Vision Flashcards
Objectives of development of binocular vision: Acquiring foveal centration:
- Acquiring foveal centration:
- Acquiring the ability to accommodate the lenses to near vision
Acquiring foveal centration:
a. Acquired ability to fix the fovea centralis of each eye on the same target
b. Fovea centralis is about 1.5 mm in diameter
c. Area of max visual acuity covers about 3 degrees of visual field
conjugate (yoked) eye movements
necessary for development of binocular vision and depth perception. Presented around ages 4 months.
Yoked (Con/ Di) vergence movements
yoked convergence and divergence movements. Usually presented at 6 months.
Lens accommodation for near vision.
This keeps near objects in focus, infants are slightly hyperopic/ slight far sighted and usually occurs at the age of 6 months. They need to learn lens accommodation for near vision
Hyperopia: far sighted
Ciliary muscles relax for far vision
Ciliary muscles contracts to accommodate for near vision
Desired results: Emmetropia
Concurrent requirement: appropriate cortical mapping: wire together, fire together
- it is activity driven:
a. lateral geniculate nuclei (LGN) in the thalamus
b. ocular dominance columns and cortical mapping
Ocular dominance columns should be?
balanced from side to side
cortical mapping: balancing these columns is a learned?
activity driven sorting process
cortical mapping: balancing these columns is key?
to future development of visual system
some evidence of this balancing should be seen by?
4-6 months of age
What is the eventual outcome of a lack of balance?
- This process is developmental and it is sometimes hard to predict the outcome and 2. The perfect balance can be very hard to achieve and very hard to maintain
reality: almost everyone has a dominant eye
Assessing corneal light reflections
Corneal light reflections from ambient light should land in the same clock position in each eye.
Evaluating accommodation and the accommodative triad
accommodative convergence, accommodative pupillary constriction and accommodation of lens for near vision
convergence/ accommodative break
one eye deviates back to the original starting position as the pencil approaches the nose
Convergence insufficiency self test
the patient looks at center vertical line as the paper is brought towards their nose from a distance of about 18’’. What’s normal? The center line remains in focus at about 5’’
Convergence insufficiency self test: abnormal
convergence insufficiency, a double image of that line is seen as the paper nears the eye
Strabismus
an eye is deviated when both eyes are open
Tropia (L “a turning”)
T for turn
Phoria (L “a bearing”
an eye that deviates only when it is covered an it’s visual stimulus is taken away
Cover- uncover test
looks for evidence of phoria, an eye deviates only when an eye is covered and losses it’s visual input.
Cardinal fields of gaze
evaluating fixation and pursuit movements
Cardinal fields of gaze test Steps:
o 1: fixation, inability to fix gaze on stationary target can imply a serious disorder
o 2: pursuit, inability to smoothly peruse a moving object can be found with a number of different disorders
Normal variants on cardinal fields of gaze:
- Hyper dominant eye
2. Physiologic end point nystagmus of brief duration
variants on cardinal fields of gaze: Abnormal: undershoot or overshoot
- may be seen with cerebral disease
2. may be seen with acute alcohol intoxication
variants on cardinal fields of gaze: Abnormal: jittery eye movements
might be an early indication of MS
variants on cardinal fields of gaze: Abnormal: lesions of vestibular/ oculomotor /cerebral systems
- Spontaneous nystagmus with no apparent cause: newly acquired? Congenital?
- Gaze evoked nystagmus: fixation or pursuit results in a very irregular nystagmas
- Tropias that occur during pursuit movements- differential: benign paroxysmal positional vertigo
