Revision Flashcards
What are the typical tests in order, in an orthoptic assessment?
VA nr + dis (s glss/c glss), CT nr + dis (s glss/c glss) + NPC (near point convergence), PCT nr + dis (s glss/c glss), PFR nr + dis (s glss), Frisby, OM (S GLSS !!!)
What are the normal ranges for PFR?
NR PFR c gls : 35-45 BO -> 15 BI
DIS PFR c gls : 15 BO -> 8 BI
(Adults)
Where do the rectus muscles originate?
From the Annulus of Zinn, which encircles the optic foramen and the medial portion of the superior orbital fissure.
Where does the medial rectus originate?
Originates at the orbital apex from the medial portion of the Annulus of Zinnin close contact with the optic nerve.
Where is the medial rectus inserted?
5.5mm from the limbus
what is the width of the insertion of the medial rectus muscle?
10.5mm
What innervates the medial rectus muscle?
inferior division of the 3rd cranial nerve (oculomotor nerve)
what is the function of the medial rectus?
Adduction
where does the lateral rectus originate?
muscle arises by two heads from the upper and lower portions of the annulus of zinn where it bridges the superior orbital fissure.
Where is the insertion of lateral rectus?
7mm from the limbus
What is the width of the lateral rectus muscle insertion ?
9.5mm
What nerve innervates the lateral rectus?
CN 6 (VI) - abducens nerve , which enters from bulbar side
what is the function of the lateral rectus muscle?
Abduction
Where does the superior rectus muscle originate?
The muscle arises from the superior position of the Annulus of Zinn (in close contact with levator muscle)
Where is the insertion of the superior rectus muscle?
7.7mm from limbus
what is the width of the insertion of the superior rectus muscle?
11mm
What nerve innervates the superior rectus muscle?
CN3 (oculomotor nerve) superior division (enters muscle on bulbar side).
What are the functions of the Superior Rectus Muscle?
Elevation, intorsion and adduction
Where does the inferior rectus muscle originate?
The muscle arises from the inferior portion of the Annulus of Zinn
Where does the inferior rectus muscle insert?
6.5mm from the limbus
what is the width of the inferior rectus muscle as it inserts?
10mm
What nerve innervates the inferior rectus muscle?
CN3 (oculomotor nerve) inferior division (enters on bulbar side)
What are the functions of the inferior rectus muscle?
depression, extorsion and adduction
Where does the superior oblique originate?
From the orbital apex from the periosteum of the body of the sphenoid bone, medial and superior to the optic foramen.
Where is the Superior oblique inserted?
It passes beneath the superior rectus and inserts on the upper temporal quadrant of the globe ventral to the superior rectus.
What is the width of the insertion of the superior oblique?
Its insertion is fanned out in a curved line 10-12mm in length
What nerve innervates the superior oblique?
CN IV (4) - trochlear nerve , enters muscle on its upper surface
What are the functions of the superior oblique?
intorsion, depression and abduction
Where does the inferior oblique muscle originate?
Arises from the floor of the orbit from the periosteum covering the anteromedial portion of the maxilla bone.
Where does the inferior oblique insert?
It crosses the inferior rectus and curves upwards around the globe to insert under the lateral rectus just anterior to the macular area
What innervates the inferior rectus muscle?
inferior division of the 3rd CN nerve (oculomotor) enters muscle on bulbar surface
what are the functions of the inferior rectus?
extorsion, elevation and abduction
Herrings law
(equal innervation) nerve impulse sent to muslce to contract, equal nerve impulse to contralateral synergist so both eyes move along paralel axis (RLR + LMR contract & RMR + LLR relax)
Sherringtons Law
(reciprocal innervation) nerve impulse sent to muscle to contract, decreased signal sent to direct antagonist to relax equal amount (RLR + RMR)
agonist
primary muscle moving in given primary direction
synergist
muscle from same eye help move eye in same direction as agonist (RSR + RSO for dextro elevation) “yolk muscles”
antagonist
opposite direction of agonist (muscle relaxing) (RMR +RLR)
contralateral synergist
contralateral = opposite eye, muscle moving in same direction in opp eye, RLR agonist = LMR contralateral synergist to look right
underaction of muscle on cover test
eye goes up on CT to fixate on light becuase undershoot
overaction of muscle on covertest
eye goes down on CT to fixate on light because overshot
what does mechanical restriction mean?
not neurogenic, other muscles not compensating
what are muscles in postions in RE
RSR (dextro elevation)
RLR (dextroversion)
RIR (dextro depression)
(RIO laevo elevation)
RMR (laveoversion)
RSO (laevodepression)
what are muscle postions in LE
LIO (dextro elevation)
LMR (dextroversion)
LSO (dextro depression)
LSR (laevo elevation)
LLR (laveoversion)
LIR (laevodepression)
acronym for muscles
S (IO) (IO) S
L M M L
I (SO) (SO) I
Common concerns in kids with eye problems
-blurred vision, eye related pain/discomfort (older kids), failed V screening, turned eye (squint), difficulty with school work
History and note taking of px
-age of onset of symptoms (earlier = more hard to return back to normal VA)
-frequency of symptoms
-time of occurrence of symptoms
-speed of onset of symptoms
-constancy of symptoms
-general health of px at time symptoms first noticed
-previous ocular investigations/treatment
What are the two stages + process of developing vision?
Critical period (up to 18 weeks) + Sensitive period (up to 8 years old)
Emmetropisation
Diploia questions
-horizontal / vertical
-when does it occur (near/dis, time of day)
-can you make it single
-mono/binoc (when you close one eye does it disappear)
-anything make it worse or better?
-kids might close one eye (not developed suppression)
Onset of strab at birth- what two types?
-infantile esotropia (most likely, not likely exo) 30-50 diopters, need operation quickly, within first two years
-congenital eso/exo
Congenital cataract
Earlier deprivation= more severe visual loss
-needs to be rested within first 6 weeks
Which eye do you cover first when doing CT if they have squint
Straight eye to observe if squinting eye takes up fixation or weaker eye first
What could a sudden onset mean?
Nerve palsy/papillodema (raised intracranial pressure)/tumour
Why is alternating squint good?
Equal VA in both eyes just not working together
Is it harder to control eso or exo?
Exophoria easier to control as easier to pull eyes in (converge) intermittent = only occasional squint
ESO = harder to control cause need to diverge
Why would someone’s phoria decompensate?
Don’t have enough fusional reserves
Why will a myope not develop amblyopia?
Stimulate all the time when looking close up (everything clear)
What is ametropia?
Both eyes have refractive error
What is amblyopia?
Developmental condition characterised by reduced vision in one eye
V/a acuity worse than 0.2 Logmar (6/9) NOT due to refractive error/retina problems = cortical condition not eye problem!!
-due to presence of sensory impediment to visual development e.g. strabismus or an anisometropia and astigmatism occurring in early life
5 types of amblyopia
-stimulus deprivation amblyopia
-stabismic amblyopia (manifest strab)
-anisometropic amblyopia
-ametropic amblyopia (high RE uncorrected bilateral
-meridianal amblyopia (uncorrected astigmatism)
What does the severity of amblyopia depend on?
-size of the imbalance between the two eyes
-the timing of the disturbance during visual development (critical worse than sensitive bc sensitive time to develop BV)
Mechanisms of amblyopia
-light deprivation (no stimuli to retina)
-form deprivation (retina receives a refocused image)
-abnormal binocular interaction (non-fusable images are formed on fovea)
What tests uses grating acuity (minutes)
Preferential looking cards (for infants)
When will patching not help?
Hypoplasia of fovea = need to do Oct = doesn’t have enough cells in fovea
How many prism diopters per degree of displacement on corneal reflections?
1 degree = 2 prism dioptres
-limbus touching nose = 45 degrees = 90 dioptres
Manifest vs latent
Manifest = tropia (movement on CT cover/un cover, opp eye)
Latent = phoria (movement on CT cover/un cover same eye)
Alternate CT = maximum deviation
ALWAYS RECORD RECOVERY TOO
Recording a manifest deviation
-size of the deviation (slight, moderate or marked)
-changes in the deviation at different distances (diff size in nr and dis)
-changes in deviation if accom exerted
-changes in deviation with and without glasses
Fully accommodative esotropia
With glasses, eyes straight. Normal retinal correspondence and BV
Distance L exotropia
Near = straight
Distance = distance L exotropia
Alternating esotropia
Vision roughly equal, able to swap fixation
Convergence excess esotropia
Only squints at near when accommodating.
Bifocals so have plus at near to relax accom and see in distance
Hyperphoria vs hypophoria
Hyperphoria = eye will move up under cover and down when cover lifted
Hypophoria = eye will move down under cover and up when cover lifted
Recording latent deviation
-direction of latent deviation
-size of deviation (slight, moderate or marked)
-the movement of eye to take up fixation (recovery) = indicates how compensated the heterophoria is = GOOD, MODERATE or SLOW
-changes in deviation at diff distances
-changes in deviation with/without glasses
What are saccades
Fast small movements of eye (smooth pursuit = look between two lights)
Vestibuloocular movements
Controlled by inner ear = when you move head down, eyes go up
Optokenitic nystagmus
-infantile esotropia
-eye flicker on train
-black and white drum (OKN drum)
3 stages of BV + tests
Sensory (worths lights, bagolini lenses, fixation disparity)
Motor (PFR, synoptopher)
Stereopsis (TNO, Frisby)
Micro tropia
4 diopter PCT
-look for suppression
-moves picture 2 diopters off fovea
Near BO bigger or smaller than near BI
Bigger, by x2 BO nr
Nr BI bigger, same or less than distance BO
Same BI nr + BO dis
Dis BO smaller or bigger than Dis BI
BO dis 2x bigger than BI dist
What do you take off clycloplegic refraction?
Take off 1D
If child is ESO, what tax do you want to give them?
As much + as possible to relax accom
What is period of adaptation for glasses?
16 weeks
What are cut-offs for glasseS?
> 2D Hypermetropia (bilateral)
1.50D myopia
0.75D Astigmatism (bilateral)
- any astigmatism + hypermetropia
1D difference in RX (anisometropia)
When is rx undercorrected?
Under corrected by 1D for mild hypermetropia +2 - +5
undercorrected by 2D for high hypermetropia
If ESO then given
How many lines expect with refractive adaptation
2-3 lines wearing glasses full time
What is max time for patching?
4-6 hours max per day
400 hours max
How long does atropine last
7-10 days , takes 45 mins to work
What base for ESO?
Measuring eso = base out
Exercising
Prism fusional reserves = base in
Sanskin va cards
Look at back of card
Pass mark for Logmar and Kay’s
Logmar - 0.2
Kays - 0.1
Tests for vision screening
-CT + npc
-20 diopter prism + fixation stick
-OM gross
-steropsis frisby
VA
How much is each letter on Logmar
-0.20 every Logmar letter
Get 1 right = 0.18
Get 5 right = 0.10
If px has eso, what PFR first?
Base in
When you have phoria, how much PFR need to control?
Double
E.g. 10 diopter eso = 20 diopter BI to keep straight
Before doing cover test, what do you ask?
Is it single or double?
What are the sizes of deviation?
Minimal (>10)
small (10-20)
Moderate (20-35)
Marked (35+)
