Behavior of visual acuity, visual fields and contrast sensitivity in simulated cataract

Visual acuity, contrast sensitivity, and visual fields were examined with and without occluders both in a group of healthy subjects and in a group of patients with field defects (mostly caused by glaucoma). The various results were compared with one another as well as with the results obtained from a group of cataract patients examined before and after surgery. The results confirm clinical experience: visual acuity enables some conclusions to be drawn on the degree and progression of opacity of a lens. The changes in contrast sensitivity and in the visual field, however, represent rather the quality of the visual degradation. Contrast sensitivity and diffuse alterations in the visual field have similar progression patterns. The alterations in contrast sensitivity are more pronounced at higher frequency levels. The contrast sensitivity test can be recommended as a simple and complementary functional test, particularly on cataract patients with severe complaints and relatively good visual acuity. The results of occlusive experiments afford some practical conclusions which enhance knowledge and differentiation of visual field changes induced by cataract and glaucoma. These conclusions can provide a basis for further and more detailed investigations.     

视力和双眼视力差异对弱视患儿立体视形成的影响

目的探讨双眼视力差异及视力对弱视患儿立体视形成的影响。方法选取4～14岁不伴斜视和其他眼病的弱视患儿160例为试验对象,屈光矫正后进行定性、定量立体视功能检查。比较不同双眼矫正视力差异及视力水平对立体视功能的影响。结果双眼矫正视力差<2行与≥2行组间立体视差异具有显著性,χ2=39.571(P<0.01);双眼矫正视力差≥3行组均无中心凹立体视。106例双眼矫正视力差<2行的患儿中,视力≥0.6组与视力<0.6组间立体视差异具有显著性,χ2=23.910(P<0.01)。视力≥1.0治愈组与正常对照组比较,中心凹和黄斑立体视差异有显著性,χ2=8.617(P<0.01)。结论双眼视力差异大及视力低下是影响立体视形成的重要原因。     

A contrast paradox in stereopsis, motion detection, and vernier acuity

Stereoacuity improves with increasing contrast, unless the increase is monocular. In this case performance paradoxically suffers. This study examined whether this contrast paradox occurs for two other classes of visual judgment: two-frame motion and vernier acuity. We constructed three homologous tasks in which the two components of a gabor stimulus (stereo half-images, motion frames, vernier components) were either both high contrast, both low contrast, or mismatched. The contrast paradox was evident in all three tasks and showed a similar spatial frequency dependence. We suggest the contrast paradox results from the combination of mismatched signals by a single filter.     

High contrast and low contrast visual acuity in age related macular degeneration*

Low contrast Bailey-Lovie visual acuity (LCBL) and high contrast Bailey-Lovie visual acuity (HCBL) were measured in subjects with age-related macular degeneration (ARM) and subjects with normal visual function. Low and high contrast visual acuities and the difference between low and high contrast acuities were significantly different for the ARM group compared with the normals, confirming previous findings of disruption to contrast discrimination in ARM. The high contrast Bailey-Lovie chart was found to be a useful screening device for macular degeneration using a pass/fail criterion of 6/7.5. Pre-ARM (PARM) subjects can be defined as those with drusen and/or pigmentary disturbance and high contrast acuity of better than 6/7.5. However, the low contrast chart used at normal clinical illuminances is of no additional diagnostic value in ARM.     

Correlation between contrast sensitivity and visual acuity in retinitis pigmentosa patients

PURPOSE: High-contrast figures such as Landolt rings are insufficient to evaluate the function of the foveal cones of retinitis pigmentosa (RP) patients. We investigated the correlation between visual function as determined with Landolt rings and with the Vistech Contrast Sensitivity Function Test (VCTS) at various spatial frequencies, in addition to the Cambridge Low Contrast Grating (CLCG). METHODS: The study included 30 retinitis pigmentosa patients (53 eyes). All patients were assessed with Landolt rings, the Vistech method, and the CLCG. We estimated the relative contribution of contrast sensitivity to visual acuity by VCTS at each spatial frequency and by CLCG by simple linear regression analysis. RESULTS: The results of the regression analysis of VCTS at 1.5, 3.0, and 6.0 cycles/degree showed a significant correlation between Landolt rings and VCTS and between CLCG and VCTS that was strongest at 6.0 cycles/degree. There was no significant correlation between Landolt rings and VCTS or between CLCG and VCTS at 12.0 and 18.0 cycles/degree. Patients with a visual acuity of 20/25 and CLCG greater than 100 were divided into two groups according to their contrast sensitivity at 18.0 cycles/degree on VCTS. CONCLUSIONS: The VCTS at the highest frequency was useful for evaluating the foveal visual function in RP patients having good visual acuity with the Landolt rings. Thus, contrast sensitivity should be useful in detecting minute impairment or improvement of visual function in RP.     

Comparison of contrast sensitivity,visual acuity,and Humphrey visual field testing in patients with glaucoma

BACKGROUND: Despite their normal or near-normal Snellen visual acuity, patients with glaucoma often complain of "poor" vision. OBJECTIVE: To investigate the relationship between large-letter contrast sensitivity, high-contrast visual acuity, and visual field defects in patients with glaucoma who have 20/40 or better visual acuity. DESIGN :Prospective, cross-sectional case series. PATIENTS AND METHODS: We evaluated 250 eyes of 144 subjects from the Glaucoma Service at the University of Illinois at Chicago College of Medicine. Subjects with a diagnosis of glaucoma, suspected glaucoma, or ocular hypertension who met the 20/40 or better vision requirement were recruited. Visual acuity was measured using the rear-illuminated Lighthouse Visual Acuity Chart at 4 m. Contrast sensitivity was measured using the Pelli-Robson Chart in a front-illuminated box with even luminance across the chart. Visual fields of the patients were measured using the 24-2 full-threshold program on the Humphrey Visual Field Analyzer. RESULTS: A significant correlation (r = 0.57, P < 0.001, n = 127) was found between the visual field mean deviations and the contrast sensitivity scores. The correlation (r = -0.322, P < 0.001, n = 127) was less between the visual field mean deviation and the log MAR visual acuity values, as was the correlation between the contrast sensitivity scores and log MAR visual acuity values (r = -0.370, P < 0.001, n = 127). In the subgroup of patients with chronic open-angle glaucoma, the correlation between the mean visual field deviation and the contrast sensitivity score was higher at 0.689 (P < or = 0.001, n = 62). CONCLUSIONS: Reduced contrast sensitivity is significantly correlated with visual field losses in patients with glaucoma and a visual acuity of 20/40 or better. The study data support the conclusion that, compared with visual acuity, the disease process preferentially affects contrast sensitivity. In our previous work, contrast sensitivity was shown to be more related than visual acuity to real-world function in patients with early glaucomatous changes.     

Binocular summation: a study of contrast sensitivity, visual acuity and recognition

Monocular and binocular sensitivities have been compared previously, mainly by consideration of the absolute threshold. The limited number of studies which has considered tasks such as detection of a contrast gradient and ability to resolve spatial detail has been concerned primarily with photopic levels of illumination. The present study takes the tasks of (1) contrast detection, (2) visual acuity, and (3) recognition, and compares binocular with monocular sensitivities over a wider range of luminances than has been considered before. Maximum summative effects have been found in the contrast domain, and it appears that summation is reduced in situations where the available accommodative-vergence cues are weak.     

Effect of yellow filter on visual acuity and contrast sensitivity under glare condition among different age groups

The aim of this study is to investigate the effect of yellow filter on visual acuity and contrast sensitivity under glare condition for various ages. A total of 60 subjects, aged 5–60 years, with no ocular pathology and no previous surgery were assessed in this cross-sectional study. We divided subjects into six subgroups according to their ages, and the number of subjects in each group was 10: group 1, aged 5–10 years; group 2, aged 11–20 years; group 3, aged 21–30 years; group 4, aged 31–40 years; group 5, aged 41–50 years; and group 6, aged 51–60 years. Snellen visual acuity and Pelli Robson contrast sensitivity with and without glare and with the use of yellow filter under glare condition were determined. Data analysis was carried out using SPSS, version 20. Our results showed a significant reduction in contrast sensitivity under glare condition in all age groups (p = 0.000), which improved significantly with the use of yellow filter (p = 0.000). Although when data in different age groups were analyzed separately, this improvement was only significant in older subjects, aged 51–60 years (p = 0.007). No significant difference was found between Snellen visual acuity with and without glare (p = 0.083), and also we found no yellow filter effect on visual acuity under glare condition. We conclude that yellow filter, which absorbs short wavelength, may provide significant contrast sensitivity benefits for individuals and influences older subjects more than younger ones.     

The importance of acuity, stereopsis, and contrast sensitivity for health-related quality of life in elderly women with cataracts

PURPOSE: To investigate the relative contribution of visual and other factors to quality of life among elderly women with bilateral cataract. METHODS: Data were analyzed from a trial of first-eye cataract surgery. Visual parameters, general health, and social variables, and disease-specific (VF-14 Index of Visual Function), generic (Euroqol: EQ-5D, London Handicap Scale, Barthel), and intermediate (anxiety, depression, and activity) outcomes were measured at baseline and 6 months later, when approximately half the group had had surgery. RESULTS: Three hundred six participants provided data at baseline, and 289 at 6 months. At baseline, acuity, stereopsis, and contrast sensitivity were all associated with quality of life. Acuity and stereopsis were most strongly and consistently associated. Change in VF-14 was associated with changes in stereopsis and contrast sensitivity, while change in handicap was associated with change in stereopsis. CONCLUSIONS: Acuity, stereopsis, and contrast sensitivity each contributed to quality of life, across a range of measures, in elderly women with cataract. Acuity was marginally the most consistently and generally the most strongly associated, but in some analyses stereopsis was more important. Change in quality of life was associated with change in stereopsis and contrast sensitivity.     

Association of lens opacities,intraocular straylight,contrast sensitivity and visual acuity in European drivers

Purpose: To study the relationship between lens opacity and intraocular straylight, visual acuity and contrast sensitivity. Methods: We investigated 2422 drivers in five clinics in different European Union (EU) member states aged between 20 and 89 years as part of a European study into the prevalence of visual function disorders in drivers. We measured visual acuity [Early Treatment Diabetic Retinopathy Study (ETDRS) chart], contrast sensitivity (Pelli–Robson chart) and intraocular straylight (computerized straylight meter). Lens opacities were graded with the Lens Opacities Classification System III (LOCS) without pupillary dilation. Participants answered the National Eye Institute Visual Functioning Questionnaire – 25. Results: Intraocular straylight was related more strongly to LOCS score than to both visual acuity and contrast sensitivity. Visual acuity and contrast sensitivity were correlated to each other well, but to intraocular straylight to a much lesser extent. Self‐reported visual quality was best related to contrast sensitivity; night driving difficulty was best related to visual acuity. Conclusion: Straylight is found to have added value for visual function assessment in drivers, whereas if visual acuity is known contrast sensitivity has limited added value.     

准分子激光原位角膜磨镶术后早期对比敏感度的研究

目的通过对低度、中度、高度近视眼行准分子激光原位角膜磨镶术术后早期对比敏感度的变化研究,完善对不同程度近视的术后视功能的评价。方法共85例(170只眼)。按等效球镜计算后分三组:低度(<3.00D)28例(56只眼);中度(≥3.00D～<6.00D)30例(60只眼);高度(≥6.00D)27例(54只眼)。患者在术前、术后1周、1个月、3个月时除常规检查外,用美国Stereooptical对比敏感度测试卡(F.A.C.T)检查对比敏感度视力,并分组内与组间比较三组患者对比敏感度视力变化的规律。结果1.术前各组间:三组在术前各频率段无明显差别。2.在各组内的结果:(1)在术后一周:三组的各频率段都有明显的下降,且以6,12cpd下降幅度最明显。(2)在术后1个月:低度组,在各频率段恢复到术前水平;而中、高度组在12,18cpd仍低于术前水平。(3)在术后3个月:低、中度组在各频率段均恢复到术前水平;高度组除12,18cpd都已达术前水平。3.在各组间的结果:(1)在术后1周:低、高度组在6,12,18cpd频率段下降程度差异有统计学意义,后者在三频率段下降更显著。(2)在术后1个月:低、中度组在恢复程度上12,18cpd差异有统计学意义(P<0.05),低、高度组在12,18cpd频率段恢复程度差异有统计学意义(P<0.01),后者较慢。(3)术后3个月:低、高度组在12,18cpd频率段恢复程度仍有差异有统计学意义(P<0.01),后者较慢。结论近视患者LASIK术后早期对比敏感度均有下降后回升,其变化特点与术前屈光状态有关。对比敏感度视力检查结合常规检查能更全面、客观地评价近视患者LASIK术后视功能的变化。     

Perceptual learning improves contrast sensitivity and visual acuity in adults with anisometropic amblyopia

To evaluate the effects of perceptual learning on contrast-sensitivity function and visual acuity in adult observers with amblyopia, 23 anisometropic amblyopes with a mean age of 19.3 years were recruited and divided into three groups. Subjects in Group I were trained in grating detection in the amblyopic eye near pre-training cut-off spatial frequency. Group II received a training regimen of repeated contrast-sensitivity function measurements in the amblyopic eye. Group III received no training. We found that training substantially improved visual acuity and contrast-sensitivity functions in the amblyopic eyes of all the observers in Groups I and II, although no significant performance improvement was observed in Group III. For observers in Group I, performance improvements in the amblyopic eyes were broadly tuned in spatial frequency and generalized to the fellow eyes. The latter result was not found in Group II. In a few cases tested, improvements in visual acuity following training showed about 90% retention for at least 1 year. We concluded that the visual system of adult amblyopes might still retain substantial plasticity. Perceptual learning shows potential as a clinical tool for treating child and adult amblyopia.     

Effect of intraocular lens implantation on visual acuity, contrast sensitivity, and depth of focus

PURPOSE: To determine the role of spherical and irregular aberrations in the optics of the natural eye and after intraocular lens (IOL) implantation in terms of visual acuity, contrast sensitivity, and depth of focus. SETTING: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. METHODS: Visual acuity and defocus-specific contrast sensitivity in 11 pseudophakic patients (IOL group) and 27 age-matched phakic subjects were compared. The results were obtained psychophysically. Spherical and irregular aberrations were subsequently estimated by comparing the measured myopic shift (optimum focus of contrast sensitivity at 4 cycles per degree [cpd] compared to that at 16 cpd) and depth of focus with those of theoretical eye models with varying amounts of irregular and spherical aberrations. RESULTS: The best corrected visual acuity and best corrected contrast sensitivity in the IOL group did not significantly differ from that in the phakic group. The depth of focus was larger in the IOL group at a pupil diameter of 6.0 mm (P<.05). Comparison with theoretical eye models suggested a higher amount of spherical aberration in the IOL group; irregular aberration was almost the same in both groups. CONCLUSIONS: There was a higher amount of spherical aberration in the IOL group, related to a larger depth of focus, without loss of contrast sensitivity at optimum focus or loss of visual acuity. This might contribute to better quality of vision in pseudophakic subjects than in presbyopic phakic subjects.     

Practical contrast sensitivity acuity testing

Summary A 2.0 neutral density (1% transmission) filter allows an easy, consistent and natural way of checking visual acuity on a low contrast Snellen test chart, and is particularly useful in documenting poor visual function in patients with certain types of cataract.     

Peripheral visual acuity and age

We measured the peripheral visual acuity of a group of eleven older subjects (mean age 54.2 years) and a group of seventeen young subjects (mean age 22.1 years). Peripheral visual acuity was measured using Konig bars with critical detail subtending 2.4 and 4.8 minutes of arc. The older group showed a substantial reduction of peripheral visual acuity.