Visual Acuity within the Area Centralis and its Relation to Eye Movements and Fixation

One main reason that we make eye movements is to solve a problem of information overload. A large field of vision allows an animal to survey the environment for food and to avoid predators, thus increasing its survival rate. Similarly, a high visual acuity also increases survival rates by allowing an animal to aim at a target more accurately, leading to higher killing rates and more food. However, there are simply not enough neurons in the brain to support a visual system that has high resolution over the entire field of vision. Faced with the competing evolutionary demands for high visual acuity and a large field of vision, an effective strategy is needed so that the brain will not be overwhelmed by a large amount of visual input. Some animals, such as rabbits, give up high resolution in favor of a larger field of vision (rabbits can see nearly 360°), whereas others, such as hawks, restrict their field of vision in return for a high visual acuity (hawks have vision as good as 20/2, about 10 times better than humans). In humans, rather than using one strategy over the other, the retina develops a very high spatial resolution in the center (i.e., the fovea), and a much lower resolution in the periphery. Although this “foveal compromise” strategy solves the problem of information overload, one result is that unless the image of an object of interest happens to fall on the fovea, the image is relegated to the low-resolution retinal periphery. The evolution of a mechanism to move the eyes is therefore necessary to complement this foveal compromise strategy by ensuring that an object of interest is maintained or brought to the fovea. To maintain the image of an object on the fovea, the vestibulo-ocular (VOR) and optokinetic systems generate eye movements to compensate for head motions. Likewise, the saccadic, smooth pursuit, and vergence systems generate eye movements to bring the image of an object of interest on the fovea. These different eye movements have different characteristics and involve different parts of the brain.

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Establishing an Objective Measurement of Visual Acuity with a Computerised Optokinetic Nystagmus Suppression Test

Klinische Monatsblätter für Augenheilkunde ◽

10.1055/a-1119-6123 ◽

2020 ◽

Vol 237 (04) ◽

pp. 502-505

Author(s):

Noemie Schwob ◽

Anja Palmowski-Wolfe

Keyword(s):

Visual Acuity ◽

Eye Movements ◽

Optokinetic Nystagmus ◽

Objective Measurement ◽

Mean Difference ◽

Alternative Option ◽

Snellen Acuity ◽

Suppression Test ◽

Infrared Cameras ◽

Acuity Test

Abstract Objective Investigating the correlation between subjective and objective VA (visual acuity) elicited with a newly developed computerised optokinetic nystagmus (OKN) suppression test (“SpeedWheel”) in adults. Methods SpeedWheel presented alternating black/white stripes moving horizontally across a LED screen. Seven VA steps were induced with Bangerter filters placed onto spectacle frames. Magnified eye movements were projected from infrared cameras inside the frames and displayed onto a smartphone. Dots whose size increased in logarithmic steps were superimposed to suppress OKN. Suppression of OKN resulted in the SpeedWheel acuity which was then correlated to Snellen acuity as measured with the Freiburg Acuity test. Results 28 eyes from 14 individuals were tested. FrACT-E correlated well to SpeedWheel (r: 0.89; p < 0.001). Snellen acuity was never lower than 0.14 LogMAR of SpeedWheel values. Bangerter filters showed greater mean difference to both methods indicating that this filter is not as predictable as suggested by the filter value. Conclusion SpeedWheel offers a fast (< 80 sec) and reliable alternative option to measure objective VA.

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Visual Discrimination Learning in Rats with Lesions of Superior Colliculus: Door-Push and Approach Errors in Modified Jumping Stand

The Quarterly Journal of Experimental Psychology Section B ◽

10.1080/14640748108400819 ◽

1981 ◽

Vol 33 (3b) ◽

pp. 141-157 ◽

Cited By ~ 11

Author(s):

Paul Dean ◽

Sian G. Pope

Keyword(s):

Eye Movements ◽

Superior Colliculus ◽

Open Field ◽

Discrimination Learning ◽

Visual Discrimination ◽

Visual Discrimination Learning ◽

Central Platform ◽

Area Centralis ◽

Scanning Head ◽

Discrimination Apparatus

It has been suggested that, for some species, lesions of the superior colliculus affect visual discrimination learning, but only in certain conditions: (a) when problems are first learnt only after operation, or (b) when discriminanda require detailed scanning, or (c) when “approach” responses to the discriminanda are measured, rather than the response of actually touching them. These suggestions were examined in rats learning visual discriminations in a modified jumping-stand apparatus, after sustaining large lesions of the superior colliculus (and in some cases also of the pretectum). The lesions produced open-field hyperactivity and reduced exploration, indicating effective tectal damage, but the rats learnt a series of difficult discriminations in a door-push task as fast as normal rats, and they did not make more approach errors. Their main abnormality in the discrimination apparatus was that they looked less often between the stimulus doors before stepping across to one of them from the central platform. It is suggested that in rats, as in other animals, lesions of the superior colliculus disrupt the control of scanning head and eye movements; in rats, however, such disruption need not affect discrimination learning (at least in some kinds of apparatus), possibly because the retina of the rat has a relatively poorly developed area centralis.

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A Neural Computation for Visual Acuity in the Presence of Eye Movements

PLoS Biology ◽

10.1371/journal.pbio.0050331 ◽

2007 ◽

Vol 5 (12) ◽

pp. e331 ◽

Cited By ~ 24

Author(s):

Xaq Pitkow ◽

Haim Sompolinsky ◽

Markus Meister

Keyword(s):

Visual Acuity ◽

Eye Movements ◽

Neural Computation

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Fifteen-minute consultation: Preseptal and orbital cellulitis

Archives of Disease in Childhood - Education and Practice ◽

10.1136/archdischild-2017-314297 ◽

2018 ◽

Vol 104 (2) ◽

pp. 79-83 ◽

Cited By ~ 1

Author(s):

Jonathan Adamson ◽

Thomas Waterfield

Keyword(s):

Emergency Department ◽

Visual Acuity ◽

Eye Movements ◽

Colour Vision ◽

Orbital Cellulitis ◽

Initial Assessment ◽

Management Options ◽

Paediatric Emergency Department ◽

Runny Nose ◽

History Of

‘It is midnight and you are called to see a thirteen-year-old boy who has been brought to the paediatric emergency department with a 24-hour history of swelling and redness of his left eye. He has had a ‘runny nose’ for a couple of days. He is systemically well. His upper and lower lids are red and swollen such that his eye is not open fully, though you elicit normal eye movements when you open his eye. Pupils are equal and reactive with no afferent pupillary defect. Visual acuity and colour vision are normal on examination.’ In this article, we consider the approach to preseptal and orbital cellulitis in children including the initial assessment and management options.

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Activity of omnipause neurons in alert cats during saccadic eye movements and visual stimuli

Journal of Neurophysiology ◽

10.1152/jn.1982.47.5.827 ◽

1982 ◽

Vol 47 (5) ◽

pp. 827-844 ◽

Cited By ~ 89

Author(s):

C. Evinger ◽

C. R. Kaneko ◽

A. F. Fuchs

Keyword(s):

Eye Movements ◽

Smooth Pursuit ◽

Visual Stimuli ◽

Pause Duration ◽

Visual Input ◽

Transient Increase ◽

Abducens Nucleus ◽

Wide Range ◽

Area Centralis ◽

Omnipause Neurons

1. In the cats trained to follow a target spot with their eyes, activity was recorded from omnipause neurons (OPNs). OPNs discharge at a relatively high steady tonic rate (50-130 spikes/s) during visual fixation and smooth-pursuit eye movements but exhibit a complete cessation of discharge that begins before saccades in any direction. They are located in a compact region of the dorsal pontine tegmentum near the midline, just rostral to the abducens nucleus. 2. The average duration of the horizontal or vertical component of a saccade increases monotonically with pause duration, but a given pause duration is associated with a large range of individual saccade parameters and the timing of the pause, such as the latency from the pause onset to saccade onset or the interval from the maximum saccade velocity to the end of the pause, is no better. However, OPNs can be divided into two distinct groups on the basis of the timing of the pause relative to the parameters of the saccade. One group ceases discharging 32.4 +/- 4.6 ms, on average, before the saccade, while the second pauses 18.2 +/- 3.4 ms before the saccade. 3. Microstimulation at the site of OPNs affects the occurrence and trajectory of saccades but not smooth pursuit or fixation. Sustained electrical stimulation (20 micro A) lasting several seconds prevents the occurrence of saccades while brief trains (10-60 ms), timed to occur early in the saccade, interrupt it in midflight for the duration of the train. The latency to the interruption is about 26 ms. These data support the view that OPNs tonically inhibit the saccadic machinery between saccades and must be turned off to allow a saccade to occur. 4. Almost every (65 of 69) feline OPN exhibited a brief transient increase in activity for visual stimuli moving in any direction with a wide range of velocities. A moving 1 degree spot was generally more effective than a moving full-field, striped background. All units also showed a transient increase in firing when the spot was turned either on or off. Receptive fields plotted with the spot were greater than 250 deg2 and always included the area centralis. Two-thirds of the cells tested also responded to auditory stimuli. 5. Interaction between the excitatory visual input and the saccade-related pause was tested by comparing OPN activity and the saccadic trajectory during eye movements in the dark versus the light and by presenting brief flashes of light during a saccade. During saccades in the dark, the steady firing of OPNs was less than during saccades in the light. Only by stabilizing a flashed spot of light to occur on the area centralis at the beginning of the saccade was it possible to activate an OPN artificially to interrupt the saccade in midflight. Therefore, rather than being instrumental in specifically controlling the saccade trajectory, the visual input, along with the auditory and other sensory inputs, probably serves, under normal visual conditions, to help establish the tonic rate of OPNs. 6...

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SPEED OF VISUAL ACUITY FOR VERTICAL EYE-MOVEMENTS WITH A CHANGE OF ACCOMMODATION

Perceptual and Motor Skills ◽

10.2466/pms.1989.69.3.751 ◽

1989 ◽

Vol 69 (3) ◽

pp. 751-754

Author(s):

DAVID M. LURIA

Keyword(s):

Visual Acuity ◽

Eye Movements

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