Nutritional influences on eye health.

BACKGROUND: As with cardiovascular disease, nutrition and environmental intervention present new clinical practice and research opportunities in eye care. This includes maximizing health potential with food choice, the use of supplementation in high-risk and noncompliant patients, avoiding toxins such as cigarettes, and encouraging exercise. METHOD: The author provides his perspective on viewing biochemical, physiological, and epidemiological research in the context of disease prevention in both common and uncommon applications. In most cases, this approach requires food frequency intake evaluation and application of physiological optics to measure efficacy when there is an alteration in diet and/or addition of supplementation. These are details of ocular integrative medical practice that are ignored or underutilized. RESULTS: There are multiple opportunities for intervention in the age-related diseases of cataract, macular degeneration, and glaucoma. A summary of the application of nutrition to create a model for treatment of age-related macular degeneration is presented. CONCLUSIONS: Economic incentives, now lacking, are required to explore new paradigms in nutritional preventative eye care. Schools and colleges of Optometry could play a vital public health role.     

Macular pigment: influences on visual acuity and visibility

There is increasing evidence that the macular pigment (MP) carotenoids lutein (L) and zeaxanthin (Z) protect the retina and lens from age-related loss. As a result, the use of L and Z supplements has increased dramatically in recent years. An increasing number of reports have suggested that L and Z supplementation (and increased MP density) are related to improved visual performance in normal subjects and patients with retinal and lenticular disease. These improvements in vision could be due either to changes in the underlying biology and/or optical changes. The optical mechanisms, i.e., preferential absorption of short-wave light, underlying these putative improvements in vision, however, have not been properly evaluated. Two major hypotheses are discussed. The acuity hypothesis posits that MP could improve visual function by reducing the effects of chromatic aberration. The visibility hypothesis is based on the idea that MP may improve vision through the atmosphere by preferentially absorbing blue haze (short-wave dominant air light that produces a veiling luminance when viewing objects at a distance).     

Ground-plane influences on size estimation in early visual processing

Ground-planes have an important influence on the perception of 3D space (Gibson, 1950) and it has been shown that the assumption that a ground-plane is present in the scene plays a role in the perception of object distance (Bruno & Cutting, 1988). Here, we investigate whether this influence is exerted at an early stage of processing, to affect the rapid estimation of 3D size. Participants performed a visual search task in which they searched for a target object that was larger or smaller than distracter objects. Objects were presented against a background that contained either a frontoparallel or slanted 3D surface, defined by texture gradient cues. We measured the effect on search performance of target location within the scene (near vs. far) and how this was influenced by scene orientation (which, e.g., might be consistent with a ground or ceiling plane, etc.). In addition, we investigated how scene orientation interacted with texture gradient information (indicating surface slant), to determine how these separate cues to scene layout were combined. We found that the difference in target detection performance between targets at the front and rear of the simulated scene was maximal when the scene was consistent with a ground-plane - consistent with the use of an elevation cue to object distance. In addition, we found a significant increase in the size of this effect when texture gradient information (indicating surface slant) was present, but no interaction between texture gradient and scene orientation information. We conclude that scene orientation plays an important role in the estimation of 3D size at an early stage of processing, and suggest that elevation information is linearly combined with texture gradient information for the rapid estimation of 3D size.     

视觉发育关键期单眼形觉剥夺对大鼠视功能和视皮层PKCζ蛋白表达的影响

目的　探讨视觉发育关键期单眼形觉剥夺对大鼠视功能和视皮层PKCζ蛋白表达的影响。方法　选取出生后13 d SPF级Long Evans大鼠28只,利用随机数字表法将大鼠随机分为两组:正常对照组、弱视模型组,每组14只,以右眼作为实验眼。建立大鼠多维度弱视模型,采用视觉诱发电位验证弱视模型的建立,HE染色观察大鼠视皮层形态结构,视觉悬崖实验检测大鼠立体视功能,计算每只大鼠的辨别指数,Western blot检测大鼠视皮层中PKCζ蛋白的表达。结果　与正常对照组相比,弱视模型组大鼠右眼（剥夺眼）的P2波潜伏期明显延长,P2波振幅明显降低,差异均有统计学意义(均为P<0.05) 。两组大鼠视觉悬崖实验检测结果显示,正常对照组大鼠探索行为轨迹集中在右侧(非悬崖侧),而弱视模型组大鼠探索行为轨迹紊乱,探索区域大多分布在左侧 (悬崖侧)。弱视模型组大鼠辨别指数明显低于正常对照组 (P<0.05)。正常对照组大鼠视皮层神经元数量丰富,结构完整,未出现明显神经元变性和坏死;弱视模型组大鼠视皮层神经元数量明显减少,结构不完整,出现不同程度的胞体固缩。弱视模型组大鼠左侧视皮层PKCζ蛋白相对表达量明显低于正常对照组（P<0.01）。结论　在视觉发育关键期单眼形觉剥夺可造成大鼠视皮层结构的改变和视功能严重损害,视皮层PKCζ蛋白表达水平下降。     

Influence of vasospasm on visual function

In a number of patients with etiologically unexplained visual field loss, a vasospastic syndrome could be found with the help of a capillaroscopic local cooling test on the fingers. In the patients with proven vasospastic syndrome, the visual field defects were increased after a cold water test and decreased after a therapy with calcium entry blockers. General aspects of the physiology and pathophysiology of the circulation and especially of the circulation in the eye are presented.This study was supported by the Swiss National Fund Nr. 3'790—0.84.     

Binocular influences on global motion processing in the human visual system

This study investigates four key issues concerning the binocular properties of the mechanisms that encode global motion in human vision: (1) the extent of any binocular advantage; (2) the possible site of this binocular summation; (3) whether or not purely monocular inputs exist for global motion perception; (4) the extent of any dichoptic interaction. Global motion coherence thresholds were measured using random-dot-kinematograms as a function of the dot modulation depth (contrast) for translational, radial and circular flow fields. We found a marked binocular advantage of approximately 1.7, comparable for all three types of motion and the performance benefit was due to a contrast rather than a global motion enhancement. In addition, we found no evidence for any purely monocular influences on global motion detection. The results suggest that the site of binocular combination for global motion perception occurs prior to the extra-striate cortex where motion integration occurs. All cells involved are binocular and exhibit dichoptic interactions, suggesting the existence of a neural mechanism that involves more than just simple summation of the two monocular inputs.     

The importance of the phase transfer function to visual function and visual quality metrics

PURPOSE: To propose a vision quality metric that directly incorporates the phase transfer function. METHODS: The process of retinal image formation from the pupil to the retina is presented to identify possible domains for calculating vision quality metrics. These domains are pupil plane metrics using ocular aberrations, and retinal plane metrics using the point spread function or optical transfer function. The importance of the phase transfer function to visual performance is demonstrated and a method is proposed for directly including phase in a vision quality metric based on ocular wavefront error. RESULTS: A family of vision quality metrics is proposed, which directly incorporates the Stiles-Crawford effect, contrast sensitivity function, and the phase transfer function. CONCLUSION: The phase transfer function is an important aspect of the quality of an image, and it may be directly included in metrics intended to quantify vision quality.     

近视眼患者诱导屈光参差对视功能的影响

目的通过观察实验性屈光参差对40岁以上近视眼患者双眼视功能的影响,探讨老视患者的屈光手术治疗。方法对40岁以上近视患者48例用综合验光仪完全矫正其屈光不正后,在单眼前加不同度数正球镜,诱导单纯近视性( 0.5D、 1.0D、 1.5D、 2.0D、 2.5D和 3.0D)屈光参差。测定诱导屈光参差后的远视力、双眼同时视、融像功能、立体视情况。结果诱导的屈光参差超过 1.5D时,欠矫眼的远视力、立体视、融像功能和同时视随着屈光参差度数的增加逐渐下降。结论近视性屈光参差可引起中年近视患者双眼视功能异常,当屈光参差超过 1.5D时可引起双眼视功能急剧下降。大于40岁近视患者行屈光手术可留有小于 1.5D的近视性屈光参差,利于视近,且对高级视功能的影响不明显。     

年龄相关的视觉功能衰退研究进展

研究显示，随着年龄的增长，人及动物的许多视觉功能出现衰退，表现出视锐度、对比敏感度和波长敏感性下降以及双眼视觉能力减弱。老年性视觉能力降低并非完全由眼的屈光系统和视网膜变性导致，不少方面可能决定于衰老引起的视觉中枢形态（如神经元夏失、树突野改变及突触密度下降等）和生理功能（如皮层内GABA能抑制作用减弱等）的改变，特别是初级视皮层及其上游的改变。对年龄相关的视觉功能衰退研究进展作一综述。     

Social and visual function in nystagmus

AIM: To investigate the influence of nystagmus on visual and social function and determine if parents are able to assess visual and social function in children with nystagmus. METHOD: A postal questionnaire comprising 14 questions related to visual function (VF-14) and questions pertaining to social function were sent to all 1013 members of the Nystagmus Network-a UK based organisation for nystagmus sufferers and their families. Visual and social function scores were compared by regression analysis. RESULTS: 180 adult, 233 parent, and 124 child questionnaires were returned. Idiopathic nystagmus was the most common cause. In adults the mean VF-14 score indicated very low visual function, in the same range as patients assessed in low vision services. Children's visual function scored better than adults, between scores of patients with age related macular disease and corneal grafts. There was a strong correlation between perceived visual and social function for adults (p<0.001) and parental assessment of their children (p<0.001), but not between child self assessment of visual and social function. There was strong correlation between parental and child assessment of visual and social function (p<0.001, p<0.001) CONCLUSION: Questionnaires indicated that nystagmus is associated with very low visual function. There is a strong correlation between visual and social impairment. The authors have shown for the first time in an ophthalmic disease that parents are able to estimate the impact of nystagmus on their child both in terms of visual and social functioning, although they underestimate the impact of nystagmus on emotional aspects of wellbeing.     

实验性屈光参差对双眼视功能的影响

目的 :探讨实验性屈光参差对健康成人双眼视功能的影响。方法 :对双眼视功能正常的大学生志愿者 32人采用在单眼前加不同度数正负球镜的方法 ,诱导单纯近视性 ( 1D , 2D , 3D)及单纯远视性 (-1D ,- 2D ,- 3D)屈光参差 ,测定诱导屈光参差后的视力、立体视敏度及Worth四点融像功能。结果 :随着屈光参差程度的增加 ,单纯“近视眼”的远视力逐渐下降 ,单纯“远视眼”的远视力几乎不下降。立体视敏度随着屈光参差度数的增加而下降 (t检验 ,P <0 .0 5 ) ,相同程度的单纯远视性屈光参差比单纯近视性屈光参差立体视敏度下降更明显 (t检验 ,P <0 .0 5 )。Worth四点定性试验证实了诱导屈光参差后双眼单视功能下降 (χ2 检验 ,P <0 .0 5 ) ,并有黄斑抑制的发生 ,Worth四点定量试验表明抑制区视角度数随着屈光参差程度的增加而增加 (t检验 ,P <0 .0 5 )。结论 :实验性屈光参差可引起成人双眼视功能异常 ,未矫治的屈光参差对儿童双眼视功能潜在性影响还需要进一步研究