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43 Cards in this Set
- Front
- Back
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Near Pupil Reflex procedure and recording disease example |
Px looks at target about 15 cm , then distant target. continues. measure extent/speed the constriction when the px looks at near and dilation of the pupils when the px looks in the distance. if the near reflex is normal but the light reflex was abnormal record light - near dissociation. e.g. Argyll Robertson Pupil |
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The normal Pupil |
2- 4 mm in the light 4-8 mm in the dark Pupils Equally round and responsive to light physiological anisocoria <1mm present for years senile miosis hippus (variation that increases with lights on) |
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Efferent Pathway |
Pretectal Nuclei Edinger Westphal Nuclei CN III Ciliary Ganglia Iris Sphincter pupillae |
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Afferent Pathway |
Pretectal Nuclei LGB Chiasm Optic Nerve Retina |
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Afferent Defects |
Commonly caused by Retina or ON lesions |
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Afferent Defects may cause |
abnormal direct reflex when consensual reflex is normal. Unilateral or assymetric defects show RAPD |
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Efferent Defects caused by |
Lesions of CN III iris or ciliary ganglia |
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Efferent defects may cause |
ANISOCORIA PRESENT differential diagnosis of anisocora Horners Syndrome : greater in the dark, reflexes normal, ptosis Adies Tonic Pupil: greater with light , abnormal direct and consensual reflex |
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When may a RAPD not mean afferent defect |
Unilateral Cataract |
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Grading pupil reflex abnormalities |
Grade 0 - none Grade 1 - v. small Grade 2 - small/ slow Grade 3 - moderate Grade 4 - large/ fast |
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In what case would binocular subjective refraction be a better option than monocular |
- Hyperopes - pseudomyopes - antimetropes - latent nystagmus - cyclophoria |
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Measure Fixation Disparity with . |
MALLET UNIT ( D and N) if sx are reported |
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Dissociation Tests include |
Maddox Rod, Maddox Wing, Modified thorington |
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When would you carry out a colour vision test |
1st time seeing child (congenital ) occupation investigating ocular disease / sxs (acquired deficiency) |
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Cycloplegic refraction Aim |
to elicit maximum amounts of hyperopia only useful on pre-presbyopes |
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Indications for Cycloplegic Refraction |
- Hx & Sx indicate accommodative problems e.g. D blur after lots of N work - SOT or convergence excess SOP - Accommodative fluctuations during ret - -Ret more plus than subjective result - Subjective result more minus than expected for unaidedVA - Myopia with SOP - Suspected latent hyperopia, pseudomyopia oraccommodative spasm –ve accommodative lag (response > stimulus) found using dynamic retinoscopy Pxs with accommodative infacilitypoor ability to change focus found using ±2.00 flippers |
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PREFERRED Cycloplegic drugs |
cyclopentolate hydrochloride ( Preferably in non-preserved single dose form) age 0 - 1 - 1 drop 0.5% cyclo, inner canthus of closed eye – Their small livers & kidneys reduce metabolism of these drugs, increasing likelihood of adverse reactions • aged 4-11 – 1 drop 1.0% cyclopentolate, inner canthus of closed eye – 3 drops of 1.0% cyclopentolate 5 mins apart (+ proxymetacaine) if strabismus & dark irides • - For adults (or children aged 13+) – - Brown/dark irides: 2 drops of 1% tropicamide instilled in lower fornix, 5 mins between drops – - Blue/light irides: 1 drop of 1% tropicamide instilled in lower fornix |
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What do you do after instilling cycle |
Check that cycloplegia has taken maximum effect– Quickly check amplitude of accommodation– static retinoscopy - Children may be asked to fixate retinoscope at 50 cm– Concentrate on central 3-4 mm of pupil • Attempt subjective refraction, if possible– Often not possible on young children • Record findings as normal Some practitioners record results of cycloplegicrefraction in red ink |
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Which statement is TRUE? A. Unaided distance vision is only measured monocularly B. A complete recording of intraocular pressure is asfollows: R 18mmHg L 18mmHg (Goldmann) C. The swinging flashlight test is used for the detection ofafferent pupillary defects D. 1 drop of 1.0% cyclopentolate is recommended forcycloplegic refraction on children aged less than 1 year E. Pupil dilation rarely persists for more than 1 hour aftercycloplegic drug instillation |
C. The swinging flashlight test is used for the detection of afferent pupillary defects |
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Binocular single vision is still possible when the visual axes aremisaligned if |
misalignment is small enough to fall within Panum’s fusional area = FIXATION DISPARITY (FD) or RETINAL SLIP (slip) |
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FD is likely to occur with |
FD is likely to occur with decompensated phoria* |
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The amount of prism required to remove FD has traditionally been called ______- BUT now |
ASSOCIATED PHORIA Strictly meaning that there should be no dissociation (disruption of fusion) at all so that the eyes are measured in their active position In practice, some degree of dissociation is essential and the term ALIGNING PRISM has been advocated |
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Sx of decompensated Heterophoria |
Asthenopia, diplopia, head ache |
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Fusion locks |
On the mallet unit . seen by both eyes (egocentric) OXO central target and peripheral surround ensure minimal dissociation |
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Nonious target |
seen by 1 eye each (oculocentric) monocular Red Lines(distance) - accommodative lag Green Lines (near) - accommodative lead become displaced with fixation disparity |
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The Mallet unit ensures that the eye is working under _______ to avoid Dont continue the test if ___ align w. ____ |
most natural conditions , to avoid false FD suppression occurs Align with weakest prism or sphere |
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EXO slip is corrected with |
Base in Negative Sphere |
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ESO slip is corrected with |
Base out Positive Sphere |
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Do we need to correct FD |
Correct FD if there are sx & poor prism adaptation. FD may be a purposeful error signal in some patients may be why direction and magnitude of FD not always related to dissociated phoria (dissociated phobia e.g. EXO w. ESO Slip may explain prism adaptation e.g. leave the prism in and then FD returns after 5 minutes visual task - unlikely to benefit from correction |
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if R nonious target stays locked (vertical) and left nonious target is above what disparity is this |
L hypo FD BU LE |
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IF THE LEFT NONIUS TARGET (VERTICAL) is above the right |
R/L OR R Hyper BD in L |
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IF THE RIGHT NONIUS TARGET (VERTICAL) is above the left |
L/R L hyper BD in R |
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For children and adults how would you prescribe for EXO FD |
BI prism in adults Negative sphere or orthoptic training in children |
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Which statement is TRUE? A. OXO targets are the only element of a Mallett unit to be seenmonocularly B. The green nonius targets on a near Mallett unit may be bought intoalignment if plus lenses are placed in front of the eyes of a patientwith near ESO slip C. Correction with prisms is indicated if a patient has retinal slip withasthenopia and good prism adaptation D. Paradoxical FD only occurs in patients with retinal slip due to stresson the oculomotor system E. Incyclophoria is indicated by clockwise tilt of the nonius target seen bythe LE |
B. The green nonius targets on a near Mallett unit may be bought into alignment if plus lenses are placed in front of the eyes of a patient with near ESO slip |
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Forced duction |
FD induced by adding prism in front eye BO prism induces Exo FD BI prism induces Eso FD Measure FD using Sheedy disparometer Plot FD as function of inducing prism |
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Components of fixation disparity curve |
Y-intercept fixation disparity X-intercept Aligning prism (associated phoria) Slope Indicates ability to adapt to prism induced stress Flat slope: desirable, good adaptation, Sx unlikely Steep slope: poor adaptation, Sx likely |
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Type 1 |
No Symptoms 60% of the population sigmoid curve |
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Type 2 |
25% of population High SOP No Aligning Prism Frequent Sx |
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Type 3 |
10 % of the population High XOP No aligning prism frequent Symptoms |
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Type 4 |
5% populations STEEP Curve unstable binocularity |
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Which statement is FALSE? A. According to Sheard’s rule, a patient with 15∆XOP at near, whosefusional reserves are BI:9/15/12 and BO:12/18/15, requires a 6∆BIprism B. According to Percival’s rule, a patient whose fusional reserves areBI:9/15/12 and BO:24/30/27, does not require prism C. The X-intercept on a forced duction fixation disparity curve ismeasured in minutes of arc D. Mallett units may not be able to determinine FD in some patientswith types II and III forced duction fixation disparity curves E. Most patients have type I forced duction fixation disparity curves |
A = True. Plug numbers into Sheard’sformula and will see true. B = True. Plug values of break point intoformula and result is 0, so true, no prism needed. C = False. Y intercept is minutes of arc. Xintercept is prism dioptres. D = True, often cannot find an aligningprism in these pxs E = True, most pxs have the type 1 shape |
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Stereopsis- binocular depth |
1. due to horizontal separation between the eyes 2. objects off the horopter are viewed from slightly different perspectives 3. produces horizontal retinal disparity within Panum’s fusional space which is the cue for stereopsis |
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Week 19 Measurement of stereopsis & suppression [Compatibility Mode] Stereo threshold (Stereoacuity) |
s = PD x b x 206265 / d2 |
