bluuebunny/crossref_metadata_2025_split huggingface dataset:
The burgeoning presbyopic population: an emerging 20th century phenomenon
Authors: Pointer Jonathan S. 
Published: March 2003

SummaryImproved social welfare in the wake of the ‘industrial revolution’ set in train in mid‐18th century Britain an escalation in population numbers which has been sustained through to the end of the 20th century—and is projected to continue into the 21st century. However, within the total population envelope the percentage‐contribution of certain age groupings shows a striking pattern when viewed across nearly five centuries. For 350 years, up to the end of the 19th century, the over–40 year old section of the population comprised a steady 25% of the total population count of England (latterly England and Wales): over the same period the 60–plus section contributed nearly 10% of the total. Throughout the ten decades of the 20th century these proportions have both increased, such that with the arrival of the next millennium a two‐fold increase in the percentage‐contribution of both age groups will have occurred: nearly one‐half (over 24 million) of the population of England andWales will be aged over 40, or more than one‐fifth (around 11 million) will be aged over 60 years.This ‘ageing’ of the general population will have economic and socio‐medical implications both at home and abroad, since this is a demographic trend which is present/projected in all countries of the European Union (as presently constituted). The future practise of optometry will certainly be touched by these changes. Naturally a potential increase in demand for presbyopic refractive corrections from the growing volume of aged 40–plus individuals is possible. However of greater significance is the certain increase in age‐related oculo‐visual problems arising from within the growing aged 60‐plus population. Greater acknowledgement and utilisation of the optometrist's skills, currently being reappraised through the profession's participation in ‘collaborative care’ schemes, may indicate the direction in which optometry should move in the early 21st century to remain a valuable—and valued—health care profession.
Daylight simulators and colour vision tests
Authors: Dain Stephen J. 
Published: March 2003

SummaryOur previous studies have shown that the influence of the illuminating source used for colour vision examination on the intended function of the test is very test dependant, some being relatively unaffected by source characteristics while others can be significantly affected. The effects can even differ between the plates of one pseudo‐isochromatic plate test set. In addition, in previous studies we have considered a large range of sources on one test at a time. For this study the emphasis is on four fluorescent tube sources, all of which meet the requirements of the CIE method for assessing the quality of daylight simulators. The colour vision tests include sorting tests (the D‐15 tests [Standard, Lanthony Desat and Adams Desat]), the Lanthony New Colour Test and the FM100 Hue Test, pseudoisochromatic plate tests (Ishihara, Standard Pseudoisochromatic Plates Volume 1, Hahn New Colour Test and Lanthony Tritan Album) and a matching test (TCU Test). Two examples are quoted here. The tests were assessed on the basis of alignment of the colours of the tests to protanopic and deuteranopic confusion axes and, where appropriate, to the tritanopic confusion axis. The data and analysis indicate that the four fluorescent tubes are essentially equivalent.
The effect of spherical and other aberrations upon the modulation transfer of the defocussed human eye
Authors: Jansonius N. M. , Kooijman A. C. 
Published: March 2003

SummaryRelative modulation transfer is defined as contrast sensitivity under blur normalised to contrast sensitivity at optimum focus. Measured relative modulation transfer exceeds relative modulation transfer as calculated for aberration free optics at higher spatial frequencies (>2 cpd). The contribution of spherical aberration to this discrepancy was studied. In the case of positive blur, spherical aberration increases relative modulation transfer for spatial frequencies of approximately 4 cpd and over. However, spherical aberration does not explain the entire difference between measured and calculated relative modulation transfer. Chromatic aberration does not provide a noticeable additional explanation. With negative blur, spherical aberration increases the relative modulation transfer much more. The effect of other monochromatic aberrations on relative modulation transfer is discussed.
The EyeSys videokeratoscopic assessment of apical radius and p‐value in the normal human cornea
Authors: Douthwaite W. A. , Hough T. , Edwards K. , Notay H. 
Published: March 2003

SummaryThe EyeSys videokeratoscope was used to assess the corneal topography in 98 subjects. Scatterplots of distance squared versus radius squared were plotted for the near horizontal and near vertical principal meridians of the two eyes. The regression lines allowed calculation of the surface apical radius and the p‐value. The group average apical radius was 7.93  mm (horizontal) and 7.78  mm (vertical). The group average p‐value was 0.76 (horizontal) and 0.82 (vertical). Both apical radius and p‐value were similar when comparing the two eyes for both the horizontal and the vertical meridians. The two meridians in a single eye, however, had different values for both apical radius and p‐value. Male apical radii were longer than those of females but the p‐values were the same. There is no apparent association between age and either apical radius or p‐value for the subjects used in this study. The asphericity of the cornea does not show any apparent association with corneal curvature in this group of subjects.
Crossed and uncrossed stereoacuity at distance and the effect from heterophoria
Authors: Lam Andrew K. C. , Tse Patrick , Choy Emily , Chung Magic 
Published: March 2003

Background: Previous studies have found that crossed disparities give better stereoacuity than uncrossed. When near phoria is considered, exophores had a better crossed stereoacuity and esophores had a better uncrossed stereoacuity. The current study investigated the effect of heterophoria on distant crossed and uncrossed stereoacuity. Methods: Seventy‐two subjects were recruited and their distant heterophoria measured. Heterophoria within two prism dioptres was considered as orthophoric. Esophoric group had esophoria greater than two prism dioptres. Exophoric group had exophoria greater than two prism dioptres. There were 40 orthophores, 23 exophores and nine esophores. Their stereoacuity was measured with a three‐rod apparatus at 6 m. Results: The mean crossed stereoacuity was 4.8″ and uncrossed stereoacuity was 7.2″ (t=−3.03, p < 0.01). The mean stereoacuity for orthophoric subjects was 5.31″, 6.02″ for exophores and 8.91″ for esophores. The distant crossed stereoacuity is better than uncrossed stereoacuity in all three groups but the difference is only significant for the exophores. Exophoric subjects demonstrated a significant difference between crossed (4.10″) and uncrossed (7.95″) stereoacuity. Conclusions: Orthophores have the best stereoacuity, followed by exophores and esophores. Exophoric subjects have a better crossed than uncrossed stereoacuity. More esophoric subjects should be recruited to confirm the difference between crossed and uncrossed stereoacuity.
The effect of coloured filters on the rate of reading in an adult student population
Authors: Evans Bruce J. W. , Joseph Florence 
Published: March 2003

AbstractMeares–Irlen Syndrome is characterised by visual stress (visual discomfort) and visual perceptual distortions that can be alleviated by individually prescribed coloured filters. The benefit from coloured filters can be demonstrated with the Wilkins Rate of Reading Test (WRRT). Previous research using individually prescribed coloured overlays (sheets of plastic placed on a page) found that between one‐fifth and one‐third of unselected school‐children show a significant (> 5%) improvement in their rate of reading with their chosen overlay. This 5% cut‐off has good sensitivity and specificity for predicting those children who will continue to voluntarily use their overlay for a sustained period. Previous research has concentrated on children, and we sought to investigate the immediate effect of overlays on rate of reading in an adult population. Subjects were 113 unselected university students who answered a symptom questionnaire and were tested with the Wilkins Intuitive Overlays and WRRT. Some symptoms were common: 73% reported sore or tired eyes when reading and 40% reported four to 12 headaches a year. One hundred of the subjects chose an overlay as improving their immediate perception of text. These subjects were significantly more likely to report perceptual distortions and visual discomfort on viewing text than subjects who did not choose an overlay. The 100 subjects read 3.8% faster with the overlay than without any overlay (p < 0.00001), whereas the 13 subjects who did not choose an overlay read 1.7% slower with a placebo overlay than without (p = 0.37). Of the subjects who chose an overlay, 38% read more than 5% faster with the overlay and 2% read more than 25% faster. These results are comparable with those obtained for children. We conclude that Meares–Irlen Syndrome is likely to be as common in adults as it is in children.
Effect of defocus on contrast sensitivity in myopes and non‐myopes
Authors: Radhakrishnan H. , Pardhan S. , Calver R. I. , O'Leary D. J. 
Published: March 2003

Purpose:  Myopes have altered accommodative responses when compared with non‐myopes. We examined the contribution of the optical input to this known altered accommodative response by assessing the defocused contrast sensitivity function in myopes and emmetropes.Methods:  Contrast sensitivity (CS) to 20 spatial frequencies was measured under cycloplegia, with up to ±3 D of defocus, in myopes and non‐myopes. The differences in the contrast sensitivity functions as a result of defocus were analysed for the different spatial frequencies in the two groups. In addition, the optimum defocus at which peak contrast sensitivity occurred was compared between the two groups.Results:  The loss in contrast sensitivity with defocus was less symmetrical with positive and negative defocus in the myopic group, although there was no latent accommodation left following cycloplegia. Defocus decreased contrast sensitivity symmetrically in non‐myopes. The magnitude of decrease in CS was dependent on the spatial frequency tested, and was significantly different in myopes and non‐myopes at 3 and 6 c deg−1.Conclusions:  Differences in the effects of blur on CS exist between myopes and non‐myopes. Existing models of spherical aberration may explain this asymmetry in positive and negative defocus in myopes.
The Role of Carotenoids in Human Health
Authors: Johnson Elizabeth J. 
Published: March 2003

AbstractDietary carotenoids are thought to provide health benefits in decreasing the risk of disease, particularly certain cancers and eye disease. The carotenoids that have been most studied in this regard are β‐carotene, lycopene, lutein, and zeaxanthin. In part, the beneficial effects of carotenoids are thought to be due to their role as antioxidants. β‐Carotene may have added benefits due its ability to be converted to vitamin A. Furthermore, lutein and zeaxanthin may be protective in eye disease because they absorb damaging blue light that enters the eye. Food sources of these compounds include a variety of fruits and vegetables, although the primary sources of lycopene are tomato and tomato products. Additionally, egg yolk is a highly bioavailable source of lutein and zeaxanthin. These carotenoids are available in supplement form. However, intervention trials with large doses of β‐carotene found an adverse effect on the incidence of lung cancer in smokers and workers exposed to asbestos. Until the efficacy and safety of taking supplements containing these nutrients can be determined, current dietary recommendations of diets high in fruits and vegetables are advised.
Cr‐rich magnesiochloritoid eclogites from the Monviso ophiolites (Western Alps, Italy)
Authors: MESSIGA  , KIENAST  , REBAY  , RICCARDI  , TRIBUZIO  
Published: March 2003

Cr‐rich magnesiochloritoid in the eclogitized ophiolites of the Monviso massif occurs in the least differentiated rocks of the gabbroic sequence (troctolites to melatroctolites). Chloritoid (XMg=0.63–0.85; Cr≤0.55, atoms) co‐exists with omphacite, talc and garnet. Minor, syn‐eclogitic minerals are chromite, rutile and sometimes magnesite and Cr–Ti oxides.Coronitic textures, indicative of a static recrystallization, characterize the analysed samples. Layers of variable mineral composition develop among igneous plagioclase, olivine, clinopyroxene and spinel. The minerals in the coronitic layers display sharp compositional zonings. The igneous minerals are commonly not preserved; their presence in the original assemblage is inferred from the mineralogical composition of the pseudomorphs.Syn‐eclogitic volatile components are indicated by the development of OH‐bearing minerals (e.g. chloritoid & talc) and carbonates (e.g. magnesite), and supported by the presence of coarse‐grained and fibrous mineral growths. The complex pseudomorphic replacements of igneous minerals suggest that these rocks changed their mineralogical composition prior to the eclogite facies recrystallization, most likely during ocean‐floor metamorphism. It is suggested that syn‐eclogitic fluids formed by breakdown reactions of pre‐eclogitic volatile‐bearing minerals.Geothermobarometry indicates that the investigated rocks recrystallized at a depth corresponding to 2.4 GPa and temperatures of 620±50 °C. The attainment of high‐pressure conditions is supported by the presence of magnesiochloritoid, magnesite and garnet with high pyrope content (up to 58 mol%). P–T  estimates point to a very low thermal gradient (about 9 °C km−1), comparable to that deduced in the adjacent Dora‐Maira ultra‐high pressure unit.
The geometry and timing of orogenic extension: an example from the Western Italian Alps
Authors: Reddy  , Wheeler  , Cliff  
Published: March 2003

Contacts between rocks recording large differences in metamorphic grade are indicative of major tectonic displacements. Low‐P upon high‐P contacts are commonly interpreted as extensional (i.e. material points on either side of the contact moved apart relative to the palaeo‐horizontal), but dating of deformation and metamorphism is essential in testing such models. In the Western Alps, the Piemonte Ophiolite consists of eclogites (T ≈550–600 °C and P≈18–20 kbar) structurally beneath greenschist facies rocks (T ≈400 °C and P≈9 kbar). Mapping shows that the latter form a kilometre‐wide shear zone (the Gressoney Shear Zone, GSZ) dominated by top‐SE movement related to crustal extension. Rb–Sr data from micas within different GSZ fabrics, which dynamically recrystallized below their blocking temperature, are interpreted as deformation ages. Ages from different samples within the same fabric are reproducible and are consistent with the relative chronology derived from mapping. They show that the GSZ had an extensional deformation history over a period of c. 9 Myr between c. 45–36 Ma. This overlaps in time with the eclogite facies metamorphism. The GSZ operated over the entire period during which the footwall evolved from eclogite to greenschist facies and was therefore responsible for eclogite exhumation. The discrete contact zone between eclogite and greenschist facies rocks is the last active part of the GSZ and truncates greenschist facies folds in the footwall. These final movements were therefore not a major component of eclogite exhumation. Pressure estimates associated with old and young fabrics within the GSZ are comparable, indicating that during extensional deformation there was no significant unroofing of the hangingwall. Since there are no known extensional structures younger than 36 Ma at higher levels in this part of the Alps, exhumation since the final juxtaposition of the two units (at 36 Ma) seems to have been dominated by erosion.Key words: deformation age, eclogite, exhumation, Rb–Sr dating, tectonic.
The garnet–clinopyroxene Fe2+–Mg geothermometer: an updated calibration
Authors: Krogh Ravna  
Published: March 2003

Multiple regression analysis on an extended dataset has been performed to refine the relationship between temperature, pressure, composition and the Fe–Mg distribution between garnet and clinopyroxene. In addition to a significant dependence between the distribution coefficientKDandXGrtCaandXGrtMg#, as shown by the experimental data, the effect ofXGrtMnhas also been incorporated using data from natural Mn‐rich garnet–clinopyroxene pairs. Multiple regression of data (n=360) covering a large span in pressure, temperature and composition from 27 experimental datasets, combined with 49 natural high‐Mn granulites from Ruby Range, Montana, USA, and Karnataka, India, yields theP–T –compositional relationship (r2=0.98):whereKD=(Fe2+/Mg)Grt/(Fe2+/Mg)Cpx,XGrtCa=Ca/(Ca+Mn+Fe2++Mg) in garnet,XGrtMn= Mn/(Ca+Mn+Fe2++Mg) in garnet, andXGrtMg#=Mg/(Mg+Fe2+) in garnet. The Fe2+–Mg equilibrium between garnet and clinopyroxene does not seem to be affected by variations in the sodic content of the co‐existing clinopyroxene in the rangeXCpxNa=0–0.51. Comparisons between the new and former calibrations of the garnet–clinopyroxene Fe2+–Mg geothermometer clearly demonstrate how the various parameters in each case affect the calculated temperatures. Application of the new expression gives reasonable results for natural garnet–clinopyroxene pairs from various rock types and settings, and should be preferred to previous formulations. Using the new calibration to the self‐consistent dataset of Pattison & Newton (Contributions to Mineralogy and Petrology, 1989,101,87–103) suggests a systematic deviation with regard to both temperature and composition between their dataset and the datasets used in the present calibration.
Metamorphism and microstructures along a high‐temperature metamorphic field gradient: the north–eastern boundary of the Královský hvozd unit (Bohemian Massif, Czech Republic)
Authors: Scheuvens D. 
Published: March 2003

AbstractA metamorphic field gradient has been investigated in the Moldanubian zone of the central European Variscides encompassing, from base to the top, a staurolite–kyanite zone, a muscovite–sillimanite zone, a K‐feldspar–sillimanite zone, and a K‐feldspar–cordierite zone, respectively. The observed reaction textures in the anatectic metapsammopelites of the higher grade zones are fully compatible with experimental data and petrogenetic grids that are based on fluid‐absent melting reactions. From structural and microstructural observations it can be concluded that the boundary between the kyanite–staurolite zone and the muscovite‐ and K‐feldspar–sillimanite zones coincides with an important switch in deformation mechanism(s). Besides minor syn‐anatectic shearing (melt‐enhanced deformation), microstructural criteria point (a) to a switch in deformation mechanism from rotation recrystallization (climb‐accommodated dislocation creep) to prism <c> slip and high‐temperature (fast) grain boundary migration in quartz (b) to the activity of diffusion creep in quartz–feldspar layers, and (c) to accommodation of strain by intense shearing in fibrolite–biotite layers. It is suggested that any combination of these deformation mechanisms will profoundly affect the rheological characteristics of high‐grade metamorphic rocks and significantly lower rock strength. Hence, the boundary between these zones marks a major rheological barrier in the investigated cross section and probably also in other low‐ to medium‐pressure/high‐temperature areas. At still higher metamorphic grades (K‐feldspar‐cordierite zone), where the rheologically critical melt percentage is reached, rock rheology is mainly governed by the melt and other deformation mechanisms are of minor importance. In the study area, the switch in deformation mechanism(s) is responsible for large‐scale strain partitioning and concentration of deformation within the higher‐temperature hanging wall during top‐to‐the‐S thrusting, thus preserving a more complete petrostructural record within the rocks of the footwall including indications for a ?Devonian high‐ to medium‐pressure/medium‐temperature metamorphic event. Thrusting is accompanied by diapiric ascent of diatexites of the K‐feldspar‐cordierite zone and infolding of the footwall, suggesting local crustal overturn in this part of the Moldanubian zone.
Discovery of eclogite facies carbonate rocks from the Lindås Nappe, Caledonides, Western Norway
Authors: Boundy T. M. , Donohue C. L. , Essene E. J. , Mezger K. , Austrheim H. 
Published: March 2003

AbstractEclogite facies carbonate rocks have been discovered associated with the granulite–eclogite transitional rocks within Bergen Arc system, Caledonian Orogen of western Norway. The local occurrences of marbles and calc‐silicates are found subparallel to the mafic eclogite facies shear zones on Holsnøy Island. Marbles contain the assemblage calcite (Ca0.99Sr0.01CO3), calcian strontianite (Ca0.18−0.44Sr0.53−0.84CO3), clinopyroxene (Jd7−32), epidote/allanite (Ps0−33), titanite, garnet (Alm52−56Grs28−33Pyp11−16), barite (Ba0.90−0.99Sr0.01−0.10SO4), celestine (Sr0.67−0.98Ba0.01−0.23Ca0.01−0.11SO4), and one apparently homogeneous grain of intermediate composition (Ba0.49Ca0.01Sr0.50SO4). Adjacent eclogites have clinopyroxene with similar jadeite contents (Jd14−34) and similar garnet (Alm51−60Grs26−36Pyp8−14) compositions. The marbles have high contents of Sr (9500–11000 p.p.m) and Y (115–130 p.p.m). However, low concentrations of some key trace elements (110–160 p.p.m. Ba and <5 p.p.m. Nb) appear to indicate that the marble is not a metamorphosed carbonatite. The 87Sr/86Sr ratios range from 0.7051 to 0.7059. Field and petrological relationships suggest that metasomatic reactions and fluids played a significant role in producing and/or modifying the marbles. The breakdown of scapolite in the granulite into carbonates and sulphates during eclogite facies metamorphism may have contributed to the metasomatic formation of the marbles along shear zones.Fluids involved during subduction are an important catalyst for metamorphism and are recognized to have played a critical role in the localized transformation from granulite to eclogite in the Holsnøy Island area. Thermobarometry indicates 640–690 °C and 18–20 kbar for adjacent eclogites and temperatures of 580–650 °C for the calc‐silicates. The marble assemblages are consistent with fluid that is dominantly comprised of H2O (XCO2 < 0.03) under high‐pressure conditions. Phase equilibria of the marbles constrain the fO2 of the fluids and imply oxidizing conditions of the deep crustal fluids. At present the source of the fluids remains unresolved. The results provide additional insights into the variable and evolving nature of fluids related to subduction and high‐pressure metamorphism.