Ординатура / Офтальмология / Английские материалы / Pediatric Opthalmology_Mukherjee_2005

III.Infective —

1.Acute

(a) Orbital cellulitis

(b) Orbital and periorbital abscess (c) Cavernous sinus thrombosis (d) Panophthalmitis

2.Chronic

(a) Pseudo tumour orbit

(b) Intraorbital parasitic cyst

IV. Neoplasm

1.Benign

(a) Dermoid and epidermoid (b) Capillary haemangioma (c) Neurofibroma

(d) Lymphangioma (e) Optic nerve glioma (f) Orbital varices (g) Fibrous dysplasia

(h) Intraorbital meningioma

2.Malignant

(a) Primary

Rhabdomyosarcoma and Burkitts lymphoma (b) Secondary

Neuroblastoma, orbital retinoblastoma, Ewing’s sarcoma Wilm’s tumour leukaemia.

V.Miscellaneous—Hand Schuller Christian disease, juvenile xantho granuloma, eosinophilic granuloma, sinus histocytosis.

Mode of onset

Acute onset and increase in proptosis is seen in orbital cellulitis, panophthalmitis, cavernous sinus thrombosis and retro bulbar hae-morrhage.

Rhabdomyosarcoma, neuroblastic and leukeamic deposits have moderate to fast progression.

Duration—Long duration with minimal symptoms are seen in congenital causes and benign growths.

Recurrence—Recurrence is common following treatment of rhabdomyosarcoma, neuroblastoma, leukaemia, retinoblastoma. Retinoblastoma treated by radiation are known to develop second non retinoblastoma malignancy.

Trauma

Frank trauma with laceration of lid, fracture base of the skull and orbit cause accumulation of blood in retro bulbar space. Accumulation of air results in orbital emphysema, which denotes fracture of paranasal sinuses. Retained intra orbital foreign bodies not only cause retro bulbar hematoma but also cause orbital cellulitis if the foreign body is infected and are known to develop foreign body granuloma.

Pain

Pain is seen in acute infective lesions like orbital cellulitis, orbital abscess, cavernous sinus thrombosis or any fast expanding mass. The pain suddenly subsides if the fluid spontaneously discharges outside the orbit via conjunctiva or in to the lid after perforating the orbital septum. Corneal involvement is a common cause of pain, lacrimation and photophobia. In case of unexplained pain, intraocular tension should be measured by tonometer. A non contact tonometer is preferred over contact tonometer.

Diminished vision

Loss of vision followed by proptosis is pathognomic of optic nerve glioma in children. However the child may not be aware of such painless loss and may not complain. Loss of vision with pain is due to corneal involvement.

Diplopia

Diplopia denotes early stage of paralytic squint or restrictive strabismus, which may subside due to loss of vision, or onset of deep amblyopia.

Ocular examination

Vision—Recording of vision should precede all other examinations. In a non-verbal child clear, bright cornea, normal anterior chamber, brisk direct and indirect pupillary reaction, clear media, absent error of refraction and normal fundus invariably denotes good vision except in case of deep amblyopia and cortical blindness.

In a slow progressive proptosis, vision is generally good and remains so for sometime. In glioma of optic nerve, visual loss is followed by proptosis, sudden painful loss of vision means

corneal involvement. Sudden painless loss of vision is due to fundus changes that may be optic neuropathy, optic atrophy, haemorrhage in the retina or vitreous, vascular obstruction, choroidal fold or hypermetropia due to growing mass behind the globe that pushes the retina forward.

Pupillary reaction—A Marcus Gunn phenomenon denotes optic nerve compression. Cavernous sinus thrombosis and superior orbital fissure syndrome may result in dilated sluggish pupil.

Inspection—A well established proptosis is not difficult to diagnose. An early proptosis requires proper examination. In such case most important is to determine if the proptosis is real or apparent (pseudo proptosis).

Pseudo proptosis is that condition where there is no pathology in the orbit. The pathology is either in the lid or eyeball. Sometimes the pathology lies in the contra lateral eye in the form of enophthalmos.

The causes in the lid that mimics proptosis are—Lid retraction and lagophthalmos in the ipsilateral eye or ptosis, pseudo ptosis of the other eye.

Ocular conditions that may be mistaken as proptosis are—Pathological myopia, buphthalmos, large ciliary staphyloma, in the eye under examination. Contra lateral microphthalmos, phthisis or enophthalmos are also sometimes mistaken as proptosis of the ipsilateral eye.

Next step involves finding out laterality of the proptosis i.e. is at unilateral or bilateral. If bilateral, is it equal in both eyes or advanced in one eye.

Causes of unilateral proptosis in children are :

Orbital cellulitis, orbital and peri-orbital abscess, early stage of cavernous sinus thrombosis, rhabdomyosarcoma, pseudo tumours, neurofibroma, capillary haemangioma, lymphangioma, dermoids, retro bulbar haemorrhage, rarely congenital.

Causes of bilateral proptosis in children are :

1.Mostly systemic condition

2.Congenital anomalies of the orbit

Systemic conditions that cause bilateral proptosis are—neuroblastoma, leukaemia, bilateral retinoblastoma, second malignancy following radiation for retinoblastoma, fully developed cavernous sinus thrombosis.

Measurement of proptosis

Relative position of cornea in relation to orbital margin gives clue regarding proptosis of ipsilateral eye, enophthalmos of the other eye, extent of proptosis when present and its progression. This can be done clinically by noting the position of corneal apex in relation to superior orbital margin. It can be conveniently done in a co-operative child. The examiner stands behind the child, asking the child to tilt the head backwards and fix at a distant object keeping both eyes open and noting the position of the cornea in relation to superior orbital rim. Normal corneal apex is generally not visible beyond the superior orbital margin. A visible cornea beyond orbital rim denotes proptosis. A false impression is given by high myopia. 3D myopia is equal to 1mm enlargement of globe in anterio posterior diameter. The other method consists of actual measurement of distance between the corneal apex and the lateral orbital

margin. There are various types of exophthalmometer (Proptometers) to measure this distance, they are - Optical and mechanical.

The optical exophthalmometer is more popular and widely used than mechanical. They are Leuddes transparent scale and Hertels mirror proptometer.

Normal exophthalmic measurement vary between a wide range of 10 to 20 mm, average is taken as 15 mm. Any reading higher than 21 mm is considered as definite proptosis. The other criteria is any difference of more than 2 mm between the two eyes provided the other eye is normal. An enophthalmic contra lateral eye gives a false positive impression.

CT pictures can also be useful in evaluating extent of proptosis.

Inspection

1.Position of upper lid. Normal lid covers upper one fifth of the cornea and lower lid just touches the lower limbus. No strip of sclera is visible either above or below the cornea. Visible sclera above, below or both denotes proptosis or lid retraction. Generally lid retraction is associated with lid lag. Lagophthalmos gives an impression of pseudo proptosis. All cases of lid retraction with or without clearcut proptosis should be investigated for dysthyroid eye disease. Incidence of dysthyroid orbitopathy is far less in children than seen in adults.

2.Direction of proptosis. Abnormal position of globe gives clue to location of orbital pathology in relation to globe.

The globe may be displaced :

1.Centrally (axially) or

2.Eccentrically—Eccentric proptosis may be unidirectional or otherwise.

The causes of axial proptosis lies in the muscle cone. Commonest causes in children are being glioma of optic nerve. Other causes are foreign body in the muscle cone, orbital varices, pus localised in muscle cone.

A growth from the medial wall displaces eye laterally. Pathology from the floor pushes the eyeball up. However the displacement always does not follow such simple rule. A growth on the superio medial aspect pushes the eyeball forward, downward and laterally. Similarly a growth from superio temporal orbit shifts the globe down, out and medially.

3.Visible pulsation. Sometimes the proptosed eye may have pulsation synchronised with heart beat. Gross pulsation is evident without magnification. However slit lamp examination may show very mild pulsation that later becomes evident without biomicroscope. Such pulsations are more common in adults, however pulsations are met with in neuro fibromatosis when associated with defect in sphenoid, fibrous dysplasia and rarely in post traumatic carotico cavernous fistula.

4.Cough impulse is visible and palpebal in cases of encephalocele and meningo encephalocele.

5.Palpation

(i) Palpation of the orbital margin—Normal orbital margin is smooth without any notch or protuberance except superior orbital notch and the trochlea occasionally. The medial palpebral ligament is palpable as a horizontal band, this is also a normal feature.

Palpation or orbital margin may reveal irregularity, bone formation or bone dehiscence. Growth arising from bony sutures i.e. dermoids can not be palpated separately from orbital margin.

(ii) Palpation of orbital mass—Anteriorly placed growths are easily palpable. While palpating a mass, if a finger can be insinuated between the mass and the orbital wall, the growths is not arising from the orbital wall or the rim. The finger can not be insinuated between the growth and the wall in case of encephalocele, meningocele, dermoids, mucocele from the paranasal sinuses and lacrimal gland growth. Lacrimal gland tumours are not met within children.

Compressibility of the proptosis

The child is asked to close the lids and the mass is pushed back through the closed lid by first three fingers of the examiner. This should be avoided when tenderness of globe is present. A compressible mass means a soft or vascular growth, solid tumours cause retro bulbar resistance.

Valselva maneuver, juglar vein compression and head bending

None of the above procedures change the position of the eyeball in any proptosis unless it is caused by vascular anomaly like capillary haemangioma and congenital varices.

In head bending test, the child is asked to bend the head and trunk forward for about a minute and then come to normal position. The position of the globe is measured, an increase in proptosis is considered positive denoting a vascular tumour.

Forced duction test20

This test, when performed properly differentiates obstructive squint due to fibrotic contracture from neurological defects. In a co-operative child this can be done as outpatient procedure under local anaesthesia, otherwise it should be done under short term general anaesthesia.

The test consists of :

1.Anaesthetise the conjunctiva by instilling local anaesthetic agent in both the eyes for two to three times. If the child feels pain, a cotton swab dipped in same anaesthetic solution may be left at the insertion of the muscle to be tested for three to four minutes.

2.Ask the patient to look in the direction of limited movement.

3.Grasp the insertion of the muscle to be tested with a conjunctival fixation forceps, move the globe passively in the direction of limited movement.

4.The procedure is repeated in the other eye and findings are compared.

A test is considered to be positive if the eye can not be moved passively in the direction of limited duction and the cause is fibrotic contracture of the muscle or entrapment of the muscle in a fracture. If the eye can be moved passively in the direction of limited action, the test is called negative and the cause of limitation is neurological.

5.While performing the test, care should be taken not to push the globe backward deep in the orbit otherwise there will be no limitation in presence of fibrotic band.

In children the test is frequently used in case of superior oblique sheath syndrome,

Duane’s retraction syndrome, entrapment of muscle in fracture orbit or in case of strabismus fixus. The test is most frequently used in adults in case of thyroid myopathy.

When the child does not allow forced duction test under local anaesthesia, a less painful test is differential intra ocular pressure test. Intraocular pressure is noted in usual manner in primary gaze. The patient is asked to look toward the field of action of the muscle under question and tension is repeated. A rise of 6 mm denotes fibrosis or entrapment of the muscle. No rise of tension or rise less than 6 mm is suggestive of neurological cause.

Special investigation in proptosis

They consist of :

1.Orbital imaging

A.Non invasive (a) Plain x ray (b) CT

(c) MRI

(d) Ultrasonography (e) Venography

(f) Arteriography

B.Invasive

(a) Fine needle aspiration (b) Biopsy

(c) Surgical excision and histopathological examination

2.Rhinological consultation

3.Blood picture

4.Blood chemistry

5.Systemic examination

Radiology of orbit in relation to proptosis

Posterio anterior view without angulation of head or beam, has very limited value in evaluation of orbital lesions. The petrous part of the temporal bone and the para nasal sinuses get superimposed on the soft fissure of the orbit and obscure their view.As most of the anatomic landmarks form various degree of angulation in anterio posterior axis, they are required to be positioned in such a way that they do not interferes with the structure of radiological interest.

Commonly used X-ray views are :

1. Caldwell view

(a) View with central X-ray tilted 25° downward

(b) Hypoangulated view—Central X-ray is tilted less than 15°

2.Water’s view

3.Lateral view

4. X-ray for optic canal and foramen

(i) Rhese view

(ii) Ruggiero

5.Axial basal view

6.Submento vertex view

7.Townes view.

1.Caldwell view. In this view the patient lies face down, the forehead and the nose touching the X-ray table with X-ray tilted downward. (a) at 25° and (b) 15°.

The advantage of this projection is that the petrous part of temporal bone is shifted down so that the orbital rim, roof, greater wing of sphenoid, lesser wing of sphenoid, the superior orbital fissure are clearly visible. The foramen rotundum is shifted below the lower rim of the orbit. The greater wing forms a larger part of lateral wall, the lesser wing of sphenoid is seen near the medial wall. The superior orbital fissure is seen in between the two wings. It also shows frontal sinuses, sphenoid ridge, floor of sellaturcia and innominate or oblique orbital line. An angulation less than 15° gives better view of some of the above structures.

2. Water’s view. This is also a posterio anterio projection. The patient lies prone on the table with the chin resting on the table and nose lifted 4 cm off the table. This makes the canthomental line form an angle of 37° to the central X-ray, which is at right angles to the X- ray plate.

It gives a clear view of maxillary, frontal and ethmoidal sinuses, the lateral wall, zygomatic arch and inferior orbital rim. This is useful when the pathology is in the sinuses and fracture of the orbit is suspected.

3. Lateral view

The X-ray plate is kept parallel to the sagital plane, the central ray is at right angle to this plane that passes 2.5 cm in front and 2 cm above the external auditory meatus.

This projection shows anterior and posterior clinoid process. The sellaturcia, sphenoid sinuses, intra orbital canal. Part of the floor of the orbit is also visible.

The projection is used to localise intraocular, intra orbital foreign bodies, calcification and pathology in sella.

4. Ray of optic canal and foramen

(i) Rhese view. This requires two separate exposures, one for each orbit. This is used to visualise the optic foramen and optic canal.

The patient lies prone on the table with zygoma, nose and chin on the table. The mid sagittal plane of the skull makes an angle of 53° with the film. The central ray is projected posterio anteriorly with 12° angulation towards feet.

(ii) Ruggiero view21. These projections show optic canal, optic foramen, ethmoid cells, lesser wing of sphenoid and superior orbital fissure.

5.Axial basal view shows ethmoid and sphenoid air cells.

6.Submento vortex view is taken on a supine patient. This view shows base of the middle cranial fossa, the maxillary sinus, and the nasal cavity.

7. Towen’s view shows infra orbital fissure. This view is exposed when the patient is supine and the X-ray is projected in anterio posterior direction.

Points to be noted of a X-ray of orbit :

—The radiologist should see the patient and the ophthalmologist see the X-ray.

—Single projection may not be sufficient to give all the required information.

—X-ray of both the orbits should be taken, this helps in comparing changes in two orbits especially in unilateral proptosis and a systemic bilateral proptosis.

1. Intraorbital distance. The intra orbital distance refers to distance between right and left junction of frontal process of maxilla and maxillary process of frontal bone. The two medial walls of the orbit are parallel to each other and the distance between the two varies between 12.5 mm in child of one year to 25 to 28 mm at 12 years of age. If the orbits are set apart, the condition results in hypertelorism. The cause of which are Crouzon’s disease,Apert’s syndrome, fibrous dysplasia, osteogenesis imperfecta, encephalocele. The intraorbital distance may be as much as 30 to 40 mm in adult.22

Hypotelorism

When the intra orbital distance is less than expected normal value of a given age. This is seen in Down’s syndrome, trigonocephaly and craniofacial anomalies.

Premature closure of cranial sutures

This is associated with deformity of skull, expansion of the skull at the right angles to the closure of suture, shallowing of the orbit, rotation of wall of the orbit and increased digital marking commonly seen in craniostenosis.

Widening of cranial suture

Normally a cranial sutures should close at 18 months of age. However if the intra cranial tension rises before the sutures are closed, the skull expands due to increased intra cranial pressure widening the cranial sutures, in such cases no digital markings are seen on the bones of the skull. However, if there is rise of intra cranial pressure after the sutures are closed, X-ray evidence of raised intra cranial tension will be observed. If some of the sutures are closed, remaining sutures will open up; the example is craniostenosis.

Enlargement of the orbits

Size of the normal eyeball is essential for the growth of the orbit. In most of the cases of proptosis the size of the eyeball is within normal limits, other orbital structures force the orbit to expand. However a large eyeball itself can cause enlargement of the orbit.

The enlargement of the orbit can be unilateral and bilateral. Unilateral enlargement is more rapid in children. The orbit of a child takes two to three months to show enlargement while similar enlargement in adults take 1 to 2 years. Unilateral enlargement can be symmetrical or asymmetrical. Unilateral buphthalmos either primary or secondary produce enlargement of orbit. Retinoblastoma produces more and frequent enlargement than primary buphthalmos, other causes of unilateral symmetrical enlargement are due to intra conal lesions i.e. optic nerve glioma, neuro fibromatosis, haemangioma, extra ocular retinoblastoma inside the muscle cone and intra conal pseudo tumour. Causes of asymmetrical enlargement of orbit

are - haemangioma, extra conal retinoblastoma, neurofibroma, dermoid, rhabdomyosarcoma, orbital dysplasia, microphthalmos with cyst, congenital teratoma.

Diminished size of orbit

Orbital size may be smaller than normal either due to small or absent eyeball, a growth encroaching from orbital wall or craniostenosis.

The common causes of small orbit are—Anophthalmos, microphthalmos, early enucleation of the eyeball, post radiation. Mucocele of the frontal sinus and growth from maxillary sinus (rare in children) also reduce size of the orbit.

Changes in shape of orbit

Orbital shape can be deformed as part of craniostenosis, orbital dysplasia and dermoids.

Changes in the bone

The changes in the orbital bones can be :

1.Increased density

2.Decreased density

3.Destruction of bone

4.Fracture of the orbit

1.Density of bone is increased in osteoblastic metastases, chronic periostitis, fibrous dysplasia.

2.Decreased bone density is seen in dermoid.

3.Dehiscence of bone is seen in neuro fibromatosis, mucocele and fracture of roof and floor.

Calcification in the orbit

Intra orbital calcification may be confined to intra ocular structure, extra ocular structure or both. In posterior anterio view, intra cranial calcification like cranio pharyngioma, congenital toxoplasmosis, Sturge Weber syndrome may be superimposed on orbit, however a lateral exposure separates intra orbital calcification from intra cranial calcification.

Causes of intraocular calcification are—Retinoblastoma, parasitic cysts, choroidal bone formation, complicated cataract, retrolental fibroplasia, phthisis blubae. Extra ocular calcification is seen in orbital retinoblastoma, orbital varix, optic nerve glioma, parasitic cysts, haemangioma, neurofibroma. Dermoids get calcified occasionally.

Changes in superior orbital fissure—The superior orbital fissure widening is more common than its narrowing which is brought about by encroachment of growth over the fissure and as a congenital malformation.

Widening of the superior orbital fissure is generally seen in adults as part of intra clinoidal aneurysm. Intra cavernous aneurysm, carotico cavernous fistula, extension of intra orbital growth backwards or spread of growth from cranium. Sometimes neurofibroma and pseudo tumours of orbit may also widen superior orbital fissure.

Changes in optic canal and foramen

Usual diameter of optic canal varies between 4.4 to 6 mm in adults. At birth the canals are narrower, reaching the adult size by 5 years of age, diameter greater than 7 mm is always pathological. Generally diameters of both the canals are more or less similar. Any difference of more than 1 mm between the two canals is also pathological. For comparison both the canals should have identical X-rays preferably taken on the same plate. The enlargement may be concentric or irregular. Uniform concentric uniocular enlargement is seen in optic nerve glioma. Other causes in children are neuro fibromatosis, intra neural extension of retinoblastoma. In children neurofibroma and retinoblastoma cause uniform irregular enlargement.

Computed tomography23

Computed tomography has emerged as an important tool in orbital imaging. It is safe with minimal radiation hazard, which is as less as in X-ray. It is a non invasive outdoor procedure which uses computer assistance. X-ray Tomography is axial as well as coronal in section. A combination of axial and coronal section when programmed enables a lesion to be seen in three dimensions. Its use in orbit is based on ability in differentiating between relative tissue densities. Retrobulbar fat is in plenty in orbit and surrounds many structures. The retrobulbar fat is hypo dense on X-ray in relation to other structure, hence a good contrast is ensured. The bones have maximum density, the orbital fat and vitreous have least density, other structures have intermediate densities. The vascular structures are best visualised by using intravenous iodine containing contrast dye.24

Besides orbit the intra cranial and paraorbital structures are also well delineated in the same exposure. This enables to visualise growths extending from the orbit into the cranial cavity and vice versa. It also demonstrates other intra cranial lesions not directly related to the orbital lesion. The structures well visualised are the walls of the orbit, optic canal, optic nerve, extra ocular muscles, globe, intra ocular mass. Intra ocular, orbital and cranial foreign bodies. It is very sensitive in detecting orbital, intra ocular, and cranial calcification. Fractures are well demonstrated. The superior orbital fissure is better visualised in contrast to inferior orbital fissure. The sclera is demarcated clearly. It is not possible to differentiate the layers of the globe separately in normal eye. However anterior chamber, lens and vitreous chambers are seen separately. Generally 4-5 mm sections are taken routinely from vertex to base of the skull, parallel to the optic nerve. The coronal plane is parallel to equator of the globe similar to Caldwell view of X-ray. The computerised tomography can not differentiate between pathological and normal tissue of same density. The walls of the orbit are clearly seen in both axial as well as coronal slices. The roof and floor are seen better in coronal section so are the superior, medial and lateral recti. The levator palpebral superior is not very clearly seen. All these muscles are seen as elliptical masses in coronal section, in axial view they have fusiform shape. The optic canal, intra orbital part of the optic nerve, sometimes its meningeal covering are seen in axial view. The medial and lateral recti are seen as dense masses extending from equator of the eyeball to the apex of the orbit.

Computed tomography is ordered in children to evaluate orbital soft tissue mass, intra ocular and intra cranial calcification. Evaluation of trauma, intra orbital and intra cranial foreign bodies.