Fixation characteristics and abnormalities

Components: Tremor, drift ad microsaccade

1. FIXATION CHARACTERISTICS
AND ANOMALIES
By:
Noor Munirah binti Awang Abu Bakar
Optometrist
(Moc No: O-0869)

2. OUTLINES:
•Binocular vision
•Eye movements
•Types of eye movements
•Eye Fixation- Concepts
•Eye Fixation- Components
•Fixation abnormalities

3. BINOCULAR VISION
•Binocular vision is a sensorimotor process.
•Eye movements to keep lines of sight pointing same target.
(Otero-Millan et al, 2014)

4. EYE MOVEMENTS
What?
Refers to voluntary or involuntary movement of the eyes, helping in
acquiring, fixating and tracking the visual stimuli.
Eye movements place the image of interest on the fovea (part of retina
with highest acuity)
Controlled by 6 extraocular muscles innervated by cranial nerves III, IV
and VI.

5. EYE MOVEMENT CONTROLLED BY 6
EXTRAOCULAR MUSCLES (SUPERIOR VIEW)

6. TYPES OF EYE MOVEMENT
(Ciuffreda & Tannen, 1995)

7. EYE FIXATION
Question:
Do our eyes move or still during
fixating on a stationary object?
Answer:
Moving

8. EYE FIXATION-CONCEPT
During attempted visual fixation at a stationary object, our eyes
continually move involuntarily.
The movement can be slow or rapid small amplitude- make us
unaware of the movement.
The fixational eye movements change the degree of alignment
between 2 eyes and continuously move the retinal images.
Even there is movement, the image of the object is still retained
within an acceptable foveal retinal locus. (±30 minutes of arc)
(Ciuffreda & Tannen, 1995)

9. EYE FIXATION-CONCEPT

10. EYE FIXATION-CONCEPT
1.Our eyes are focusing at a fly

11. EYE FIXATION-CONCEPT
2. At macular area, there is a central foveal fixation point.
Macula

12. EYE FIXATION-CONCEPT
3. At macular area, there is a central foveal fixation point.

13. EYE FIXATION-CONCEPT
4. Central fovea is highly dense with cone photoreceptor.s

14. EYE FIXATION-CONCEPT
5. During the eye fixation, the image moving in the central fovea (across a
cone, a dozen to hundreds of photoreceptors).

15. EYE FIXATION-CONCEPT
(Otero-Millan et al, 2014)
While our eyes are constantly moving, why we do
not suffer DIPLOPIA?

16. EYE FIXATION-CONCEPT
(Martinez-Conde et al., 2004)

17. EYE FIXATION-CONCEPT
ALTERNATE EYE SACCADE AND FIXATION
• This is the typical pattern of eye movement during reading.
•The eyes never move smoothly over still text.
•Fixation lengths ~ 100 to 600 milliseconds  length shows information processing.
• During this stop the brain starts to process the visual information received from the eyes
An example of fixations and saccades over text

18. EYE FIXATION-CONCEPT
PATTERN FOR SHOWING FIXATIONAL EYE MOVEMENTS
To experience it, look at the
central black dot for about a
minute, then look at the
white dot in the adjacent
dark square.
The dark after-image of the
white line pattern should be
seen in constant motion
owing to fixational eye
movements.

19. EYE FIXATION-COMPONENTS

20. NEED TO UNDERSTAND…

21. EYE FIXATION COMPONENTS
Microsaccades
( Martinez-Conde et al, 2004 & Otero-Millan et al, 2014)

22. EYE FIXATION COMPONENTS
Tremors
( Martinez-Conde et al, 2004 & Otero-Millan et al, 2014)

23. EYE FIXATION COMPONENTS
Drifts
( Martinez-Conde et al, 2004 & Otero-Millan et al, 2014)

24. TREMOR, DRIFT & MICROSACCADES ACROSS
PHOTORECEPTORS
Curved lines:
High frequency tremors & drifts
Straight lines:
-Fast, jerk-like movements of
microsaccades
-Bring the image back towards
the centre of vision
Fovea diameter: 0.05mm

25. EYE FIXATION
EYE MOVEMENTS DURING VISUAL FIXATION
•An observer views a picture (left) while
eye positions are monitored (right).
•The eyes jump, seem to fixate or rest
momentarily, producing a small dot on the
trace, then jump to a new region of
interest.
•However, even during these fixation, or
‘rest’ times, the eyes are never still, but
continuously produce fixational eye
movements — drifts, tremor and
microsaccades.

26. EYE FIXATION

27. VISUAL FADING: TROXLER’S EFFECT
1.Fixate at red spot.
2.After few secs, bluish annulus
will disappear.
3.Red spot surrounded by white
field.

28. FIXATIONAL EYE MOVEMENT:
MONOCULAR VS BINOCULAR VIEWING
Binocular performance can be superior to monocular
performance of the same visual task. Why?
Binocular summation – An ability of the brain to combine the info from two
eyes.
Binocular summation predicts improved fixation stability under binocular
viewing as compared to monocular viewing.
Increased fixation instability during monocular viewing,
especially for the occluded eye (González et al.,2012)

29. FIXATIONAL EYE MOVEMENT:
NEAR VS FAR VIEWING
No differences in fixational eye movement characteristics
between far and near viewing (Krauskopf et al., 1960)

30. FIXATION ABNORMALITIES
(Ciuffreda & Tannen,
1995)

31. FIXATION ABNORMALITIES
(Ciuffreda & Tannen,
1995)

32. FIXATION ABNORMALITIES
(Ciuffreda & Tannen,
1995)

33. FIXATION ABNORMALITIES
(Ciuffreda & Tannen,
1995)

34. FIXATION ABNORMALITIES
2. Saccadic intrusions
(Ciuffreda & Tannen,
1995)

35. 2. Saccadic intrusions

36. FIXATION ABNORMALITIES
(Ciuffreda & Tannen,
1995)

37. FIXATION ABNORMALITIES
3. Nystagmus- Involuntary rhythmic oscillation of the eye
(Ciuffreda & Tannen,
1995)

38. FIXATION ABNORMALITIES
P
e
n
d
u
la
r

N
y
s
t
a
g
m
u
s
(Ciuffreda & Tannen,
1995)

39. FIXATION ABNORMALITIES
J
e
r
k

N
y
s
t
a
g
m
u
s
(Ciuffreda & Tannen,
1995)

40. 3. Nystagmus- Involuntary rhythmic oscillation of the eye

41. FIXATION ABNORMALITIES
3. Nystagmus

42. FIXATION ABNORMALITIES

43. REFERENCES
Ciuffreda, K.J. 1995. Eye Movement Basics for The Clinician. Mosby.
Martinez-Conde, S. Macknik, S.L. & Hubel, D.H. Role of Fixational Eye in Visual
Perception. Nat Rev Neurosci. 2004 Mar;5(3):229-40.
Martinez-Conde, S. Fixational Eye Movements in Normal and Pathological Vision.
Prog Brain Res. 2006;154:151-76.
Otero-Millan, J., Macknik, S. & Martinez-Conde, S. Fixational Eye Movements and
Binocular Vision. Front Integr Neurosci. 2014; 8: 52. Published online 2014 July 7.
doi: 10.3389/fnint.2014.00052 PMCID: PMC4083562
Rucci, M. & Poletti, M. Control and Functions of Fixational Eye Movements.
Annual Review of Vision Science, Vol. 1: 499 -518 (Volume publication date
November 2015)
Shaikh A.G.

, Otero-Millan J., Kumar P., Ghasia F.F. Abnormal Fixational Eye
Movements in Amblyopia. PLoS One. 2016 Mar 1;11(3):e0149953. doi:
10.1371/journal.pone.0149953. eCollection 2016.