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PubMed1976

Bicycle-pedal model for the first step in the vision process.

Computer simulation of the molecular dynamics of retinal during its photoisomerisation inside a restrictive active site gives a detailed model for the sequence of events in the first step of the vision process. It is proposed that the prelumirhodopsin intermediate contains a strained all-trans retinal molecule produced directly and rapidly from the 11-cis, 12-s-trans conformation in rhodopsin by a bicycle-pedal isomerisation. The model reproduces the main experimental observations and explains how the protein makes the photoisomerisation path unique.

Binding Sites↗
PubMed1992

Computational aspects of motion perception in natural and artificial vision systems.

In this paper a computational scheme for motion perception in artificial and natural vision systems is described. The scheme is motivated by a mathematical analysis in which first-order spatial properties of optical flow, such as singular points and elementary components of optical flow, are shown to be salient features for the computation and analysis of visual motion. The fact that different methods for the computation of optical flow produce similar results is explained in terms of the simple spatial structure of the image motion of rigid bodies. Singular points and elementary flow components are used to compute motion parameters, such as time-to-collision and angular velocity, and also to segment the visual field into areas which correspond to different motions. Then a number of biological implications are discussed. Electrophysiological findings suggest that the brain perceives visual motion by detecting and analysing optical flow components. However, the cortical neurons, which seem to detect elementary flow components, are not able to extract these components from more complex flows. A simple model for the organization of the receptive field of these cells, which is consistent with anatomical and electrophysiological data, is described at the end of the paper.

Artificial Intelligence↗
PubMed1991

Problems in the diagnosis and management of unilateral retinoblastoma.

The improved prognosis for life in retinoblastoma challenges us to readdress the severe morbidity associated with late presentation and treatment, particularly in unilateral disease. Three cases of unilateral sporadic retinoblastoma are presented to illustrate the range of therapeutic options that need to be considered in management and to show that early recognition of the tumour and local treatment have the potential to minimise morbidity and to enable binocular vision to be retained.

Antineoplastic Agents↗
PubMed1991

Steroid-induced visual recovery in fibrous dysplasia.

Fibrous dysplasia is a rare disorder of bone that may be associated with acute loss of vision. Surgical intervention is generally advocated and sometimes restores vision in these patients. We report a case of a patient with unilateral optic neuropathy from fibrous dysplasia who suffered two acute episodes of visual impairment. The first episode of vision loss was reversed by surgery and the second by corticosteroid treatment. A trial of corticosteroid therapy may be beneficial in cases of acute vision loss due to fibrous dysplasia.

Adult↗
PubMed1992

Human vision combines oriented filters to compute edges.

The experiments examined the perceived spatial structure of plaid patterns, composed of two or three sinusoidal gratings of the same spatial frequency, superimposed at different orientations. Perceived structure corresponded well with the pattern of zero crossings in the output of a circular spatial filter applied to the image. This lends some support to Marr & Hildreth's (Proc. R. Soc. Lond. B 207, 187 (1980)) theory of edge detection as a model for human vision, but with a very different implementation. The perceived structure of two-component plaids was distorted by prior exposure to a masking or adapting grating, in a way that was perceptually equivalent to reducing the contrast of one of the plaid components. This was confirmed by finding that the plaid distortion could be nulled by increasing the contrast of the masked or adapted component. A corresponding reduction of perceived contrast for single gratings was observed after adaptation and in some masking conditions. I propose the outlines of a model for edge finding in human vision. The plaid components are processed through cortical, orientation-selective filters that are subject to attenuation by forward masking and adaptation. The outputs of these oriented filters are then linearly summed to emulate circular filtering, and zero crossings (zcs) in the combined output are used to determine edge locations. Masking or adapting to a grating attenuates some oriented filters more than others, and although this changes only the effective contrast of the components, it results in a geometric distortion at the zc level after different filters have been combined. The orientation of zcs may not correspond at all with the orientation of Fourier components, but they are correctly predicted by this two-stage model. The oriented filters are not 'orientation detectors', but are precursors to a more subtle stage that locates and represents spatial features.

Adaptation, Ocular↗
PubMed1977

Syndrome of agitated delirium and visual impairment: a manifestation of medial temporo-occipital infarction.

Three patients presented with sudden visual impairment followed by agitated delirium one to three days later. Examination revealed marked agitation, dementia, and loss of vision. Computerised axial tomography demonstrated temporo-occipital infarctions. All recovered from the agitated state in four days to two months, but their visual impairment and dementia persisted one to four years later.

Adult↗
PubMed1992

Acute monocular blindness secondary to fibrous dysplasia of the skull: a case report.

An unusual case of acute monocular visual loss secondary to fibrous dysplasia is presented. Orbital and optic canal decompression restored vision completely. A review of the pertinent literature revealed that operative intervention may be curative in patients with acute monocular visual loss. This finding contrasts with the chronic visual decline found secondary to fibrous dysplasia of the skull.

Adult↗
PubMedDate not supplied

Intravascular thrombosis as a possible cause of transient cortical brain lesions: CT and MRI.

Cortical brain lesions were identified on MRI and CT in 14 patients with a variety of diseases. Each of these patients developed neurologic symptoms, the most prominent of which were seizures, depressed mental status, and blurred vision or cortical blindness. Both the imaging and the neurologic abnormalities resolved spontaneously within a period ranging from 5 to 30 days. Due to location and evolution of the lesions over time we hypothesize that they are secondary to small cortical venous thromboses.

Adolescent↗
PubMed1992

Visual evoked potentials during the early phase of optic nerve compression in the orbital cavity.

We obtained case histories and electrophysiologic recordings from four patients with transient vision impairment due to acute orbital compression. The visual evoked potentials (VEPs) displayed alterations that depended on the size and consistency of the compressing pathology and also on the duration of the compression. This study provides evidence of the utility of the VEP in the assessment of the severity and reversibility of optic nerve lesions. The case histories also emphasized the necessity to elucidate the pathologic process of compressive lesions of the optic nerve.

Acute Disease↗
PubMed1978

[Impaired visual perception in progressive multifocal leukoencephalopathy; a clinical diagnosis based on sequential computerized axial tomography (author's transl)].

Progressive multifocal leukoencephalopathy (PML) is a viral illness affecting principally cerebral white matter of patients, who have diminished immunologic resistance. A patient is presented, whose initial complaint was blurred vision. Relentless progression over a period of seven months to left hemianopsia, prosopagnosia, alexia with agraphia and eventually cortical blindness was observed. Accompanying the visual impairment was a steady deterioration of mental function. Sequential computerized axial tomography defined low density lesions in the occipital white matter with sparing of the cortical ribbon. As hemianopsia progressed to cortical blindness, the scans confirmed the evolution of bilaterial occipital lesions. The diagnosis was made clinically and established on histological and cultural grounds. Computerized tomography seems to be valuable in diagnosis and monitoring progress of PML.

Aged↗
PubMed2026

Spatial inheritance patterns across maize ears are associated with alleles that reduce pollen fitness.

Often, more pollen grains land on recipient flowers than there are ovules to fertilize. Consequently, the haploid male gametophyte engages in post-pollination competition, one way that pollen genotype can influence inheritance. The maize (Zea mays subsp. mays L.) inflorescence (ear), with its elongated stigma and style structures (silks), has a conspicuous spatial heterogeneity, with longer silks at the base of the ear than at the apex. To evaluate the hypothesis that alleles with reduced pollen fitness influence the spatial distribution of progeny genotypes along the ear, we developed an updated phenotyping platform that maps fluorescently marked mutant (Ds-GFP) kernel phenotypes on the ear via an implementation of the Faster R-CNN machine vision model (EarVision.v2) and a statistical pipeline that evaluates the relationship between kernel position and transmission ratio (EarScape). Our dataset (1384 ears) represents 58 Ds-GFP insertion alleles. None of the 48 alleles with Mendelian inheritance showed any significant spatial trend. In contrast, 50% of alleles with a pollen-specific transmission defect (5/10) exhibited significant spatial effects. An insertional mutant of the gene encoding a putative actin-binding protein, base-to-apex gradient1* (bag1*), is associated with decreased mutant transmission at the ear base relative to the apex. Surprisingly, a mutant allele of another pollen-expressed gene (Zm00001eb236740) generates the opposite trend, decreased mutant transmission toward the ear apex; and two mutant alleles of the sperm cell attachment factor gamete expressed2 (gex2) can produce ears with transmission highest at both base and apex. We conclude that pollen fitness mutants cause unexpectedly diverse spatial patterns of progeny genotypes.

Zea mays↗
PubMed1977

Anatomic considerations for computed tomography of the optic chiasm.

When the clinical distinction between lesions of the optic nerves or the chiasm is not apparent, computed tomographic scans should be performed at both 0 degrees and 25 degrees or 35 degrees to the orbital-meatal line (Reid's baseline). The former plane is preferable for the demonstration of the optic nerves or orbital structures, while the latter allows superior visualization of perichiasmatic structures.

Female↗
PubMed1992

Occipital lobe epilepsy: clinical characteristics, seizure spread patterns, and results of surgery.

Twenty-five patients with occipital lobe seizure origin were retrospectively evaluated to determine clinical seizure characteristics and electroencephalographic manifestations. Certain symptoms and signs served to identify occipital lobe origin in 22 (88%). These included elementary visual hallucinations, ictal amaurosis, eye movement sensations, early forced blinking or eyelid flutter, and visual field deficits. Eye or head deviation, or both, was observed frequently and was contralateral to the side of seizure origin in 13, but 3 patients exhibited ipsilateral deviation in some or all their seizures. After the initial signs and symptoms, clinical seizure characteristics resembled those of seizures originating elsewhere. Seizures typical of temporal lobe origin with loss of contact and various types of automatic, semipurposeful activity occurred in 11 patients. Seizures in 3 patients exhibited asymmetrical tonic or focal clonic motor patterns characteristic of frontal lobe seizures. Eleven of the 25 patients had, on two occasions, two or more distinctly different seizure types. Scalp electroencephalographic findings were seldom helpful for occipital lobe localization and were frequently misleading. Intracranial electroencephalographic recording correctly identified occipital lobe seizure origin in most, but not all, patients who had such studies. Intracranial electroencephalic recording also proved the variability in clinical seizure characteristics was related to different seizure spread patterns, medially or laterally above and below the sylvian fissure, both ipsilateral and contralateral to the occipital lobe of seizure origin. Eighteen patients had occipital lobe lesions detected with computed tomographic or magnetic resonance imaging scans or both. Resection of the lesions in 16 patients produced excellent results in 14 (88%). Five patients had temporal lobectomies, with good results in 3, but poor results in 2. Two patients with unlocalized seizures had complete section of the corpus callosum, 1 with a good result and the other with a poor result.

Adolescent↗
PubMed2026

Applications of artificial intelligence in robot-assisted surgery: a systematic review.

To characterize applications of artificial intelligence (AI) in robot-assisted surgery, summarize technical and clinical performance, and assess the quality of the available evidence. PubMed, Web of Science Core Collection, and Scopus were searched for English-language journal articles published from 1 January 2020 through 31 October 2025. Randomized, observational, model-development, validation, and feasibility studies evaluating AI in robot-assisted surgery or closely related image-guided minimally invasive workflows were eligible. Two reviewers independently performed study selection, data extraction, and risk-of-bias assessment. Owing to heterogeneity in surgical procedures, AI tasks, analytical units, validation strategies, and outcomes, findings were synthesized descriptively without statistical pooling. The review was registered in the International Prospective Register of Systematic Reviews (CRD420251175699). Seventeen studies were included: seven clinical prediction or decision-support studies, eight intraoperative recognition, segmentation, or image-guided studies, and two training or workflow studies. Five prediction studies reported area-under-the-curve values of 0.74-0.95. Technical studies reported F1 or Dice scores of 0.525-0.995 and task-specific accuracies of 0.840-0.998. Two randomized studies suggested benefits for personalized suturing feedback and automated camera control, but neither established improved patient outcomes. Only one study had low overall risk of bias; the remaining studies were at high or unclear risk or raised some concerns. AI applications in robot-assisted surgery show promise for prediction, intraoperative perception, training, and workflow support. Evidence primarily demonstrates technical feasibility rather than established clinical effectiveness. Independent multicenter validation and prospective evaluation of patient, educational, and workflow outcomes are required before widespread implementation.

Robotic Surgical Procedures↗
PubMed1979

A practical approach for the evaluation of women with abnormal polytomography or elevated prolactin levels.

Based upon the experience gained in the evaluation of 60 patients with abnormal polytomography and/or elevated prolactin levels, the following observations can be made: Patients with amenorrhea, amenorrhea and galactorrhea, galactorrhea alone, or anovulatory cycles and infertility may or may not have pituitary tumors. Clinical symptoms do not always correlate with the prolactin level, and patients with normal prolactins may have pituitary tumors. The incidence of empty sella is significant (15.8% in this series). Visual field examination is not a useful screening procedure, but evaluation of thyroid function is important to detect the occasional patient with hypothyroidism (3.5% in this series). The insulin tolerance test is not helpful in detecting the presence of pituitary tumors or in guiding management decisions, and the CT scan contributes little and should be omitted from the evaluation process. A straightforward, economical, and efficient approach to this clinical problem is presented.

Adenoma↗