Inferior Oblique Overaction (IOOA)

INFERIOR OBLIQUE
OVERACTION
MEIRONI WAIMIR
Literatur Review
Strabismus Sub Division
Department of Ophthalmology
Medical Faculty of Andalas University/ DR. M. Djamil Hospital
Padang
2019
copyright: dokter.ronnie@gmail.com

INTRODUCTION
•Extraocular muscles play an important role in the
visual system  Binocular alignments  Stereopsis
and maintain visual target that shadows fall on the
fovea.
•Strabismus  a disorder in which no visual
alignment of the axes in both eyes which caused by
abnormalities in the extraocular muscle that cannot
function properly.

INTRODUCTION
Inferior Oblique Overaction/ IOOA
(Strabismus Sursoadductorius)
Overelevation (Up shoot )during
adduction  version
Can occur unilateral or bilateral
IOOA
Primary IOOA  It is not related to superior oblique mu
Secondary IOOA  Parese or palsy from the antagonist

INTRODUCTION
•IOOA is related to horizontal deviation.
Reported about 70% of patients with esotropia and 30% of
patients with exotropia
IOOA
Recess
Disinsertion
Myectomy
Myotomy
Anterior
Transposition
Denervation
and
Extirpation
In the case of IOOA,
a procedure is needed to
weaken the muscle.

ANATOMY AND PHYSIOLOGY OF
MUSCULUS OBLIQUE INFERIOR
• The shortest muscle among
all EOM.
• IOM has a length of about 36
mm, width 9.6 mm and
tendon length 1 mm.
• Origin: From a depression on orbital
floor near orbital rim (maxilla).
• Insertion: At the lower edge of the
lateral rectus muscle, about 12 mm
from the insertion of the lateral
rectus muscle.

• Blood supply : a oftalmica and
infraorbital artery
• Innervated : inferior division of
the oculomotor nerve (N III).
The orbital portion of IOM enters
partially and joins the inferior rectus
muscle  the muscular sheath of
the IOM binds to the inferior rectus
muscle sheath
Ligament of Lockwood

The IOM  near the vortex vein and
macular position.
IOM insertion  2 mm inferolateral
to the macula

The IOM forms an angle of 51 degrees
in the primary position
Extortion (excloduction)
Elevation
Abduction
In the abduction position 39 degrees
 main function extortion, secondary
function is abduction.

CLINICAL DESCRIPTION
• Primary IOOA can be a distraction of motion alone or associated
with horizontal deviation.
• Found between the ages of 2-4 years.
• Primary IOOA  bilateral or unilateral
• Primary IOOA  overelevation during adduction and vertical
deviation in the primary position.

Bilateral primary IOOA
left-eye hypertropia when glancing to the right, right-eye hypertropia
when glancing to the left, and no vertical deviation at the primary
positioncopyright: dokter.ronnie@gmail.com

•The amount of overaction in IOM can be
measured on a scale of +1 to +4
Overaction
+1
• There is no hypertropia in horizontal version, there is little overaction when the
eye moves vertically toward the field of action of the oblique muscle.
Overaction
+2
• Mild hypertropia is found when the eyes glance horizontally.
Overaction
+3
• Hypertropia is clearly visible when glance horizontally.
Overaction
+4
• Large hypertropia when glancing horizontally with abduction along with
vertical eye movements

• Weakness of the superior oblique muscle or superior rectus muscle in
the contralateral eye.
• There is a vertical deviation in the primary position and ecyclodeviation.
Secondary IOOA

•Difference between primary IOOA and
secondary IOOA

Differential Diagnosis
Dissociated vertical deviation (DVD) is conditions that can cause excessive
elevation in one or two eyes in adduction.
DVD usually appear after the age of 2 years, with horizontal deviation.

Difference between IOOA and DVD
Differential Diagnosis

MANAGEMENT IOOA
IOOA
Recess Disinsertion Myectomy Myotomy
Anterior
transposition
Denervation
and
Extirpation
IOOA  Weaken IOM
All surgical procedures for IOM are performed distally of the muscle.
Access  incision of the conjunctival fornix and the incision through the tenon
capsule in the inferotemporal quadrant.

MANAGEMENT IOOA
The selection of inferior oblique
weakening is based on degree of
inferior oblique overaction
The IOM weakening procedure is
indicated in patients with an IOOA
of +2 degree or more, whereas +1
degree or less are only observed.

Recess Inferior Oblique Muscle
Placing the inferior oblique muscle insertion closer to its origo  the muscle
becomes more relaxed and muscle tension is reduced.
• The IOM is released from its insertion.
• Transected with scissors between the hemostats and muscle insertion .
• Cautery the proximal edge of the muscle.
• The muscle is sutured to the sclera.

Recess Inferior Oblique Muscle
Inferior oblique muscle is titrated based on the degree of overaction.
The length of the inferior oblique muscle recessed:
Overaction +2 is 6 mm
Overaction +3 is 10 mm
Overaction + 4 is 14 mm

Disinsertion
IOM is released from insertion without sewing the muscle into the sclera.
The weakness of this technique is the possibility of the muscles attaching
back to the sclera in an unpredictable position.
Cauterization at the edge of the muscle, the muscle is released, and the
conjunctiva is sewn with thread that can be absorbed.

Myectomy
Removing a portion of muscle
• The hemostat is placed in the IOM with a distance about 5-10 mm. The
muscle located between two hemostats excised and removed.
• Cauter the edge of the muscle.
• The muscle is released and the proximal portion is allowed to be pulled
back into the tenon capsule.

Myectomy
• Duration of the operation is fast, easy.
The advantage
• The muscles attach back to the sclera in
an unpredictable position.The weakness

Myotomy
Cutting across of muscle
Complete myotomy
• One or two hemostats are placed across the inferior oblique muscle.
• The muscle is transected and cautery.
• The conjunctiva is closed with interrupted absorbable suture.

Myotomy
Marginal myotomy
• A hemostat is placed across and removed after 30–60 second.
• The marginal myotomy is then performed along the area crushed by the
hemostat and cautery applied.

Anterior Transposition
Moving the IOM insertion more anteriorly than the initial position.
• After exposure, isolation, dissection of the muscle capsule, release the IOM
from its insertion.
• IOM insertion is reattached to the sclera, near the temporal edge of the
inferior rectus muscle insertion.

• Wright (1980)  developed a modification of the anteriorizing
procedure  Graded Anteriorization
Anterior Transposition
Graded recession or
anteriorization of the IOM for
a. mild to moderate,
b. moderate,
c. moderate to severe,
d. severe IOOA

• This procedures are rarely used.
• Carried out in the case of the very prominent IOOA and significantly
recurrent IOOA who had undergone the previous IOM weakening
procedure.
• IOM is isolated and cauterized in the neurovascular bundle combined
with removing the distal inferior oblique segment.
Denervation and Extirpation
Damaging the neurovascular bundle innervation into the inferior
oblique at the posterior edge when crossing with the inferior rectus.

After detachment of IOM at its insertion, mild anterior traction
is placed on the muscle.
A small hook is used to grasp the neurovascular bundle and
place it under mild traction.
Cautery is used to cut and coagulate the neurovascular
bundle.

If the neurovascular bundle has been completely transected,
The muscle can be shifted anteriorly .
A hemostat is placed on the IOM as close to the muscle
origin and a large distal portion of the muscle is removed.

CONCLUSION
Inferior oblique overaction (IOOA) is characterized by overelevation in
adduction. IOOA is called primary if it is not related to superior oblique
muscle paralysis. If weakness is found in the contralateral superior
rectus muscle or the ipsilateral superior oblique muscle called the
Secondary IOOA.
In patients with IOOA found overelevation during adduction and
vertical deviation in the primary position. In the head tilt position, no
vertical deviation was found.

CONCLUSION
In the case of inferior oblique overaction, a procedure is needed to
weaken the muscle. The procedure can be performed by recess,
disinsertion, myectomy, myotomy, anterior transposition, or
denervation and extirpation.
In the case of a very prominent IOOA and significantly recurrent
IOOA that has undergone the previous inferior oblique muscle
weakening procedure, denervation and extirpation of the inferior
oblique muscle can be performed.

Thank you

Inferior Oblique Overaction (IOOA)

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