Measurement of Different Types of deviations with Maddox Rod and Double Maddox Test

1. Maddox Rod And
Double Maddox Rod
By:
Anu Musyakhwo
M.Optometry

2. 1. Maddox Rod (Introduction, Objective, Equipment
required, Set-up, Procedures, Recording,
Interpretation,, Disadvantages)
 Distance Horizontal Deviation
 Distance Vertical Deviation
 Near horizontal and Vertical Deviation
2. Double Maddox Rod (Introduction, Set-up,
Procedures, Recording, Interpretation,,
Disadvantages)
 Distance and near cyclodeviation
3. References

3.  a red or white lens consisting of a series of parallel
cylinders that converts a point source of light into a streak
of light or a line image perpendicular to the axis of
parallel cylinders
 a dissimilar image test in which a single target is
artificially made dissimilar in both eyes
1. Maddox Rod

4. Principle:
 Here, a point source of light is seen as spotlight with one
eye and a red line with other eye, before which the maddox
rod is placed. Therefore, the test is based on the principle
of ‘Diplopic Projection’.
 position of the red line/streak in relation to the image of
the light source seen by fellow eye indicates the presence
and the amount of deviation of the eye subjectively

5.  results of the test may be influenced by a head
position, so the test should be performed in the
habitual position
 since use of a phoropter will limit the patient’s
ability to adopt a habitually abnormal head
position, the measurement of vertical deviations
using maddox rod is best performed using a trial
frame or a hand-held maddox rod in free space

6.  this test is performed to assess the type and
size of a latent or manifest horizontal,
vertical or torsional strabismus for distance
and near fixation subjectively

7. Equipment required
 Maddox rod
 Source of spotlight
 Prism bar or loose prisms
 Trial frame
Set up
 patient should wear his/her optimal refractive
correction
 patient should be explained about the test and the
procedures of the test
 room light should be dimmed and make sure that
other source of light does not disturb the patient’s
view of the streak and target spotlight

8. Distance Horizontal Deviation
1) place the maddox rod in front of the right eye making sure the grooves in
the maddox rod are absolutely horizontal so that the patient sees vertical
streak
2) spotlight is provided at distance of 6 meter using projector chart or
Snellen Yellow light
3) ask the patient to see on the spotlight
4) ask the patient whether s/he sees both the vertical streak and spotlight
a) if s/he finds difficulty in recognizing or seeing the streak demonstrate the
patient by alternately covering the eyes
b) if s/he sees only streak or spot, suppression may be present. To confirm
the presence of suppression, maddox rod is transferred to the left eye and
try again. If the patient has suppression, the spotlight or the streak cannot
be seen again and follow up test should be performed

9. 5) With the maddox rod on right eye (see Fig. 3):
a) if the patient sees streak passing through or overlapping the spotlight s/he
is orthophoric i.e. patient does not have any deviation
b) if the patient sees streak and spot light separated; streak on right side and
spot on the left side which are uncrossed images, the patient has
esodeviation
c) if the patient sees crossed images that is the streak on the left side and the
spotlight on the right side, the patient has exodeviation
Fig. 3 :Positions of the streak and the spotlight in different types of deviations when
maddox rod is placed before the right eye. (green dot represents the white/yellow
spotlight)

10. 6)Measurement of deviations is done by placing loose
prisms or prism bar in front of the either eye according
to the type of deviation of eyes(see Fig. 3):
a) to determine the amount of esodeviation, base out
prism is placed in front of any eye until the patient
sees the streak passing through the spot light
a) to determine the amount of exodevaition, base in
prism is placed in front of any eye until the patient
sees the streak passing through the spotlight

11. Distance Vertical Deviation
1. rotate the maddox rod so that the grooves are absolutely
vertical in orientation
2. ask the patient to see the spotlight
3. ask the patient if the streak is above or below the spotlight
4. With the maddox rod on the right eye (see Fig. 3):
a. if the streak passes through the spotlight then the patient has
no vertical deviation
b. if the streak is above the spotlight then, the patient has right
hypodeviation or left hyperdevaition. It is possible to specify
vertical deviations with respect to other eye. Thus, this type
of deviation can also be called as left over right.
c. if the streak is below the spotlight then, the patient has right
hyperdeviation or left hypodeviation. This type of deviation
can also be called as right over left.

12. 5. To determine the amount of vertical deviations base
up or base down prisms are used (see Fig. 3):
a. if the deviation is left over right, base down prism is
placed before the left eye (or base up prism before
the right eye) until the streak passes through the
spotlight
b. if the deviation is right over left, base down prism is
placed before the right eye (or base up prism before
the left eye) until the streak passes through the
spotlight

13.  the horizontal and vertical deviations at near can
be similarly measured
 the penlight (used as spotlight) is shone at nose
bridge between the eyes at about 40 cm
 the near horizontal deviation measurements with
maddox rod are considered unreliable in young
patients due to the lack of a good accommodative
stimulus
 in presbyopes, near deviation should be measured
with the addition. The measurement technique is
exactly the same as measurement of deviation at
distance

14. Recording
a. ortho is recorded for absence of horizontal, vertical as well as
cyclodeviation or in other words for absence of any kind of
deviation
b. record the horizontal deviation and amount of deviation in prism
diopters (▲) as:
 6▲E for 6 prism diopter esophoria
 4▲X for 4 prism diopter exophoria
c. record the vertical deviation and amount of deviation in prism
diopters (▲) as:
 6▲R/L, or 6▲Rhyper, or 6▲Lhypo for 6 prism diopter for right over
left.
 4▲L/R, or 4▲Lhyper, or 4▲Rhypo for 4prism diopter for left over
right.

15. Interpretation
 Most of the people with true normal binocular vision have some
amount of latent deviation (heterophoria). In children and young adults
the mean distance heterophoria is 1▲ exophoria ±1▲ and mean near
heterophoria is 3▲exophoria ±3▲ (Scheiman and Wick 2002). In
older adults, exophoria upto 6▲is common (Evans 2002). The vertical
phoria of about 0.50 ▲ only is considered normal in both children and
adults. In some patients even this amount of vertical phoria can cause
symptoms.
 The amount of deviation with optimal correction got from maddox rod
test should be compared with the cover test. If there is no significant
change in refractive error after subjective refraction, the deviation got
with maddox rod test should be similar to cover test.
 If there is change in refractive correction there occurs changes in
horizontal deviation determined using the cover test and subjective
assessment. For instance: if the optimal refractive correction shows an
increase in plus or decrease in minus power from patient’s previous
glass prescription then increase in exodeviation or decrease in
esodeviation is expected and vice versa.

16. Disadvantages
a) a spotlight represents a poor stimulus for accommodation.
Some clinicians consider that this limits the usefulness of
maddox rod to the measurement of vertical deviations which
are assumed to be unaffected by accommodation changes
a) cannot be performed under certain circumstances:
sensory anomalies
 Suppression
 Abnormal Retinal Correspondence
 (This may mask the true size of deviation).
c) cannot differentiate between tropias and phorias.

17. 2. Double Maddox Rod Test
 subjective test which uses two maddox rods, one before each eye
 used to determine cyclodeviation or torsion
 the test can be done in all the position of gazes for comparison
 traditionally, a red Maddox rod was placed before the right eye and a
white Maddox rod before the left, but evidence suggests the different
colors can cause fixation artifacts that do not occur if the same color is
used bilaterally
 therefore, nowadays red maddox rods are preferred before both the
eyes during the test

18. Set-up:
 place each maddox rod in the trial frame aligning the grooves of
the rods at 90◦ making the red line/streaks seen by the patient
horizontal (see Fig. 4).
 explain the patient about the test and procedures of the test
 dim the room light and make sure other light source does not
disturb the view of the streaks for the patient
Fig. 4: A patient wearing a trial frame in which a pair of maddox rods
are placed, one before each eye

19. Procedures
1) use a source for spotlight at 33cm at the bridge of nose at the eye level for
near measurement and for distance use a source of spotlight at 6 meter
2) ask the patient what the patient sees
3) ask the patient to show the orientation of the streaks using his/her arms
4) if patient feels difficult to compare the orientation of streaks, place the
loose prism in the trail frame
 if the patient does not have any vertical or horizontal deviation, the streaks
can be difficult to compare. Thus, loose prisms can be used to separate the
images/streaks to let easy comparision
 or, if the patient has large horizontal or vertical deviation, prisms can be
used to bring the streaks closer together to let the easy comparision

20.  examiner can either use base-out, base-in, base-up or base-down prism
depending on the deviation. For example: a patient with an large esotropia may
need a base-out prism placed in front of deviated eye to bring the streak
corresponding to this eye closer to other streak
5) ask the patient whether the streaks are parallel to each other
•if the two streaks are parallel to each other, patient does not have cyclodeviation
•if the patient sees the streaks not parallel to each other, rotate the maddox rod
or ask the patient to rotate the maddox rod with help of dial in trial frame to
make the lines parallel

21. Recording
When recording the result, remember to list the name of the
test as well as the direction and degrees of the torsion.
Degrees taken from 90◦
(When maddox rod is vertical in trial frame)
15◦ excyclo
(When maddox rod is before either of the eye rotated 15◦
outward/temporally from 90◦)
Note: You are recording the position of the eye not the image.

22. Interpretation
1) Starting from 90◦; rotation of grooves of the maddox rod towards the
nose (nasally) measures the incyclodeviation and towards the lateral
side (temporally) measures the excyclodeviation.
2) The amount of cyclodeviation is measured in degrees, shown by the
scale in the trial frame. For example: if the axis or grooves of maddox
rod is rotated at 100◦, the patient has 10◦ excyclodeviation but if the axis
of maddox rod is rotated at 80◦, the patient has 10◦ incyclodeviation.
 Along with the results gathered from other tests, you can use this
information to consider the action of each muscle and also to indicate
which muscle is likely to be affected. In most of the cases double
maddox rod test helps in detection of the defect of the oblique muscles.
For patients with unilateral superior oblique weakness the excyclophoria
is generally between 1 and 7 degrees, whereas in bilateral superior
oblique weakness the excyclophoria is typically greater than 10 degrees.

23. Disadvantages
a) patients with congenital/longstanding cyclodeviation
may not report torsion as it is subjective test. (Fundus
Photography should therefore be performed to
determine the presence or absence of cyclodeviation
in such cases)
b) cannot be performed under certain circumstances:
 sensory anomalies
 suppression
 abnormal Retinal Correspondence

24. References
1. David B. Elliot, Butterworth Heinamann Elsevier. Clinical Procedures
in Primary Eye Care, Third Edition, 2007. Maddox Rod.
2. Mitchell Scheiman, Bruce Wick. Clinical Management of Binocular
Vision, Fourth Edition, 2015. Dissimilar Image Tests.
3. Keneth W. Wright. Handbook of Pediatric Strabismus and Amblyopia,
2006. The Ocular Motor Examination. Sensory Aspects of Strabismus,
204.
4. Sandeep. Pediatric Ophthalmology and Strabismus. 2007-2008.
Dissimilar Image Tests.
5. Md. Azizul Islam. Ispahana Islamia Eye Institute and Hospital.
Maddox Rod Test. Slideshare
6. Simons, Kurt. Brown, Mary H. Dissociation artifacts in double
Maddox rod cyclodeviation testing. Ophthalmology 101(12):1897-
901 · January 1995.