Interocular suppressive interactions in amblyopia depend on spatial frequency

Glare visual acuity and contrast sensitivity are important indicators of visual quality. Studies have shown that the glare visual acuity and contrast sensitivity in dry eye patients tend to degenerate, further affecting their quality of life. The objective of this study was to investigate the effect of notch filters on glare VA and contrast sensitivity in patients with dry eye or with dry eye syndrome. 36 subjects in the 20‒65 age group were diagnosed as having dry eye disease or perceived dry eye syndromes themselves who were included after the initial screening with the OSDI questionnaire, and one was subsequently excluded as they had undergone retinal detachment surgery. Finally, 35 subjects (14 male and 21 female) with a mean age of 40.66 ± 15.62years participated in this study. All subjects wore their habitual prescriptions and four different filter lenses (namely 480, 620, dual 480 & 620 notch filter, and FL-41 tinted lens), and measured the parameters of glare visual acuity and contrast sensitivity using CSV-1000 and sine wave contrast test (SWCT), respectively. Student t-test and Repeated measurement analysis (R-ANOVA) were utilized by using SPSS 26.0 software. A dual-wavelength 480 & 620nm optical notch filter had a significant anti-glare effect decreasing glare disabilities or discomfort, and leading to better visual quality, the same effect was also shown on a 480nm notch filter lens. All participants showed a significant difference among the baseline, three notch filters (480nm, 620nm, dual-wavelength 480 & 620nm), and FL-41 tinted lens were used on SWCT_A (1.5cpd, F = 3.054, p = 0.019) and SWCT_E (18cpd, F = 2.840, p = 0.049); but did not show statistical different on SWCT_B (3cpd, F = 0.333, p = 0.771), SWCT_C (6cpd, F = 1.779, p = 0.159), and SWCT_D (12cpd, F = 1.447, p = 0.228). The baseline showed the best visual performance on CS at a low spatial frequency (SWCT_A, 1.5cpd), any filter might reduce the contrast sensitivity at low spatial frequencies in the clinical trial, whereas 480nm notch filter showed the best effectiveness on CS at a high spatial frequency (SWCT_E, 18cpd), the FL-41 lens that also filters out the 480nm band does not achieve the same effect. Moreover, patients with dry eye or those older than 40years old preferred optical multilayer notch filters to FL-41 tinted lenses. The 480- & 620-nm dual-wavelength and 480-nm single-wavelength notch filters have the best effect on the glare visual acuity and contrast sensitivity (CS) at high spatial frequencies in dry eye patients. The 620-nm notch filter performs better in CS at low and mid-low spatial frequencies; the FL-41 tinted lens performs poorly for glare VA and CS spatial frequencies examination. Patients with glare disabilities or CS disturbance at high spatial frequencies may choose a 480-nm notch filter lens, and patients who have CS disturbance at low spatial frequencies may consider a 620-nm notch filter for the prescription.

To elucidate the difference in the pathogenesis between strabismic and anisometropic amblyopia. It was a case-control study.We used psychophysical methods, including grating acuity, edge contrast sensitivity, contrast sensitivity function tests, and examined the visual functions of 150 cases from 8 to 40-year-old. Then we applied the Origin 8.0 software for statistical analysis of experimental data, we did the correlation analysis between the grating acuity, edge contrast sensitivity and optotype acuity, and the similarity comparison of the contrast sensitivity function curve between the strabismic and anisometropic amblyopia. The grating acuity had a strong correlation with optotype acuity, the correlation value was 0.81. The grating acuity of the strabismic group was roughly 15% lower than the whole abnormal population, for any given level of optotype acuity; the edge contrast threshold had a weak correlation with optotype acuity, the correlation value was 0.24. Anisometropia, for a given level of optotype acuity, had edge contrast thresholds that were 15% higher (worse) than the whole population, while strabismic and strabismic-anisometropia had edge contrast thresholds that are 17% lower (better) than the whole population. The CSF of all amblyopic eyes were reduced in comparison with the non-amblyopic eye of the same person, the peak sensitivity shifted toward to the low spatial frequency region, the CS curve was depressed especially in the middle and high spatial frequencies, there were no significant difference, but at low frequency area(1.0 c/d) there were statistically significant between the two types of amblyopia(t = 2.239, P < 0.05). There were differences in the patterns of visual loss between strabismic and anisometropic amblyopic patients.

ABSTRACTCurrent models of visual perception suggest that, during scene categorization, low spatial frequencies (LSF) are rapidly processed and activate plausible interpretations of visual input. This coarse analysis would be used to guide subsequent processing of high spatial frequencies (HSF). The present study aimed to further examine how information from LSF and HSF interact and influence each other during scene categorization. In a first experimental session, participants had to categorize LSF and HSF filtered scenes belonging to two different semantic categories (artificial vs. natural). In a second experimental session, we used hybrid scenes as stimuli made by combining LSF and HSF from two different scenes which were semantically similar or dissimilar. Half of the participants categorized LSF scenes in hybrids, and the other half categorized HSF scenes in hybrids. Stimuli were presented for 30 or 100 ms. Session 1 results showed better performance for LSF than HSF scene categorization. Session 2 scene categorization was faster when participants attended and categorized LSF than HSF scene in hybrids. The semantic interference of a semantically dissimilar HSF scene on LSF scene categorization was greater than the semantic interference of a semantically dissimilar LSF scene on HSF scene categorization, irrespective of exposure duration. These results suggest a LSF advantage for scene categorization, and highlight the prominent role of HSF information when there is uncertainty about the visual stimulus, in order to disentangle between alternative interpretations.

Amblyopia is a common childhood vision disorder with a prevalence of 1.6-3.5% worldwide. It has different causes such as anisometropia, strabismus and visual deprivation. This study aimed to determine the effect of patching operation of the better eye on visual acuity (VA) and contrast sensitivity function (CSF) of the amblyopic eye. Thirty four children (18 boys; 16 girls) with mean age of 6.88±1.48 (SD) years participated in the study. Twenty six children had anisometropic and eight had combined (anisometropia and strabismus) amblyopia. VA and CSF of the subjects were measured through YANG vision tester before and three months after patching therapy.The VA between both eyes and CSF at four spatial frequencies, 1.5,6, 12 and18 cycles per degree (cpd) in two phases, were compared. In the better eye, the best corrected VA did not show any significant difference before and after treatment. In amblyopic eyes, postoperative VA significantly improved (P<0.001). Furthermore, the postoperative CSF at high and low spatial frequencies did not show statistically significant difference, whereas at the medium levels significantly increased(P=0.003, 0.001).VA increased in 64% participants and CSF improved 1.16, 1.57, 3.91 and 2.44 times in 1.5, 6, 12 and 18 spatial frequencies respectively. Complete (VA 20/20) and relative improvement (at least 2 lines) of VA was achieved in 60.61% and 39.39% of amblyopic cases respectively. Based on our results, patching of the better eye in amblyopic children can improve VA and CSF, especially in intermediate frequencies. Therefore, our findings recommend the CSF as an accompanying and complementary test for VA at pre and post patch operation evaluation in amblyopia treatment.

Contrast sensitivity was measured in 12 subjects for different spatial frequencies of sinusoidal grating patterns, generated by oscilloscope, for pupil diameters 2-8 mm and for defocus of +1-4 D, following homatropine eyedrops. Changes in pupil diameter, without correction for the change in retinal illumination, had no significant effect on contrast sensitivity, except at 0.5 and 1 c deg-1 when a significant reduction occurred with the 2 mm pupil. Defocus caused a large reduction in contrast sensitivity at spatial frequencies higher than the peak of the contrast sensitivity function (3 c deg-1) and a smaller reduction below the peak. In both individual and group results, there was no significant effect of defocus in causing a disproportionately greater reduction in contrast sensitivity at higher spatial frequencies nor were the zero mimina predicted by optical theory observed. The results were confirmed in eight subjects viewing with the natural eye, though the reduction in contrast sensitivity caused by +1 D defocus was not significant: this was attributed to the relaxation of accommodation in response to defocus. To predict the performance of the visual system, multiple regression equations were derived to incorporate terms for pupil diameter, defocus and spatial frequency. These equations reflected the lack of effect of pupil diameter, while defocus caused a 51% loss in contrast sensitivity per dioptre at higher spatial frequencies (3-38 c deg-1) and a 19% reduction at low spatial frequencies.

Spatial vision was studied in the bluegill sunfish, Lepomis macrochirus (9.5-14 cm standard length) to assess the limitations imposed by the optics of the eye, the retinal receptor spacing and the retinotectal projection during regeneration. Examination of images formed by the dioptric elements of the eye showed that spatial frequencies up to 29 c/ degrees could be imaged on the retina. Cone spacing was measured in the retina of fresh, intact eyes. The spacing of rows of double cones predicted 3.4 c/degrees as the cutoff spatial frequency; the spacing between rows of single and double cones predicted 6.7 c/degrees. Contrast sensitivity functions were obtained psychophysically in normals and fish with one regenerating optic nerve. Fish were trained to orient to gratings (mean luminance = 25 cd/m2) presented to either eye. In normals, contrast sensitivity functions were similar in shape and bandwidth to those of other species, peaking at 0.4 c/degrees with a minimum contrast threshold of 0.03 and a cutoff at about 5 c/degrees, which was within the range predicted by cone spacing. Given that the optical cutoff frequency exceeds that predicted by cone spacing, it is possible that gratings could be detected by aliasing with the bluegill's regular cone mosaic. However, tests with high contrast gratings up to 15 c/ degrees found no evidence of such detection. After crushing one optic nerve in three trained sunfish, recovery of visual avoidance, dorsal light reflex and orienting to gratings, were monitored over 315 days. At 64-69 days postcrush, responses to gratings reappeared, and within 2-5 days contrast sensitivity at low (0.15 c/degrees) and medium (1.0 c/ degrees) spatial frequencies had returned to normal. At a high spatial frequency (2.93 c/degrees) recovery was much slower, and complete only in one fish.

Cerebral regions and hemispheric specialization for processing spatial frequencies during natural scene recognition. An event-related fMRI study

Motion detection and the coincidence of structure at high and low spatial frequencies

Objective To compare outcomes in visual acuity,refraction,higher-order aberrations (HOAs),and contrast sensitivity function (CSF) in myopic patients undergoing wavefront-guided sub-bowman-keratomileusis (WG-SBK) or sub-bowman-keratomileusis (SBK).Methods In this prospective,randomized,comparative study,244 eyes (122 patients) of myopia or myopic astigmatism were recruited randomized from the myopic surgery candidates and were random allocated into WG-SBK group and SBK group using random digits table.Wavefront-guided custom ablation was performed on the patients from WG-SBK group and standard ablation was performed on the patients from SBK group.Visual acuity,refraction,HOAs and CSF were measured preoperatively at 1 day,1 week,1 month,3 months and 6 months postoperatively.The results were compared between the two groups.Results After 6 months,98.07％ of Wavefront-guided ablation eyes and 98.57％ of standard ablation had uncorrected visual acuity of 1.0 or better (P =0.764).None treated eyes in either group lost more than two lines of best corrected visual acuity (BCVA).The percentage of eyes gained 1 line or more improved in BCVA was 84.61％ and 65.71％ in the WG-SBK and SBK groups (P ＜0.01),respectively.WG-SBK group 69.23％ eyes and SBK group of 57.86％ eyes spherical equivalent within ±0.50 D (P =0.069),WG-SBK group of 92.31％ eyes and SBK group of 86.43％ eyes spherical equivalent within ±1.00 D (P =0.148).Mean residual astigmatism in WG-SBK group and SBK group were-0.30±0.32 DC and-0.34±0.33 DC,respectively (P =0.344).There were no statistically significant in mean residual spherical equivalent between WG-SBK group and SBK group at preoperative,postoperative 1 day and 1 week,respectively (P ＞0.05).However,there were statistically significant in mean residual spherical equivalent between WG-SBK group and SBK group at postoperative 1 month,3 months and 6 months.Mean postoperative absolute changes of six months in HOAs,coma,trefoil and spherical aberration root-mean-square (RMS) in the WG-SBK group and SBK group were 0.25±0.26μm,0.05±0.15μm,0.05±0.12μm,0.14±0.24μm and 0.39±0.34μ m,0.10±0.27μm,0.03±0.10μm,0.29±0.26μm,respectively (P ＜0.01,P =0.089,P =0.157,P ＜0.01).Mean postoperative changes in 3 c/d,6 c/d,12 c/d and 18 c/d CSF in the WG-SBK group and SBK group were 0.17±0.36,-0.04±0.35,0.18±0.29,0.29±0.31 and-0.22±0.44,-0.01±0.51,-0.05± 0.40,-0.02±0.46,respectively (P ＜0.01,P =0.6062,P ＜0.01,P ＜0.01).Conclusions Both wavefront-guided ablation and standard ablation in sub-bowman-keratomileusis for myopia can gain satisfactory postoperative visual acuity and refraction,however,wavefront-guided SBK is efficient to decrease the new induce higher-order aberrations and improve low and high spatial frequency contrast sensitivity of postoperative compared with standard SBK. Key words: Sub-Bowman-Keratomileusis (SBK) ; Wavefront-guided ; Myopia ; Comparative study ;

The red-green axis of colour vision evolved recently in primate evolutionary history. Signals serving red-green colour vision travel together with signals serving spatial vision, in the parvocellular (PC) division of the subcortical visual pathway. However, the question of whether receptive fields of PC pathway cells are specialized to transmit red-green colour signals remains unresolved. We addressed this question in single-cell recordings from the lateral geniculate nucleus of anaesthetized marmosets. Marmosets show a high proportion of dichromatic (red-green colour-blind) individuals, allowing spatial and colour tuning properties of PC cells to be directly compared in dichromatic and trichromatic visual systems. We measured spatial frequency tuning for sine gratings that provided selective stimulation of individual photoreceptor types. We found that in trichromatic marmosets, the foveal visual field representation is dominated by red-green colour-selective PC cells. Colour selectivity of PC cells is reduced at greater eccentricities, but cone inputs to centre and surround are biased to create more selectivity than predicted by a purely 'random wiring' model. Thus, one-to-one connections in the fovea are sufficient, but not necessary, to create colour-selective responses. The distribution of spatial tuning properties for achromatic stimuli shows almost complete overlap between PC cells recorded in dichromatic and trichromatic marmosets. These data indicate that transmission of red-green colour signals has been enabled by centre-surround receptive fields of PC cells, and has not altered the capacity of PC cells to serve high-acuity vision at high stimulus contrast.

目的 应用计算机图像分析软件评价后发性白内障(posterior capsule opacification,PCO)的形态,以探讨不同类型、部位PCO对最佳矫正视力(best corrected visual acuity,BCVA)、对比敏感度(contrast sensitivity,CS)和眩光敏感度glare sensitivity,GS)的影响.方法 收集拟行激光后囊切开术的PCO患者61例(67眼),充分散瞳,行详细眼科检查后,应用裂隙灯照相获取PCO后照法照片,使用PCO计算机分析软件(FOCOman软件)对其进行形态学分析.同时分别测量所有患者激光后囊切开术术前及术后1周BCVA、CS、GS.分析不同类型、不同部位PCO对BCVA、CS、GS的影响.结果 珍珠型PCO的BCVA、各频段CS和CS均低于纤维型PCO,且两者之间的差异有统计学意义(P<0.05).其中,4.0 mm珍珠型PCO在低、中频段CS和中频段GS均低于中央2.0 mm珍珠型PCO,差异有统计学意义(P<0.05);中央2.0 mm纤维型PCO在中、高频段CS和低、中频段GS均低于中央4.0 mm纤维型PCO,差异有统计学意义(P<0.05).中央2.0 mm珍珠型PCO时BCVA的影响最为显著:中央4.0 mm珍珠型PC0对CS和GS的影响最为显著.结论 珍珠型PCO对BCVA、各频段CS和GS的彩响大于纤维型PCO.珍珠型PCO在中央4.0 mm区对视功能的影响大于中央2.0 mm区:纤维型PCO在中央2.0 mm区对视功能的影响大于中央4.0 mm区。

Divergent contrast sensitivity findings have been reported in patients with intraocular lens implants. The purpose of this study was to determine contrast thresholds of patients with good visual acuity after uncomplicated cataract extraction and posterior chamber conventional IOL implantation. Fifty-two eyes of fifty two patients, who had undergone uncomplicated extracapsular cataract extraction and posterior chamber intraocular lens implantation together with 48 eyes of 48 control subjects were tested for contrast sensitivity function. All of the patients had best corrected visual acuity 0.8 (20/25) or better, on the Snellen scale. Patients with concomitant eye disease were excluded. Contrast sensitivity was measured using stationary sine-wave gratings of four spatial frequencies (3.0 to 18.0 cycles/degree), at the testing distance of 8 feet. A loss of contrast sensitivity was found in patients with intraocular lens implants, compared with control subjects of similar age, sex and visual acuity. The loss was statistically significant at intermediate (6 cyc/deg) and high spatial frequencies (12.0 and 18.0 cycles/degree), while it was not statistically significant at low spatial frequencies (3 cyc/deg). This may be the reason of nonspecific visual complaints ('washed-out images'), despite normal Snellen acuity, after cataract surgery and monofocal IOL implantation.

Eye movements transform a spatial scene into luminance modulations on the retina. Recent work has shown that this transformation is highly structured: within human temporal sensitivity, saccades deliver power that increases in proportion to spatial frequency (SF) up to a critical frequency and remains constant beyond that. Importantly, the critical SF increases with decreasing amplitude. Therefore, at sufficiently low SFs, larger saccades effectively deliver stronger input signals to the retina. Here we tested whether this input reformatting has the predicted perceptual consequences, by examining how large and small saccades (6o & 1o) affect contrast sensitivity. We measured relative sensitivity at two SFs: a reference (0.5 cpd), equal to the critical SF for the small saccade, and a probe at either a lower or higher SF (0.1/2.5 cpd). We predicted that large saccades enhance visibility only when the probe has a lower SF than the reference. Subjects (N=7) made instructed saccades while presented with a plaid of overlapping orthogonal gratings at the two SFs and reported which grating was more visible. Results closely follow theoretical predictions: psychometric functions following small and large saccades only differed with the lower SF probe, in which case the larger saccade significantly enhanced visibility. In sum, saccades enable selectivity not only in the spatial domain, but also in the spatial-frequency domain.

A method of producing red-green and blue-yellow sinusoidal chromatic gratings is used which permits the correction of all chromatic aberrations. A quantitative criterion is adopted to choose the intensity match of the two colours in the stimulus: this is the intensity ratio at which contrast sensitivity for the chromatic grating differs most from the contrast sensitivity for a monochromatic luminance grating. Results show that this intensity match varies with spatial frequency and does not necessarily correspond to a luminance match between the colours. Contrast sensitivities to the chromatic gratings at the criterion intensity match are measured as a function of spatial frequency, using field sizes ranging from 2 to 23 deg. Both blue-yellow and red-green contrast sensitivity functions have similar low-pass characteristics, with no low-frequency attenuation even at low frequencies below 0.1 cycles/deg. These functions indicate that the limiting acuities based on red-green and blue-yellow colour discriminations are similar at 11 or 12 cycles/deg. Comparisons between contrast sensitivity functions for the chromatic and monochromatic gratings are made at the same mean luminances. Results show that, at low spatial frequencies below 0.5 cycles/deg, contrast sensitivity is greater to the chromatic gratings, consisting of two monochromatic gratings added in antiphase, than to either monochromatic grating alone. Above 0.5 cycles/deg, contrast sensitivity is greater to monochromatic than to chromatic gratings.

The contrast sensitivity function (CSF) is a fundamental signature of the visual system and has been measured extensively in numerous species. It is defined by measurements of the visibility threshold for sinusoidal gratings at all spatial frequencies. Here, we measured the CSF in artificial visual systems, namely deep neural networks (DNNs), using the same contrast discrimination paradigm as used in human psychophysical experiments. During training, networks are exclusively exposed to natural images, and the task is to identify which one of two input images has higher contrast. The contrast discriminator networks learn a linear classifier over frozen features of pretrained DNNs. At the testing stage, we measured the network's CSF by presenting sinusoidal gratings of different orientations and spatial frequencies. Our results demonstrate that the pretrained DNNs show the band-limited, inverted U-shaped CSF, that is characteristic of the human CSF. The exact shape of the DNNs' CSF appears to be task-dependent. The human CSF is better captured by scene segmentation DNNs than image classification ones (tested under identical settings such as the architecture and computational complexity). When the network was trained to discriminate the contrast in natural images from scratch (i.e., with no previous training task), a relatively flat CSF emerged, dissimilar to the human CSF. The environment of pretrained DNNs proved influential as well. Those with a diet of natural images, similar to human experience (e.g. objects or faces), obtain more human-like CSF. Pretrained DNNs with aerial pictures, such as a bird flying in the sky would see, obtain a shifted CSF towards higher spatial frequencies, similar to that of an eagle. In conclusion, the CSFs derived from the DNNs are the result of efficient processing of the natural world around us. Different visual environments have succinct effects on the shape of the CSFs.