Eye Movements

Questão	Responda
Why is it necessary for our eyes to move?	Bring points of interest into our focal area. We also move our eyes to prevent blurring of the visual scene
Describe a saccade	Very fast eye movements, 40-200ms, bring points of interest into the focal point of the eye.
What is the difference between corrective saccades and dysmetric saccades	Corrective saccade - we normally undershoot with a saccade and then make a small corrective saccade to get to the exact right place. Dysmetric saccade - where we significantly over or undershoot a target then have to make a large corrective eye movement, significantly under showing is called hypometric while hypermetric is significantly overshooting
When reading our eyes make predictive saccades to words ____ of the ones we are reading, normally about __ or __ words)	ahead, 3-4
Describe the Vestibulo-ocular Reflex.	Mof the eyes to cancel out small movements of the head or body such as vibrations while walking or head movements. There are only 3 neurones involved in this system so it is very quick to react.
Suggest simple physiological evidence as to why the vestibulo-ocular reflex is not dependant on a visual input.	we still get a vestibulo-ocular reflex in the dark or when our eyes are closed if a subject is asked to imagine looking at one point
Describe a nystagmus	Eye movements characterised by a slow phase followed by a fast (rest kind of) phase.
If the vestibular system is not working properly what would we expect to happen to a subjects eye movements when we move their head left and right in a dark room while they try and focus on the same spot?	We wouldn't see the VOR occurring as they don't have any sense of their head movements and therefore aren't able to correct for them with eye movements
If the VOR is working perfectly what would the gain be?	1
Describe the velocity storage system with relation to eye movements	during rotation the vestibular signals die out after 6 seconds because the vestibular fluid catches up with the rotation however eye movements continue for up to 15 seconds after this. The brain stem has a velocity storage system for prolonged eye stabilization. This will decline with continued rotation and eventually fail
Describe a real life situation which shows that the VOR adapts.	When you get a new pair of glasses your VOR adapts to the new vision, and then when you go to a different strength glasses or take them off your VOR is still responding to the previous strenght glasses for a while.
Give some things which can affect VOR	Vestibular loss through Viral infection, Head injury, Surgical intervention Aging- Vestibular hairs gradually lost with age Alcohol Oscillopsia = blurring of the visual world
What is the difference between the VOR and the optokinetic response?	Occurs as a result of the visual world moving not our bodies/head. E.g. piece of paper being moved in front of you instead of spinning on a chair
the optokinetic reflex is more suited to _____ frequency movements while the VOR is more suited to ____ frequency movements.	Optokinetic reflex - Low VOR - High
What is a congenital nystagmus?	Where you have continual involuntary eye movements, random development of this can indicate brain damage
Describe smooth eye movements and how they are different from saccades	where we are able to track a moving object in a smooth manner, without making quick jumps from spot to spot. Can only be done involuntarily. whereas a saccade is very quick movements which result in visual suppression as the movement is made.
What is vergence?	Our ability to direct our eyes to the same point. For example we can direct both eyes to our finger held in front of your nose to give a clear image from the combined images.
Give 4 methods of recording eye movements.	Scleral Coil Infrared reflectance electro-oculography Video-oculography
Describe a scleral coil, giving its positives and negatives.	Contact lense embedded with a little wire, gives very accurate readings for values of yaw, pitch and roll however they are uncomfortable to wear and could potentially causes a corneal scratch.
Describe infrared reflectance and give some posetives with the technique	Shine an infrared beam onto the eye, as the eye rotates it is refracted differently. Change in position detected by the infrared detector. Can be used in the dark
Describe electro-oculography and give some positives and negatives of the technique.	Potential difference between the cornea and the retina. Created a potential difference between front and back of the eye which we can measure. It is NOT the EMG we record. As the eye changes position the electrical potential between the two electrodes changes. Horizontal and vertical movements can be measured by placing electrodes in the right place. Works in the dark and with eyes closed. it can provide gaze tracking information but we need to calibrate first and head must remain totally still else calibration thrown out.
Describe how video oculography works?	Simultaneous recording of the eye and the visual scene. We record the pupils using infrared cameras track the pupils and when calibrated it can allow us to track the gaze. Positives- we can easily record where people are looking while their head is allowed to move freely. Negatives head piece can be knocked throwing collaboration out.
Give a study which looked at gaze in every day life, and give some examples of what activities were studied	Land 2006, looked at how many steps we look when walking, its about 2 steps in advance. Also looked at tea making, reading etc
Give a paper which looked at eye movements of elite cricket players and give the findings	Yarrow et.al 2009 more skilled batters make predictive eye movements better and sooner. Also novice people show more less synchronized eye movement with the balls speed and eye movement speed.
Give a paper which shows gaze is predictive and say how they did it.	Flanagan & Johnasson, 2003. Looked at where people looked in a block moving tasks, found that we look over to the place we are going to put the block before we have even got there
Describe the Land 2000 study and their findings	Looked at three cricketers; novice, intermediate and elite. intermediate and elite tracked the balls path but then elite made a predictive saccade to the bounce point. Elite can also discriminate between ball flight paths better than non-elite.

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	Criado por alexlpeart mais de 10 anos atrás