A presentation on Macular function tests.

1. MACULAR FUNCTION
TESTS
Dr Saurabh Kushwaha
Resident (Ophthalmology)

2. SCOPE
 Macular function tests - uses and classification
 Photostress test
 Amsler grid
 Two point discrimination test
 Maddox rod test
 Entoptic phenomena
 Laser Interferometry
 Microperimetry

3. MACULAR FUNCTION TESTS
 Uses:
• For diagnosing
• For follow up of macular diseases
• For evaluating the potential macular function in eyes
with opaque media such as cataract and dense vitreous
hemorrhage.
• As a prelude to surgery, in order to provide a
preoperative prognosis for the condition.

4. CLINICAL ASSESSMENT
OF THE MACULA
 Symptoms:
• Blurred vision and difficulty with close work
• Scotoma
• Metamorphopsia (distortion of perceived images)
• Micropsia (decrease in image size)
• Macropsia (increase in image size)
• Colour discrimination may be disturbed, but is generally
less evident than in even relatively mild optic neuropathy.
• Difficulties related to dark adaptation, such as poor vision
in dim light and persistence of after-images

5. MACULAR FUNCTION TESTS
MFT
MFT with
clear media
MFT with
opaque media
Depending on ocular media
Electrophysiological
tests
Psychophysical
tests
Depending on technique

6. MFT WITH CLEAR MEDIA
 Visual Acuity
 Colour Vision
 Photostress test
 Amsler grid
 Two point discrimination
 Microperimetry
 FFA
 OCT

7. MFT WITH OPAQUE MEDIA
 Laser interferometry
 Potential visual acuity meter test
 Entopic phenomena
 ERG
 EOG
 VEP

8. PSYCHOPHYSICAL TESTS
 Subjective test
 A physical stimulus is presented and patient indicates
verbally or by other subjective means, his detection of the
stimulus
 They are as follows:
• Visual acuity
• Color vision
• Photostress test
• Amsler’s grid
• Two point discrimination test
• Entoptic imagery
• Maddox Rod test

9. ELECTROPHYSIOLOGICAL TESTS
 Objective tests
 A stimulus is presented and a response parameter is
measured by electrophysiological means
 One of the most effective modes of testing for macular
functions in eyes with total media opacities
 They are as follows:
• Electroretinogram (ERG)
• Electrooculogram (EOG)
• Visual evoked potential (VEP)

10. PHOTOSTRESS TEST
 Differentiates visual loss caused by macular disease
from that caused by an optic nerve lesion
 Principle:
• The visual pigments are bleached by light which
causes a temporary state of retinal insensitivity,
perceived by the patient as a scotoma.
• The recovery of vision is dependent on the ability of
the photoreceptors to re-synthesize visual pigments.

11.  The test is performed as follows:
• BCVA is determined
• Pt is asked to fixate on the light of a pen torch or an
indirect ophthalmoscope held about 3 cm away for
about 10 seconds.
• Photostress recovery time (PSRT) is measured by
the time taken to read any 03 letters of the pre-test
acuity line.
• Test is performed on the other, presumably normal
eye and the results are compared.
• In a patient with macular lesion, the PSRT will be
longer (50 seconds or more) as compared with the
normal eye whereas in a patient with an optic nerve
lesion there will be no difference.

12. AMSLER GRID
 The grid was developed by Marc Amsler, a Swiss
ophthalmologist.
 It is a grid of horizontal and vertical lines used to
evaluate the 20 degrees of visual field centered on fixation.
 There are 07 charts, each chart consisting of 10 cm
square.
 It is a diagnostic tool that aids in the detection of visual
disturbances caused by changes in the retina, particularly
the macula as well as the optic nerve and the visual
pathway to the brain.
 Presence of abnormalities like blurred areas, holes,
distortions, or blank spots are noted

13.  Chart 1
• First grid is standard grid that tests for any general
subjective patient responses to faults or distortions in
the pattern.
• White lines on a black background and a central white
dot on which the patient fixates.
• Grid encloses 400 small squares, each square
measures 5 mm
• When grid is held at 30 cm from the patient, each
square subtends 1 degree on the retina.
• If pt reports on the first chart that
he cannot see the central white spot,
this indicates a scotoma.

14.  Chart 2
• This chart has diagonal lines which help maintain
central fixation.
• If pt reports on the first chart that he cannot see the
central white spot, this indicates a positive scotoma.
• This helps them point out the limits of the scotoma.
 Chart 3
• It has red lines on a black background
• Helpful in detecting color scotomas and
desaturation, that may occur in optic nerve, chiasmal or
toxic amblyopia related problems.

15.  Chart 4
• This chart comprises random dots only
• used to differentiate scotoma from metamorphopsia
 Chart 5
• This chart has horizontal lines
• helps detect metamorphopsia along specific meridians

16.  Chart 6
• This chart is similar to chart 5 but has white
background and central lines are oriented closer for
detailed evaluation
 Chart 7
• This chart has fine central grid
• Each square subtends an angle of half a degree
when the chart is held at 30 cm from the patient

17.  Central scotoma as
seen by a patient
 For example this
might be secondary to
central areolar choroidal
dystrophy or congenital
toxoplasmosis .

18.  A space ocuupying 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.
 This is known as "macropsia"

19.  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".

20.  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 condition Is termed
Metamorphopsia.

21. TWO POINT DISCRIMINATION TEST
 The ability to distinguish 2 illuminated points of light 2
mm diameter in size and 2 inches apart, placed 2 feet
away from the patient’s eye suggests good retinal
functions.
 Excellent method for testing macular functions in
children and uncooperative adults in the outpatient’s
clinic
 Ideally be performed in all patients during initial
examination of the eye

22. MADDOX ROD TEST
 It is a high power cylindrical lens used to form a line
image perpendicular to the axis of the parallel cylinders
from a point source of light.
 The light source placed between 33 cm to 40 cm in front
of each eye to get appropriate objective results.
 Any breaks/ holes; discoloration/ distortion in this line
indicates a macular lesion
 This is a very sensitive test that can be performed in the
outpatient clinic without requirement of any specific
equipment.

23. ENTOPTIC PHENOMENON
 Entoptic phenomenon is referred to visual perceptions
that are produced or influenced by the native structures of
one’s own eye.
 Illumination of the fundus by parallel light rays allows
visualization of small opacities located close to the retina.
 Since the columns of blood contained within retinal
blood vessels are linear opacities situated in front of the
retinal photoreceptors, this makes retinal blood vessels
visible.
 If a focal source of light (such as small penlight) is
pressed firmly against the exterior of the eye through
closed lids, the arborizing pattern of retinal blood vessels
can be briefly made visible. This test is used as test of
retinal function.

24. ENTOPTIC PHENOMENON

25.  The blue field entoptic phenomenon (flying spots)
perception is performed in the following manner:
• If one looks at a bright and diffusely illuminated surface
with no contrasting features, a series of fast moving,
luminous points are seen which tend to move in a generally
curved pattern, with trailing short, tapering segments behind
them.
• The spots are best seen if the background is illuminated
by blue light in the spectral region of 350 to 450 nm.
• Since this region contains the spectral absorption peak of
hemoglobin, the moving particles represent red blood cells
passing through the retinal capillaries.
• Normally - 15 or more of moving corpuscles are seen.
• Abnormal blue field entoptic phenomenon - failure to see
any corpuscles or partial loss of corpuscles in one part of
the field, visibility of less number of corpuscles and slow
corpuscular movement.

26. HAIDINGER’S BRUSHES
 If one views a diffusely illuminated source of plane
polarized white or blue light, brushes radiating from the
point of fixation in the form of Maltese cross can be seen.
The brushes have contrasting yellow and blue hues.
 The darker portions of the Maltese pattern are yellow,
whereas the brighter portions are blue.

27.  This phenomenon is caused by variations in
absorption of plane polarized light by oriented molecules
of xanthophyll pigment in the foveal retina.
 If the yellow pigment arrangement in the fovea is
disrupted by pathology in the inner retinal layers, the
brushes will not be seen.
 Commonly used as a screening test for retinal
pathology in strabismus patients with amblyopia.

28. LASER INTERFEROMETRY
 The resolving power of the macula is tested by using two
coherent beams of light, which create a three-dimensional
fringe pattern on the retina.
 The beams produce two point sources behind the lens
opacity; the light waves emitted from these two points
overlap.
 Where the crest of one wave overlaps the trough of the
other, the effect is cancelled and a black band is produced.
 Where crests or troughs coincide with one another, the
enhancement produces bright bands of light.
 Laser interferometry can thus be used in eyes with
immature cataracts.

29.  The test is performed as follows:
• Pupils are widely dilated and light beam is directed into
the centre of the pupil in the plane of the iris.
• The pupil is scanned until the fringe pattern is seen and
patient indicates the orientation of the bands of light.
• Initially, large gratings are used and then gradually
diminished until patient is unable to detect correct
orientation
• The potential visual acuity is estimated from the width of
the gratings resolved.
• Laser generated fringes are not dependent on the optical
components of the eye for focusing. Therefore, ametropia
has little influence on the patterns produced by retina.
• It also over-predicts the visual potential in amblyopic
eyes because laser fringe vision is better than the letter
acuity.

30. POTENTIAL VISUAL ACUITY
METER
 The potential acuity meter (PAM) projects standard
Snellen chart through a small clear area of an immature
cataract
 Main components of PAM are a bright light source,
miniature transilluminated Snellen chart and a +12D lens.
 Most accurate with visual acuities of 6/60 or better.
 In performing the test, the pupils should be
widely dilated and the patient is asked to read
the letters on the chart and the level recorded.

31. MICROPERIMETRY
 Also k/as fundus perimetry, it allows for exact
topographic correlation between fundus details and its light
sensitivity.
 The principle 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 individually selected
location.
 Because light projection is just related to previously
selected anatomical landmarks and is independent of
fixation and any other eye movement, the examiner obtains
the functional response of the selected area.
 The characteristics of fixation (location and stability) are
easily and exactly quantified with microperimetry.

32.  Automatic follow-up examination quantifies retinal
threshold exactly over the same retinal points tested during
baseline examination (even if fixation changes during
follow-up time).
 Static microperimetry is more commonly used, but a
kinetic test is also available.

33. CONCLUSION
 Evaluation of the macular function of a patient with
opaque media is a commonly faced challenging problem
 No single test is impeccable

34. THANK YOU