Proptosis in ENT
Dr. T. Balasubramanian M.S.
Definition: Proptosis is defined
as abnormal protrusion of the eyeball. It is also used
interchangeably with exophthalmos. Purists are comfortable defining
exophthalmos as proptosis associated with lid lag.
Anatomy of orbit and its relationships with
Orbit is related to paranasal sinuses in two
ways: 1. Anatomically by its location and by 2. venous drainage
(They both share the same venous drainage).
The paranasal sinuses surround the orbit from 11
o clock position superiorly to 6 o clock position inferiorly.
The orbit is pyramidal shaped formed by several
bones. The superior wall of the orbit is shared by the floor of the
frontal sinus, the floor of the orbit is shared by the roof of the
maxillary sinus, the medial wall of the orbit is shared by the
lateral wall of ethmoidal sinus. These shared bones are really thin
enabling infections to travel from either direction. The medial wall
of the orbit is so thin that it is termed as lamina papyracea.
Peculiarities of venous drainage in this area:
The veins draining this area are peculiar in the following
1. The whole venous system in this area is devoid
of valves, consequently a two way pathway of infection between the
orbit, nasal cavity and paranasal sinuses become a reality.
2. The superior ophthalmic vein connects the
facial veins to the cavernous sinus thus causing infections from
face to spread to the cavernous sinus.
3. One branch of the inferior ophthalmic vein
connects the orbit with that of the veins of pterygoid plexus and
the other branch connects the orbit with that of the cavernous
The approximate volume of the orbital cavity is
about 30 ml. Since the contents of the orbit are within a rigid
confines of the orbital walls any disease process within the orbit
or adjacent region has a tendency to displace the orbital contents
forwards, this displacement of the globe is known as the proptosis.
Other symptoms of globe displacement include diplopia, and visual
Proptosis must be distinguished from
pseudoproptosis. Enophthalmous involving the opposite eye may cause
apparent proptosis of the uninvolved eye. Similarly unilateral high
myopia and lid retraction may cause apparent proptosis. A careful
history will go a long way in ascertaining the exact cause of
proptosis. Clinically significant proptosis is defined as a minimum
difference of 2mm or more as measured by
showing Hertel exophthalmometer
Measuring proptosis using
Hertel mirror exophthalmometers are used to
measure the degree of protrusion of the eyeball. The distance
between the lateral orbital rim and corneal apex is used as an index
for measuring proptosis. Under normal conditions this distance is
roughly 18 mm, there may be individual and racial variations.
Procedure: The examiner is seated infront of the
patient at the eye level of the patient. The exophthalmometer is
then positioned with the blue arched support at the temporal lateral
orbital walls. The instrument is maneuvered using both hands and
firmly propped first against the right-hand orbital wall on the
temporal side (which should be felt against the lowest part of the
support point). The moveable part is then set in such a way that the
left-hand orbital wall lies against the lowest part of the arched
support. The distance between the lateral orbital walls can then be
read from the upper side of the scale; this distance can be noted
for future reference. The examiner asks the patient to look straight
ahead with eyelids wide open. The examiner measures for proptosis in
each eye Seperately by looking into the mirror (which has a
millimeter scale marked on it) with one eye and moving the head
horizontally until the red fixations line is at 22mm. The examiner
can now determine the position of the corneal apex of the patient
from the millimeter reading.
The mnemonic VEIN is helpful in remembering the
causes of proptosis.
V - Vascular causes
E - Endocrine causes
I - Inflammation and infective
N - Neoplastic causes
CT scan and MRI scan of the orbit may prove
beneficial in diagnosing the cause for proptosis. The presence of
fat in the orbit serves as an inherent contrast medium for the
study. 3 mm cuts are ideal for the study of orbit. Ultrasound
studies using either A or B mode may help in rapid diagnosis of the
cause for proptosis.
CT scan of paranasal sinuses showing
Vascular causes of proptosis:
Vascular causes of proptosis can be classified
into arterial and venous causes. Venous causes are due to the
formation of dilated veins known as varices. Patients with these
varices give a classic history of positional proptosis (proptosis
varying with positions) or proptosis being induced by valsalve
manuver. In patients with long standing varices there is also an
associated orbital fat atrophy leading on to a transient stage of
enophthalmos. In these patients a valsalva manuver may reveal
proptosis. CT scan performed with jugular venous compression or
during a valsava manuver may prove diagnostic. Surgical intervention
in these patients may prove disastrous, hence observation and
treatment of complications is advisable.
In dural venous sinus fistula the shunt is low
flow in type and proptosis is insiduous in onset, high index of
suspicion is necessary in diagnosing these patients.
Carotid cavernous fistula (high flow shunts) may
arise as a result of trauma or spontaneously. These patients have
subjective bruits, proptosis, chemosis and vision loss. The
conjunctival vessels become arteriolised assuming a cock screw
pattern. A fistula of spontaneous occurence has a better chance of
spontaneous resolution, but in intractable cases the shunt must be
closed with a baloon or carotid artery ligation.
Endocrine causes of proptosis: are the most
common cause of exophthalmos. The diagnosis is fairly simple because
it is invariable associated with lid signs like lid lag. The major
endocrine cause for proptosis is thyrotoxicosis. This condition is
also known as Graves disease.
Characteristic features of endocrine causes of
1. Presence of lid lag / lid
2. Presence of temporal flare in the upper
3. Presence of orbital congestion
CT scan of the orbit show enlarged extra ocular
muscles, there may also be a bulging of orbital septum due to
protrusion of fat. This is pathognomonic of Grave's disease. TSH
estimation show elevated levels in the serum.
Inflammatory causes of proptosis: In inflammatory
proptosis the lesion could be either an idiopathic inflammatory
orbital pseudotumor, or due to specific orbital inflammation.
Proptosis in these patients appear suddenly and acutely. These
patients are invariably toxic and febrile. Myositis of
extra ocular muscles may cause pain when eyes are
being moved. There may also be associated acute dacryo adenitis.
There may also be peri optic neuritis causing blindness. Orbital
inflammation, perioptic neuritis and dacryo adenitis are highly
responsive to oral prednisolone.
Inflammations involving the paranasal sinuses may
involve the orbit causing proptosis. The interveining walls between
the medial orbital wall and the ethmoidal sinuses is paper thin
(lamina papyracea) which can be easily breached by infections from
the ethmoidal sinuses causing spread to the orbit. In proptosis
caused by ethmoidal sinus pathology the eye is pushed laterally,
where as proptosis due to maxillary sinus pathology causes deviation
of the eye upwards and outwards. In frontal sinus pathology the eye
is deviated downwards and outwards. Commonest sinus inflammatory
cause for proptosis is the formation of mucoceles in the paranasal
sinuses. This commonly occur in the fronto ethmoidal
showing proptosis due to frontal
Neoplastic causes of proptosis: Neoplasms
involving orbit may cause proptosis. Here the eye is pushed directly
forwads. This type of proptosis is known as axial proptosis.
Tumors involving the optic nerve can cause axial
proptosis. These patients have pain free disease. The only exception
to lack of pain is patients with adenocystic carcinoma of lacrimal
gland. These patients have excessive pain because the tumor
infiltrates the nerves.
Neoplastic lesions involving the paranasal
sinuses can also cause proptosis. The common benign tumor involving
the sinuses causing proptosis are:
1. Inverted papilloma
2. Fungal infections involving the paranasal
3. Mucoceles involving the paranasal
4. Fibrous dysplasia of the maxilla
5. Osteomas involving the frontal and ethmoidal
6. Juvenile nasopharyneal angiofibroma
showing proptosis left eye due to fibrous dysplasia of
Malingnant tumors involving the nasal cavity and
paranasal sinuses can involve the orbit causing proptosis. This is
because of the common intervening walls between the orbit and the
Preventing complications like drying of the
cornea should take precedence. This is done by prescribing
artificial tears. Specific management is directed towards treating
the cause for proptosis. Orbital decompression may be resorted to in
extreme cases of proptosis due to Grave's disease. Common type of
orbital decompression is medial orbitotomy where the medial wall of
the orbit is removed facilitating collapse of the orbital contents
into the nasal cavity. It can also be combined with lateral
orbitotomy if the result of medial orbitotomy is not satisfactory.
Inflammatory causes of proptosis must be treated with antibiotics.
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