Strabismus Flashcards
Define strabismus.
This is a condition characterized by misalignment of the eyes when looking at an object
Define visual axis.
An imaginary line that that connects the center of fovea to an object being fixated in space
What is Binocular Single Vision (BSV)?
The ability to use both eyes together so that separate and slightly dissimilar images arising in each eye are appreciated as a single image by the process of fusion in the brain.
Define orthophoria.
Refers to perfect ocular alignment in the absence of any stimulus for fusion.
Define heterophoria.
A tendency of the eyes to deviate when fusion is blocked. Also known as a latent squint.
Define heterotropia.
Manifest deviation in which the visual axes do not intersect at the point of fixation.
Name the 3 types of strabismus.
- Apparent(pseudo-strabismus)
- Latent (heterophoria)
- Manifest (heterotopia)
What is latent strabismus?
It involves misalignment that occurs intermittently, typically when the eyes are not focusing on any object
What is apparent strabismus?
This is the condition where the eye appear misaligned due to factors other than true misalignment. This can be created by certain morphological features of the face including the eyelids.
What is manifest strabismus?
Involves a consistent misalignment of the eyes which is present all the times.
What are the terms used when the eye is facing the following direction:
a) inward
b) outward
c) upward
d) downward
a) Esotropia
b) Exotropia
c) Hypertropia
d) Hypotropia
Define concomitant strabismus.
The angle of deviation remains the same in all directions of gaze, misalignment is consistent regardless of where the person is looking, occurs early in childhood.
Define non-accommodative strabismus
Form of strabismus characterized by inward deviation of the eye regardless of whether the person is focusing on near or distant objects.
Define accommodative esotropia
The eyes turn inward when focusing on nearby objects. Commonly associated with refractive errors of hyperopia.
Define paralytic strabismus.
Strabismus caused by partial or complete paralysis of the EOM. The angle of deviation alters depending on the direction of gaze. however, the abnormality may occur in the brainstem, nerve, neuromuscular junction, muscles
Give 5 risk factors of strabismus.
- Family history of strabismus
- Cerebral palsy
- Infections (meningitis, encephalitis, measles)
- Head injury
- Genetic disorders i.e. down syndrome
- Low birth weight or prematurity
- Prenatal drug exposure i.e. alcohol
How does strabismus present? (5)
- Ocular discomfort
- Headaches
- Abnormal head posture
- Inability to read properly
- Asthenopia (eyestrain)
- Double vision (diplopia) - This occurs when the brain receives two different images from the eyes.
- Suppression - The brain may ignore the image from the misaligned eye to avoid double vision, which can lead to amblyopia (lazy eye).
Give 2 differential diagnosis for strabismus.
- Pseudo-strabismus
- Nystagmus
Name 4 investigations that should be carried out in strabismus.
- Hirschberg test
- Krimksy test/prism test
- Cover-uncover test
- Worth 4-dot test
What is the non-surgical management of strabismus? (5)
Vision Therapy
Eye Exercises
Computerized Programs
Occlusion Therapy
Patching
Atropine Drops
Correct refractive errors
Glasses or Contact Lenses
Prism Lenses
What is the surgical management of strabismus? (3)
Repositioning of muscles
Tucking
Myectomy
Adjustable Sutures
Give 3 complications of strabismus.
- Amblyopia
- Vision loss
- Double vision
- Cosmetic concerns
