1. 1
Functional Vision Loss
Functional vision loss - the symptomatic and measured loss of vision that is unassociated with an identifiable lesion of the visual
pathways
Other associated terms- hysteria, hysterical visual loss, malingering, nonphysiologic visual loss, factitious visual loss, nonorganic
visual loss, psychogenic visual loss, Münchausen syndrome, and conversion disorder of vision
First consider the following ocular pathologies
with subtle clinical signs:
-keratoconus
-cone dystrophies
-early Stargardt’s disease
-amblyopia
-retrobulbar optic neuritis
-optic nerve compression
Management: Ocular/Medical/Further testing Management: Reassurance, report suspected Child
abuse
1 2 3 4 Differentiating Sources of Symptoms (though it
may not be possible to do so)
1 – purely organic
2—mostly organic, with small functional
component/overlay
3—mostly functional (overlay) with small organic
component
4—purely functional

2. 2

3. 3
Overview of Tests of Functional Vision Loss
Tests mostly based on the behavior of truly blind individuals
Tests that masquerade as tests of acuity and fields
-tests of proprioception
Indirect tests of acuity and fields
-observation
Direct tests of vision (mostly acuity)
-objective tests of vision
-pupil testing
-involuntary reflex, requires cooperative pt
-(electrodiagnostics and other mostly objective testing, may still require a cooperative pt)
-nontraditional tests of vision
-surprise, could be involuntary if involves menace reflex
-subjective tests of
-binocular
-test a binocular-only function, like stereopsis
-reading bar
-binocular and monocular
-get better eye to read first then trick the other eye into reading
-monocular targets in a binocular field using filters
-monocular
-interferometry
-varying testing method
-varying testing distance
-suggestive tests
-magic drop
-lenses
-subjective tests of visual fields
-motility testing, especially saccadic testing
-confrontation, including pantomime
-automated
-Goldmann
-Tangent Screen
-electrodiagnostics and mostly objective testing, may still require a cooperative pt

4. 4
Functional Vision (mostly acuity) Loss Table
-Generally the following test items are used once a baseline of
vision has been established, and the goal is to demonstrate and
document vision better than baseline.
-Items are organized by how the information about vision is
obtained
-Generally the worse the vision the items higher up in the
following list are more useful, the better the vision the items
lower on the list are more useful
Tests Reduced
acuity:
good in one,
moderately
reduced the
other; ie.
20/20 and
20/40-20/60
Reduced
acuity:
good in one,
severely
reduced the
other; ie.
20/20 and
20/400-NLP
Reduced
acuity:
moderate
loss both; ie.
20/40-20/60
both
Reduced
acuity:
moderate
loss one,
severe loss
the other; ie.
20/40-20/60
and 20/400-
NLP
Reduced
acuity:
severe loss
both:
Ie. Total
blindness
Tests
mostly
based on
the
behavior
of truly
blind
individuals
Tests that
masquerade
as tests of
acuity and
fields
Tests of proprioception (can be
done binocularly in total blindness
pt)
signing name on
paper; making
index finger of
two hands touch
Patch better
seeing eye
then:
Very Useful
Functional:
difficulty
Organic:
No difficulty
Patch better
seeing eye
then:
Very Useful
Functional:
difficulty
Organic:
No difficulty
Very Useful
Functional:
difficulty
Organic:
No difficulty
Indirect tests
of vision
(acuity and
fields)
Observation (can be done
binocularly in total blindness pt)
blind pt wearing
sunglasses into
clinic, walking
into and around
obstacles in
exam room,
avoiding looking
at examiner or
other object of
interest (like
when pt
directed to look
at their own
hand)
Patch better
seeing eye
then:
Very Useful
Functional:
quicker
purposeful
movements,
avoid looking
at examiner
Organic:
Cautious
slower
movements,
feeling their
way with
hands and
feet
Patch better
seeing eye
then:
Very Useful
Functional:
quicker
purposeful
movements,
avoid looking
at examiner
Organic:
Cautious
slower
movements,
feeling their
way with
hands and
feet
Very Useful
Functional:
quicker
purposeful
movements,
avoid looking
at examiner
Organic:
Cautious
slower
movements,
feeling their
way with
hands and
feet, look in
direction of
examiner’s
voice

5. 5
Functional Vision (mostly
acuity) Loss Table continued
Direct tests of
vision
Tests Reduced acuity:
good in one, moderately
reduced the other; ie.
20/20 and 20/40-20/60
Reduced acuity:
good in one, severely
reduced the other; ie.
20/20 and 20/400-NLP
Reduced acuity:
moderate loss both;
ie. 20/40-20/60 both
Reduced acuity:
moderate loss one,
severe loss the other; ie.
20/40-20/60 and
20/400-NLP
Reduced acuity:
severe loss both:
Ie. Total blindness
objective tests of vision
(mostly of acuity, but
also fields) involving
involuntary reflexes
pupil testing (stimulus is
light)
-can be confounded by
pharmacological
manipulation
-only cortical blindness
associated with normal
pupils
-photophobia with
orbicularis contraction
and reflex tearing during
pupil testing
Most important
test
Functional: no
APD
Organic: small to
large APD
Most Important
When worst eye is
NLP
Functional:
possible
symmetrically
strong reaction to
light in 20/400 eye;
any reaction to light
in NLP eye
Organic:
any (previously
undocumented)
APD in worst eye
Functional:
Any reaction to
light either
Organic:
No reaction to light
either
OKN Drum or Sheet
(stimulus is blur)
Useful if vision is
worse than
20/400 in worst
eye
Functional: jerk
nystagmus
present
Organic: jerk
nystagmus only if
vision 20/400
otherwise no
nystagmus if
vision worse than
20/400
Useful if vision is
worse than 20/400
in worst eye
Functional: jerk
nystagmus present
Organic: jerk
nystagmus only if
vision 20/400
otherwise no
nystagmus if vision
worse than 20/400

6. 6
objective tests of vision
(mostly of acuity, but
also fields) involving
involuntary reflexes
Tests Reduced acuity:
good in one, moderately
reduced the other; ie.
20/20 and 20/40-20/60
Reduced acuity:
good in one, severely
reduced the other; ie.
20/20 and 20/400-NLP
Reduced acuity:
moderate loss both;
ie. 20/40-20/60 both
Reduced acuity:
moderate loss one,
severe loss the other; ie.
20/40-20/60 and
20/400-NLP
Reduced acuity:
severe loss both:
Ie. Total blindness
Mirror test (stimulus is
pt’s own face) elicits
nystagmoid movement
means hand motion vision
or better, requires a
cooperative pt
Very Useful
Functional:
nystagmoid
movement
Organic:
No movement
Horizontal prism shift
(stimulus is diplopia) test
with prism over affected
eye and single letter
distant target of smaller
size than affected eye’s
acuity and larger than
better eye’s acuity.
Very useful, this is
the only objective
test for moderate
unilateral vision loss
Functional:
Compensatory eye
movements of
saccade towards
apex of prism and
then convergence
Organic:
No eye movement
because no diplopia
created
Functional:
Compensatory
eye movements of
saccade towards
apex of prism and
then convergence
Organic:
Absolutely No eye
movement
because no
diplopia created
Functional:
Compensatory eye
movements of
saccade towards
apex of prism and
then vergence
movement
Organic:
Absolutely No eye
movement because
no diplopia created
nontraditional tests of
vision (acuity and fields)
surprise, could be
involuntary if involves
menace reflex (can be
done binocularly in total
blindness pt)
stimulus is perceived
threat
-Bell’s phenomenon
-could be humor or any
other stimulus that evokes
a noticeable response
demonstrating purely
visual recognition
(-loud sounds)
Patch better
seeing eye then:
Very Useful
Functional: any
reaction
Organic:
No reaction
because there is
no perceived
threat
Patch better seeing
eye then:
Very Useful
Functional: any
reaction
Organic:
No reaction because
there is no
perceived threat
Very Useful
Functional: any
reaction
Organic:
No reaction
because there is no
perceived threat

7. 7
subjective
tests of
acuity
mostly
Binocular Tests Reduced acuity:
good in one, moderately
reduced the other; ie.
20/20 and 20/40-20/60
Reduced acuity:
good in one, severely
reduced the other; ie.
20/20 and 20/400-NLP
Reduced acuity:
moderate loss both;
ie. 20/40-20/60 both
Reduced acuity:
moderate loss one,
severe loss the other; ie.
20/40-20/60 and
20/400-NLP
Reduced acuity:
severe loss both:
Ie. Total blindness
Stereopsis (a binocular
only function) (see graph
of acuity corresponding to
local stereopsis values
achieved using
stereocircle test part of
Stereo Fly Test)
Very useful because can
get an acuity; inconclusive
if no stereopsis present
Functional:
7th
-9th
dots seen
Organic:
1st
-6th
dots seen
Functional:
3rd
-9th
dots seen
Organic:
No dots seen
Functional:
7th
-9th
dots seen
Organic:
1st
-6th
dots seen
Functional:
3rd
-9th
dots seen
Organic:
No dots seen
Reading bar
Can test for moderate
unilateral vision loss
May be harder if affected
eye is the left eye and
that target’s print is left to
right
Choose smaller print
Functional:
Read smoothly
across the line of
print
Organic:
Difficulty reading on
same side of page as
affected eye
Option of
choosing larger
print
Functional:
Read smoothly
across the line of
print
Organic:
Difficulty reading
on same side of
page as affected
eye
Possible with 20/80-
20/200 print:
Functional:
Read smoothly
across the line of
print
Organic:
Difficulty reading on
same side of page as
affected eye

8. 8
subjective
tests of
acuity
mostly
Binocular
and
monocular
Get
better
eye to
read
first
then
trick the
other
eye into
reading
Tests Reduced acuity:
good in one, moderately
reduced the other; ie.
20/20 and 20/40-20/60
Reduced acuity:
good in one, severely
reduced the other; ie.
20/20 and 20/400-NLP
Reduced acuity:
moderate loss both;
ie. 20/40-20/60 both
Reduced acuity:
moderate loss one,
severe loss the other; ie.
20/40-20/60 and
20/400-NLP
Reduced acuity:
severe loss both:
Ie. Total blindness
Gradually
fogging good
eye with plus
(is the better
test b/c can
start with DSRx
on good eye) or
cyl or polarized
lenses and
using distance
manifest over
affected eye
Functional:
Reads 20/25-20/30
with affected eye
Organic:
Does not read
better than 20/40
with affected eye
Functional:
Reads 20/200 or
better with
affected eye
Organic:
Does not read
better than
20/400 with
affected eye
Functional:
Reads 20/200 or
better with affected
eye
Organic:
Does not read
better than 20/400
with affected eye
Vertical prism
dissociation
The letter
was 2 lines larger
than the best
corrected visual
acuity of the
better eye. The
patient was asked
to identify the
letter with both
eyes open. A 4
prism diopters
prism was then
held base down
in front of the
better eye with
best correction
in place and both
eyes open. The
patient was asked
what he
or she saw on the
Snellen chart.
Functional:
two letters seen
(the patient was asked
what letters, how they
are oriented, and if
one was clearer than
the other)
Organic:
One letter seen
(test is over)
Functional:
two letters seen
(the patient was
asked what letters,
how they are
oriented, and if
one was clearer than
the other)
Organic:
One letter seen
(test is over)
Functional:
two letters seen
(the patient was asked
what letters, how they
are oriented, and if
one was clearer than
the other)
Organic:
One letter seen
(test is over)

9. 9
subjective
tests of
acuity
mostly
Binocular
and
monocular
Mono-
cular
targets
in a
bino-
cular
field
using
filters
Tests Reduced acuity:
good in one, moderately
reduced the other; ie.
20/20 and 20/40-20/60
Reduced acuity:
good in one, severely
reduced the other; ie.
20/20 and 20/400-NLP
Reduced acuity:
moderate loss both;
ie. 20/40-20/60 both
Reduced acuity:
moderate loss one,
severe loss the other; ie.
20/40-20/60 and
20/400-NLP
Reduced acuity:
severe loss both:
Ie. Total blindness
red green
glasses and red
green
phoropter filter
-------------------
An alternative
test uses a
pink pen on
white paper (ie.
objectionable
words). In this
case the pink
pen is seen by
the green
filtered “bad”
eye. Could also
try green pen
with red filter
on “bad” eye
Functional:
Green good eye
sees all letters on
green side
Red affected eye
sees 20/20-20/30
letters on red side
Organic:
Green good eye
sees all letters on
green side
Red affected eye
sees no better than
20/40
Functional:
Green good eye
sees all letters on
green side
Red affected eye
sees 20/200
(20/100 on
projector) or
smaller letters on
red side
Organic:
Green good eye
sees all letters on
green side
Red affected eye
sees no better
than 20/400
Functional:
Green better eye
sees 20/30 or better
and/or
Red worse eye sees
20/200 (20/100 on
projector) or smaller
letters on red side
Organic:
Green better eye
sees 20/40-20/60
Red worse eye sees
no better than
20/400 (and no
reaction is noted to
what is written)
Monocular Interferometry Very useful
Functional:
sees 20/25-20/30
Organic:
Does not see better
than 20/40
Very useful
Functional:
sees 20/150 or
better
Organic:
Does not see lines
An important test
because one of
the few for
binocular
moderate loss of
acuity
Functional:
sees 20/25-20/30
Organic:
Does not see
better than 20/40
Very useful
Functional:
sees better
Organic:
Does not see better
Very useful
Functional:
sees better
Organic:
Does not see
better

10. 10
subjective
tests of
acuity
mostly
Monocular Tests Reduced acuity:
good in one, moderately
reduced the other; ie.
20/20 and 20/40-20/60
Reduced acuity:
good in one, severely
reduced the other; ie.
20/20 and 20/400-NLP
Reduced acuity:
moderate loss both;
ie. 20/40-20/60 both
Reduced acuity:
moderate loss one,
severe loss the other; ie.
20/40-20/60 and
20/400-NLP
Reduced acuity:
severe loss both:
Ie. Total blindness
Varying the VA test
method: starting at 20/10
or counting the number of
letters
Functional:
Reads 20/25-20/30
Counts 20/10
letters;
Organic:
Does not read
better than 20/40 or
count 20/10 letters
Functional:
Reads 20/200 or
better
Counts 20/60 or
smaller letters;
Organic:
Does not read
better than
20/400 or count
20/60 or smaller
letters
Functional:
Reads better both
Counts 20/60 or
smaller letters in
worse eye;
Organic:
Does not read
better both or count
20/60 or smaller
letters in worse eye
Varying the VA test
distance (ie. Low Vision
chart)
Could be difficult
since only smallest
low vision chart
characters useful
here
Functional:
Reads 20/10
characters at 10 feet
Organic: Does not
read better than
20/20 letters at 10
feet
Functional:
Reads 20/200 or
better characters
at 10 feet
Organic:
Does not read
better than 20/80
characters at 10
feet
Functional:
Reads smaller
equivalent
characters at 10 feet
Organic:
Does not smaller
equivalent
characters at 10 feet
Suggestive tests, like
magic drop or very low
power lenses or lenses
which neutralize each
other
(magic drop test uses
topical anesthetic with
distanceRx and pinhole)
Functional:
Reads 20/25-20/30
Organic:
Does not read
better than 20/40
Functional:
Reads 20/200 or
better
Organic:
Does not read
better than
20/400
Functional:
Reads better in
either eye
Organic:
Does not read
better in either eye

11. 11
-subjective tests of visual fields
-motility testing, especially saccadic testing (Functional: an accurate saccade to a location beyond their baseline field;
organic: no accurate saccade to location beyond baseline field)
-confrontation (functional: tubular fields), including pantomime (functional: copies peripherally located purely visual hand
movement)

12. 12
-automated
Functional: cloverleaf pattern
Organic: fits pattern of known retinal/visual pathway
disease; corresponds with detected disease
Functional: spontaneous improvement, no detected
disease
Organic: persistence with corresponding disease

13. 13

14. 14
-Goldmann
Options for the stimulus
Size: 0, I, II, III, IV, V : 0 is the smallest, V is the largest
Intensity: 1, 2, 3, 4 : 1 is the dimmest, 4 is the brightest
Intensity: a, b, c, d, e : a is the dimmest, e is the brightest

15. 15

16. 16

17. 17
-Tangent Screen

18. 18
-electrodiagnositics (recommended in all cases (S
Beatty 1999)) and other mostly objective testing
-evoked potential- change in electrical activity of
neurons/neuron system when stimulated;
compare one eye’s activity to the other
-Cone or rod dystrophies can have ERG
abnormalities
-cone dystrophies can also have reduced color
vision
----------------------------------------------------------
-complaints of night blindness in some hereditary
retinal conditions can be investigated with dark
adaptometry
----------------------------------------------------------
- neuro-imaging indicated for: reproducible field
defects, suspected cortical blindness, normal
vision cannot be restored during the course of
the examination (S Beatty 1999)