Orthoptics Flashcards
What is orthoptics?
“straight eyes”orthoptists are involved in the investigation, diagnosis and management if binocular vision and ocular motility disorders
What is binocular vision?
the brains ability to perceive an image with each eye simultaneously as a single image
What are the two types of strabismus/squint?
Manifest Latent
What is a manifest squint?
an inward/outward/upward/downward deviation of one eye, so that the visual axes are not aligned detected using cover-uncover-cover test
What is a latent squint?
a tendency for the eyes to deviate inwards/outwards/upwards/downwards under normal circumstances the visual axes are aligned the tendency for the eyes to deviate is detected using alternate cover test
What are the two things/consequences of a manifest squint?
DIPLOPIA SUPPRESSION
What is diplopia?
- double vision - each eye perceives the image of what it is looking at - common when onset of manifest squint is after visual development
What is suppression?
- no double vision - patient ignores/supresses the image from the squinting eye - common when squint onset is during visual development (<7 yrs)
What is amblyopia?
a reduction of vision in one eyedue to lack of stimulation during the critical period of visual development
How is amblyopia managed?
can be reversed is treated within the critical period (<7 years) treatment = occlusion of the ‘good eye’e.g. with a patch
How can squints be managed?(nice to know)
Refractive Error - convex lenses (long sighted) help convergent deviations - concave lenses (short-sighted) help divergent deviationsSurgery - realigning the eyes can be functional or cosmetic
How is vision recorded?Snellen vs LogMAR
Snellen is recorded as a fraction LogMAR vision is recorded as a decimal normal vision - 6/6 (0.0) defective vision - 6/60 (1.0) above average vision - 6/5 (-0.10)
What are the two types of squint?
concomitant strabismus - remains the same in all positions of gazeincomitant strabismus - strabismus which changes in different positions of gaze- due to extraocular mm imbalance
What does the 3rd nerve innervate?
medial rectus inferior rectusinferior oblique superior rectus levator papebral superiorispupil
What does the 4th nerve innervate?
superior oblique
What does the 6th nerve innervate?
lateral rectus
How does a 3rd nerve palsy present?
extropia and hypotropia of the affected eye (eye = down and out)ptosis dilated pupil
How does a 4th nerve palsy present?
hypertropia and excylotorsion of the eye (up and out)patient may tilt their head
How does a 6th nerve palsy present?
esotrophia (eye deviated inwards) esotrophia bigger in distance than in the near
What is the difference in the effects of nerve palsies in children and adults?
in children suppression is likely - risk of developing amblyopia in adults diplopia is likely
What are the two different severities of nerve palsy?
partial - nerve is partially affected/nerve palsy is subtle. patient may not have diplopia in all positions of gaze complete - diplopia in all positions of gaze
What are the causes of nerve palsies?
trauma - head injury SOL - tumour SOL - vascular Microvascular - pts with HTN/DMInflammatory - post viralInfection - inner earDymyelination
What is important to remember about the actions of the extraocular muscles?
They DO NOT WORK in ISOLATION, they have secondary and tertiary actions
Could look at eye muscle anatomy and muscle insertions etc
mentioned in LO
How is diplopia managed?
Prisms - join up the two images Occlusion - cover up one eye to block the diplopic image Surgery - aim to realign eyes in primary position and reduce/eliminate diplopia
