Macular Function Tests By Dr.Vibhav

1. Moderator: Dr.GKG.Prasad
Presenter Dr.Vaibhav

2.  Macula is a round area at the posterior pole
temporal to the optic disc 5.5mm in diameter.
 Recently term area centralis has been given to
this.
 It corresponds to 15 degrees of visual
field,photopic vision,colour vision.
 It is yellowish color derived from the presence
of xanthophyll pigment

3.  Fovea centralis is the central depressed part
of macula.1.85mm diameter,0.25 mm thick.
 Most sensitive part of retina.
Foveola forms the central part
Umbo is the tiny depression in the centre of
foveola
Foveal avascular zone is located inside the
fovea but outside the foveola.

5.  Densest concentration of cones
 a one to one photoreceptor-
ganglion cell relationship
 Cones more elongated and slender
 Absence of rods at the foveola
 RPE cells are taller, thinner and
deeply pigmented
 Presence of xanthophyll pigment

6. This special anatomy enable the
fovea for:
 highest discriminative ability(VA)
 color perception

7.  Diagnosis and Follow up of macular diseases
 For evaluating the potential macular function
in eyes with opaque media such as cataract
and dense vitreous hemorrhage
Uses of macular function tests

8. Symptoms
• Central vision impairment
• Metamorphopsia
• Micropsia
• Macropsia

9.  Tests utilizing gross recognisation responses.
 Based on entoptic phenomenon
 Interference fringe techniques
 Based on hyperacuity
 Electrophysiological tests
 Direct visualisation & assessment of anatomic
integrity.

10.  Psycho physical tests
1. Visual acuity
2. Colour vision
3. Photostess test
4. Amslers grid test
5. Two point discrimination test
6. Entoptic imagery
7. Maddox rod test
8. Perinauds near vision chart testing
9. Self illuminated near vision chart

11.  Visual evoked potential
 Electro retinogram.

12.  Slitlamp examination.
 OCT
 Presence or absence of perception of light
 history

13.  They utilise gross recognisation response.
 A. Two light discrimination test:
 The ability to distinguish two illuminated
points of light 2mm diameter in size 2 inches
apart placed 2 feet away suggests good
functions.
 < or equal to 12.5cm- VA of HM/PL
 < or equal to 7.5cm-VA of CF to 6/60
 <5cm –VA >6/60

14.  Pinhole increases the depth of focus and
limits scattering effect of corneal scars,
lenticular opacities.
 In macular disorders pinhole worsens the
visual acuity.

15.  Simple and reliable test and
can be used in semi opaque
media
 Pt is asked to fixate light at a
distance of 1/3m through M.R.
with opposite eye occluded
 Any breaks/holes;
discoloration/distortion
indicates a macular lesion

16.  Parinaud near reading chart
 8 D trial lens
 First position the chart 12cm
from trial lens with best
correction for long distance
and hyper addition of 8D in
trial frame.
 Patient is asked to read
smallest number on the chart.
If patient reads it give + score
If not give – score.
+ score indicates good macular
function.

17.  Evaluates the 10 ̊ of visual
field centered on fixation
 Used in screening and
monitoring macular diseases
 square 10*10 cm divided
into 400 5*5 mm squares to
be held at 30 cm

18.  The First Grid Has White Lines On A Black
Back Ground And Central White Dot On Which
The Patient Is To Fixate.

19.  If The Patient Reports On
The First Chart They Cannot
See The Central White Spot.
This Would Indicate A
Positive Scotoma. The
Following Chart Should Be
Used On Which Diagonal
Lines Help Maintain Central
Fixation. This Helps Them
Point Out The Limits Of The
Scotoma. This Chart Also
Has White Lines On A Black
Back Ground And Central
White Fixation Dot.

20.  The Third Chart Has
Red Lines On A Black
Back Ground And Is
Very Helpful In
Diagnosis Of Optic
Nerve, Chiasmal, Or
Toxic Amblyopia
Related Problems.

21.  Central Scotoma As
Seen By A Patient With
A Positive Or Absolute
Scotoma. For Example
This Might Be
Secondary To Central
Areolar Choroidal
Dystrophy Or
Congenital
Toxoplasmosis .

22.  A Space-Taking
Pathology Such as A
Tumor That Forces The
Cones Closer Together
Will Cause The Grid To Be
Seen Distorted. The
Retinal Image Will Fall On
More Cones Than Normal
And The Lines Of The
Amsler Grid Will Be Seen
As Larger And Bend
Outward As In The
Above. This Is Known As
"Macropsia".

23.  A Patient With Macular
Edema Or Any Other
Pathology That Forces
The Cones Apart The
Retinal Image Will
Stimulate Fewer Cones
Than Normal And The
Lines Of The Amsler Grid
Will Be Seen As Smaller
And Tend To Bend Away
From The Patient. This
Condition Is Termed
"Micropsia".

24.  A Combination Of
Squeezing And Spreading
Of The Cones Causes An
Overall Distortion Of The
Image. The Lines Of The
Amsler Grid Become
Distorted And Non-
Uniform. This Can Occur
In A Number Of Macular
And Retinal Conditions.
This Condition Is Termed
Metamorphopsia.

26.  Colour vision is the function of three
populations of retinal cones
 Blue ( tritan) 414-424 nm
 Green ( deuteran) 522-539nm
 Red (protan) 549-570nm
 Normal person possess all these three cones
and called trichromat

27.  Acquired macular diseases tends to produce
blue yellow defects and optic nerve lesions
red green defects
 Deutran anomaly is the most common and
those subjects can not differentiate between
red and green colours

29.  Farnsworth-Munsell
100 Hue test is the
most sensitive but
seldom used

30.  It is refer to visual perceptions that have their
origin in the structure of an observer's eye.
 Three types are used for testing the macula in
opaque media
 1/ PURKINJE VASCULAR E.P
 2/ Flying spot( blue field entoptic phenomenon)
 3/Haidinger’s Brushes

31.  The Purkinje’s vascular entoptic
test is a simple method which
elicits the response by placing a
penlight against a closed eyelid
or the globe and moving it back
and forth, creating images of the
patient’s retinal vascular tree

32.  Blue field entoptoscopy relies on
the observation of leucocytes
flowing in the macular retinal
capillaries. The leucocytes appear
as ‘Flying Corpuscles’ when the
retina is diffusely illuminated with
a bright blue light.

33.  Subject looks at a surface
illuminated with blue light
through a polarizer
 hourglass shaped yellowish
brushes seen radiating from the
point of fixation. On rotating
polarizer, brushes rotate

34.  Phenomenon caused by variations in
absorption of plane polarized light by
oriented molecules of xanthophyll
pigment in foveal retina
 Used to sensitize the fovea in
amblyopic child with eccentric fixation

35.  limited by the patient’s subjective
interpretation
 May yield false negatives if the retina cannot
be sufficiently illuminated through a dense
cataract

36.  Utilizes coherent white light or helium-neon
laser generated interference stripes or fringes
that are projected onto the retina through the
ocular media.
 Useful in mild to moderate media opacities.
 Principle: light interference.

37.  Projection of target directly on macula after
bypassing the opacities of media is done
 Since these are not the images in usual sense
they are not affected by ordinary optical
defects, defects of focus, and imperfections of
refraction what ever observer sees depends
only on the ability of retina to conduct signals
from photoreceptors into nervous system.

38.  1. subjective
 2. Laser fringe vision>vision of letter acuity.
 3. over predicts visual potential in amblyopes

39.  PAM introduced in1983
 This is attached to a slit lamp and projects a
reduced Snellen’s chart via narrow beam of light
through a pinhole clear area in the cataract
towards the macular region
 The resulting potential acuity is the smallest line
where the patient was able to read three
characters

40.  Subjective
 methods that require an alert and cooperative
patient and skilled compassionate examiner
 But it is easier than laser interferometry

41.  Hyperacuity: visual performance that is a level
above achieved by measurement of visual
acuity.
 Physiological basis of use of hyperacuity as
macular function test is vernial hyperacuity is
highly dependent on retinal stimulus location
with lowest threshold being at macula.

42.  PHP relies on the concept of hyperacuity
which is the ability to discern a subtle
misalignment of an object.
 This can be explained by the fact that an
extended edge will stimulate an array of
cones and when there is a break in this line
the fovea can perceive it.

43.  Stereo acuity: detection of difference in depth
or distance of pair or more objects in space
 Vernial acuity: consists of targets like butting
vertical lines,2 dots or vertical lines separated
by gap, misalignment is to be recognised.
 Oscillatory displacement threshold: tasks
requires smallest change in position of
oscillating object, judged in relation to 2
stationary reference bars.

44.  These are objective
 Stimulus is presented and a response
parameter is measured by
electrophysiological means.
 One of the most effective modes for macular
function assesment in total media opacities.

45.  VEP Measure of the electrical potential
generated in response to a visual stimulus
 it represents integrity of entire visual pathway
from retina to occipital lobe so can not
differentiate between macula ,ON and cortical
pathology

46.  It measures the cortically evoked electrical
activity providing about integrity of optic
nerve and primary visual cortex.
 There is a large representation of macula in
occiptal cortex.
 Types: flash VEP & pattern VEP.
 Pattern VEP has a measure denoted as P100 a
positive wave at 100 milli sec.
 This wave occurs more than 100 milli sec
indicates delay due to optic nerve
demyelination.

47. If the issue is the V/A then
the amplitude is measured
If the issue is the lesion in
the visual pathway then the
latency is measured

48.  ERG is only abnormal when a large area of
retina is functionally impaired
 Focal ERG needs a stimulus localized to one
area without scattering of light to stimulate
the rest of the retina

49.  This is the ERG response to a pattern
stimulus
 Luminance is constant but contrast reversing
of pattern is seen.
 N35,P50,P95 waves are analysed.
 This is abnormal in macular disorders
irrespective of peripheral retinal function.

50.  It is a hand held foveal ERG
 It employs a 3-4 degrees
white flickering light focused
on the fovea with a 10
degrees annulus of constant
white light to desensitize
surrounding retina

51.  The luminance of flickering test light is
sinusoidally modulated i.e. it increases and
decreases in in a sinusoidal fashion above
and below the mean luminance.

52.  For each temporal frequency value the
threshold is the minimum modulation depth
at which detection of flicker occurs.
 The reciprocal of threshold is sensitivity.
 This is highly sensitive macular function test.

53.  It is a simple clinical test that can differntiate
between retinal (macular) & post retinal (optic
nerve disease)
 Introduced by bailliart in 1954.

54.  Principle:
 Basis of test is to utilise induced fatigue of
macula.
 It is a gross test of dark adaptation in which
visual pigments are bleached by light.
 Causes a temporary state of retinal
insensitivity perceived by patient as scotoma.
 Recovery of vision is dependent on ability of
photoreceptors to resynthesise visual
pigments.

55.  A) best corrected distance visual acuity is
determined.
 B) pt fixes light of pentorch held at 3cm away.
 C) photo stress recovery time:time taken to
read any 3 letter of pretest acuity line & is
normally between between 15 and 30 sec.
 Test is performed on other presumably
normal eye & results are compared.
 It is prolonged in relation to normal eye in
macular diseases (50 sec or more) but not in
optic neuropathy.

56.  Advantages:
 It is easiest to perform
 Opd procedure
 Gives fairly accurate results
 Doesn’t need expensive instruments.

57.  The principle of microperimetry rests on the
possibility to see —in real time— the retina
under examination (by infrared light) and to
project a defined light stimulus over an
individual, selected location

58.  SLO microperimetry was the first technique
which allowed to obtain a fundus-related
sensitivity map
 SLO uses a near infrared diode laser
(675nm)beam that rapidly scan the posterior
pole.
 The reflected light is detected by a confocal
photodiode and the digitized image is stored in
a computer

60.  SLO fundus perimeter did not allow to
perform fully automatic examination.
 Moreover, automatic follow-up examination
to evaluate exactly the same retinal points
tested during baseline microperimetry was
not available with this instrument.

61.  The limitations of SLO have been
overcome by MP1 microperimetr a
recently developed automatic
fundus perimeter
 MP1 microperimeter automatically
compensates for eye movements
during the examination via a
software module that tracks the
eye movements

62.  To know the anatomical integrity of macula.
 Can perform cross sectional images of biological
tissues within less than 10micron resolution.
 OCT scan protocols in macula:
1. Line scan
2. Radial line
3. Macular thickness map
4. Fast macular thickness map
5. Raster lines
6. Macular scan

63.  Evaluation of the macular function of a
patient with opaque media is a challenging
problem commonly faced by us
 No single test is infallible