The relation between visual sensitivity and intraocular pressure in normal eyes

Intraocular pressure and flicker modulation sensitivity at 25 and 40 Hz were measured in 22 normal observers, with an age range from 20-71 years. Significant correlations up to 0.67 were found between intraocular pressure and flicker sensitivity at several points in the visual field. There was no correlation between flicker sensitivity and age of the observers. Thus intraocular pressure may affect neuronal function in the normal eye.     

Monocular fixation and acuity in amblyopic and normal eyes

We studied the relation between eccentricity of monocular fixation and the minimum angle of resolution invisually normal subjects and in both the amblyopic and dominant eyes of amblyopes. For the amblyopic and visually normal eyes, this relation was linear; resolution was poorer at the eccentrically fixating locus than at the corresponding region of the normal eye. The dominant eyes of the strabismic amblyopes had a nasal component of eccentric fixation that was less than that of the companion amblyopic eyes, but greater than the that found in the visually normal eyes. In terms of the eccentricity of monocular fixation, the domonant eyes of strabismic amblyopes were different from the normal eyes.     

The peripheral critical flicker frequency

Measurements of critical flicker frequency (CFF) were taken in steps of 5° along the horizontal meridian in the nasal visual field under systematic variation of luminance, area and temporal modulation (ripple ratio) of the test stimulus: for photopic luminances CFF increases from the fovea to the periphery for about 5–15 c/sec. passes several maxima and minima and falls off again at greater values of eccentricity (individually different at 30–60°). showing that parts of the retinal periphery clearly surpass the fovea in the capability of processing temporal information. It is shown that the Ferry-Porter and Granit-Harper laws are only valid in the fovea and at several points in the periphery up to about 30° of eccentricity: for greater values of eccentricity deviations occur from a strongly logarithmic relationship. The non-monotonic course of peripheral CFF is compared to Payne's measurements of reaction times to peripherally presented stimuli (Vision Res. Vol. 6, p. 729) revealing a similar behaviour.     

弱视眼与正常眼视网膜厚度的比较

目的 探讨成人弱视眼黄斑部视网膜厚度与正常眼的差异.方法 使用光学相干断层成像技术分别对弱视眼组（47例,65眼）与正常眼组（35例,70眼）黄斑区进行水平和垂直扫描,测定黄斑中心小凹和距离中心小凹鼻侧、上方、颞侧、下方700 μm的中心凹区及1000 μm黄斑旁中心凹区的视网膜厚度,所得数据进行t检验分析.结果 弱视眼组黄斑中心小凹及距离中心小凹鼻侧、上方、颞侧、下方700 μm视网膜厚度分别为（153.45±12.37）μm、（257.68±12.73）μm、（263.27±15.17）μm、（247.55±13.62）μm、（262.41±16.37）μm,正常眼组相应位置的视网膜厚度分别为（142.27±9.61）μm、（251.39±16.29）μm、（254.92±13.83）μm、（240.27±14.54）μm、（256.71±15.81）μm,弱视眼视网膜厚度较正常眼大,差异均有统计学意义（t=5.39、2.49、3.34、2.99、2.05,P〈0.05）;弱视眼距离中心小凹鼻侧、上方、颞侧、下方1000 μm视网膜厚度分别为（262.09±13.67）μm、（266.46±12.76）μm、（252.11±13.47）μm、（264.32±15.23）μm,正常眼组相应位置的视网膜厚度分别为（264.25±14.42）μm、（269.61±13.66）μm、（250.91±13.27）μm、（261.75±14.18）μm,两组相比差异无统计学意义（t=0.89、1.38、0.52、1.06,P〉0.05）.结论 弱视患者的黄斑中心小凹及中心凹处视网膜较正常服厚,弱视的发生可能与黄斑中心小凹及中心凹处视网膜异常有关.     

Spatial frequency dependence of accommodative responses in amblyopic eyes

Monocular, steady-state accommodative responses were measured as a function of spatial frequency of simple sinusoidal gratings presented at high contrast and target vergence levels in amblyopes. as well as in strabismics without amblyopia and in visually-normal control subjects. In general, spatial frequency dependence of the accommodative response was the rule. However, the amblyopic eyes exhibited markedly reduced accommodative responses over most of the spatial frequency range tested, and this was attributed to reduced accommodative controller gain in the sensory pathways involved in the control of accommodation in the amblyopic eye. Due to the diversity of accommodative response spatial frequency profiles found across all groups, the results suggest that reflex, voluntary, and higherlevel perceptual aspects of accommodation may interplay in a complex manner in the act of accommodation on a simple sinusoidal grating.     

Reliability of visual acuity measures of amblyopic eyes

Ten amblyopes had their visual acuity measured once a week for 6 weeks using a Snellen chart (whole chart and single line) and a newly developed E chart was designed specifically for testing the acuity of amblyopes. For each test at each trial, the subject's acuity responses were graphically plotted and were fitted by a least-squares straight line to the central-most data. The reliability (repeatability) of the 50% threshold acuity was compared for the 3 acuity tests. The new E chart was the most reliable and the Snellen single-line test was the least reliable. These results have complications for quantifying acuity improvement during and following amblyopia therapy. The slope of the fitted acuity line may have value in assessing the prognosis for treatment.     

优良视力正视眼不同对比度下视力与高阶像差的关系

目的 分析优良视力正视眼低、中、高对比度视力与高阶像差的关系。方法 描述性研究。选择优良视力正视眼,在流明值为260背景亮度下,测量对比度为100%、25%、10%和5% 4种状态下的视力;同时采集瞳孔直径为3.11 mm和5.96 mm眼高阶像差。分析3.11、5.96 mm瞳孔直径眼高阶像差与不同对比度视力之间的相关性。采用线性回归分析,拟合出回归方程。结果 低对比度状态下视力的个体差异性更大。瞳孔直径为3.11 mm时,高阶像差均方根值（RMS）与不同对比度视力之间存在着线性相关关系（mini R2＝0.1129）。结论 高阶像差对于对比度视力的影响特点是全频率。     

Development of critical flicker frequency in human infants

The forced-choice preferential looking (FPL) technique was used to trace the development of critical flicker frequency (CFF) in human infants. CFF was found to improve markedly between 4 and 8 weeks of age and to a lesser extent between 8 and 12 weeks. The CFF of the 12-week-olds was not significantly different from the adult CFF measured under similar conditions. A decrease in luminance level resulted in a decrease in the CFF of 8-week-old infants that was qualitatively similar to the decrease found for adults.     

Comparison of higher order aberration profiles between normal and amblyopic eyes in children with idiopathic amblyopia

Aim: To evaluate the higher order aberrations and resultant bilateral wavefront patterns in paediatric patients with idiopathic amblyopia. Material and Methods: In this cross sectional observational trial, seventeen consecutive patients of previously diagnosed idiopathic amblyopia underwent wavefront analysis on Zyoptix platform (Bausch and Lomb, Rochester, NY, USA). Results: The mean age was 9 ± 3 years. There was no significant difference in comparison with means for the Zernike coefficients between normal and amblyopic eye. However, interrelation between Zernike coefficients, which is responsible for their interaction leading to difference in visual function, was different between amblyopic and fellow eyes. This was noticed using stepwise regression analysis. Predicting variables and R² (r squared) values for each Zernike polynomial were calculated. The sets of significantly predicting coefficients were different in mostpatients, with only seven common pairs and 42 dissimilar dependent‐predictor sets. Maximum difference in the R‐squared values between amblyopic and normal (fellow) eyes was seen with coma‐like and trefoil‐like aberrations (third order and fifth order terms). Conclusion: It seems a strong possibility that a subset of ‘idiopathic’ amblyopia may be associated with loss of symmetry in wavefront patterns of the two eyes.     

Foveal flicker sensitivity discriminates ARM-risk from healthy eyes.

The "good" eyes of 13 patients with monocular exudative ARM were compared with age-matched healthy eyes of 19 subjects. Membership in the two study groups was based upon careful clinical evaluation of the tested eye as well as upon status of the fellow eye. We asked whether temporal contrast sensitivity for a long-wavelength, low spatial frequency stimulus can be used to identify the group in which a given eye belongs. Using step-wise discriminant analysis, we found that the ARM-risk and healthy eyes could be classified with 78% accuracy on the basis of foveal flicker sensitivity at two temporal frequencies--14 and 10 Hz (in order of estimated weight.)     

屈光不正性弱视患者视网膜厚度的变化

目的:探讨视网膜厚度分析仪(retinalthicknessanalyzer,RTA)对弱视患者的诊断价值。方法:采用RTA测量正常人6例11眼及弱视患者22例31眼,眼后极部视网膜厚度值及厚度地形图,所得数据经SPSS统计软件包进行分析。结果:正常人平均视网膜厚度为172.4±13.4μm,鼻侧较颞侧厚(P<0.05),其中黄斑上方为177.1±9.0μm,黄斑下方为169.9±11.0μm;鼻侧为180.5±1.3μm,颞侧为161.0±9.2μm。弱视患者平均视网膜厚度为176.4±7.4μm。在黄斑中心凹X5区,弱视明显厚于正常人。黄斑上方为178.7±20.2μm,黄斑下方为173.4±26.2μm;鼻侧为177.3±9.6μm,颞侧为173.4±6.2μm。结论:正常眼鼻侧视网膜明显较颞侧厚。弱视眼在黄斑中心凹X5区视网膜厚度明显较正常眼厚。     

Comparison of pupil perimetry and visual perimetry in normal eyes: decibel sensitivity and variability

PURPOSE: To compare the sensitivity and variability of pupil perimetry with visual perimetry at the same retinal locations in normal subjects. METHODS: Pupil perimetry was performed on the right and left eyes of 10 normal subjects using a computerized infrared pupillometer equipped to present perimetric light stimuli and record pupil light reflexes. Eleven locations were tested at different intensities along the horizontal meridian of each eye, and the decibel sensitivity of the pupil light reflex was compared with the visual threshold at the same location. RESULTS: The shape and height of the hill of vision (retinal sensitivity) was very similar between the right and left eyes of each individual using either pupil perimetry (R2 = 0.69) or standard threshold perimetry (R2 = 0.62) but was less similar between subjects. Comparisons between pupil and visual sensitivity revealed a lack of correlation at the same retinal location in normal eyes (R2 = 0.19). CONCLUSIONS: The high intereye correlation for either pupil or visual sensitivity may provide an important tool for detecting focal or asymmetric visual field damage. Although the basic shape of the sensitivity profile of pupil and visual responses was similar under the conditions of testing, the two did not correlate well within each eye among the normal subjects. This highlights that similarities do exist in the sensitivity profile of the two pathways, but they do not seem to vary in the same proportion between normal individuals.     

Aging-related foveal flicker sensitivity losses in normal observers.

Photopic flicker sensitivity for healthy subjects over 60 years of age was compared with that of subjects in their 20s and 30s. The stimulus was achromatic and viewed foveally through a 2.0-mm artificial pupil which assured a constant pupil size in all subjects. As a group, older subjects had lower flicker sensitivity than younger subjects. This was found even when the retinal illuminance difference between age groups that arises from increased lens absorption in older adults was taken into account. The results indicate that a reduction in retinal illuminance with age cannot account for all the flicker sensitivity losses in older adults.     

Perimetry of critical flicker frequency in human rod and cone vision

Photopic critical flicker frequency (CFF) to green and yellow-red targets became independent of visual field location when the decrease in the density of retinal ganglion cells and increase in their receptive-field size towards the retinal periphery were compensated for by increasing stimulus area in inverse proportion to the human cortical magnification factor squared (M-scaling) and by reducing stimulus luminance in inverse proportion to Ricco's area (F-scaling). In mesopic and scotopic vision CFF to green targets increased monotonically with eccentricity despite MF-scaling. Instead, CFF to MF-scaled yellow-red targets that predominantly stimulated cones was independent of eccentricity at all luminance levels tested.