functions such as mediating cell‐cell interactions and possibly a role in permeability. The aim of this study was to investigate the expression of endothelial cell (EC) glycoconjugates in retinal microvessels. Paraffin sections of fixed adult rat retina were treated with a range of biotinylated lectins followed by an avidin‐FITC conjugate. Binding sites for the lectins Canavalia ensiformis (Con A), Ricinus communis (RCA) and Triticum vulgaris (WGA) were expressed Sambicus nigra (SNA), which labels terminal sialic acid residues (NeuNAc) in a 2–6 glycosidic linkage to β galactose (βGal), and Maakia amurensis (MAA), which labels terminal sialic acid when joined in a 2–3 linkage to β galactose, both labelled strongly. In contrast, Ulex europaeus (UEA) and Glycine max (SBA) were negative Arachis hypogaea (PNA), which labels the terminal disaccharide sequence galactose β 1–3 N‐acetylgalactosamine (GalNAc), was strongly positive only after pre‐treatment with the sialic acid digesting enzyme neuraminidase. These suggest a predominance of the oligosaccharide sequence:NeuNAc α 2–3 Gal β 1–3 GalNAc and NeuNAc α 2–6 Gal β 1–3 Gal. These sugar sequences may be significant in the function of the glycocalyx in retinal microvessels.Acknowledgement Supported by the Nuffield Foundation.