Visual functions after photorefractive keratectomy

1. 45 myopes (-3.0 to -6.0 D) were examined before and 1 and 6 months after photorefractive keratectomy (PRK). Visual acuity (VA) was tested using Snellen and logMAR charts. Contrast sensitivity (CS) was measured using a computerized system. 2. Preoperative best corrected VA (BCVA) in myopes was significantly lower in comparison with a control group using logMAR charts only. A reduction of BCVA by both methods at 1. month and its return after 6 months nearly to original values was noted. 3. Significantly lower values of CS were found in patients before PRK compared to the control group. After 1 and 6 months stayed the values on preoperative level.     

Visual functions of the elderly

This review of the literature describes the limitations in visual functions that affect the elderly's ability to accomplish the tasks of daily living. Decline in accommodation for near vision begins as early as 10 years of age, while visual acuity begins to diminish at 18 years of age. These and other limitations are the result of normal age-related physiological changes in the mechanisms underlying visual function. In order to compensate for the visual limitations of the elderly, environmental modifications are recommended. The planners of institutional and other environments need to consider architectural features that allow optimal visual performance and, thereby, encourage safe mobility. Adaptations are suggested to assist the elderly in the accomplishment of daily living tasks.     

Visual learning and memory as functions of age

Age-related changes have been reported for a range of perceptual and cognitive functions. We investigated visual acuity and vernier acuity, as well as visual memory and learning, in four age groups, each comprising 10 subjects and ranging from adolescence to an age group up to 66 years. The groups were matched on general abilities for visuospatial information processing. Visual acuity decreased slightly with increasing age. The reproduction of more complex geometrical material which exceeded short-term memory capacities was significantly impaired in the oldest group relative to young adults. However, vernier acuity thresholds and improvement of thresholds with training did not differ in the four groups. Short-term retention of visual stimuli across 1 or 4 sec was also comparable in the different age groups. Those visual abilities that are limited primarily by cortical, not retinal, factors remained relatively unchanged in our observers despite age-related changes in the eye. Visual memory functions which tap working and long-term memory abilities, on the other hand, showed a significant age-associated decline during adulthood.     

Do Multielement Visual Tracking and Visual Search Draw Continuously on the Same Visual Attention Resources?

Multielement visual tracking and visual search are 2 tasks that are held to require visual-spatial attention. The authors used the attentional operating characteristic (AOC) method to determine whether both tasks draw continuously on the same attentional resource (i.e., whether the 2 tasks are mutually exclusive). The authors found that observers can search and track within the same trial significantly better than would be predicted if the 2 tasks were mutually exclusive. In fact, the AOC for tracking and search is similar to that for tracking and auditory monitoring. The results of additional experiments support an attention-switching account for this high level of dual-task performance in which a single attentional resource is efficiently switched between the tracking and search. The results provide important constraints for architectures of visual selective attention and the mechanisms of multielement tracking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual fields and hysteria

Hysteria has long been recognized as a cause of subjective visual field defects. This paper will review the visual field associated with hysteria and examine patient characteristic of those who have shown this type of visual field loss.     

基于VB和Microsoft Excel的高程控制网可视化程序设计

随着计算机技术和测绘行业的发展,利用计算机软件进行测量解算已成为必需。水准测量是测绘学科的一个重要分支,开发水准测量程序具有重要的现实意义。文章介绍了用VB6 0开发水准测量程序及其实现。该程序采用相关间接平差模型,适用于各等级的水准网、三角高程网。它具有水准电子手簿、平差计算和精度评定的功能,操作简单、界面友好,能满足实际工程需要。     

Serum glucose determination with dextrostix and the eyetone reflectance meter

A simple, modified procedure for the Dextrostix-Eyetone system has been evaluated in order to enable the system to measure the concentration of glucose in serum as well as in whole blood. A reduction of the ordinary time of reaction on the Dextrostix from 60 to 45 sec gave serum glucose determinations by the Dextrostix-Eyetone system that correlated almost perfectly with those obtained by a specific conventional laboratory procedure. Thus, the coefficient of correlation was 0.99 and the regression line very close to the ideal line. As the modification is very simple and does not involve any changes in the adjustment of the instrument, it is recommendable in all cases where only serum samples are available.     

焦炭反射率与强度指标及反应性之间的相关性

通过控制偏光显微镜的起偏镜旋转角度可以实现焦炭气孔壁平均最大反射率Rˉmax和平均双反射率Rˉbi的自动测定。经回归分析发现,Rˉmax和焦炭反应性CRI,以及反应后强度CSR之间存在显著的相关关系,相关系数r分别达到－0.926和0.949。Rˉmax和焦炭机械强度DI 15015之间的相关性相对较弱,r为0.704。Rˉbi和焦炭各强度指标之间没有发现明显的相关关系。     

Visual perception and aging.

Reviews a series of studies on aging and its effect on perceptual processing and working memory capacity for visual stimuli. Specifically, studies on luminance, color, motion, texture, and symmetry processing are reported. Furthermore, experiments on the capacity to retain size and spatial frequency information are also discussed. The general conclusion is that there are a number of perceptual abilities that diminish with age. However, the extent of these deficits will depend on the complexity of the neural circuitry involved for processing a given task. This is also true for visual working memory where no evidence of loss due to aging is demonstrated for processing low-level visual information, when individual differences in sensory input are compensated for. It is concluded that perceptual processing deficits due to aging (like working memory) will become evident when the computational load reaches a certain level of complexity (larger or more complex network) even if the tasks remain cognitively simple. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Near-infrared reflectance analysis for predicting beef longissimus tenderness

Near-infrared reflectance spectra (1,100 to 2,498 nm) were collected on beef longissimus thoracis steaks for the purpose of establishing the feasibility of predicting meat tenderness by spectroscopy. Partial least squares (PLS) analysis (up to 20 factors) and multiple linear regression (MLR) were used to predict cooked longissimus Warner-Bratzler shear (WBS) force values from spectra of steaks from 119 beef carcasses. Modeling used the combination of log(1/R) and its second derivative. Overall, absorption was higher for extremely tough steaks than for tender steaks. This was particularly true at wavelengths between 1,100 and 1,350 nm. For PLS regression, optimal model conditions (R2 = .67; SEC = 1.2 kg) occurred with six PLS factors. When the PLS model was tested against the validation subset, similar performance was obtained (R2 = .63; SEP = 1.3 kg) and bias was small (<.3 kg). Among the 39 samples in the validation data set, 48.7, 87.7, and 97.4% of the samples were predicted within 1.0, 2.0, and 3.0 kg, respectively, of the observed Warner-Bratzler shear force value. The optimal PLS model was able to predict whether a steak would have a Warner-Bratzler shear force value < 6 kg with 75% accuracy. The R2 of MLR model was .67, and 89% of samples were correctly classified (< 6 vs > 6 kg) for Warner-Bratzler shear force. These data indicate that NIR is capable of predicting Warner-Bratzler shear force values of longissimus steaks. Refinement of this technique may allow nondestructive measurement of beef longissimus at the processing plant level.     

Shape from shading: estimation of reflectance map

The reflectance map used by the visual system for perception of shape from shading was estimated. In Experiment 1, an image of a cylinder or a sphere illuminated from the viewer's direction was presented, and subjects estimated the cross-section of perceived 3D-shape. The reflectance map was estimated from the relationship between the stimulus image intensities and the slants of the measured cross-section. The estimated reflectance maps were not the ones based on Lambertian reflectance properties. In Experiment 2, whether perceived shapes could be predicted based on the reflectance maps obtained in Experiment 1 was examined. Subjects performed the same shape estimation task with images of cylinders generated by the reflectance map obtained in Experiment 1. The perceived shapes coincided well with the shapes used for stimulus image generation. These results indicate that the visual system's estimation of shape from shading can be fully understood based on empirically obtained reflectance maps without mentioning its inaccurate nature which has been claimed by past studies.     

炼焦煤镜质体反射率及其分布图辨识与分析

为了更好地解析炼焦煤的镜质体反射率及其分布图,阐述了各类混煤的镜质体反射率分布的形态和特征,提出一种直观辨别镜质体反射率分布图中凹口的方法.分析了各类混煤在炼焦配煤中的作用——天然的简单无凹口混煤可视为单一煤层煤;1个凹口的相同煤阶的混煤可视为简单无凹口混煤;天然的1个凹口的相邻煤阶的混煤可视为介于两种相邻煤阶间的一种...