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
Explain eccentric viewing
a reading strategy/technique used with CVL where people with AMD make the most of their peripheral vision without central vision
-involves pseudo fovea (training to use/determine the best area of vision and involves looking above, below or to a side of a word to focus on it more clearly)
Explain study 1 central scotoma procedure
1.P’s informed about the eccentric viewing technique
2.Read passages of standardised text taken from the York Assessment of Reading
3.Then practice passages
4.Questions given after to assess comprehension – literal, inferential, summary
5.All participants read aloud
6.Speed of text based on previous pilot study (n=18) – matched dynamic speed (Akthar et al., 2021)
What were the results of study 1?
RVSP was better for:
-literal comprehension
-eye movement/eccentric viewing
Scrolling text was better for:
-inferential comprehension (poor with RSVP)
-higher % of key points remembered compared to RSVP
-reading accuracy high but poor with RSVP
What was the participant sample for study 2 macular degeneration?
- Diagnosis of Wet / Dry macular degeneration + CVL in either (RE, LE, BOTH)
- 37 participants (mean age = 80 years old)
- English as first language
- Six-Item Cognitive Impairment Test
- All participants aware of EV technique
How was study 2 different to study 1?
- Conducted in own homes
- YARC Primary Passages of text used
- Scrolling - iPad – MDevReader app
- RSVP = Samsung (custom-coded in-house app)
- Static text (SL+ML) – iPad - PowerPoint
- Scrolling text is given before RSVP text (practice session ONLY)
study 1=simulated/lab based which study 2 wasn’t
What were the results for reading performance?
- Overall reading comprehension better with scrolling than all other text displays
- Higher proportion of errors observed for the RSVP format
- Literal comprehension with scroll better – compared to simulated CVL – better with RSVP.
What are the conclusions of study 1?
- Adherence to EV in the simulated scotoma group was poor
- Adherence to EV was better with RSVP BUT resulted in poor comprehension and accuracy
- Reading performance - best with the scrolling text format
What are the conclusions of study 2?
- BETTER reading performance with scrolling text than with static text
- Reading performance POOR overall with RSVP
What are the 3 advantages of dynamic text?
- RSVP and horizontal scrolling text can be used for reading eccentrically as using atypical eye movement behaviour may support reading
- Horizontally scrolling text read by sighted observers using a combo of leftward pursuit fixations and rightward saccades that resembles nystagmus
- Scrolling text can also be read with a steady gaze, so it moves smoothly across the retina (basically demonstrates dynamic text helps people with AMD for reading these 3 points more explain how)
Define Nystagmus
an involuntary rhythmic side-to-side, up and down or circular motion of the eyes that occurs with a variety of conditions.
What is the overall conclusion for the effectiveness of scrolling text?
Scrolling text may support effective reading in people with CVL and has great potential as a reading aid.
