Otrhoptics Flashcards
Define strabismus (squint)?
A squint is when both eyes are not pointing in the same direction.
What is binocular vision and what are the 3 components of it?
Binocular vision is using our eyes together as a pair.
Made up of:
Simultaneous perception: each eye perceives an image of the world simultaneously.
Fusion: the brain puts these 2 images together so we only see one image.
Stereopsis: the fused images are seen in depth.
Describe the difference between a manifest and latent squint?
Manifest squints are when the eyes visual axis are not aligned and therefore binocular vision is not possible. Detected using a cover-uncover test. Also known as a concomitant squint.
Latent squints are when one eye has a tendency to deviate. Under normal circumstances the visual axis are aligned. Detected using a alternate cover test. Also known as a incomitant squint.
What is diploplia and supression?
Diploplia is double vision, can occur in people with squints as each eye is perceiving a different image. Usually occurs in squints which occur after 7 years of age.
Suppression is when the patient has learnt to suppress the image from the squinting eye and therefore they do not get diploplia. This usually occurs in squints which occur in people under the age of 7
Why is visual acuity screened for in young children?
Visual acuity is screened for to try and identify amblyopia.
Amblyopia is a reduction of vision in one or both eyes with no evidence of structural abnormality.
What is the criteria for amblyopia?
A difference of 2 or more line on the vision chart.
OR
Visual acuity of 20/30
What is the aetiology of amblyopia?
It is caused by lack of visual stimulation during the critical period 0-7 years.
Lack of visual stimulation reaching the retina causes the eye and vision not to grow and develop properly.
What is the treatment of amblyopia?
Amblyopia can only be reversed if treated in the critical period 0-7 years
Treatment surrounds covering the good eye to encourage the use of the amblyopic eye.
The good eye is usually covered with a sticky eye patch for a period of the day.
It is important to closely monitor the visual acuity of both eyes as check improvement and as you can induce amblyopia in the other eye if it is covered too much.
What are the different functions of all the different extraocular muscles?
Middle rectus: Adduction
Lateral rectus: Abduction
Superior rectus: Elevation, Intorsion, Adduction.
Inferior rectus: Depression, Extorsion, Abduction
Superior Oblique: Intorsion, Depression, Abduction
Inferior Oblique: Extorsion, Elevation, Abduction.
RADSIN
Recti ADduct
Superior INtort
What will you see in a 3rd nerve palsy?
Full ptosis
Mydriasis
Eye deviated downwards and out
What will you see in a 4th nn palsy?
Hypertropia (Affected eye is on a higher visual axis than the other eye)
Extorsion of the eye
Patient may tilt there head to try and align the images.
What will you see in a 6th nn palsy?
Eye deviate inwards more evident if patient is looking in the distance.
What are common causes of nn palsys are from?
Trauma
SOL or metastatic spread
Microvascular due to diabetes or hypertension
