eye movement/reading Flashcards
What is Age-Related Macular Degeneration?
an age-related disease resulting in loss of vision usually affecting ages 50+
Define Macular Degeneration
the decline/breakdown of the macular (a oval shaped yellow dot in the centre of the retina)
What are the two main types of AMD?
Dry MD and Wet MD
What is the macular?
a group of oval yellow shaped light-sensitive cells in the centre of the retina responsible for crisp central vision and seeing things in fine/shape detail
how is the macular involved in AMD?
the AMD gradually destroys the macular impacting our central vision and daily life e.g., reading, driving due to loss of fine detail/seeing things clearly
Explain Dry AMD
-affects 85-90% of AMD patients causing blurry vision
-can occur in both eyes tends to start in one and progressively develops
-tissue supporting photoreceptors(rods/cones) thins and lose their pigment causing the macular to break down.
State the 3 stages of Dry AMD
1.early-yellow deposits (drusen) under the retina
2.intermediate-larger deposits causing some visual loss
3.advanced-tissue in centre of retina breaks down
true or false: fluid leaks in Dry AMD
false BUT it can still lead to Wet AMD
Explain Wet AMD
it doesn’t occur in stages BUT is caused by fragile abnormal blood vessels in the retina growing behind the macular leaking blood/fluids rapidly damaging the macular raising it from its original place.
What are 4 key points in relation to the development of AMD?
1.people with Wet AMD had the dry form initially
2.Dry AMD can advance/cause vision loss without becoming the wet form
3.BUT it can still turn into the wet form even in the early stages
4.Can’t tell if or when the dry form turns into wet form but this development affects 1 in 7 people with AMD
What is the most common complaint with people suffering from AMD
the inability to read
Why is reading a complex task?
requires high and low level systems e.g., perceptual, attentional, cognitive and oculomotor(which is in relation to eye movements)
What are 6 risk factors for AMD?
1.blue eyes
2.genetics
3.exposure to sunlight
4.nutrition
5.smoking
6.hypertension (high blood pressure in blood vessels)
What does antiVEGF treatment for Wet AMD involve?
Ranibizumab eye injections (usually aimed to be near retina) is given once a month for 4 months
What are the two main functions of the human eye movement system?
1.shift the fovea onto objects (saccades)
2.hold fixation onto the object (microsaccades, smooth pursuit and vestibulo-ocular reflex)
Define vestibulo-ocular reflex
a reflex which stabilises gaze during head/eye movement due to vestibular system activation allowing images on the retina to be stabilised.
Define smooth pursuit
slower tracking movements of the eyes designed to keep a moving stimulus on the fovea. (is voluntary to the observer)
Why is highly overlearned eye movement behaviour difficult?
fixating on a word brings it onto the impaired central scotoma
What does fixation instability lead to?
reduced perceptual span
Whats the impact of people with CVL (central vision loss) making their own saccades on simple reorienting tasks?
longer latency + tend to undershoot the target location
What’s slow reading speed associated with in AMD?
reduction in the size of forward saccades
What does eye movement behaviour show for slow reading?
1.increased number of fixations (+ fixating eccentrically)
2.atypical clustering of fixations made to words
3.adaptive oculomotor strategies
4.research-dynamic text formats enable reading speed to be measured using psychophysical methods.
5.e.g., Horizontally Scrolling text (drifting text) and Rapid Serial Visual Presentation
Describe scrolling/drifting text
single line of text scrolling across display from right to left e.g., like on a tram/train when it says the next destination
Describe Rapid Serial Visual Presentation (RSVP)
one word sequentially presented one after the other
