Strabismus/decompensating phorias

Question 1

What tests would you carry out for a symptomatic decompensating phoria

Answer 1

Cover test 
Fusional reserves 
Fixation disparity
Npc 
AoA

Question 2

Causes of decomp phorias

Answer 2

Optical - uncorrected rx/over/under correction/ill fitting specs/aniseikonia

Medical - poor GH/fatigue/trauma/alcohols /drugs affecting accom

Question 3

Types of esophoria

Answer 3

Divergence weakness - sop @ dist>near
Convergence excess - sop @near>dist
Basic sop - dist=near

Question 4

Types of exophoria

Answer 4

Divergence excess - xop@dist>near
Convergence insufficiency - xop @near>dist
Basic xop - dist=near

Question 5

How many prism dioptres of vertical phoria can be symptomatic

Answer 5

1-2

Question 6

Accom sot

Answer 6

Present always 
Increases with accom
Early onset 1-3yo - +ve FH?
Hyperopic - deviation decreased with rx
May have amblyopia - esprit unilateral

Question 7

Non-accom sot

Answer 7

Always present
Not affected by accom
Assoc with latent nystagmus/dvd

Question 8

Infantile sot

Answer 8

First 6/12
Assoc: prem/low birth weight/APGAR score
Corneal reflex approx 30pd

Question 9

Late onset sot

Answer 9

2-4yo
Intermittent for short time then constant
High risk for amblyopia I’d untreated

Question 10

Fully accom sot

Answer 10

Onset - 2-5yo
Ortho with rx
+ve FH squint/hyperopia

Question 11

Convergence excess sot

Answer 11

@near with accom 
Onset 2-5yo
Noticed with near work /+ve FH 
CT: sop@Dist /sot@near
High ac:a ratio

Question 12

Near sot

Answer 12

@near w/o accom
+/-rx
Normal AC:A

Question 13

Dist sot

Answer 13

suppression @dist
BSV @near
Rule out 6th nerve palsy

Question 14

Secondary sot

Answer 14

2dry to severe sight loss/impairment
Onset: 6month-7yrs
CT: unilateral sot /poor fixation

Question 15

Consecutive sot

Answer 15

Surgical overcorrection

Question 16

Constant xot

Answer 16

Early onset
Kids close 1eye/head on table etc
Slow mental/physical development
Reduced AoA esp if late onset - may contribute to decompensation

Question 17

Near xot

Answer 17

Intermittent 
Usually assoc with myopia/presbyopia
Poss diplopia/HAs @near
Poor convergence 
Ddx; CI

Question 18

Dist xot

Answer 18

Onset usually before 2yo
Intermittent
More in brighter conditions - constriction - more depth of focus - less accom - less convergence
CT: xot@dist/xop@near

Question 19

Secondary xot

Answer 19

Vision loss/impairment - trauma/congenital vision loss @birth/after7-8yo
Mod xot @all dist
Severe va reduction
Unilateral/bilateral

Question 20

Consecutive xot

Answer 20

Sot/sop surgery

Question 21

DVD

Answer 21

One eye drifts up when dissociated 
Unclear cause 
Common in strab pxs early age
Unilateral/bilateral
No dip/affected eye suppressed 
Assoc with amblyopia
Good fusion = less likely dvd

Question 22

Pseudostrabismus

Answer 22

No misalignment
Birth-18months
Wide bridge/epicanthal folds
Hirschberg to diagnose