Purpose: Traditional visual acuity (VA) measurements depend on subjective responses, which can be unreliable, especially with uncooperative participants. Objective measurements with visual evoked potentials (VEP) address this issue but can overestimate VA in amblyopia. This study aims to establish the P300 component of the event-related potential as an objective VA test for amblyopia and compare its performance to subjective (psychophysical) and VEP-based VA estimates. Methods: Psychophysical, VEP-based, and P300-based VA estimates were obtained for amblyopic and fellow eyes of 18 participants (aged 19–65) in a bicentric study. VEP-based VA was determined from the spatial frequency threshold derived from occipital cortex pattern-pulse responses to check-sizes ranging from 0.048° to 8.95°. P300 responses were collected using visual oddball sequences with circular optotypes. The threshold was estimated from the sigmoid function of parietal P300 amplitude versus optotype gap size. Mean VA values for amblyopic eyes were compared across methods. Results: VEP-based VA of the amblyopic eyes overestimated psychophysical VA by 0.18 ± 0.06 logMAR (P = 0.0016). In contrast, P300-based VA showed no significant difference from psychophysical VA (0.00 ± 0.04 logMAR, P > 0.05). Conclusions: In amblyopia, P300-based optotype VA aligns more closely with psychophysical VA than VEP-based VA, suggesting that P300-based VA is a valid objective alternative for estimating VA in amblyopic eyes. Translational Relevance: This study highlights the potential of P300-based VA testing as a reliable and objective method for assessing VA in amblyopic eyes, offering a promising tool for clinical and research applications where traditional methods fall short.
Aims (1) To test the feasibility of simultaneous steady-state pattern electroretinogram (ssPERG) and intraocular pressure (IOP) measurements with an implanted IOP sensor. (2) To explore the scope of this approach for detecting PERG changes during IOP manipulation in a model of lateral decubitus positioning (LDP; lateral position). Methods 15 healthy controls and 15 treated glaucoma patients participated in the study. 8 patients had an IOP sensor (Eyemate-IO, Implandata Ophthalmic Products GmbH) in the right eye (GLA IMP ) and 7 had no sensor and with glaucoma in the left eye. (1) We compared PERGs with and without simultaneous IOP read-out in GLA IMP . (2) All participants were positioned in the following order: sitting1 (S1), right LDP (LD R ), sitting2 (S2), left LDP (LD L ) and sitting3 (S3). For each position, PERG amplitudes and IOP were determined with rebound tonometry (Icare TA01i) in all participants without the IOP sensor. Results Electromagnetic intrusions of IOP sensor read-out onto ssPERG recordings had, due to different frequency ranges, no relevant effect on PERG amplitudes. IOP and PERG measures were affected by LDP, for example, IOP was increased during LD R versus S1 in the lower eyes of GLA IMP and controls (5.1±0.6 mmHg, P 0.025 =0.00004 and 1.6±0.6 mmHg, P 0.025 =0.02, respectively) and PERG amplitude was reversibly decreased (−25±10%, P 0.025 =0.02 and −17±5%, P 0.025 , respectively). Conclusions During LDP, both IOP and PERG changed predominantly in the lower eye. IOP changes induced by LDP may be a model for studying the interaction of IOP and ganglion-cell function.
Intraocular pressure (IOP) monitoring in glaucoma management is evolving with novel devices. We investigated the reproducibility of 24 hour profiles on two consecutive days and after 30 days of self-measurements via telemetric IOP monitoring.
The albino visual cortex receives input from the ipsilateral visual field. To investigate how the visual cortex of humans albinos organizes this abnormal input we applied retinotopic mapping fMRI procedures. Two subjects with albinism and only small nystagmus and two control subjects underwent T2* MRI scanning of the occipital lobe during visual stimulation. In separate experiments we stimulated monocularly the nasal and temporal retina with phase encoded visual stimuli (Engel et al. 1997). BOLD responses were projected to the flattened representation of T1 weighted images, fourier analysed and correlated with the stimulus fundamental frequency. Retinotopic mapping yielded phase maps that allowed the identification of V1 and dorsal and ventral representations of V2 and V3 in both controls and albino subjects. In the controls V1 comprised a representation of the contralateral visual field, while it comprised a representation of both the contralateral and the ipsilateral visual field in the albino subjects. The normal contralateral and the abnormal ipsilateral representations are, at the resolution of fMRI, arranged as an overlay. We obtained evidence for a similar arrangement in other early visual areas. Our results indicate that, in the albinos tested, there has been no reordering of the geniculostriate projection in human as has been reported in other species. Furthermore, there appears to be an absence of the complete suppression of the abnormal input to the cortex that has also been documented in cat and ferret. In the human albino, we conclude that representations of mirror symmetric positions in the visual field occupy neighbouring regions of the cortex. This feature may have behavioural significance for tasks performed in regions of the visual field where fibres project aberrantly. Engel, S.A., Glover, G.H. & Wandell, B.A. (1997) Retinotopic organization in human visual cortex and the spatial precision of functional MRI. Cereb. Cortex, 7, 181–92.
Head-mounted displays (HMDs) virtually augment the visual world to aid visual task completion. Three types of HMDs were compared [look around (LA); optical see-through with organic light emitting diodes and virtual retinal display] to determine whether LA, leaving the observer functionally monocular, is inferior. Response times and error rates were determined for a combined visual search and Go-NoGo task. The costs of switching between displays were assessed separately. Finally, HMD effects on basic visual functions were quantified. Effects of HMDs on visual search and Go-NoGo task were small, but for LA display-switching costs for the Go-NoGo-task the effects were pronounced. Basic visual functions were most affected for LA (reduced visual acuity and visual field sensitivity, inaccurate vergence movements and absent stereo-vision). LA involved comparatively high switching costs for the Go-NoGo task, which might indicate reduced processing of external control cues. Reduced basic visual functions are a likely cause of this effect.
Purpose: Numerous animal studies demonstrated the importance of components of the ephrin/Eph system for correct visual system development. Analogous investigations in humans are entirely missing. Here, we examined the visual system in humans with ephrin-B1 deficiency, which is x-linked and associated with the cranio-fronto-nasal syndrome (CFNS) in heterozygous females. Methods: For one male hemizygous for ephrin-B1 deficiency and three affected heterozygous females with molecular-genetically confirmed mutations, the integrity of the partial decussation of the optic nerves was assessed with visual evoked potentials (VEPs) and compared with albinotic, achiasmic, and control participants with healthy vision. Further, retinal morphology and function and the gross-retinotopic representation of the primary visual cortex were examined with spectral-domain optical coherence tomography (SD-OCT), ERG, and multifocal (mf) VEPs for the male participant and part of the carriers. Results: Strabismus and lack of stereovision was evident in the male and two of the females. Other characteristics of the visual system organization and function were normal: (1) retina: SD-OCT and funduscopy indicated normal foveal and optic nerve head morphology. Electroretinograms indicated normal retinal function, (2) optic chiasm: conventional (c)VEP showed no evidence for misrouting and mfVEPs were only suggestive of, if any, very minor local misrouting, and (3) visual cortex: mfVEP characteristics indicated normal retinotopic gross-representations of the contralateral visual hemifield in each hemisphere. Conclusions: While ephrin-B1 deficiency leads to abnormal visual pathways in mice, it leaves the human visual system, apart from deficits in binocular vision, largely normal. We presume that other components of the ephrin-system can substitute the lack of ephrin-B1 in humans.
Abstract Autosomal recessive Achromatopsia (ACHM) is a rare inherited disorder associated with dysfunctional cone photoreceptors resulting in a congenital absence of cone input to visual cortex. This might lead to distinct changes in cortical architecture with a negative impact on the success of gene augmentation therapies. To investigate the status of the visual cortex in these patients, we performed a multi-centre study focusing on the cortical structure of regions that normally receive predominantly cone input. Using high-resolution T1-weighted MRI scans and surface-based morphometry, we compared cortical thickness, surface area and grey matter volume in foveal, parafoveal and paracentral representations of primary visual cortex in 15 individuals with ACHM and 42 normally sighted, healthy controls (HC). In ACHM, surface area was reduced in all tested representations, while thickening of the cortex was found highly localized to the most central representation. These results were comparable to more widespread changes in brain structure reported in congenitally blind individuals, suggesting similar developmental processes, i.e., irrespective of the underlying cause and extent of vision loss. Our findings indicate that there may be an optimum time window for gene therapy to counteract developmental cortical changes related to the absence of sensory input. Highlights We assessed cortical anatomy of a large cohort of patients with genetically confirmed cone photoreceptor dysfunction (achromatopsia) using surface-based morphometry. We found widespread reduction in cortical surface area across foveal, parafoveal and paracentral proportions of primary visual cortex in participants with achromatopsia. highly localized cortical thickening in participants with achromatopsia at the region of visual cortex that lacked inputs from the retinal region occupied solely by cones. Further evidence that the visual cortex is unlikely to take on normal properties if vision were restored after the developmental plastic period. Early intervention is preferable when considering vision restoration treatment in achromatopsia.
To explore the effect of gaze direction and eyelid closure on intraocular pressure (IOP).Eleven patients with primary open-angle glaucoma previously implanted with a telemetric IOP sensor were instructed to view eight equally-spaced fixation targets each at three eccentricities (10°, 20°, and 25°). Nine patients also performed eyelid closure. IOP was recorded via an external antenna placed around the study eye. Differences of mean IOP between consecutive gaze positions were calculated. Furthermore, the effect of eyelid closure on gaze-dependent IOP was assessed.The maximum IOP increase was observed at 25° superior gaze (mean ± SD: 4.4 ± 4.9 mm Hg) and maximum decrease at 25° inferonasal gaze (-1.6 ± 0.8 mm Hg). There was a significant interaction between gaze direction and eccentricity (P = 0.003). Post-hoc tests confirmed significant decreases inferonasally for all eccentricities (mean ± SEM: 10°: -0.7 ± 0.2, P = 0.007; 20°: -1.1 ± 0.2, P = 0.006; and 25°: -1.6 ± 0.2, P = 0.006). Eight of 11 eyes showed significant IOP differences between superior and inferonasal gaze at 25°. IOP decreased during eyelid closure, which was significantly lower than downgaze at 25° (mean ± SEM: -2.1 ± 0.3 mm Hg vs. -0.7 ± 0.2 mm Hg, P = 0.014).Our data suggest that IOP varies reproducibly with gaze direction, albeit with patient variability. IOP generally increased in upgaze but decreased in inferonasal gaze and on eyelid closure. Future studies should investigate the patient variability and IOP dynamics.
Die Achromatopsie oder Stäbchenmonochromasie ist eine kongenitale autosomal-rezessiv vererbte Netzhautdystrophie, die zu Zapfenfehlfunktion mit verminderter Sehschärfe, extrem eingeschränktem Farbsehvermögen, Nystagmus und Photophobie führt. Aufgrund der zunächst normal erscheinenden okulären Morphologie wird die Diagnose oft verzögert gestellt. Mit bildgebenden Verfahren (Fundusautofluoreszenz [FAF], optische Kohärenztomographie [OCT]) werden verschiedene morphologische Formen der Achromatopsie unterschieden, allerdings ohne differenziellen Einfluss auf das Sehvermögen. Entscheidend ist die Versorgung mit spezifischen Kantenfiltern. Von 6 Genen ist bekannt, dass ihre Mutation Achromatopsie auslösen kann. Für die häufigsten dieser Gene, CNGA3 und CNGB3, werden aktuell Genadditionstherapien geprüft, deren mögliche spätere Anwendung vor der Manifestation sensorisch bedingter Amblyopie sinnvoll erscheint. Entsprechend ist im zeitgemäßen Achromatopsiemanagement eine Diagnose im frühen Kindesalter mit Genotypisierung bedeutsam.
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