Orthoptics & Neuro Flashcards
What nerves control the muscles of the eyes?
SO: Trochlear n (CNIV)
LR: Abducens n (CNVI)
MR, IO, SR, IR: Oculomotor n (CNIII)
Levator Palpebrae Superioris: CNIII Elevates eyelid
Muller’s muscle/ tarsal muscle: Sympathetic supply lifts eyelid small amount
Orbicularis Occuli: CNVII closes eyelids
What are the features of a CNIII palsy?
Total Ptosis- interrupted supply to levator palpebrae superioris.
Fixed dilated pupil due to interrupted parasympathetic output to sphincter pupillae.
Affected eye is positioned down and out in primary gaze (i.e. staring straight ahead) due to unopposed action of SO and LR. (strabismus)
no accommodation or consensual reflex (efferent pupillary defect).
consensual reflex in other eye is maintained.
Patient presents early with diplopia which is found in extremes of gaze (particularly looking in direction of weakened/ paralysed muscle) where affected eye is unable to move as much as unaffected and therefore the gaze provides 1 image on the fovea of the normal eye and this same image is extrafoveal on the other eye.
What are the features of a CNIV palsy?
SO is unable to function so cannot intrort the eye or depress the eye in adducted position i.e. rotate eye inferomedially.
Diplopia on looking down i.e. looking in position in which SO cannot move the eye and therefore get 2 diff images.
At rest, eye is extorted and elevated in primary position due to unopposed action of IO.
head tilt towards unaffected side causing intorsion of unaffected eye and reducing double vision.
What are the features of a CNVI palsy?
LR is unable to function to abduct the affected eye
e.g. L LR palsy, look Left, L eye remains medial due to inability to abduct eye.
Convergent squint due to affected eye being drawn medially due to unopposed action of MR on that side. when trying to look at images to e.g. the L if L LR palsy, will get double vision.
What is an Adie pupil?
fixed dilated pupil (resulting in anisocoria) that is unresponsive/ to changes in light i.e. absent/reduced light reflex
The pupil shows a slow near response on accommodation testing (10-20secs)
May be associated with reduced tendon reflexes (Holmes-Adie syndrome)
usually affects young women unilaterally
Prodrome of flu like viral illness
What is traumatic mydriasis?
trauma sustained to eye damages the vessels supplying the muscles of the iris causing hyphaema (blood in ant chamber) and corneal oedema. sphincter muscles of pupil suffer permanent ischaemia due to rupture of these vessels therefore get fixed dilated pupil.
PC photosensitivity, glare, watering of eyes, headaches due to dilated pupil (other eye compensates so blurred vision is not an issue).
What is posterior synechiae?
A sequelae of iritis where the iris becomes adhered to the anterior lens due to the formation of adhesions. During iritis as part of the inflammation process, the iris becomes more permeable to cells, plasma proteins, fibrin which when mixed with aqueous form a glue like substance.
Tx for iritis= steroids (control inflammation) + dilating agents which both prevent and break adhesions but in a small number these adhesions remain causing an irreg shaped fixed pupil.
What is visual neglect? How does it differ from a visual field defect?
Visual neglect: patient is aware of stimuli in each field when tested individually but not when testing simultaneously.
Visual fields: patient is unaware of a visual stimulus presented in the affected field.
What is the PC and examination findings of Optic Neuritis?
Usually monocular
Blurred vision, retrobulbar pain especially on eye movements and globe (eyeball) tenderness
Disc may/ may not be swollen (if nerve swelling is retrobulbar i.e. behind the disc) on ophthalmoscopy
RAPD test +ve
Red desaturation i.e. red hatpin looks pink/ orange
Central scotoma on field testing
may have other transient neurological symptoms
HIGH RISK OF MS if recurring episode
What is the PC and examination findings of Papilloedema?
transient visual obscurities
enlarged blindspot
due to ICP increased therefore MUST be bilateral
What is strabismus? What are the types? How are they identified?
- Manifest: a deviation of one eye in any direction so visual axes are not aligned. Detected with cover/ uncover test
- Latent: tendency for eyes to deviate but under normal circumstances visual axes are aligned. Alternate cover test is used for detection.
What happens to binocular vision when a manifest squint is present?
- Diplopia: double vision due to the perception of each eye of different images. Occurs if onset of squint is after visual development > 7 years old.
- Suppression: image from deviated eye is suppressed by brain and therefore no double vision is perceived. Suppression occurs if squint is present during visual development from =<7 years old.
When is the visual development period? What can result if inadequate visual stimulation is provided during this time?
0-7 years. Amblyopia where there is a reduction in vision in one/ both eyes due to 1) a strabismus where the brain suppresses the image from the deviated eye, 2) stimulation deprivation e.g. cataract, or 3) when refractive error between eyes is significant (more than 1 diopter) i.e. anisometropia. It is a very common cause of visual impairment in children affecting their development and may result in them lacking binocular vision if not corrected. Lack of visual stimulation reaching eye affects the growth of the eye and development of vision. Can be reversed if “treated” within development period.
What is the treatment for amblyopia?
occlusion of the good eye using a patch to encourage visual development in the amblyopic eye. It can be reversed if performed during visual development period.
How are squints managed?
By orthoptists
- Most common by correction of refractive error. Convex lenses (+ lenses) relax eyes outwards for convergent squints, usually hypermetropic eye squinter. Concave lenses (- lenses) help control divergent squints by inducing focusing.
- Surgery if no refractive errors, or if refractive error correction not helped. Work on extrocular muscles to realign eye into better position