COVER TEST

TROPIA: a manifest deviation of the visual axes

occurring when stimuli to fusion is operation

(Actual name for tropia: strabismus or manifest deviation)

present even if eyes are fusing image

PHORIA: latent deviation

by eliminating all stimuli of fusion

heterophoria

Cover test

one eye at a time

Determines manifest or latent deviation

DIPLOPIA: perception of one object that projects on two diff non-corresponding retinal areas

Causes confusion and uncomfort

Problems driving

>it looks double. does not become one clear image

*diplopia only occurs if acute or acquired

VISUAL CONFUSION: 2 diff images. Overlapping

Not the same image

We see one image on top of the other

Happens when were trying to see something but there’s other things infront

Looks like one is in top of each other

Can cause with strabismus if change in angle of deviation

i.e. driving: cant identify correcelty where road is

ADULTS: strabismus may be related to neurological condition such as a brain tumor, head trauma, stroke or MG

>sudden onset: diplopia

>longlasting (present from childhood): no diplopia

suppression may have developed

Case hx key!

HPI

>when 1st present?

>trauma hx?

>eye sx

PMH

>if kid: gestational, birth and dev hx, vax status (if suspect viral)

ROS

>recent viral syndrome, fever, malaise, HA, nausea, sick?

Lethargic if they’re usual active?

Head titlts??

Wt loss

Gross defect

POH

>ocular and visual

LEE, ocular dx, refractive correction

FOH

Strabismus (un ojo que entra/sale?), refractive error

General physical: neurological findings

Ocular exam: Vas, Hirschberg, cover test, EOMs, Bruckner and pupillary responses

STRABISMUS EVAL

Hx

Onset

Present at all time or sometimes

Distance or near

OU? Favor one eye?

>uni

Intermentally: when tired? Unattentive?

Same when not doing near work?

Trauma

Physical stress

HA??

Vertigo

CLASSIFICATION OF DEVIATION

Only tropias classified in this matter

Unilateral or alternating

uni: only one eye!

Alt: manifested in either eye even if it prefers one eye

Some pts can fix it! You tell them to look straight and they will 

Constant or intermittent

Constant: all the timeeee

Intermittent: sometimes

Comitancy

Size of angle of deviation in

Concomitant: all position gazes within 5PD

Incomitant: difference > 5PD

i.e Primary: 10 PD

Up: 20PD

Down: 2 prism D

Periodic tropia: only at only one testing distance

i.e. either near OR far

just one, not both 

Paralytic tropia: due to the paralysis

CN 3

CN4

CN 6

Example of incomitance:

A patient might be a 5PD Esotrope in primary gaze (ask them what primary gaze is) but when they look up, the deviation increases to 15PD Esotropia. This is incomitant,, the difference is larger than 5PD.

DIRECTION OF DEVIATION

Ortho: no mvnt. Perfect alignment

Lateral/horizontal

Exo (tropia or phoria): outward deviation

>measure with BI prism

Eso (tropia or phoria): inward deviation

>measure with BO prism

Wherever eye moves in cover test

I.e. moves out = eso

Use base out

Vertical

Always one moves up- other moves down!

Always report the HYPER eye

Upward deviation: hyper

>Measure with BD prism

Downward deviation: hypo

>measure with BU prism

*will see seesaw mvnt

Combined:

Later and vertical mvnt

Cyclodeviatin: torsional deviations

TROPIA VS PHORIA

Tropia: manifest deviation when stimuli to fusion is operating

Heterotropia, strabismus

Exotropia (XT): one eye deviates outward

Esotropia (ET): one eye deviates inward

Hypertropia: one eye deviates upward

Hypotropia: one eye deviates downward

Phoria: latent deviation brought by eliminating all stimuli to fusion

IDENTIFIED BY: direction and magnitude and testing distance

>NOT MEASURED SEPARATELY

-so only have to measure one

COVER TEST

Provides an objective magnitude of the deviation

Deviation may be:

Latent (phorias):

Manifest (strabismums -tropia):

Cover test

Unilateral: one eye at the time

No mvnt: ortho

Mvnt: Strabismums

Alternate: switch between the two

Phoric dev (heterophoria)

If mvnt: direction + magnitude

No mvnt: ortho

MUST EVALUATE:

1. Presence or absence of deviation

2. Direction of dev

a. horizontal

b. vertical

c. torsional

3. magnitude of deviation

>full room illumination

TARGET: one line above best VA of worse eye with habitual SRx

@ 40cm

@ eye level but do not obstruct line of sight

UCT

any deviation of uncovered eye indicates presence of tropia

Pt has to be fixated well at distance

Moves out: exo

BI

Cover an uncover for 2-3 times

Leave it on there for 1-2 secs!

>ADDITIONAL QUESTIONS TO ASK

is it moving?

with or against the paddle?

ACT

-Determine phoria or latent dev

Magnitude and direction of dev

Cover OD -> switch over nose to OS

>observe the eye that you just uncovered

>sometimes may need to remind them to blink otherwise it may not be presenting properly

DIRECTION AND MAGNITUDE

Which eye? Direction? (exo, eso, hyper)

Phorias: NO LATERAL

Bc happen in both eyes at same time and mag

Only report direction & magnitude

PRISMS

Image shifted towards base and eye toward apex

NEUTRALIZING WITH PRIS

*always orient the prism with the apex in direction of deviation

Base in direction that eye moves

Ie Eso: place Prism base out, apex IN

Manifest: ID dominant eye

Measure non-fixating eye!

continue adding prism until you see a reversal

1st no mvnt

2nd: opposite

Add both numbers/2

i.e. dev 1st no mvnt: 10pd

2nd opp mvnt: 12pd

11 

ORTHOPHORIA

1. Induce by using BASE IN prism until first mvnt

2. BO until first mvnt

3. Subtract the two and /2

If really ortho: BI & BO should be same and =0 at end 

RECORDING ABBREVATIONS

XT: Exotropia

ET: Esotropia

HT: Hypertropia

Only the hyper eye is recorded

R: OD

L: OS

A: Alternating

(T): Intermittent

T: Distance

T’: Near

XP: Exophoria

EP: Esophoria

ɸ: Ortho

cc: with correction

sc: without correction

EXPECTED FINDINGS

1Δ XP ± 2Δ at distance

3Δ XP ± 3Δ at near

Presbyopes tend to have larger XP at near

-It is expected to increase in exophoria as we increase in age

-Also expected to have less convergence

HIRSCHBERG TEST

used to: identify strabismus when other precise methods can’t be used

screening tool

-any symmetry indicates: direction & magnitude of an eye turn

-30-100cm

PROCEDURE:

1. pt look at light

2. occlude OS to look at OD

3. remove with OD occluded

4. compare corneal reflex when one eye Is fixating vs when both

a. 1mm od deviation is = 22Δ

CORNEAL LIGHT REFLEX

>CLR nasal

(+) value

>CLR temporal

(-)

expected: +0.5mm CLR in both eyes

notice if the CLR is in the same position on each pupil

if not equal = pt has strabismus

KRIMSY

uses prisms to move the deviated reflex back to the expected position

measures the deviation

BRUCKNER TEST

ophthalmoscope @ 1m away

equal: binocular fixation

not equal:

darker reflex (red): fixating eye

brighter reflex (whiteish): non-fixating eye