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1.
Optom Vis Sci ; 98(5): 483-489, 2021 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-33967252

RESUMO

SIGNIFICANCE: This pilot study compared subjective and objective vision of children wearing single-vision and +2.00, +3.00, and +4.00 D add power soft multifocal contact lenses to determine whether the higher add power-thought to provide better myopia control-resulted in visual compromise. PURPOSE: This study aimed to determine the maximum add power children wearing center-distance soft multifocal contact lenses could accept objectively and subjectively. METHODS: Myopic children were assigned in random order to wear omafilcon A single-vision or multifocal "D" contact lenses with +2.00, +3.00, or +4.00 D add power for 1 week each. High-contrast distance and near visual acuity, low-contrast distance visual acuity, and contrast sensitivity were measured at each visit along with a quality of vision questionnaire to assess their vision. The Friedman test was performed to evaluate the impact of add power on all outcome measures. RESULTS: Eleven subjects were enrolled, and nine subjects completed the study. The median age of completed subjects was 11 years. Median logMAR low-contrast distance visual acuity was reduced in the +3.00 (+0.20) and +4.00 (+0.28) D add lenses compared with the +2.00 (+0.16) D add and single-vision lenses (+0.10, P < .001). All three multifocal lenses resulted in reduced contrast sensitivity (+1.35 to +1.40) compared with single-vision lenses (+1.60, P < .001). In general, +3.00 and +4.00 D add lenses resulted in worse glare/starbursts, ghost images, computer vision, changing fixation distance, and overall vision, but results varied. There were no differences among the lenses with respect to subjective assessments of distance vision, near vision, strain or tiredness, contact lens comfort, or sporting activities. CONCLUSIONS: The +3.00 D and higher add powers result in more objective and subjective vision-related issues than single-vision lenses, but the +2.00 D add multifocal lenses were well tolerated.


Assuntos
Lentes de Contato Hidrofílicas , Sensibilidades de Contraste/fisiologia , Miopia/terapia , Acuidade Visual/fisiologia , Criança , Feminino , Humanos , Masculino , Miopia/fisiopatologia , Projetos Piloto , Inquéritos e Questionários
2.
Optom Vis Sci ; 98(4): 394-403, 2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-33828037

RESUMO

SIGNIFICANCE: Contrast sensitivity changes across the visual field with age and is often measured clinically with various forms of perimetry on plain backgrounds. In daily life, the visual scene is more complicated, and therefore, the standard clinical measures of contrast sensitivity may not predict a patient's visual experience in more natural environments. PURPOSE: This study aims to determine whether contrast thresholds in older adults are different from younger adults when measured on a 1/f noise background (a nonuniform background whose spatial frequency content is similar to those present in the natural vision environments). METHODS: Twenty younger (age range, 20 to 35 years) and 20 older adults (age range, 61 to 79 years) with normal ocular health were recruited. Contrast thresholds were measured for a Gabor patch of 6 cycles per degree (sine wave grating masked by a Gaussian envelope of standard deviation 0.17°) presented on 1/f noise background (root-mean-square contrast, 0.05 and 0.20) that subtended 15° diameter of the central visual field. The stimulus was presented at four eccentricities (0°, 2°, 4°, and 6°) along the 45° meridian in the noise background, and nine contrast levels were tested at each eccentricity. The proportion of correct responses for detecting the target at each eccentricity was obtained, and psychometric functions were fit to estimate the contrast threshold. RESULTS: Older adults demonstrate increased contrast thresholds compared with younger adults. There was an eccentricity-dependent interaction with age, with the difference between groups being highest in the fovea compared with other eccentricities. Performance was similar for the two noise backgrounds tested. CONCLUSIONS: Our results revealed a strong eccentricity dependence in performance between older and younger adults, highlighting age-related differences in the contrast detection mechanisms between fovea and parafovea for stimuli presented on nonuniform backgrounds.


Assuntos
Envelhecimento/fisiologia , Sensibilidades de Contraste/fisiologia , Fóvea Central/fisiologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Psicometria , Limiar Sensorial/fisiologia , Testes de Campo Visual/métodos , Campos Visuais/fisiologia , Adulto Jovem
3.
Optom Vis Sci ; 98(3): 272-279, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-33771957

RESUMO

PURPOSE: The purpose of this study was to examine the visual performance of center-distance MFCLs in nonpresbyopic adults under different illumination and contrast conditions compared with a single-vision contact lens (SVCL). METHODS: Twenty-five adult subjects were fit with three different lenses (CooperVision Biofinity D MFCL +2.50 add, Visioneering Technologies NaturalVue MFCL, CooperVision Biofinity sphere). Acuity and reading performance were evaluated. RESULTS: A statistically significant difference in high-contrast distance acuity was observed (Biofinity, -0.18 ± 0.06; Biofinity MFCL, -0.14 ± 0.08; NaturalVue MFCL, -0.15 ± 0.03; repeated-measures [RM] ANOVA, P = .02). Under mesopic, high-contrast conditions, MFCLs performed worse than SVCLs (Biofinity, -0.05 ± 0.091; Biofinity MFCL, +0.03 ± 0.09; NaturalVue MFCL, +0.05 ± 0.091; RM-ANOVA, P < .0001). Under low-contrast conditions, MFCLs performed one line worse in photopic lighting and two lines worse under mesopic conditions (RM-ANOVA, P < .0001). Glare reduced acuity by 0.5 logMAR for all lenses (RM-ANOVA, P < .001). A statistically significant difference in near acuity was observed (RM-ANOVA, P = .02), but all lenses achieved acuity better than -0.1 logMAR (Biofinity, -0.16 ± 0.06; Biofinity MFCL, -0.17 ± 0.04; NaturalVue MFCL, -0.13 ± 0.08). Reading performance in words per minute (wpm) was worse with MFCLs (Biofinity MFCL, 144 ± 22 wpm; NaturalVue MFCL, 150 ± 28 wpm) than with SVCLs (156 ± 23 wpm; RM-ANOVA, P = .02) regardless of letter size (RM-ANOVA, P = .13). No difference in acuity between the MFCLs was detected (RM-ANOVA: all, P > .05). CONCLUSIONS: Multifocal contact lenses perform similarly to SVCLs for high-contrast targets and display reduced low-contrast acuity and reading speed. Practitioners should recognize that high-contrast acuity alone does not describe MFCL visual performance.


Assuntos
Lentes de Contato , Miopia/terapia , Acuidade Visual/fisiologia , Adulto , Visão de Cores/fisiologia , Sensibilidades de Contraste/fisiologia , Estudos Cross-Over , Feminino , Ofuscação , Humanos , Luz , Masculino , Miopia/fisiopatologia , Ajuste de Prótese , Refração Ocular/fisiologia , Método Simples-Cego , Adulto Jovem
4.
Optom Vis Sci ; 98(2): 121-126, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33534375

RESUMO

SIGNIFICANCE: Lipid deficiency due to meibomian gland (MG) dysfunction is believed to account for the vast majority of patients with dry eye compared with aqueous deficiency. Clinicians commonly evaluate MG length to determine a disease, but our research with isotretinoin users suggests that MG contrast is also an important characteristic to consider. PURPOSE: This study aimed to determine the sensitivity and specificity of MG contrast for the diagnosis of lipid-deficient dry eye (LDDE). METHODS: This case-control study used demographic data, Standard Patient Evaluation of Eye Dryness (SPEED) scores, average tear lipid layer thickness (TLLT), fluorescein tear breakup time (FTBUT), upper eyelid meibography images, and meibum quality and quantity scores for individuals with LDDE (SPEED score ≥10 and TLLT ≤35 interferometric color units) and normal individuals (SPEED ≤2 and TLLT ≥80 interferometric color units). RESULTS: Thirty-one eyes of 22 controls (mean ± SD age, 22.7 ± 5.5 years) and 13 eyes of 12 cases (mean ± SD age, 43.9 ± 17.2 years) were included. Normalized MG contrast was significantly correlated with FTBUT (r = 0.35, P = .02), percent MG atrophy (r = -0.50, P < .001), and SPEED scores (r = -0.49, P < .001). The receiver operating characteristic curve for LDDE diagnosis classifiers MG contrast, MG atrophy, and meibum quantity score had areas under the curve of 0.83, 0.64, and 0.73, respectively. Meibomian gland contrast cutoff at 28.3 intensity units yielded optimal correct classification of subjects (84.1%; sensitivity, 0.69; specificity, 0.90). Cases had shorter FTBUT (P < .001), worse meibum quality (P = .02) and quantity (P = .02) scores, and lower MG contrast (P < .001) compared with controls. Subjects with low MG contrast (≤28.3) had 14.9 higher odds of having LDDE (95% confidence interval, 2.84 to 78.4) compared with subjects with high MG contrast (>28.3). CONCLUSIONS: Meibomian gland contrast correlates well with clinical parameters and symptoms, shows good sensitivity and excellent specificity for diagnosing LDDE, and can be a useful diagnostic parameter for monitoring MG changes due to age, disease, or intervention.


Assuntos
Sensibilidades de Contraste/fisiologia , Síndromes do Olho Seco/diagnóstico , Disfunção da Glândula Tarsal/diagnóstico , Glândulas Tarsais/fisiopatologia , Lágrimas/metabolismo , Adolescente , Adulto , Estudos de Casos e Controles , Síndromes do Olho Seco/fisiopatologia , Feminino , Humanos , Interferometria , Masculino , Disfunção da Glândula Tarsal/metabolismo , Pessoa de Meia-Idade , Projetos Piloto , Estudos Retrospectivos , Sensibilidade e Especificidade , Adulto Jovem
5.
Optom Vis Sci ; 98(2): 150-158, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33534376

RESUMO

SIGNIFICANCE: High-contrast acuity in individuals with infantile nystagmus syndrome (INS) is poorer than expected from their ongoing retinal image motion, indicating a sensory loss. Conversely, acuity for larger low-contrast letters in these observers may be limited by image motion alone. PURPOSE: The aim of this study was to assess visual acuity for letters of different contrast in normal observers and individuals with idiopathic INS under conditions of comparable retinal image motion. METHODS: Visual acuity was measured using projected Landolt C charts in 3 normal observers and 11 observers with presumed idiopathic INS. Normal observers viewed each chart after reflection from a front-surface mirror that underwent continuous 4-Hz ramp motion with amplitudes ranging from 4 to 9.6° and simulated foveation durations of 20 to 80 milliseconds. Observers with INS viewed the charts directly. By reciprocally varying the luminance of the projected charts and a superimposed veiling source, Landolt C's were presented on a background luminance of 43 cd/m2 with Weber contrasts between -12 and -89%. RESULTS: Whereas normal observers' high-contrast acuity during imposed image motion depends only on the duration of the simulated foveation periods, acuity for low-contrast optotypes also worsens systematically as motion intensity (frequency × amplitude) increases. For comparable parameters of retinal image motion, high-contrast acuity in all but one of the observers with INS was poorer than in normal observers. On the other hand, low-contrast acuity in the two groups of observers was similar when the retinal image motion was comparable. CONCLUSIONS: Reduced high-contrast acuity in observers with INS appears to be attributable primarily to a sensory deficit. On the other hand, the reduction of low-contrast acuity in observers with INS may be accounted for on the basis of retinal image motion.


Assuntos
Sensibilidades de Contraste/fisiologia , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Percepção de Movimento/fisiologia , Nistagmo Congênito/fisiopatologia , Acuidade Visual/fisiologia , Adolescente , Adulto , Movimentos Oculares/fisiologia , Feminino , Humanos , Masculino , Retina/fisiologia , Adulto Jovem
6.
J Vis ; 21(2): 12, 2021 02 03.
Artigo em Inglês | MEDLINE | ID: mdl-33630026

RESUMO

Our eyes are never still, but tend to "freeze" in response to stimulus onset. This effect is termed "oculomotor inhibition" (OMI); its magnitude and time course depend on the stimulus parameters, attention, and expectation. We previously showed that the time course and duration of microsaccade and spontaneous eye-blink inhibition provide an involuntary measure of low-level visual properties such as contrast sensitivity during fixation. We investigated whether this stimulus-dependent inhibition also occurs during smooth pursuit, for both the catch-up saccades and the pursuit itself. Observers followed a target with continuous back-and-forth horizontal motion while a Gabor patch was briefly flashed centrally with varied spatial frequency and contrast. Catch-up saccades of the size of microsaccades had a similar pattern of inhibition as microsaccades during fixation, with stronger inhibition onset and faster inhibition release for more salient stimuli. Moreover, a similar stimulus dependency of inhibition was shown for pursuit latencies and peak velocity. Additionally, microsaccade latencies at inhibition release, peak pursuit velocities, and latencies at minimum pursuit velocity were correlated with contrast sensitivity. We demonstrated the generality of OMI to smooth pursuit for both microsaccades and the pursuit itself and its close relation to the low-level processes that define saliency, such as contrast sensitivity.


Assuntos
Sensibilidades de Contraste/fisiologia , Músculos Oculomotores/fisiologia , Acompanhamento Ocular Uniforme/fisiologia , Adolescente , Adulto , Atenção/fisiologia , Piscadela , Feminino , Humanos , Inibição Psicológica , Masculino , Movimentos Sacádicos/fisiologia , Adulto Jovem
7.
J Vis ; 21(1): 13, 2021 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-33502438

RESUMO

The features of perceptual surround suppression vary with eccentricity, such that the suppression strength is increased for horizontally oriented stimuli relative to other orientations near the fovea, but is strongest for radially oriented stimuli more peripherally. Perceptual suppression also varies with age, which has been well-studied for central fixation. However, only limited data are available regarding perceptual suppression in older adults for nonfoveal vision, and none of those studies have taken orientation biases of contrast sensitivity into account. Here, we explored the effects of older age on the eccentricity dependency of orientation biases of perceptual suppression. We found increased perceptual suppression in older adults at both 6° and 15° eccentricities relative to younger adults. A main effect of the horizontal orientation bias was found at 6° and a main effect of the radial orientation bias was found at 15° in both groups. In summary, perceptual surround suppression of contrast is stronger for older adults compared with younger adults at 6° and 15° eccentricities, but retinotopic orientation anisotropies are maintained with age. This study provides new insight into parafoveal visual perception in older adults, which may be particularly important to understand the visual experience of those who depend on nonfoveal vision owing to common age-related eye diseases.


Assuntos
Envelhecimento/fisiologia , Orientação Espacial/fisiologia , Adulto , Idoso , Anisotropia , Sensibilidades de Contraste/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Percepção Visual , Adulto Jovem
8.
Am J Ophthalmol ; 224: 246-253, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-32950508

RESUMO

PURPOSE: Myopic vitreopathy features precocious fibrous vitreous liquefaction and early posterior vitreous detachment (PVD). It is unclear whether visual function is affected by myopic vitreopathy and PVD. This study assessed the relationships among axial length, structural vitreous density, PVD, and visual function. DESIGN: Retrospective case-control study. METHODS: Ultrasonography measurements were made of axial length, logMAR VA, contrast sensitivity function (CSF [Freiburg acuity contrast test]), and quantitative B-scan ultrasonography. RESULTS: Seventy-nine subjects (45 men and 34 women; mean age: 49 ± 14 years) were analyzed. Axial lengths ranged from 22 to 29.2 mm (mean: 24.9 ± 1.8 mm; myopic eyes: 26.35 ± 1.35 mm; and nonmyopic eyes: 23.45 ± 0.75 mm; P < .001). With increasing axial length there was greater vitreous echodensity (R: 0.573; P < .01) and degradation in CSF (R: 0.611; P < .01). Subgroup analyses found that myopic eyes (>- 3 diopters) had 37% more vitreous echodensity than nonmyopic eyes (762 ± 198 arbitrary units [AU] vs. 557 ± 171 AU, respectively; P < .001) and that CSF was 53% worse in myopic eyes (3.30 ± 1.24 Weber index [%W]) than in nonmyopic eyes (2.16 ± .59 %W; P < .001). Myopic eyes with PVD had 33% greater vitreous echodensity (815 ± 217 AU; P < .001) and 62% degradation in CSF (3.63 ± 2.99 %W) compared to nonmyopic eyes with PVD (613 ± 159 AU; 2.24 ± 0.69 %W; P < .001, each). Limited vitrectomy was performed in 11 of 40 cases (27.5%), normalizing vitreous echodensity and CSF in each case. CONCLUSIONS: Axial myopia is associated with increased fibrous vitreous liquefaction and echodensity, as well as profound degradation of CSF. PVD in myopic eyes is associated with even more structural and functional abnormalities, normalized by limited vitrectomy. These findings may explain some common complaints of myopic patients with respect to vision and quality of life.


Assuntos
Oftalmopatias/fisiopatologia , Miopia/fisiopatologia , Acuidade Visual/fisiologia , Corpo Vítreo/patologia , Descolamento do Vítreo/fisiopatologia , Adulto , Idoso , Comprimento Axial do Olho/patologia , Estudos de Casos e Controles , Sensibilidades de Contraste/fisiologia , Oftalmopatias/diagnóstico por imagem , Oftalmopatias/etiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Tomografia de Coerência Óptica , Ultrassonografia , Vitrectomia , Corpo Vítreo/diagnóstico por imagem , Descolamento do Vítreo/diagnóstico por imagem , Descolamento do Vítreo/etiologia
9.
Exp Eye Res ; 202: 108331, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33152390

RESUMO

As a result of longitudinal chromatic aberration (LCA), longer wavelengths are blurred when shorter wavelengths are in focus, and vice versa. As a result, LCA affects the color and temporal aspects of the retinal image with hyperopic defocus. In this experiment, we investigated how the sensitivity to temporal color contrast affects emmetropization. Ten-day-old chicks were exposed for three days to sinusoidal color modulation. The modulation was either blue/yellow flicker (BY) (n = 57) or red/green flicker (RG) (n = 60) simulating hyperopic defocus with and without a blue light component. The color contrasts tested were 0.1, 0.2, 0.3, 0.4, 0.6, and 0.8 Michelson contrast. The mean illuminance of all stimuli was 680 lux. Temporal modulation was either of a high (10 Hz) or low (0.2 Hz) temporal frequency. To test the role of short- and double-cone stimulation, an additional condition silenced these cones in RG_0.4 (D-) and was compared with RG_0.4 (D+) (n = 14). Changes in ocular components and refractive error were measured using Lenstar and a photorefractometer. With high temporal frequency BY representing an in-focus condition for shorter-wavelengths, we found that high temporal frequency BY contrast was positively correlated with vitreous expansion (R2 = 0.87, p < 0.01), expanding the vitreous to compensate for hyperopic defocus. This expansion was offset by low temporal frequency RG, which represented blurred longer wavelengths. The reduction in vitreous expansion in RG_0.4, was enhanced in D+ compared to D- (p < 0.001), indicating a role for short- and/or double-cones. With high temporal frequency RG representing an in-focus condition for longer-wavelengths, we found that high temporal frequency RG contrast was also positively correlated with a linear increase in vitreous chamber depth (R2 = 0.84, p < 0.01) and eye length (R2 = 0.30, p ≤ 0.05), required to compensate for hyperopic defocus, but also with RG sensitive choroidal thickening (R2 = 0.18: p < 0.0001). These increases in the vitreous and eye length were enhanced with D+ compared to D- (p = 0.003) showing the role of short- and double-cones in finessing the vitreous response to hyperopic defocus. Overall, the increase in vitreous chamber depth in RG was offset by reduced expansion in BY, indicating sensitivity to the shorter focal length of blue light and wavelength defocus. Predictable changes in cone contrast and temporal frequency of the retinal image that occur with LCA and defocus result in homeostatic control of emmetropization.


Assuntos
Percepção de Cores/fisiologia , Sensibilidades de Contraste/fisiologia , Emetropia/fisiologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Animais , Comprimento Axial do Olho/fisiopatologia , Biometria , Galinhas , Luz , Modelos Animais , Refração Ocular/fisiologia
10.
Sci Rep ; 10(1): 20886, 2020 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-33257759

RESUMO

Age-related macular degeneration (AMD) is a progressive and degenerative disorder of the macula. In advanced stages, it is characterized by the formation of areas of geographic atrophy or fibrous scars in the central macula, which determines irreversible loss of central vision. These patients can benefit from visual rehabilitation programmes with acoustic "biofeedback" mechanisms that can instruct the patient to move fixation from the central degenerated macular area to an adjacent healthy area, with a reorganization of the primary visual cortex. In this prospective, comparative, non-randomized study we evaluated the efficacy of visual rehabilitation with an innovative acoustic biofeedback training system based on visual evoked potentials (VEP) real-time examination (Retimax Vision Trainer, CSO, Florence), in a series of patients with advanced AMD compared to a control group. Patients undergoing training were subjected to ten consecutive visual training sessions of 10 min each, performed twice a week. Patients in the control group did not receive any training. VEP biofeedback rehabilitation seems to improve visual acuity, reading performances, contrast sensitivity, retinal fixation and sensitivity and quality of life in AMD patients.


Assuntos
Biorretroalimentação Psicológica/fisiologia , Potenciais Evocados Visuais/fisiologia , Degeneração Macular/fisiopatologia , Degeneração Macular/reabilitação , Idoso , Idoso de 80 Anos ou mais , Sensibilidades de Contraste/fisiologia , Feminino , Atrofia Geográfica/fisiopatologia , Humanos , Masculino , Estudos Prospectivos , Qualidade de Vida , Leitura , Retina/fisiopatologia , Transtornos da Visão/fisiopatologia , Baixa Visão/fisiopatologia , Acuidade Visual/fisiologia
11.
J Vis ; 20(13): 4, 2020 12 02.
Artigo em Inglês | MEDLINE | ID: mdl-33275663

RESUMO

Although the contrast sensitivity function (CSF) changes markedly during infancy, there is no consensus regarding whether, how, and why it continues to develop in later childhood. Here, we analyzed previously published data (N = 1928 CSFs), and present new psychophysical findings from 98 children (4.7-14.8 years) and 50 adults (18.1-29.7 years), in order to answer the following questions: (1) Does the CSF change during childhood? (2) How large is the developmental effect size? (3) Are any changes uniform across the CSF, or frequency-specific? and (4) Can some or all of the changes be explained by "non-visual" (i.e. procedural/cognitive) factors, such as boredom or inattentiveness? The new data were collected using a four-alternative forced-choice (4AFC) Gabor-detection task, with two different psychophysical procedures (Weighted Staircase; QUEST+), and suprathreshold (false-negative) catch trials to quantify lapse rates. It is shown that from ages 4 to 18 years, the CSF improves (at an exponentially decaying rate) by approximately 0.3 log10 units (a doubling of contrast sensitivity [CS]), with 90% of this change complete by 12 years of age. The size of the effect was small relative to individual variability, with age alone explaining less than one sixth of variability (16%), and most children performing as well as some adults (i.e. falling within the 90% population limits for adults). Development was frequency-specific, with changes occurring primarily around or below the CSF peak (≤ 4 cpd). At least half - and potentially all - of the changes observed could be explained by non-visual factors (e.g. lapses in concentration), although possible biological mechanisms are discussed.


Assuntos
Sensibilidades de Contraste/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Processamento Espacial/fisiologia , Adolescente , Adulto , Envelhecimento/fisiologia , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Psicofísica/métodos , Adulto Jovem
12.
J Vis ; 20(13): 14, 2020 12 02.
Artigo em Inglês | MEDLINE | ID: mdl-33355596

RESUMO

Detection of target objects in the surrounding environment is a common visual task. There is a vast psychophysical and modeling literature concerning the detection of targets in artificial and natural backgrounds. Most studies involve detection of additive targets or of some form of image distortion. Although much has been learned from these studies, the targets that most often occur under natural conditions are neither additive nor distorting; rather, they are opaque targets that occlude the backgrounds behind them. Here, we describe our efforts to measure and model detection of occluding targets in natural backgrounds. To systematically vary the properties of the backgrounds, we used the constrained sampling approach of Sebastian, Abrams, and Geisler (2017). Specifically, millions of calibrated gray-scale natural-image patches were sorted into a 3D histogram along the dimensions of luminance, contrast, and phase-invariant similarity to the target. Eccentricity psychometric functions (accuracy as a function of retinal eccentricity) were measured for four different occluding targets and 15 different combinations of background luminance, contrast, and similarity, with a different randomly sampled background on each trial. The complex pattern of results was consistent across the three subjects, and was largely explained by a principled model observer (with only a single efficiency parameter) that combines three image cues (pattern, silhouette, and edge) and four well-known properties of the human visual system (optical blur, blurring and downsampling by the ganglion cells, divisive normalization, intrinsic position uncertainty). The model also explains the thresholds for additive foveal targets in natural backgrounds reported in Sebastian et al. (2017).


Assuntos
Sensibilidades de Contraste/fisiologia , Percepção de Forma/fisiologia , Luz , Retina/fisiologia , Sinais (Psicologia) , Humanos , Psicofísica , Limiar Sensorial
13.
J Vis ; 20(13): 17, 2020 12 02.
Artigo em Inglês | MEDLINE | ID: mdl-33369613

RESUMO

The contrast sensitivity function (CSF) is an informative measure of visual health, but the practical difficulty of measuring it has impeded detailed analyses of its relationship to different visual disorders. Furthermore, most existing tasks cannot be used in populations with cognitive impairment. We analyzed detailed CSFs measured with a nonverbal procedure called "Gradiate," which efficiently infers visibility from eye movements and manipulates stimulus appearance in real time. Sixty observers of varying age (38 with refractive error) were presented with moving stimuli. Stimulus spatial frequency and contrast advanced along 15 radial sweeps through CSF space in response to stimulus-congruent eye movements. A point on the CSF was recorded when tracking ceased. Gradiate CSFs were reliable and in high agreement with independent low-contrast acuity thresholds. Overall CSF variation was largely captured by two orthogonal factors ("radius" and "slope") or two orthogonal shape factors when size was normalized ("aspect ratio" and "curvature"). CSF radius was highly predictive of LogMAR acuity, as were aspect ratio and curvature together, but only radius was predictive of observer age. Our findings suggest that Gradiate holds promise for assessing spatial vision in both verbal and nonverbal populations and indicate that variation between detailed CSFs can reveal useful information about visual health.


Assuntos
Sensibilidades de Contraste/fisiologia , Movimentos Oculares/fisiologia , Adolescente , Adulto , Idoso , Criança , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Percepção de Movimento/fisiologia , Processamento Espacial , Acuidade Visual/fisiologia , Adulto Jovem
14.
J. optom. (Internet) ; 13(4): 227-234, oct.-dic. 2020. ilus, tab
Artigo em Inglês | IBECS | ID: ibc-201486

RESUMO

PURPOSE: To assess the visual effects of wearing both an activated and an inactivated photochromic contact lens, with a direct comparison to a non-photochromic contact lens worn in the fellow eye. This study focused on the visual effects of scatter quantified as the minimum distance between two points of light, and the diameter of the halo and starbursts that surround a bright white point source. METHODS: 60 subjects (aged 18-65 years) were measured in a contralateral design where lens type was randomly assigned, one type to each eye. During activated testing, all visual measures of both study lenses were made while each eye was illuminated by a violet (Lambdamax = 365, half bandwidth 20 nm) activator, which caused steady-state activation of the photochromic lens during the period of testing. Two-point thresholds were determined by measuring the minimum distance between two points of broadband xenon light. Glare geometry was measured using an aperture (∼ 4 mm) that created a bright point source of light 45 inches from the plane of the eye. Between the point source and subject, a centering precision caliper was used to measure lateral spread of halos (diffusion around the source) and visual spokes. The head was stabilized using an adjustable head-rest assembly and the eye was aligned and monitored with a bore camera. RESULTS: Compared to the non-photochromic lens, and based on the stimulus conditions used in these measurements, the activated and inactivated photochromic lens reduced the light spread using the two-point threshold technique by 32% and 19% respectively; the diameter of the halos were reduced by 44% and 16% respectively; and the spokes were narrowed by 39% and 20% respectively. Based on 95% confidence interval testing, these effects were all statistically significant (p < 0.05). CONCLUSIONS: These results are consistent with previous data showing that soft contact lenses with a photochromic additive can improve many aspects of visual function, consistent with their level or activation. Our past data focused on visual function under bright light conditions (e.g., glare disability, discomfort, photostress recovery and chromatic contrast) with an activated photochromic. In this study, we found differences even in the inactivated state, using less intense stimuli (10cd/m2 at the source). This suggests that the photochromic lens improves the effects of light scatter even at lower luminance


OBJETIVO: Evaluar los efectos visuales del uso de lentes de contacto con activación e inactivación fotocromática, mediante comparación directa con el uso de lentes de contacto no fotocromáticas en el ojo contralateral. Este estudio se centró en los efectos visuales de la dispersión, cuantificada mediante la distancia mínima entre dos puntos luminosos, y el diámetro del halo y los destellos que rodean a una fuente fija blanca brillante. MÉTODOS: Se realizaron mediciones a 60 sujetos (de edades comprendidas entre 18 y 65 años) en un diseño contralateral en el que se asignó aleatoriamente un tipo a cada ojo. Durante la prueba con activación, se realizaron todas las medidas visuales de ambas lentes en estudio, mientras se iluminaba cada ojo con un activador violeta (lambdamáx.=365, ancho de banda medio 20 nm), que causó una activación del estado de equilibrio de las lentes fotocromáticas durante el periodo de prueba. Se determinaron los umbrales de dos puntos, midiendo la distancia mínima entre dos puntos de luz de xenón de banda ancha. Se midió la geometría del reflejo utilizando una apertura (∼ 4 mm) que creó una fuente fija brillante de luz a 45 pulgadas del plano del ojo. Entre la fuente fija y el sujeto se utilizó un calibrador de precisión de centrado para medir la expansión lateral de los halos (difusión alrededor de la fuente) y los destellos. La cabeza se estabilizó utilizando un reposacabezas, alineándose y supervisándose el ojo con una cámara. RESULTADOS: Realizando una comparación con las lentes no fotocromáticas, y sobre la base de las condiciones de estímulo utilizadas en estas medidas, las lentes con activación y desactivación fotocromática redujeron la expansión de la luz utilizando la técnica del umbral de dos puntos en un 32% y un 19% respectivamente; el diámetro de los halos se redujo en un 44% y 16% respectivamente; y los brillos se estrecharon en un 39% y 20% respectivamente. Basándonos en la prueba del intervalo de confianza del 95%, todos estos efectos fueron estadísticamente significativos (p < 0,05). CONCLUSIONES: Estos resultados son consistentes con los datos previos, que reflejan que las lentes de contacto fotocromáticas pueden mejorar muchos aspectos de la función visual, en consistencia con su nivel de activación. Nuestros datos anteriores se centraron en la función visual en condiciones de luz brillante (ej.: incapacidad por deslumbramiento, incomodidad, recuperación de foto-estrés y contraste cromático) con activación de adición fotocromática. En este estudio, encontramos diferencias incluso en el estado de inactivación, utilizando estímulos menos intensos (10 cd/m2 en la fuente), lo cual sugiere que las lentes fotocromáticas mejoran los efectos de la dispersión luminosa incluso con una luminancia menor


Assuntos
Adolescente , Adulto Jovem , Adulto , Pessoa de Meia-Idade , Idoso , Lentes de Contato Hidrofílicas , Visão Ocular/fisiologia , Sensibilidades de Contraste/fisiologia , Estudos Cross-Over , Estudos Prospectivos , Acuidade Visual/fisiologia
15.
Optom Vis Sci ; 97(12): 1034-1040, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33252542

RESUMO

SIGNIFICANCE: The options that can help patients with congenital color vision defect, to a better professional and leisure adaptation, are very limited. Different haploscopic lenses can be considered, and their effects need to be investigated in patients with different defects. PURPOSE: The purpose of this study was to present and discuss the effect of a pair of asymmetric long-pass filters fitted for deuteranopia, with the result of a 60% improvement in distinguishing red-green plates when compared with baseline. CASE REPORT: We report the case of a 51-year-old man with congenital deuteranopia fitted with haploscopic ChromaGen filters. During the 2-month follow-up, we observed a decrease in left-eye logMAR visual acuity and contrast sensitivity with an increased ability to discriminate the plates of different color vision tests (Ishihara, Farnsworth, and Hardy-Rand-Rittler). The visual outcomes are discussed considering the spectral sensitivity curves of each filter, measured with a spectrophotometric device. CONCLUSIONS: This report describes an improvement in the ability to resolve color vision plates after using asymmetric haploscopic filters showing a left-eye decrease in logMAR visual acuity and contrast sensitivity function. Subjects with a history of color vision deficiency might benefit from using haploscopic filters that selectively minimize the transmittance within a specific bandwidth to improve the color discrimination in deutan color vision deficiency. The simultaneous analysis of the color vision outcomes and transmittance spectrum of the haploscopic filters might contribute to a better understanding of the mechanisms behind the claimed efficacy of these devices.


Assuntos
Defeitos da Visão Cromática/terapia , Sensibilidades de Contraste/fisiologia , Óculos , Filtração/instrumentação , Percepção de Cores/fisiologia , Testes de Percepção de Cores , Defeitos da Visão Cromática/congênito , Defeitos da Visão Cromática/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade
16.
Afr Health Sci ; 20(2): 758-767, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33163041

RESUMO

Purpose: To investigate the effects of spectacle and telescope corrections on visual acuity (VA), contrast sensitivity (CS) and reading rates (RR) in students with oculocutaneous albinism (OCA). Methods: An observational study design was conducted on 81 students with OCA. Distance and near VA, CS and RR were measured without correction, with spectacle correction and with a combination of spectacle correction and telescopes. Results: The mean distance and near VA values with a combination of spectacle correction and telescopes were significantly better than those without correction and with spectacle correction alone (p = 0.01). Mean CS values achieved with spectacles alone were significantly better than those obtained with a combination of spectacles and telescopes (p = 0.01). There was no significant difference between logCS values obtained without correction compared to those obtained with a combination of spectacle correction and telescopes. There were no significant differences between RR values obtained with a combination of spectacles and telescopes and those without and with spectacle correction alone (all p > 0.05). Conclusion: This article provides valuable information to eye care practitioners on the effects of spectacles and telescopes on visual acuity, contrast sensitivity and reading rate in students with OCA.


Assuntos
Albinismo Oculocutâneo/diagnóstico , Sensibilidades de Contraste/fisiologia , Óculos , Leitura , Telescópios , Acuidade Visual/fisiologia , Adolescente , Albinismo Oculocutâneo/terapia , Criança , Humanos , Adulto Jovem
17.
Invest Ophthalmol Vis Sci ; 61(13): 33, 2020 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-33231621

RESUMO

Purpose: Individuals with pentosan polysulfate sodium (PPS) maculopathy commonly report symptoms of prolonged dark adaptation and difficulty reading. We hypothesize that PPS maculopathy causes degradation of visual function not fully captured with visual acuity testing. Methods: Subjects with PPS maculopathy underwent multimodal evaluation of retinal structure and function. Structural changes were graded as moderate or advanced. Patient-reported visual function was assessed with the National Eye Institute Visual Function Questionnaire 39 (NEI-VFQ-39) and Low Luminance Questionnaire (LLQ). Objective functional evaluations included Early Treatment of Diabetic Retinopathy Study (ETDRS) best-corrected visual acuity (BCVA), Pelli-Robson contrast sensitivity, mesopic microperimetry, and dark adaptometry. Functional testing results were correlated with structural disease category. Results: Thirteen patients (26 eyes), median age 62 years (range, 37-76), completed the study. Median ETDRS letter score was 82 (Snellen equivalent 20/25). Median NEI-VFQ-39 and LLQ composite scores were 65 (range, 33-88) and 41 (range, 20-92), respectively. Median contrast sensitivity was 1.65 (range, 0.15-1.95), and median mesopic microperimetry average thresholds and percent reduced thresholds were 26 decibels (range, 0.4-28.6) and 21.6% (range, 0-100%), respectively. Median rod intercept time was 14.1 minutes (range, 4.4-20.0). Eyes with advanced disease based on retinal structure had significantly worse retinal function for several testing modalities. Conclusions: PPS maculopathy causes considerable visual function degradation that is not fully captured with BCVA testing. There was good correlation between other measures of visual function and disease severity. These findings deepen our concern regarding this patient safety issue.


Assuntos
Anticoagulantes/efeitos adversos , Poliéster Sulfúrico de Pentosana/efeitos adversos , Doenças Retinianas/induzido quimicamente , Transtornos da Visão/induzido quimicamente , Acuidade Visual/fisiologia , Adulto , Idoso , Sensibilidades de Contraste/fisiologia , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doenças Retinianas/fisiopatologia , Perfil de Impacto da Doença , Inquéritos e Questionários , Transtornos da Visão/fisiopatologia , Testes de Campo Visual , Campos Visuais/fisiologia
18.
J Vis ; 20(12): 8, 2020 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-33206127

RESUMO

Previous studies have shown that the binocular summation of luminance contrast signals depends on the parameters involved in stereopsis when the luminance contrast is at the detection threshold. However, less attention has been paid to the perception of luminance modulation in stereoscopic patterns at suprathreshold contrast. To address this issue, we determined the contrast of stereoscopic patterns at the perceptual match to a standard contrast as a function of binocular disparity. The matched contrast was close to the standard contrast at 0 degrees disparity, but decreased as disparity deviated from 0 degrees, suggesting that sufficient disparity perceptually enhances luminance contrast. The reduction of matched contrast was more evident for uncrossed disparities than for crossed disparities, which almost disappeared when the contrast was near the threshold and also occurred when vertical disparity was introduced. We argue that the perceptual enhancement of the luminance contrast is due to the weaker interocular suppression for stimuli with large disparities.


Assuntos
Percepção de Profundidade/fisiologia , Luminescência , Disparidade Visual/fisiologia , Visão Binocular/fisiologia , Percepção Visual/fisiologia , Sensibilidades de Contraste/fisiologia , Humanos
19.
Optom Vis Sci ; 97(11): 995-1004, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33181732

RESUMO

SIGNIFICANCE: The selective reduction in visible wavelengths transmitted through commercially available blue-blocking lenses (BBLs) is known to influence the appearance and contrast detection of objects, particularly at low light levels. This influence may impair the human retinal receptor response time to dynamic light changes during photostress events. PURPOSE: This study aimed to assess whether BBLs selectively affect photostress recovery times (PSRTs) for chromatic and achromatic stimuli of different Weber contrasts that were viewed on a dark black background. METHODS: Photostress recovery times were measured in 12 younger participants (18 to 39 years old) with no history of ocular disease or abnormal vision. Photostress recovery times were evaluated for four brands of BBLs, which were compared with a control lens. In these experiments, after exposure to an intense light source for 5 seconds, the time taken to recover vision and correctly identify a computer-generated letter stimulus viewed under low and high luminance levels was determined, which means perception is likely to be governed by mesopic and photopic conditions. Across conditions, the letter stimulus was achromatic and chromatic and could differ in luminance contrast. RESULTS: Under photopic stimulus conditions, although reducing luminance contrast increased PSRTs, BBLs had no significant effect on PSRTs relative to control lens. However, under mesopic stimulus conditions, BBLs significantly affect PSRTs for both achromatic (F2.006,8.02 = 61.95, P < .0001) and chromatic stimuli (F3,16 =139.01, P < .0001), particularly for blue targets, which had considerably longer PSRTs (38.40 seconds). The brand of BBL was also shown to selectively affect PSRTs, with those with transmittance profiles that block the most blue light having longer PSRTs. CONCLUSIONS: The present study suggests that, although the color and contrast of the target stimuli affected recovery times, the difference in recovery times between different types of BBLs was noticed only under low-light-level stimulus conditions.


Assuntos
Óculos , Recuperação de Função Fisiológica/fisiologia , Estresse Fisiológico/fisiologia , Transtornos da Visão/fisiopatologia , Adolescente , Adulto , Visão de Cores/fisiologia , Sensibilidades de Contraste/fisiologia , Avaliação da Deficiência , Feminino , Humanos , Luz , Masculino , Adulto Jovem
20.
J Vis ; 20(10): 13, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33052408

RESUMO

Humans do not notice small displacements to objects that occur during saccades, termed saccadic suppression of displacement (SSD), and this effect is reduced when a blank is introduced between the pre- and postsaccadic stimulus (Bridgeman, Hendry, & Stark, 1975; Deubel, Schneider, & Bridgeman, 1996). While these effects have been studied extensively in adults, it is unclear how these phenomena are characterized in children. A potentially related mechanism, saccadic suppression of contrast sensitivity-a prerequisite to achieve a stable percept-is stronger for children (Bruno, Brambati, Perani, & Morrone, 2006). However, the evidence for how transsaccadic stimulus displacements may be suppressed or integrated is mixed. While they can integrate basic visual feature information from an early age, they cannot integrate multisensory information (Gori, Viva, Sandini, & Burr, 2008; Nardini, Jones, Bedford, & Braddick, 2008), suggesting a failure in the ability to integrate more complex sensory information. We tested children 7 to 12 years old and adults 19 to 23 years old on their ability to perceive intrasaccadic stimulus displacements, with and without a postsaccadic blank. Results showed that children had stronger SSD than adults and a larger blanking effect. Children also had larger undershoots and more variability in their initial saccade endpoints, indicating greater intrinsic uncertainty, and they were faster in executing corrective saccades to account for these errors. Together, these results suggest that children may have a greater internal expectation or prediction of saccade error than adults; thus, the stronger SSD in children may be due to higher intrinsic uncertainty in target localization or saccade execution.


Assuntos
Sensibilidades de Contraste/fisiologia , Movimentos Sacádicos/fisiologia , Percepção Visual/fisiologia , Adulto , Criança , Feminino , Humanos , Masculino , Incerteza , Adulto Jovem
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