Loss Of Visual Sensitivity Research Articles

Visual Sensitivity Loss in Geographic Atrophy: Structure-Function Evaluation Using Defect-Mapping Microperimetry.

To examine the structure-function relationship in eyes with geographic atrophy (GA) using defect-mapping microperimetry, a testing strategy optimized to quantify the spatial extent of deep visual sensitivity losses. Fifty participants with GA underwent defect-mapping microperimetry testing of the central 8°-radius region (208 locations tested once with a 10-decibel stimuli) and fundus autofluorescence imaging in one eye. The GA extent in the corresponding central 8°-radius was derived by manual annotations and image co-registration to examine the global structure-function relationship. The distance of each test location from the GA margin was also derived, and regions defined, to examine the local structure-function relationship. GA extent in the central 8° explained a substantial proportion of variance in the percentage of locations missed (nonresponse) on microperimetry at the global level (R2=0.90). At a local level, the probability of missing stimuli at the outer junctional zone (0-500 µm outside the GA margin) and GA margin (probability=7% and 34%, respectively) was higher than at the outer nonlesional zone (>500 µm outside the GA margin; probability=2%; P<0.001 for both). The probability of missing stimuli at the inner junctional zone (0-250 µm inside the GA margin) was also lower than at the inner lesional zone (>250 µm inside the GA margin; probability=64% and 88%; P<0.001). This study confirms the expected functional relevance of the region with GA on fundus autofluorescence imaging and underscores the potential effectiveness of defect-mapping microperimetry testing for capturing visual function changes when evaluating new GA treatments.

Systematic Underestimation of Visual Sensitivity Loss on Microperimetry: Implications for Testing Protocols in Clinical Trials.

To examine whether systematic changes in visual sensitivity measurements on microperimetry occur over tests within the same session and whether these changes vary according to the level of visual sensitivity loss. Eighty individuals with glaucoma or atrophic age-related macular degeneration underwent three microperimetry tests in one eye during one session using the 4-2 staircase strategy. Changes in mean sensitivity (MS) and pointwise sensitivity (PWS) between the first and second test pairs were examined, with PWS was examined separately based on its average value across the three tests in 6-dB bins. The coefficient of repeatability (CoR) for MS between each sequential test pair was also calculated. There was a significant decline in MS from the first to second test (P = 0.001), but no significant difference in MS was seen between the second and third tests (P = 0.562). This significant decline in the first test pair was observed in locations with an average PWS of <6 dB or between 6 to 12 dB and between 12 to 18 dB (P < 0.001), but not for all other average PWS bins (P ≥ 0.337). The CoR of MS was significantly lower in the second compared to the first test pair (1.4 dB and 2.5 dB, respectively; P < 0.001). The 4-2 staircase strategy conventionally used on microperimetry testing systematically underestimates visual sensitivity loss on the first test. The consistency and accuracy of visual sensitivity measurements on microperimetry in clinical trials could be markedly improved by using estimates from an initial test to seed subsequent tests and excluding this first test from analyses.

Design of a novel smartphone-based photostress recovery time test for detecting abnormalities in the macula. A cross-sectional study

BackgroundThe study aims to present a new smartphone-based photostress recovery time test (K-PSRT test) that measures the stimulus-specific loss of visual sensitivity, as well as the differentiation between normal from abnormal macular function. This novel test defines a new standardized photostress application as an alternative tool for incorporation into clinical practice. Materials and methodsA total of 48 visually impaired eyes and 47 normal sighted age-matched controls eyes were enrolled in the study. The median age in subjects with impairment was 71.0 years, while the median age in normal subjects was 70.0 years. A light produced by the smartphone camera at approximately 5 cm distance, perpendicular to the eye up 10 s filled the pupil. The photostress recovery time was assessed immediately after the exposure by asking the subjects to read correctly at least three successive letters of size corresponding to the previous line of the BCVA line at a distance of 40 cm. The digital photostress testing was performed with the best-corrected visual acuity (BCVA). The patients were examined twice within 2 weeks. Correlations among the recovery times, the visual acuity, and the contrast sensitivity function as well as correlations concerning each specific ocular disease were also performed. Furthermore, correlations among technology, usability, and ease of performance in both groups were analyzed. ResultsThe initial median photostress recovery time in patients with impaired eyes was 83.5 (68.5, 126.0), while in the normal individuals was 39.0 (14.0, 43.0). The median visual acuity in individuals with impairment was 0.59 logMAR (0.40, 0.90), whereas in the normal individuals was −0,06 logMAR. Test-retest reliability study was performed on 26 eyes (16 males, 10 females) for visually impaired eyes as well as on 35 normal eyes (19 males, 16 females). Concerning the reliability, the average Intraclass Correlation Coefficients (with 95% confidence intervals) ICC (95% CI) = 0,99 (0,98–1,00), indicating significant correlation between them (p < 0.01). The coefficient of repeatability for eye measurements reaches clinically acceptable levels, which is demonstrated with increased repeatability and consistency. The recovery time in patients with diabetic retinopathy was statistically significantly lower than in those with dry age-related macular degeneration (p = 0.027) and those with wet age-related macular degeneration (p = 0.032). The patient group has lower scores concerning technology, usability, and ease of performance compared to the normal. ConclusionsThis new testing modality (K-Photostress Recovery time test), is designed to be an easily implemented measurement in ophthalmic practice, and it can expand our understanding of macular function. The above findings support the usefulness of a novel reproducible photostress application as an indicator of macular pathology.

Rehabilitation of visual functions in adult amblyopic patients with a virtual reality videogame: a case series

Amblyopia or lazy eye is a dysfunction of the visual system that appears during childhood and traditionally has been considered untreatable in adults. Its main consequences are the loss of visual acuity and contrast sensitivity of the amblyopic eye and binocular vision impairments. During the last years videogames have been used as a therapeutic tool for amblyopia with the inconclusive results. The present work has assessed the effectiveness of a virtual reality videogame (AmbliOK®) in the neurorehabilitation of four adult clinical cases with anisometropic amblyopia. Visual acuity, contrast sensitivity, stereopsis and interocular suppression were assessed before, during, immediately after, one month and one year (in one patient) after the training. The intervention was conducted along four weeks (10 h) and yielded the variable results. In general, all patients showed an improvement in visual functions although not all ameliorated in the same way. Visual acuity measures improved in all patients, falling outside the amblyopia criterion at the end of the treatment. However, the improvement was not maintained one month later in two patients. Contrast sensitivity progressively improved for the amblyopic and the fellow eyes with all patients showing better results one month after the treatment. The patient assessed one year after still showed better results than in the baseline. Patients showing bad stereopsis in the baseline reached a performance considered normal one month and even one year after the treatment. The effectiveness of the treatment seems to be related to the characteristics of patients.

Chapter 2 - Amblyopia

Amblyopia is a neurodevelopmental abnormality that results in physiological alterations in the visual pathways and impaired vision in one eye, less commonly in both. It reflects a broad range of neural, perceptual, oculomotor, and clinical abnormalities that can occur when normal visual development is disrupted early in life. Aside from refractive error, amblyopia is the most common cause of vision loss in infants and young children. It causes a constellation of perceptual deficits in the vision of the amblyopic eye, including a loss of visual acuity, position acuity, and contrast sensitivity, particularly at high spatial frequencies, as well as increased internal noise and prolonged manual and saccadic reaction times. There are also perceptual deficits in the strong eye, such as certain types of motion perception, reflecting altered neural responses and functional connectivity in visual cortex (Ho et al., 2005). Treatment in young children consists of correction of any refractive error and patching of the strong eye. Compliance with patching is challenging and a substantial proportion of amblyopic children fail to achieve normal acuity or stereopsis even after extended periods of treatment. There are a number of promising experimental treatments that may improve compliance and outcomes, such as the playing of action video games with the strong eye patched. Although there may be a sensitive period for optimal effects of treatment, there is evidence that amblyopic adults may still show some benefit of treatment. However, there is as yet no consensus on the treatment of adults with amblyopia.

Nutritional Optic Neuropathies: State of the Art and Emerging Evidences.

Nutritional optic neuropathy is a cause of bilateral, symmetrical, and progressive visual impairment with loss of central visual acuity and contrast sensitivity, dyschromatopsia, and a central or centrocecal scotoma. The clinical features are not pathognomonic, since hereditary and toxic forms share similar signs and symptoms. It is becoming increasingly common due to the widespread of bariatric surgery and strict vegetarian or vegan diets, so even the scientific interest has recently increased. In particular, recent studies have focused on possible pathogenetic mechanisms, and on novel diagnostic and therapeutic strategies in order to prevent the onset, make a prompt diagnosis and an accurate nutritional supplementation, and to avoid irreversible optic nerve atrophy. Nowadays, there is clear evidence of the role of cobalamin, folic acid, thiamine, and copper, whereas further studies are needed to define the role of niacin, riboflavin, and pyridoxine. This review aims to summarize the etiology, diagnosis, and treatment of nutritional optic neuropathy, and it is addressed not only to ophthalmologists, but to all physicians who could come in contact with a patient with a possible nutritional optic neuropathy, being a fundamental multidisciplinary approach.

Experimental Model of Far Temporal Field Negative Dysphotopsia Generated in Phakic Eyes.

PurposeThe axial separation between the iris and the intraocular lens (IOL) in pseudophakic eyes can cause rays originating from the far temporal field to miss the IOL, resulting in negative dysphotopsia (ND). We developed an experimental model to test the hypothesis that obstruction of rays from the far temporal field can generate ND and an accompanying loss of visual sensitivity in the far temporal field.MethodsThe right eyes of 10 phakic subjects were fitted with soft contact lenses containing a 5.50-mm central clear zone and a 12-mm outer diameter opaque annulus. In three of the subjects, eyes were dilated with 1% tropicamide solution, and effective aperture diameters were determined optically (pupil camera) and psychophysically (narrow beam detection). Visual field extent (Goldmann bowl) and temporal and inferotemporal meridian sensitivities (Octopus perimeter) were measured. A wide-angle model was constructed to quantify the impact of the annular opacity on retinal illuminance.ResultsAll 10 subjects observed a dark crescent in the far temporal and inferotemporal fields. The opaque annulus reduced effective horizontal pupil diameters from 8 mm to 5.5 mm on-axis and from >2 mm to <1 mm at 90°. Perimetry revealed a 10° reduction in temporal and inferotemporal field extent and increasing loss of sensitivity beyond 70°. The wide-angle model confirmed significant vignetting (>50% beyond 70°), approaching zero retinal illuminance beyond 85°.ConclusionsVignetting of rays originating from the far temporal field by axially separated apertures can create symptoms mirroring perceptual reports of negative dysphotopsia in symptomatic pseudophakic patients.

Deep Phenotyping of PDE6C-Associated Achromatopsia.

PurposeTo perform deep phenotyping of subjects with PDE6C achromatopsia and examine disease natural history.MethodsEight subjects with disease-causing variants in PDE6C were assessed in detail, including clinical phenotype, best-corrected visual acuity, fundus autofluorescence, and optical coherence tomography. Six subjects also had confocal and nonconfocal adaptive optics scanning light ophthalmoscopy, axial length, international standard pattern and full-field electroretinography (ERG), short-wavelength flash (S-cone) ERGs, and color vision testing.ResultsAll subjects presented with early-onset nystagmus, decreased best-corrected visual acuity, light sensitivity, and severe color vision loss, and five of them had high myopia. We identified three novel disease-causing variants and provide phenotype data associated with nine variants for the first time. No subjects had foveal hypoplasia or residual ellipsoid zone (EZ) at the foveal center; one had an absent EZ, three had a hyporeflective zone, and four had outer retinal atrophy. The mean width of the central EZ lesion on optical coherence tomography at baseline was 1923 μm. The mean annual increase in EZ lesion size was 48.3 μm. Fundus autofluorescence revealed a central hypoautofluorescence with a surrounding ring of increased signal (n = 5). The mean hypoautofluorescent area at baseline was 3.33 mm2 and increased in size by a mean of 0.13 mm2/year. Nonconfocal adaptive optics scanning light ophthalmoscopy revealed residual foveal cones in only one of two cases. Full-field ERGs were consistent with severe generalized cone system dysfunction but with relative preservation of S-cone sensitivity.ConclusionsPDE6C retinopathy is a severe cone dysfunction syndrome often presenting as typical achromatopsia but without foveal hypoplasia. Myopia and slowly progressive maculopathy are common features. There are few (if any) residual foveal cones for intervention in older adults.

TSG-6 in conditioned media from adipose mesenchymal stem cells protects against visual deficits in mild traumatic brain injury model through neurovascular modulation

BackgroundRetinal inflammation affecting the neurovascular unit may play a role in the development of visual deficits following mild traumatic brain injury (mTBI). We have shown that concentrated conditioned media from adipose tissue-derived mesenchymal stem cells (ASC-CCM) can limit retinal damage from blast injury and improve visual function. In this study, we addressed the hypothesis that TNFα-stimulated gene-6 (TSG-6), an anti-inflammatory protein released by mesenchymal cells, mediates the observed therapeutic potential of ASCs via neurovascular modulation.MethodsAbout 12-week-old C57Bl/6 mice were subjected to 50-psi air pulse on the left side of the head overlying the forebrain resulting in an mTBI. Age-matched sham blast mice served as control. About 1 μl of ASC-CCM (siControl-ASC-CCM) or TSG-6 knockdown ASC-CCM (siTSG-6-ASC-CCM) was delivered intravitreally into both eyes. One month following injection, the ocular function was assessed followed by molecular and immunohistological analysis. In vitro, mouse microglial cells were used to evaluate the anti-inflammatory effect of ASC-CCM. Efficacy of ASC-CCM in normalizing retinal vascular permeability was assessed using trans-endothelial resistance (TER) and VE-cadherin expression in the presence of TNFα (1 ng/ml).ResultsWe show that intravitreal injection of ASC-CCM (siControl-ASC-CCM) but not the TSG-6 knockdown ASC-CCM (siTSG-6-ASC-CCM) mitigates the loss of visual acuity and contrast sensitivity, retinal expression of genes associated with microglial and endothelial activation, and retinal GFAP immunoreactivity at 4 weeks after blast injury. In vitro, siControl-ASC-CCM but not the siTSG-6-ASC-CCM not only suppressed microglial activation and STAT3 phosphorylation but also protected against TNFα-induced endothelial permeability as measured by transendothelial electrical resistance and decreased STAT3 phosphorylation.ConclusionsOur findings suggest that ASCs respond to an inflammatory milieu by secreting higher levels of TSG-6 that mediates the resolution of the inflammatory cascade on multiple cell types and correlates with the therapeutic potency of the ASC-CCM. These results expand our understanding of innate mesenchymal cell function and confirm the importance of considering methods to increase the production of key analytes such as TSG-6 if mesenchymal stem cell secretome-derived biologics are to be developed as a treatment solution against the traumatic effects of blast injuries and other neurovascular inflammatory conditions of the retina.

Myopia and age-related macular degeneration: structural and anatomical changes of the eye

The purpose of the study was to find out how age-related macular degeneration and medium-high degree myopia affect the structural and anatomical parameters of the eyeball, and to find whether a relationship exists between various types of myopic staphylomas and changes of visual functions.Material and methods. 120 patients (236 eyes), with medium and high degree myopia and age-related retinal changes, aged 44 to 81 years were tested for two groups of parameters: quantitative and qualitative. The former included the patients’ age, best corrected visual acuity (BCVA), computer perimetry data, the axial length, and the thickness of the retina in the central zone. The latter included retinal changes, in particular pigment epithelium (PE) defects, drusen, PE detachment, choroidal neovascular membrane (CNV), Fuchs spot and diffuse chorioretinal atrophy. The impact of various types of staphylomas on visual functions was evaluated. Results. Visual functions were found to directly depend on retinal PE integrity. If defects, detachment, or drusen are present, computer perimetry parameters and BVCA are reducing. Fuchs spot presence and diffuse chorioretinal atrophy reduces BCVA and causes an MD decrease. The lowest visual acuity and considerable light sensitivity loss was noted in patients with combined staphylomas. Conclusion. The obtained data confirm that retinal dystrophic processes directly affect visual functions: BCVA and retinal photosensitivity levels drop in all retinal changes studied. The presence of staphyloma, being a factor that aggravates myopia, undoubtedly worsens the most of the parameters studied.

Unilateral application of cathodal tDCS reduces transcallosal inhibition and improves visual acuity in amblyopic patients

Amblyopia is a neurodevelopmental disorder characterized by visual acuity and contrast sensitivity loss, refractory to pharmacological and optical treatments in adulthood. We studied the response of the visual cortex to transcranial Direct Current Stimulation (tDCS) applied over the primary visual area (V1) contralateral to the “lazy eye”. Visual acuity (logMAR) was assessed before (T0), immediately after (T1) and 60′ following the application of cathodal tDCS (2.0 mA, 20′). At each time point, Visual Evoked Potentials (VEPs) triggered by grating stimuli of different contrasts (K90%, K20%) were recorded in both hemispheres and compared to those obtained in healthy volunteers. Cathodal tDCS improved visual acuity (Holm–Sidak, p

Multi-line Adaptive Perimetry (MAP): A New Procedure for Quantifying Visual Field Integrity for Rapid Assessment of Macular Diseases.

PurposeIn order to monitor visual defects associated with macular degeneration (MD), we present a new psychophysical assessment called multiline adaptive perimetry (MAP) that measures visual field integrity by simultaneously estimating regions associated with perceptual distortions (metamorphopsia) and visual sensitivity loss (scotoma).MethodsWe first ran simulations of MAP with a computerized model of a human observer to determine optimal test design characteristics. In experiment 1, predictions of the model were assessed by simulating metamorphopsia with an eye-tracking device with 20 healthy vision participants. In experiment 2, eight patients (16 eyes) with macular disease completed two MAP assessments separated by about 12 weeks, while a subset (10 eyes) also completed repeated Macular Integrity Assessment (MAIA) microperimetry and Amsler grid exams.ResultsResults revealed strong repeatability of MAP and high accuracy, sensitivity, and specificity (0.89, 0.81, and 0.90, respectively) in classifying patient eyes with severe visual impairment. We also found a significant relationship in terms of the spatial patterns of performance across visual field loci derived from MAP and MAIA microperimetry. However, there was a lack of correspondence between MAP and subjective Amsler grid reports in isolating perceptually distorted regions.ConclusionsThese results highlight the validity and efficacy of MAP in producing quantitative maps of visual field disturbances, including simultaneous mapping of metamorphopsia and sensitivity impairment.Translational RelevanceFuture work will be needed to assess applicability of this examination for potential early detection of MD symptoms and/or portable assessment on a home device or computer.

Concentrated Conditioned Media from Adipose Tissue Derived Mesenchymal Stem Cells Mitigates Visual Deficits and Retinal Inflammation Following Mild Traumatic Brain Injury.

Blast concussions are a common injury sustained in military combat today. Inflammation due to microglial polarization can drive the development of visual defects following blast injuries. In this study, we assessed whether anti-inflammatory factors released by the mesenchymal stem cells derived from adipose tissue (adipose stem cells, ASC) can limit retinal tissue damage and improve visual function in a mouse model of visual deficits following mild traumatic brain injury. We show that intravitreal injection of 1 μL of ASC concentrated conditioned medium from cells pre-stimulated with inflammatory cytokines (ASC-CCM) mitigates loss of visual acuity and contrast sensitivity four weeks post blast injury. Moreover, blast mice showed increased retinal expression of genes associated with microglial activation and inflammation by molecular analyses, retinal glial fibrillary acidic protein (GFAP) immunoreactivity, and increased loss of ganglion cells. Interestingly, blast mice that received ASC-CCM improved in all parameters above. In vitro, ASC-CCM not only suppressed microglial activation but also protected against Tumor necrosis alpha (TNFα) induced endothelial permeability as measured by transendothelial electrical resistance. Biochemical and molecular analyses demonstrate TSG-6 is highly expressed in ASC-CCM from cells pre-stimulated with TNFα and IFNγ but not from unstimulated cells. Our findings suggest that ASC-CCM mitigates visual deficits of the blast injury through their anti-inflammatory properties on activated pro-inflammatory microglia and endothelial cells. A regenerative therapy for immediate delivery at the time of injury may provide a practical and cost-effective solution against the traumatic effects of blast injuries to the retina.

Unilateral Application of Cathodal tDCS Reduces Transcallosal Inhibition and Improves Visual Acuity in Amblyopic Patients.

Objective: Amblyopia is a neurodevelopmental disorder characterized by visual acuity and contrast sensitivity loss, refractory to pharmacological and optical treatments in adulthood. In animals, the corpus callosum (CC) contributes to suppression of visual responses of the amblyopic eye. To investigate the role of interhemispheric pathways in amblyopic patients, we studied the response of the visual cortex to transcranial Direct Current Stimulation (tDCS) applied over the primary visual area (V1) contralateral to the “lazy eye.”Methods: Visual acuity (logMAR) was assessed before (T0), immediately after (T1) and 60’ following the application of cathodal tDCS (2.0 mA, 20’) in 12 amblyopic patients. At each time point, Visual Evoked Potentials (VEPs) triggered by grating stimuli of different contrasts (K90%, K20%) were recorded in both hemispheres and compared to those obtained in healthy volunteers.Results: Cathodal tDCS improved visual acuity respect to baseline (p < 0.0001), whereas sham polarization had no significant effect. At T1, tDCS induced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a facilitation of responses in the hemisphere ipsilateral to the amblyopic eye; compared with controls, the facilitation persisted at T2 for high contrasts (K90%; Holm–Sidak post hoc method, p < 0.001), while the stimulated hemisphere recovered more quickly from inhibition (Holm–Sidak post hoc method, p < 0.001).Conclusions: tDCS is a promising treatment for amblyopia in adults. The rapid recovery of excitability and the concurrent transcallosal disinhibition following perturbation of cortical activity may support a critical role of interhemispheric balance in the pathophysiology of amblyopia.

Phosphorylated α-synuclein in the retina is a biomarker of Parkinson's disease pathology severity.

PD patients often have visual alterations, for example, loss of visual acuity, contrast sensitivity or motion perception, and diminished electroretinogram responses. PD pathology is mainly characterized by the accumulation of pathological α-synuclein deposits in the brain, but little is known about how synucleinopathy affects the retina. To study the correlation between α-synuclein deposits in the retina and brain of autopsied subjects with PD and incidental Lewy body disease. We evaluated the presence of phosphorylated α-synuclein in the retina of autopsied subjects with PD (9 subjects), incidental Lewy body disease (4 subjects), and controls (6 subjects) by immunohistochemistry and compared the retinal synucleinopathy with brain disease severity indicators. Whereas controls did not show any phosphorylated α-synuclein immunoreactivity in their retina, all PD subjects and 3 of 4 incidental Lewy body disease subjects had phosphorylated α-synuclein deposits in ganglion cell perikarya, dendrites, and axons, some of them resembling brain Lewy bodies and Lewy neurites. The Lewy-type synucleinopathy density in the retina significantly correlated with Lewy-type synucleinopathy density in the brain, with the Unified Parkinson's disease pathology stage and with the motor UPDRS. These data suggest that phosphorylated α-synuclein accumulates in the retina in parallel with that in the brain, including in early stages preceding development of clinical signs of parkinsonism or dementia. Therefore, the retina may provide an in vivo indicator of brain pathology severity, and its detection could help in the diagnosis and monitoring of disease progression. © 2018 International Parkinson and Movement Disorder Society.

Programas de acondicionamiento físico para prevenir caidas en personas mayores.

La falta de tonificación muscular, una menor movilidad en MMII, mayor rigidez articular y la pérdida del control postural provocan fragilidad y caídas en las personas mayores que pueden tener graves consecuencias para mantener la autonomía e independencia (fracturas, miedo a caerse,etc). Con la edad, la pérdida de fuerza en las piernas, el deterioro sensorial y los hábitos posturales hacen que el equilibrio dinámico y estático se vean afectados. Se producen cambios en el sistema visual (pérdida de agudeza visual, de profundidad de percepción, de sensibilidad a los contrastes y reducción del campo visual) que afectan negativamente a la capacidad de los mayores para percibir con precisión o anticiparse a las condiciones normales del suelo y a la presencia de peligros a su alrededor. El envejecimiento también afecta al sistema somatosensorial (nos proporciona información sobre la localización espacial y el movimiento del cuerpo respecto a la superficie de sustentación), provocando una reducción de la capacidad para percibir con calidad el contacto entre los pies y el suelo. Respecto al sistema vestibular, ubicado en el oído interno y cuya misión es percibir los movimientos de la cabeza e informar de ello al cerebro, se inicia una reducción gradual de los cilios sensoriales que actúan de sensores biológicos del movimiento de la cabeza y nos ayudan a alinear el cuerpo frente a la fuerza de gravedad. El entrenamiento físico específico es fundamental para su prevención: fortalecimiento muscular, equilibrio, movilidad articular, coordinación, velocidad de reacción, agilidad, capacidad aeróbica, percepción espacio temporal, etc.

F142. Corpus callosum and amblyopia: New evidence for an old debate

Introduction Amblyopia is a neurodevelopmental disorder characterized by visual acuity and contrast sensitivity loss, refractory to pharmacological and mechanical treatments in adulthood. In animal models, the corpus callosum (CC) plays a critical role in the development of the ocular dominance, thus strengthening the hypothesis of an involvement of both striate and extrastriate areas in the pathogenesis of amblyopia. To investigate the role of interhemispheric pathways in amblyopia, we studied the response of the visual cortex to transcranial Direct Current Stimulation (tDCS) applied over the primary visual area (V1) contralateral to the amblyopic eye. Methods Visual evoked potentials (VEPs) triggered by grating stimuli of different contrasts (K90%, K50%, K20%) were recorded in both hemispheres before and after inactivation of the occipital cortex of one side via cathodal tDCS (2.0 mA, 20′). VEPs were recorded before (T0), immediately after (T1) and 60′ following tDCS (T2). The display was either centered on the vertical meridian (central stimulation) or positioned in the right hemifield (with its inner edge at a distance of 1 degree from the fixation point). Visual acuity was tested at each time interval, to assess behavioral changes between active and sham stimulation. Results Cathodal tDCS improved visual acuity respect to baseline (recovery of 8.4 ± 3.3 letters, Holm-Sidak post hoc method p Conclusion tDCS is a promising treatment for amblyopia in adults. The rapid recovery of excitability and the persistent transcallosal disinhibition following perturbation of cortical activity strongly supports a critical role of interhemispheric balance in the pathophysiology of amblyopia.

Diagnostic Ability and Structure-function Relationship of Peripapillary Optical Microangiography Measurements in Glaucoma.

The aim of this study was to evaluate the diagnostic abilities of peripapillary optical microangiography (OMAG) measurements in eyes with primary open-angle glaucoma (POAG) and to evaluate the relationship of these measurements with retinal nerve fiber layer (RNFL) thickness and visual sensitivities in different peripapillary sectors. In a cross-sectional study, 97 eyes of 57 control subjects and 101 eyes of 66 POAG patients underwent OMAG and RNFL imaging with optical coherence tomography. POAG was diagnosed on the basis of the masked evaluation of optic disc stereo photographs. Area under receiver operating characteristic curves and sensitivities at 90% specificity of the OMAG and RNFL thickness measurements in different peripapillary sectors were evaluated. Association between OMAG, RNFL thickness, and visual sensitivity measurements were evaluated using fractional polynomial regression models. All OMAG and RNFL measurements were significantly less in the POAG compared with the control eyes. Diagnostic abilities of the best OMAG measurement (inferior sector vessel length density, area under receiver operating characteristic curves: 0.84, sensitivity at 90%, specificity: 65%) were significantly less (P<0.05) than that of the best RNFL measurement (inferior sector RNFL thickness, 0.94 and 81%). Inferior sector vessel length density showed the strongest association with inferior sector RNFL thickness (R=0.66, P<0.001) and the superior sector visual sensitivity loss (R=0.21, P=0.006). The inferior sector OMAG measurements had the best diagnostic ability in glaucoma and the strongest association with RNFL and the visual sensitivity measurements. Diagnostic ability of OMAG measurements, however, were significantly less than the RNFL thickness measurements.

Relationship of Optic Nerve Structure and Function to Peripapillary Vessel Density Measurements of Optical Coherence Tomography Angiography in Glaucoma.

To evaluate the sectoral and global structure-structure (vessel density-retinal nerve fiber layer thickness) and structure-function (vessel density-visual sensitivity loss) relationships of peripapillary vessel density measurements on optical coherence tomography angiography in primary open-angle glaucoma and to determine if fractional polynomial (FP) models characterize the relationships better than linear models. In a cross-sectional study, structure-structure and structure-function relationships of peripapillary vessel densities were determined in 227 eyes of 143 subjects (63 control and 164 primary open-angle glaucoma eyes) who had undergone standard automated perimetry and optical coherence tomography testing within 6 months of each other, using linear and FP models. FP model evaluates the relationship between the dependent and the best-fitting fractional powers of the independent variable. Strength of relationship was reported as coefficient of determination (R). R values for structure-structure associations using linear models (0.53 for superotemporal sector, 0.61 for inferotemporal, and 0.53 for average measurements) were significantly less (P<0.05) than that determined using FP models (0.57, 0.65, and 0.55, respectively). R values for structure-function associations using linear models (0.35 for superotemporal vessel density-inferotemporal visual sensitivity loss, 0.49 for inferotemporal vessel density-superotemporal visual sensitivity loss, and 0.39 for average vessel density-average visual sensitivity loss) were significantly less than that determined using FP models (0.43, 0.58, and 0.47, respectively). The inferotemporal peripapillary vessel density showed the strongest association with the corresponding retinal nerve fiber layer thickness and visual sensitivity loss in the global and sectoral regions studied. The FP models were significantly better than linear models in describing these relationships.

Visual sensitivity of frontal eye field neurons during the preparation of saccadic eye movements

Primate vision is continuously disrupted by saccadic eye movements, and yet this disruption goes unperceived. One mechanism thought to reduce perception of this self-generated movement is saccadic suppression, a global loss of visual sensitivity just before, during, and after saccadic eye movements. The frontal eye field (FEF) is a candidate source of neural correlates of saccadic suppression previously observed in visual cortex, because it contributes to the generation of visually guided saccades and modulates visual cortical responses. However, whether the FEF exhibits a perisaccadic reduction in visual sensitivity that could be transmitted to visual cortex is unknown. To determine whether the FEF exhibits a signature of saccadic suppression, we recorded the visual responses of FEF neurons to brief, full-field visual probe stimuli presented during fixation and before onset of saccades directed away from the receptive field in rhesus macaques (Macaca mulatta) We measured visual sensitivity during both epochs and found that it declines before saccade onset. Visual sensitivity was significantly reduced in visual but not visuomotor neurons. This reduced sensitivity was also present in visual neurons with no movement-related modulation during visually guided saccades and thus occurred independently from movement-related activity. Across the population of visual neurons, sensitivity began declining ∼80 ms before saccade onset. We also observed a similar presaccadic reduction in sensitivity to isoluminant, chromatic stimuli. Our results demonstrate that the signaling of visual information by FEF neurons is reduced during saccade preparation, and thus these neurons exhibit a signature of saccadic suppression.