Spontaneous chromosomal instability in peripheral blood lymphocytes from two molecularly confirmed Italian patients with Hereditary Fibrosis Poikiloderma: insights into cancer predisposition.

Two Italian patients with the initial clinical diagnosis of Rothmund-Thomson syndrome were negative for RECQL4 mutations but showed in peripheral blood cells a spontaneous chromosomal instability significantly higher than controls. Revisiting after time their clinical phenotype, the suggestive matching with the autosomal dominant syndrome Poikiloderma, Hereditary Fibrosing with Tendon Contracture, Myopathy and Pulmonary fibrosis (POIKTMP) was confirmed by identification of the c.1879A>G (p.Arg627Gly) alteration in FAM111B. We compare the overall clinical signs of our patients with those of reported carriers of the same mutation and present the up-to-date mutational repertoire of FAM111B and the related phenotypic spectrum. Our snapshot highlights the age-dependent clinical expressivity of POIKTMP and the need to follow-up patients to monitor the multi-tissue impairment caused by FAM111B alterations. We link our chromosomal instability data to the role of FAM111B in cancer predisposition, pointed out by its implication in DNA-repair pathways and the outcome of pancreatic cancer in 2 out of 17 adult POIKTMP patients. The chromosomal instability herein highlighted well connects POIKTMP to cancer-predisposing syndromes, such as Rothmund-Thomson which represents the first hereditary poikiloderma entering in differential diagnosis with POIKTMP.

The pattern of color change in small mammal museum specimens: is it independent of storage histories given museum-specific conditions?

OBJECTIVE: Determination of color and evaluating its variation form the basis for a broad range of research questions. For studies on taxonomy, systematics, etc., resorting to mammal specimens in museum collections has a number of advantages over using field specimens. However, if museum specimens are to be for studying color, they should accurately represent the color of live animals, or we should understand how they differ. Basically, this study addresses this question: How does coat color vary when dealing with specimens of Akodon budini (Budin's grass mouse, Thomas 1918), stored in one museum collection for different periods of time? RESULTS: We measured color values through a spectroradiometer and a diffuse illumination cabin and used the reflectance values in the form of CIELab tri-stimulus values, considering CIE standard illuminant A. We observed that there is a relationship between specimen storage antiquity and pelage color and it seems that it is general for at least a number of small mammals and this could indicate a universal phenomenon across several mammal species and across several storage conditions. Our results, as others, emphasize the importance of considering storage time, among other circumstances, in research studies using mammal skins and where color is of importance.

Objective measurement of Akodon budini dorsal coloration: methodological concerns.

The role of color in taxonomic and systematic studies of several taxa is central. Color data are more valuable if they permit comparisons. We aimed to provide pelage objective color measurements of a series of Akodon budini and to use those color data to test and to quantitatively analyze the influence of both the lighting source and the measuring point, in the determination of pelage color of museum skins. We used a spectroradiometer to measure the pelage color at five points over the dorsal midline of 54 Akodon budini museum skins. PCAs and ANOVAs were conducted over the color data. The characteristics of the studied series also allowed us to include and assess the potential effects of some main sources of intra-specific variation. Determinations of fur color strongly depend on the lighting source, and therefore it is essential that lighting conditions are controlled during color measurements and then made explicit when communicating the color characterization of particular taxonomic units. Furthermore, color determinations strongly depend on the measuring point, even on the same body area, and therefore it is critical that the color characterization of a taxon includes the variation between different points of the different body parts of the studied specimens.

The Appropriateness of Contrast Metric for Reaction Times.

We analyzed different contrast metrics to scale the stimulus strength for suprathreshold reaction times (RTs) when it is modulated along an achromatic channel (L + M) and both chromatic channels L/M and S/(L + M) considering increments and decrements along these axes. RTs were examined as a function of the Weber luminance contrast; spatial luminance ratio (SRL) and, in terms of threshold units. The results show that when there is only luminance decreasing or increasing, RTs cluster around a single RT/luminance contrast function regardless the stimulus sign and our results indicate that both SRL, Weber luminance contrast or threshold units, equate RT values. While, if the stimulus is modulated along an isoluminant plane, the appropriate contrast is Weber (RMS) or SRL for stimuli modulated along L/M axis and for stimuli modulated along S/L + M, showing an asymmetry between S-cone decrements and increments in L/M cone pathway. Threshold units are not appropriate, showing inconsistencies: The stimulus with chromatic direction equal to 90° appears as the most informative with a maximum gain. Even more so, the shared contrast gain grows as the size of the stimulus decreases.

Straylight and Visual Quality on Early Nuclear and Posterior Subcapsular Cataracts.

PURPOSE: To measure log(s) and OSI parameters, both related to forward light scattering in the eye, in subjects with different kinds of early cataracts-nuclear or posterior subcapsular-and corrected visual acuity (CVA). METHODS: 34 eyes of 19 patients ranged between 50 and 75 years old with diagnosed nuclear (14 eyes) or posterior subcapsular cataract (20 eyes) were recruited. Only NO1, NO2, P1, and P2 opacity scores according to LOCS III were included. Observer examination included visual acuity, contrast threshold (Ct), and measurements performed by straylightmeter (straylight parameter log(s)) and double-pass instrument (objective scatter index (OSI)). RESULTS: OSI and log(s) were correlated with LOCSIII in nuclear opacities (p = 0.015 and 0.004, respectively) and in the whole data (p = 0.027 and 0.019, respectively) but did not for posterior subcapsular opacities alone. OSI was strongly correlated with log(s) in nuclear (r = 0.885 and p < 0.001) but not in posterior subcapsular cases (r = 0.382 and p = 0.097). Ct was correlated with log(s) for both cataract types (p = 0.043 for nuclear and p= 0.005 for posterior subcapsular cataract) but not with OSI (p = 0.093 for nuclear and p = 0.064 for posterior subcapsular cataract). CONCLUSIONS: OSI and log(s) discriminate early stages of nuclear cataracts when taking LOCS III as reference, so these opacities could be graded by any of those parameters. LOCSIII does not represent the visual condition for posterior subcapsular cataract. Straylightmeter measurements express the loss in contrast sensitivity caused by nuclear and posterior subcapsular opacities. Studies of lens opacities must be separated according to the type of opacity present in eyes.

Discrimination between surgical and nonsurgical nuclear cataracts based on ROC analysis.

PURPOSE: The aim of this article is to propose a quantitative methodology for determining a criterion to discriminate the nonsurgical nuclear cataract from the surgical one taking into account objective measures of intraocular scattering in patients with good visual acuity (>0.6). METHODS: Two groups of subjects were taken into account: a control group and a group with nuclear cataracts. At a first stage, eyes belonging to the cataract group were classified into "nonsurgical" and "surgical" cataracts by ophthalmologists at their clinical settings. At a second stage a double-pass instrument was also used to determine the objective scatter index (OSI) at the laboratory. Receiver operating characteristic (ROC) curves were used to analyze OSI values to determine a value able to separate between nonsurgical and surgical cataracts. RESULTS: We obtained statistically significant differences among the control and both nuclear cataract groups (p < 0.05). ROC curves determined an OSI criterion level (of 2.1) to suggest surgery in nuclear cataracts with an area under curve of 0.83, i.e. with 80% of sensitivity and 80% of specificity. CONCLUSIONS: ROC analysis allows separating both groups of nuclear cataract, and we determined a value of OSI in nuclear cataract quantification for surgery.

Functional vision barriers: a new concept analyzed in terms of human visual performance

In this work we introduce a new category of barriers that we call "functional vision barriers." This expression refers to lighting and visual elements that may complicate or hinder functional vision and may make life even more difficult for people with visual defects. These barriers appear as a consequence of certain negative effects caused by the poor design of the visual stimulus or visual environment that surrounds it in which lighting is one of the main factors. We use the term "functional vision" because this expression refers to the ability of the visual system to perform everyday tasks. We analyzed some of our previous results with regard to situations that can be considered "functional vision barriers": (1) stimuli with low luminance contrast information in which the addition of chromatic contrast improves visual performance and (2) tasks that are performed in the presence of a glare source in the visual field, diminishing visual performance and reducing brightness perception...

Functional vision barriers: a new concept analyzed in terms of human visual performance

In this work we introduce a new category of barriers that we call "functional vision barriers." This expression refers to lighting and visual elements that may complicate or hinder functional vision and may make life even more difficult for people with visual defects. These barriers appear as a consequence of certain negative effects caused by the poor design of the visual stimulus or visual environment that surrounds it in which lighting is one of the main factors. We use the term "functional vision" because this expression refers to the ability of the visual system to perform everyday tasks. We analyzed some of our previous results with regard to situations that can be considered "functional vision barriers": (1) stimuli with low luminance contrast information in which the addition of chromatic contrast improves visual performance and (2) tasks that are performed in the presence of a glare source in the visual field, diminishing visual performance and reducing brightness perception.(AU)

Veiling luminance as a descriptor of brightness reduction caused by transient glare.

The presence of a glare source in the visual field produces a veiling luminance (L(v)), which generates a brightness reduction that can be expressed in terms of the glare index (V). The relation between the veiling luminance caused by glare and the apparent brightness reduction of a reference target has already been established for steady conditions. In this paper, the relationship is derived for transient glare. First, the relation is tested empirically, and then previous results concerning the effect of transient glare on brightness are summarized and analyzed. From this analysis, a power function relation between L(v) and V is encountered.

Comparison between an objective and a psychophysical method for the evaluation of intraocular light scattering.

In this study we present the comparison of the performance of two systems to measure intraocular scattering. Measurements were made by using a psychophysical system based on a brightness comparison method that provides a glare index and a physical system based on the double-pass technique, which gives an objective scatter index by measuring the optical quality of the eye. Three external diffuser filters that simulated different grades of intraocular scattering were used in subjects with normal vision. The two measured indexes showed a graded rise with increasing level of scattering. The discrimination ability obtained for both systems showed that they were able to distinguish among conditions ranging from normal to early cataracts.

Effect of glare on reaction time for peripheral vision at mesopic adaptation.

When a bright light is present in the field of view, visibility is dramatically reduced. Many studies have investigated the effect of glare on visibility considering foveal vision. However, the effects on peripheral vision have received little attention. In a previous work [J. Opt. Soc. Am. A 25, 1790 (2008)], we showed that the effect of glare on reaction time (RT) for foveal vision at mesopic adaptation depends on the stimulus spatial frequency. In this work, we extend this study to peripheral vision. We measured the RT of achromatic sinusoidal gratings as a function of contrast for a range of spatial frequency, and eccentricity, and for two glare levels, in addition to the no-glare condition. Data were fitted with Piéron's law, following a linear relationship. We found that glare increases the slope of these lines for all conditions. These slopes seem to depend critically on eccentricity for 4 cycles/degree (c/deg), but not for 1 and 2 c/deg. We explain our results in terms of the contrast sensitivity (gain) of the underlying detection mechanisms.

Foveal spatial summation in human cone mechanism.

We measured at the fovea the chromatic contrast threshold for stimuli modulated along different chromatic directions in the isoluminant plane of MBDKL colour space, considering the two cardinal axes (L/M) and S/(L + M) and other intermediate non-cardinal directions. This psychophysical determination was conducted as a function of stimulus size. The test stimulus was a foveal isoluminant Gaussian patch with a raised cosinusoidal temporal profile superimposed on a neutral background. The task was performed binocularly. The increment threshold was measured for three observers by a Bayesian adaptive psychometric method (QUEST). The Ricco area of complete spatial summation was estimated from the threshold-versus-area curves. The perceptive fields are smaller for the L/M-cone opponent direction than the S/(L + M)-cone opponent. The perceptive field sizes for the stimuli in non-cardinal chromatic directions and stimuli modulated at the (L/M)-cone opponent direction present similar values. Measurements were made at two luminance levels, 5 and 40 cd m(-2), but the differences found were small. The perceptive field sizes found could be associated with LGN area.

Comparación de dos test psicofísicos de sensibilidad al contraste en un entorno clínico / Comparison of two contrast sensitivity tests in a clinical setup / Comparaison de deux tests psychophysiques de sensibilité au contraste en clinique / Comparação de dois testes psicofísicos de sensibilidade ao contraste em um ambiente clínico

El objetivo de este estudio fue comparar el desempeño de dos test psicofísicos de sensibilidad al contraste, uno basado en un sistema informatizado - FVC 100 - y otro en láminas impresas - VCTS 6500, ambos empleando la discriminación de redes sinusoidales en condiciones de adaptación fotópica. Fueron medidos 45 ojos de 23 personas con edades entre 28 y 70 años. Los sujetos fueron reclutados en un Servicio de Oftalmología al cual concurrieron tanto por consulta como por control. A partir de tomar el criterio clínico como referencia, los resultados muestran que, de los 23 sujetos, en 16 casos ambos sistemas detectaron correctamente su estado visual, en cinco casos (10 ojos) sólo el FVC 100 consiguió hacerlo, mientras que en dos casos este sistema no detectó el problema visual y sí lo hizo el VCTS 6500. Considerando los datos obtenidos se aprecia un mejor desempeño del test informatizado, destacándose la necesidad de continuar trabajando para conseguir un atlas con información de la función de sensibilidad al contraste que considere las diferentes patologías visuales.

The purpose of this study was to compare the performance of two psychophysical contrast sensitivity tests, one based on a computerized system - FVC 100 - and the other based on printed charts - VCTS 6500, both using the discrimination of sinusoidal grating orientation under photopic adaptation. Altogether, 45 eyes of 23 people with ages ranging from 28 to 70 years were tested in this study. Subjects were recruited in an Ophthalmological Service to which they went looking for medical supervision or consult. Taking the clinical criterion as a reference, the results show that of the 23 subjects, both systems correctly identify 16 cases, in five cases (10 eyes) only the FVC 100 performed well, whereas in two cases this system did not detect the visual problem and the VCTS 6500 did. Considering the obtained data, a better performance of the computerized system can be observed, pointing out the need to keep working in order to obtain a contrast sensitivity atlas which takes into account the different visual pathologies.

L'objectif de cette étude était de comparer les performances de deux tests psychophysiques de la sensibilité au contraste, l'un basé sur l'ordinateur - FVC 100 - et un autre imprimé feuilles - VCTS 6500. Avec les deux systèmes est évaluée discrimination des réseaux sinusoïdaux dans des conditions d'adaptation photopique. Ont été mesurées 45 yeux de 23 personnes âgées entre 28 et 70. Les sujets ont été recrutés dans un service d'ophtalmologie. Ce service a été suivi par la consultation et de contrôle. Après avoir fait référence au critère clinique, les résultats montrent que, parmi les 23 sujets, dans 16 cas, les deux systèmes correctement identifié état visuel. Dans cinq cas (10 yeux) FVC100 seulement réussi à le faire, tandis que dans deux cas, ce système n'a pas détecté les problèmes visuels. Toutefois, s'il est détecté VCTS6500 le problème dans ces deux derniers cas. Considérant les résultats obtenus avec les deux systèmes, vous pouvez voir une meilleure performance du test informatisé par rapport à celui basé sur des feuilles imprimées. Il souligne la nécessité de continuer à travailler vers un atlas des informations sur la fonction de sensibilité au contraste qui tient compte des différentes pathologies visuelles.

O objetivo deste estudo foi comparar o desempenho de dois testes psicofísicos de sensibilidade ao contraste, um baseado num sistema informatizado - FVC 100 - e um outro em lâminas impressas -VCTS 6500, ambos empregando a discriminação de grades sinusoidais em condições fotópicas de adaptação. Foram avaliados 45 olhos de 23 pessoas com idades entre 28 e 70 anos. Os sujeitos foram recrutados num Serviço de Oftalmologia onde compareceram tanto para consulta como para controle. Tomando o critério clínico como referência, os resultados mostram que, dos 23 sujeitos, em 16 casos ambos sistemas detectaram corretamente seu estado visual, em cinco casos (10 olhos) só o FVC 100 conseguiu fazê-lo, contudo em um dos casos este sistema não detectou o problema visual e sim o VCTS. Considerando os dados obtidos, aprecia-se um melhor desempenho do teste informatizado, evidenciando-se a necessidade de continuar trabalhando para conseguir um atlas com informação da função de sensibilidade ao contraste que considere as diferentes patologias visuais.

Comparación de dos test psicofísicos de sensibilidad al contraste en un entorno clínico / Comparison of two contrast sensitivity tests in a clinical setup / Comparaison de deux tests psychophysiques de sensibilité au contraste en clinique / Comparação de dois testes psicofísicos de sensibilidade ao contraste em um ambiente clínico

El objetivo de este estudio fue comparar el desempeño de dos test psicofísicos de sensibilidad al contraste, uno basado en un sistema informatizado – FVC 100 – y otro en láminas impresas – VCTS 6500, ambos empleando la discriminación de redes sinusoidales en condiciones de adaptación fotópica. Fueron medidos 45 ojos de 23 personas con edades entre 28 y 70 años. Los sujetos fueron reclutados en un Servicio de Oftalmología al cual concurrieron tanto por consulta como por control. A partir de tomar el criterio clínico como referencia, los resultados muestran que, de los 23 sujetos, en 16 casos ambos sistemas detectaron correctamente su estado visual, en cinco casos (10 ojos) sólo el FVC 100 consiguió hacerlo, mientras que en dos casos este sistema no detectó el problema visual y sí lo hizo el VCTS 6500. Considerando los datos obtenidos se aprecia un mejor desempeño del test informatizado, destacándose la necesidad de continuar trabajando para conseguir un atlas con información de la función de sensibilidad al contraste que considere las diferentes patologías visuales(AU)

The purpose of this study was to compare the performance of two psychophysical contrast sensitivity tests, one based on a computerized system – FVC 100 – and the other based on printed charts – VCTS 6500, both using the discrimination of sinusoidal grating orientation under photopic adaptation. Altogether, 45 eyes of 23 people with ages ranging from 28 to 70 years were tested in this study. Subjects were recruited in an Ophthalmological Service to which they went looking for medical supervision or consult. Taking the clinical criterion as a reference, the results show that of the 23 subjects, both systems correctly identify 16 cases, in five cases (10 eyes) only the FVC 100 performed well, whereas in two cases this system did not detect the visual problem and the VCTS 6500 did. Considering the obtained data, a better performance of the computerized system can be observed, pointing out the need to keep working in order to obtain a contrast sensitivity atlas which takes into account the different visual pathologies(AU)

L'objectif de cette étude était de comparer les performances de deux tests psychophysiques de la sensibilité au contraste, l'un basé sur l'ordinateur – FVC 100 – et un autre imprimé feuilles – VCTS 6500. Avec les deux systèmes est évaluée discrimination des réseaux sinusoïdaux dans des conditions d'adaptation photopique. Ont été mesurées 45 yeux de 23 personnes âgées entre 28 et 70. Les sujets ont été recrutés dans un service d'ophtalmologie. Ce service a été suivi par la consultation et de contrôle. Après avoir fait référence au critère clinique, les résultats montrent que, parmi les 23 sujets, dans 16 cas, les deux systèmes correctement identifié état visuel. Dans cinq cas (10 yeux) FVC100 seulement réussi à le faire, tandis que dans deux cas, ce système n'a pas détecté les problèmes visuels. Toutefois, s'il est détecté VCTS6500 le problème dans ces deux derniers cas. Considérant les résultats obtenus avec les deux systèmes, vous pouvez voir une meilleure performance du test informatisé par rapport à celui basé sur des feuilles imprimées. Il souligne la nécessité de continuer à travailler vers un atlas des informations sur la fonction de sensibilité au contraste qui tient compte des différentes pathologies visuelles(AU)

O objetivo deste estudo foi comparar o desempenho de dois testes psicofísicos de sensibilidade ao contraste, um baseado num sistema informatizado – FVC 100 – e um outro em lâminas impressas –VCTS 6500, ambos empregando a discriminação de grades sinusoidais em condições fotópicas de adaptação. Foram avaliados 45 olhos de 23 pessoas com idades entre 28 e 70 anos. Os sujeitos foram recrutados num Serviço de Oftalmologia onde compareceram tanto para consulta como para controle. Tomando o critério clínico como referência, os resultados mostram que, dos 23 sujeitos, em 16 casos ambos sistemas detectaram corretamente seu estado visual, em cinco casos (10 olhos) só o FVC 100 conseguiu fazê-lo, contudo em um dos casos este sistema não detectou o problema visual e sim o VCTS. Considerando os dados obtidos, aprecia-se um melhor desempenho do teste informatizado, evidenciando-se a necessidade de continuar trabalhando para conseguir um atlas com informação da função de sensibilidade ao contraste que considere as diferentes patologias visuais(AU)

The effect of chromatic and luminance information on reaction times.

We present a series of experiments exploring the effect of chromaticity on reaction time (RT) for a variety of stimulus conditions, including chromatic and luminance contrast, luminance, and size. The chromaticity of these stimuli was varied along a series of vectors in color space that included the two chromatic-opponent-cone axes, a red-green (L-M) axis and a blue-yellow [S - (L + M)] axis, and intermediate noncardinal orientations, as well as the luminance axis (L + M). For Weber luminance contrasts above 10-20%, RTs tend to the same asymptote, irrespective of chromatic direction. At lower luminance contrast, the addition of chromatic information shortens the RT. RTs are strongly influenced by stimulus size when the chromatic stimulus is modulated along the [S - (L + M)] pathway and by stimulus size and adaptation luminance for the (L-M) pathway. RTs are independent of stimulus size for stimuli larger than 0.5 deg. Data are modeled with a modified version of Pieron's formula with an exponent close to 2, in which the stimulus intensity term is replaced by a factor that considers the relative effects of chromatic and achromatic information, as indexed by the RMS (square-root of the cone contrast) value at isoluminance and the Weber luminance contrast, respectively. The parameters of the model reveal how RT is linked to stimulus size, chromatic channels, and adaptation luminance and how they can be interpreted in terms of two chromatic mechanisms. This equation predicts that, for isoluminance, RTs for a stimulus lying on the S-cone pathway are higher than those for a stimulus lying on the L-M-cone pathway, for a given RMS cone contrast. The equation also predicts an asymptotic trend to the RT for an achromatic stimulus when the luminance contrast is sufficiently large.

The effect of spatial layout on motion segmentation.

We present a series of experiments exploring the effect of the stimulus spatial configuration on speed discrimination and two different types of segmentation, for random dot patterns. In the first experiment, we find that parsing the image produces a decrease of speed discrimination thresholds such as was first shown by Verghese and Stone [Verghese, P., & Stone, L. (1997). Spatial layout affects speed discrimination threshold. Vision Research, 37(4), 397-406; Verghese, P., & Stone, L. S. (1996). Perceived visual speed constrained by image segmentation. Nature, 381, 161-163] for sinusoidal gratings. In the second experiment, we study how the spatial configuration affects the ability of a subject in localizing an illusory contour defined by two surfaces with different speeds. Results show that the speed difference necessary to localize the contour decreases as the stimulus patches are separated. The third experiment involves transparency. Our results show a little or null effect for this condition. We explain the first and second experiment in the framework of the model of Bravo and Watamaniuk [Bravo, M., & Watamaniuk, S. (1995). Evidence for two speed signals: a coarse local signal for segregation and a precise global signal for discrimination. Vision Research, 35(12), 1691-1697] who proposed that motion computation consists in, at least, two stages: a first computation of coarse local speeds followed by an integration stage. We propose that the more precise estimate of speed obtained from the integration stage is used to produce a new refined segmentation of the image perhaps, through a feedback loop. Our data suggest that this third stage would not apply to the processing of transparency.

Effect of glare on simple reaction time.

We systematized the study of the effect of glare on reaction time (RT), for visual conditions similar to the ones found during night driving: Mesopic range of adaptation (0.14 cd/m2), glare levels of the order of those produced by car headlights (E(G)=15, 60 lx), suprathreshold luminance contrasts, and a variety of spatial frequencies covering the selected range of visibility (1, 2, 4, and 8 c/deg). We found that for the no-glare situation, RT increases with decreasing contrast and increasing spatial frequency, which agrees with previous findings. When data are plotted as a function of the inverse of contrast, RT varies linearly, with k--the RT-contrast factor of Pieron's law--representing the slope of the lines. The effect of glare on RT is an increase in the slope of these lines. This effect is different for each spatial frequency, which cannot be accounted for in the classic approach considering that glare can be replaced by a single veiling luminance. We show that the effect of glare on RT must be modeled by an equivalent glare luminance that depends on spatial frequency.

Brightness for different surround conditions: the effect of transient glare.

We measured the effect of a transient glare source on t heperceived brightness of astandard luminance (L(STD)) patch (0.5 cd/m2) as a function of the surround luminance (Ls). In the experiment, both increment and decrement stimuli were dependent on the value of the Ls (0.01, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, or 2.0 cd/m2). We adopted a magnitude comparison paradigm using constant stimuli to determine the test matching luminance (L(M)). When L(S) was lower than the luminance of the patch, which corresponds to increments, LM was lower than L(STD), and this effect was highest for the lowest L(S). There was a small but noticeable cusp as increments shifted to decrements. As L(S) increased further (i.e., as the decrement grew), L(M) flattened out below L(STF). The overall pattern of results could be interpreted in terms of the concept of contrast brightness, with consideration of the intrinsic differences in brightness evaluations between decrements and increments.

Time course of brightness under transient glare condition.

It was shown that a peripheral glare source reduces the brightness of a foveal stimulus. We hypothesized that this brightness reduction is governed by an inhibitory effect of the glare source on the test. We reported the results of an investigation of the dynamic of brightness reduction of an incremental stimulus immediately after the onset of a glare source in the field of view. A magnitude comparison paradigm using constant stimuli was adopted to determine the luminance that appeared equal in brightness to the standard patch. The luminance of the standard stimulus was in the mesopic range (0.5 cd/m2), and the levels of glare were 15 and 60 lx. Results showed that the time course of brightness reduction followed the typical shape attributed to the Broca-Sulzer effect. Data were fitted with a model that first considers the response of a peripheral ganglion cell to glare and then its inhibitory effect on the test signals. We discussed the plausibility of a postretinal stage of processing.