Orthoptics & Neuro

Question 1

What nerves control the muscles of the eyes?

Answer 1

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

Question 2

What are the features of a CNIII palsy?

Answer 2

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.

Question 3

What are the features of a CNIV palsy?

Answer 3

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.

Question 4

What are the features of a CNVI palsy?

Answer 4

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.

Question 5

What is an Adie pupil?

Answer 5

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

Question 6

What is traumatic mydriasis?

Answer 6

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).

Question 7

What is posterior synechiae?

Answer 7

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.

Question 8

What is visual neglect? How does it differ from a visual field defect?

Answer 8

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.

Question 9

What is the PC and examination findings of Optic Neuritis?

Answer 9

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

Question 10

What is the PC and examination findings of Papilloedema?

Answer 10

transient visual obscurities
enlarged blindspot
due to ICP increased therefore MUST be bilateral

Question 11

What is strabismus? What are the types? How are they identified?

Answer 11

1. Manifest: a deviation of one eye in any direction so visual axes are not aligned. Detected with cover/ uncover test
2. Latent: tendency for eyes to deviate but under normal circumstances visual axes are aligned. Alternate cover test is used for detection.

Question 12

What happens to binocular vision when a manifest squint is present?

Answer 12

1. 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.
2. 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.

Question 13

When is the visual development period? What can result if inadequate visual stimulation is provided during this time?

Answer 13

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.

Question 14

What is the treatment for amblyopia?

Answer 14

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.

Question 15

How are squints managed?

Answer 15

By orthoptists

1. 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.
2. Surgery if no refractive errors, or if refractive error correction not helped. Work on extrocular muscles to realign eye into better position

Question 16

What is visual acuity? How is it tested?

Answer 16

A measure of the patient’s ability to resolve fine detail with the optimum optical correction in place (i.e. following correction of any defects).
Snellen’s chart used at distance 6m to minimise effect on accommodation.
(6/6 is normal. less than 1 in fraction form is abnormal)
0 or -ve on LogMAR is normal or better than normal.
Central 5° of visual field is measured in acuity therefore not all pathology e.g. glaucoma can be recognised in acuity testing.
crowding more accurately assesses visual acuity than uncrowded single letters do.
Can also use LogMAR chart that is more accurate for low vision.

Question 17

What is hypermetropia? How is it managed?

Answer 17

Long sightedness
either bc refractive power of eye is too small or the eye is too small.
Light rays are focussed behind the retina.
Corrected using convex lenses that converge the light. (+)

Question 18

What is astigmatism?

Answer 18

asymmetrically shaped eye (cornea/ lens) causing light striking the eye at diff points to be refracted in a different manner creating several points of focus of the light rays.
the refractive power of the eye varies depending on where on the surface the light rays fall.
A cylindrical lens corrects error in one direction only (i.e. in a specific Meridien). Meridiens are found at 90° to each other and can have diff powers to correct for diff refractive errors.

Question 19

What is presbyopia?

Answer 19

reduced accommodation ability due to sclerosing of the lens as ageing occurs.

Question 20

What is emmetropia?

Answer 20

Normal eye sight

Question 21

What is the purpose of a pinhole test?

Answer 21

helps differentiate reduced visual acuity due to uncorrected refractive error or path cause. It induces a point focus within the eye cutting the peripheral blur.
If no sig improvement in acuity using the pinhole, suggests pathology e.g. macula degeneration.

Question 22

What are the following prescriptions?
1. -3.00 DS
2.

Answer 22

1. Myopic patient, convex lens to diverge light. Relative power is 3 diopters. S= spherical lens (equal correction in all meridians of the eye)

Question 23

What are the following prescriptions?

1. -3.00 DS
2. +3.00/ -0.75 x 180
3. -1.25 x 30
4. -2.00 x 95 Add +2.00

Answer 23

1. Myopic patient, convex lens to diverge light. Relative power is 3 diopters. S= spherical lens (equal correction in all meridians of the eye)
2. Hypermetropic in horizontal axis due to astigmatism and myopic in other eye ???
3. Oblique astigmatism
4. Astigmatism (hypermetropic) + Bifocals for near vision.

Question 24

What is a concomitant squint?

Answer 24

Common in kids

squint that remains the same in size and direction in all gaze positions.

Question 25

What is an incominant squint?

Answer 25

results from an imbalance in the extra ocular muscles due to damage to the n or muscles. The squint changes in size as gaze position shifts. primarily in adults.

Question 26

What are the action of the Sup Rectus, Inf Rectus muscles? Where do they insert on the eyeball?

Answer 26

SR: 1° action is elevation (maximally in abduction), 2° intorsion, 3° adduction IR: 1° action is depression (max in abduction), 2° extortion, 3° adduction These both insert at an angle of 23° to the medial wall of the globe. SR to the superior surface of the globe, IR to the inferior surface of the globe.

Question 27

What are the action of the Sup Oblique, Inf Oblique muscles? Where do they insert on the eyeball?

Answer 27

SO: 1° action is intorsion (maximally in abduction) ; 2° is depression (max in adduction); 3° is abduction IO: 1° action is extortion (max in abduction), 2° is elevation (max in adduction), 3° is abduction SO inserts at 51° onto the medial surface of the globe onto the superior surface. IO inserts at 51° onto the medial surface of the globe onto the inferior surface. Depending on the position of the eye i.e. primary position or abducted/ adducted, the primary action of these muscles changes.

Question 28

What are the diff between soft and rigid contact lenses? What are their uses?

Answer 28

SOFT: good O2 transmission, large diameter securing fit, can be disposable, more expensive, can get infections due to poor hygiene. RIGID: fixed shape and durable, less risk of hypoxia due to smaller diameter but easier to dislodge, better results for astigmatism, poor comfort, easy to clean, fewer problems with deposits. USES: aphakia (no lens in eye e.g. post cataract removal), ametropia (refractive error), Anisometropia (sig refractive diff between eyes), keratokonus (irreg corneal surface) use rigid lens to prevent tearing of the cornea, medical- therapeutic to prevent corneal irritation.

Question 29

What is Anisometropia?

Answer 29

significant refractive power diff between two eyes. usually >2dioptres diff.

Question 30

What is the ddx for a CN palsy? What are other causes of ocular motility issues?

Answer 30

- Vascular is most common in the older population (HT and DM are RF: due to disrupted blood supply to the nerves via vasa nervorum - In children it is a space occupying lesion until proven otherwise. (compression of eye) - Trauma is also another poss - Inflammatory/ Infective causes Other causes: 1. mechanical e.g. blow out orbital # (muscles get trapped in bone fragments), thyroid eye disease (inflammation of muscles swollen in socket get exophthalmos and diff with eye movements, and poss compression of optic n) 2. myogenic cond: e.g. myasthenia gravis (fatigue and ptosis), tumour, inflammation, disease of extra ocular muscle.

Question 31

How is diplopia managed?

Answer 31

1. Prisms to try to join 2 images as one. 2. occlusion of one eye to stop the diplopic image 3. surgery on extra ocular muscles to try to realign them

Question 32

What is the role of the orthoptist? Who needs urgent referral?

Answer 32

to manage diplopia, binocular vision, strabismus (squint), treat amblyopia, ocular motility. Kids with CN palsies (Space occupying lesion until proven otherwise) CNIII palsies with pupil involvement is an aneurysm until proven otherwise bc pupillary n fibres run with but not within CNIII.

Question 33

What is the cover- uncover test? What does a cover- uncover test look for?

Answer 33

Ask the patient to look at your light. Cover one of their eyes, closely observing the uncovered eye for any movements. repeat on other side. When the contralateral eye is covered, if the uncovered eye moves to fixate then a squint is present in the uncovered eye. A manifest squint i.e. a deviation in the eye under normal circumstances.

Question 34

What is the Alternate cover test? What does it look for?

Answer 34

used to show a latent squint i.e. one that is not present under normal circumstances but that has a tendency to deviate. Cover one eye, and then when you remove the cover from that eye look for any corrective movement of the eye. And do the same on the other side. Basically the eye drifts when it is covered and this test aims to detect that.