Diseases Of The Orbit

Diseases Of The Orbit

PROPTOSIS

Causes of unilateral proptosis

Congenital conditions. Dermoid cysts, congenital cystic eyeball, and orbital teratomas.
Traumatic lesions: Orbital haemorrhage, retained intra-orbital foreign body, traumatic aneurysm and emphysema of the orbit.
Inflammatory lesions: Acute inflammations are orbital cellulitis, abscess, thrombophlebitis, panophthalmitis and cavernous sinus thrombosis (proptosis is initially unilateral but ultimately becomes bilateral). Chronic inflammatory lesions include: pseudotumours, tuberculoma, gumma and sarcoidosis.
Circulatory disturbances and vascular lesions: Angioneurotic oedema, orbital varix and aneurysms.
Cysts of orbit: Haematic cysts, implantation cysts and parasitic cysts (hydatid cyst and cysticercus cellulosae).
Tumours of the orbit: These can be primary, secondary or metastatic.

Causes of bilateral proptosis

Developmental anomalies of the skull: craniofacial dysostosis e.g., oxycephaly (tower skull).
Osteopathies: Osteitis deformans, rickets and acromegaly.
Inflammatory conditions: Mikulicz’s syndrome and late stage of cavernous sinus thrombosis.
Endocrinal exophthalmos: It may be thyrotoxic or thyrotropic.
Tumours: Symmetrical lymphoma or lymphosarcoma, secondaries from neuroblastoma, nephroblastoma, Ewing’s sarcoma and leukaemic infiltration.
Systemic diseases: Histiocytosis, systemic amyloidosis, xanthomatosis and Wegner’s granulomatosis.

Causes of acute proptosis are orbital emphysema following fracture of the medial orbital wall, orbital haemorrhage and rupture of ethmoidal mucocele.

Causes of intermittent proptosis are orbital varix (most common), periodic orbital oedema, recurrent orbital haemorrhage and highly vascular tumours.

Causes of pulsating proptosis are carotico- cavernous fistula (most common), saccular aneurysm of ophthalmic artery,congenital meningocele or meningo-encephlocele, neurofibromatosis and traumatic or operative hiatus in the roof of the orbit.

Causes of proptosis in infants. Craniostenosis, meningoencephalocele, microphthalmia with teratoma, retino-blastoma, capillary haemangioma, juvenile xanthogranuloma and metastatic neuroblastoma.

Causes of proptosis beginning in childhood: Dermoid cyst, lymphangioma, cavernous haemangioma, orbital varices, neurofibroma, rhabdomyosarcoma, optic nerve glioma, intraorbital meningioma, orbital cellulitis, leukaemic infiltration, granulocytic sarcoma, Burkitt’s lymphoma, eosinophillic granuloma, Hand-Schuller Christian disease, sinus histiocytosis, hydatid cyst and fibrous dysplasia.

Causes of proptosis beginning in adulthood. Graves’ ophthalmopathy (commonest cause), lymphopro- liferative disorders, fibrous histocytoma, haemangio- pericytoma, cavernous haemangioma, secondary orbital meningioma, osteoma, mucocele, orbital varices, lesions of lacrimal gland, secondary tumours of the orbit.

Causes of pseudoproptosis are buphthalmos, axial high myopia, retraction of upper lid and enophthalmos of the opposite eye;

Proptosis: findings in x-ray orbit

Causes of symmetrical enlargement of orbital cavity in X-rays of the orbit
• Optic nerve glioma
• Haemangioma
• Neurofibroma
• Retinoblastoma

Cause of asymmetrical enlargement of orbit
• Rhabdomyosarcoma
• Dermoid cyst
• Lacrimal gland tumour.

Causes of increased bone density (hyperostosis) in X-rays of orbit
• Sphenoidal ridge meningioma
• Chronic periostitis
• Fibrous dysplasia
• Paget’s disease
• Osteoblastic metastasis

Causes of intraorbital calcification
• Retinoblastoma
• Optic nerve sheath meningioma
• Phlebolith in orbital varix
• Phthisical eye

Changes in optic canal (optic foramina) in X-rays
• Uniform regular concentric enlargement
– optic nerve glioma
• Uniform irregular enlargement
– retinoblastoma
– optic nerve sheath meningioma
– orbital neurofibroma
• Erosion of the upper margin
– raised intracranial pressure
• Erosion of the inferolateral margin
– infraclinoid aneurysm
– infraclinoid meningioma

Diseases Of The OrbitENOPHTHALMOS

Congenital: Microphthalmos and maxillary hypoplasia
Traumatic: Blow-out-fractures of floor of the orbit
Post-inflammatory: Cicatrization of extraocular muscles as in the pseudotumour syndromes
Paralytic enophthalmos: It is seen in Horner’s syndrome
Atrophy of orbital contents: Senile atrophy of orbital fat, atrophy due to irradiation of malignant tumour, following cicatrizing metastatic carcinoma and due to scleroderma.

GRAVES’ OPHTHALMOPATHY

Pathology. The histopathologic reaction of various tissues is dominated by a mononuclear cell inflammatory reaction. Presence of mucopoly¬saccharides, predominantly hyaluronic acid, together with interstitial oedema and inflammatory cells accounts for the proptosis. Most data presently support the postulate that the orbital fibroblast is the primary target of inflammatory attack, with extraocular muscle being secondarily involved.

Lid signs. These are (i) retraction of the upper lids producing the characteristic staring and frightened appearance (Dalrymple’s sign), (ii) Lid lag (von- Graefe’s sign) i.e., when globe is moved downward, the upper lid lags behind, (iii) Fullness of eyelids due to puffy oedematous swelling (Enroth’s sign), (iv) Difficulty in eversion of upper lid (Gifford’s sign), (v) Infrequent blinking (stellwag’s sign).

Ocular motility defects. The most common ocular motility defect is a unilateral elevator palsy caused by fibrotic contraction of the inferior rectus muscle followed by failure of abduction due to contracture of medial rectus muscle. Sequence of involvement of muscle is: IR, MR, SR and LR.

Exophthalmos. As a rule both eyes are symmetrically affected; but it is frequent to find one eye being more prominent than the other. Even unilateral proptosis is not uncommon.

ORBITAL CELLULITIS AND INTRAORBITAL ABSCESS

• Suppurative inflammation of the fat and cellular tissues of the orbit.
• It may result from penetrating injury especially when associated with retention of intraorbital foreign body, following operations like evisceration, enucleation, dacryocystectomy and orbitotomy.
Extension of infection from neighbouring structures (most common-ethmoiditis especially in children) is the commonest mode of orbital infections.
• The important blinding complications are: central retinal artery occlusion, optic neuritis and corneal ulceration.
Orbital apex syndrome is characterised by a triad of: (i) ophthalmoplegia due to paresis of third, fourth and sixth cranial nerves, (ii) anaesthesia in the region of supply of ophthalmic division of fifth nerve and (iii) amaurosis due to involvement of optic nerve.

CAVERNOUS SINUS THROMBOSIS

• Cavernous sinus thrombosis starts initially as a unilateral condition, which soon becomes bilateral in more than 50 percent of cases due to intercavemous communication.
• Paralysis of opposite lateral rectus muscle is often the first sign of involvement of contralateral cavernous sinus.
Oedema in mastoid region is a pathogmic sign.
• The rapidly developing, acute inflammatory type of proptosis seen in cavernous sinus thrombosis needs to be differentiated from orbital cellulitis and panophthalmitis.

ORBITAL TUMOURS

Primary orbital tumours

Dermoids are common developmental tumours in which the cystic component is lined with keratinizing epithelium and may contain one or more dermal adnexal structures such as hair follicles and sebaceous glands.

Lipodermoids are solid tumours usually seen beneath the conjunctiva.

Teratomas are composed of ectoderm, mesoderm and endoderm. These may be solid, cystic or a mixture of both.

Capillary haemangioma is commonly seen at birth or during the first month.

Cavernous haemangioma is the commonest benign orbital tumour among adults. The tumour is usually located in the retrobulbar muscle cone and produces unilateral axial proptosis.

Rhabdomyosarcoma is the most common primary orbital tumour among children, usually occurring below the age of 15 years (90%).

Lacrimal gland tumours. Pleomorphic adenoma (mixed cell tumour) is the most common benign tumour of lacrimal gland. It causes down and medial displacement of the eyeball. Malignant tumours of lacrimal gland are: adenoid cystic carcinoma, pleomorphic adenocarcinoma, and mucoepidermoid carcinoma.

Optic nerve glioma may present either as a solitary tumour or as a part of Von Recklinghausen’s neurofibromatosis (55%). It is characterised by early visual loss associated with a gradual, painless, unilateral axial proptosis occurring in a child usually between 4 and 8 years of age (female > male). CT scan typically shows fusiform enlargment of optic nerve along with enlargement of optic canal.

Primary intraorbital meningiomas produce visual loss associated with limitation of ocular movements, optic disc oedema or atrophy, and a slowly progressive unilateral proptosis. The presence of opticociliary shunt is pathognomic of an optic nerve sheath meningioma.

Lymphomas. Other are involved more commonly by non-Hodgkin’s lymphomas.

Hand-Schuller-Christian disease is characterised by a triad of proptosis, diabetes insipidus and bony defects in the skull.

BLOW-OUT-FRACTURE OF THE ORBITAL FLOOR

• ‘Blow-out fractures’ mainly involve orbital floor and medial wall.
• Three factors responsible for producing enophthalmos in blow-out-fracture are: (a) escape of orbital fats into the maxillary sinus; (b) backward traction on the globe by entrapped inferior rectus muscle and (c) enlargement of the orbital cavity from displacement of fragments.
• The common roentgen finding are: fragmentation and irregularity of the orbital floor, depression of bony fragments and hanging drop opacity of the superior maxillary antrum from orbital contents herniating through the floor.

SOME SALIENT POINTS

• The most common and most virulent fungal disease involving the orbit are caused by Mucor (Mucormycosis) and Rhizopus organism of the class Phycomycetes (phycomycosis). Orbital mucormycosis occur most often in patients with diabetic ketoacidosis.

• The mucoceles of paranasal sinuses affecting the orbit most commonly occur in frontal sinus.

• The most common cause of intermittent proptosis is orbital varices.

• The most common cause of pulsating proptosis is carotico-caveraous fistula.

• The most common primary tumour of the orbital cavity presenting as proptosis is cavernous haemangioma.

• Rhabdomyosarcoma of the orbit is the commonest primary malignant tumour of childhood.

• The commonest histological type of rhabdomyosarcoma of the orbit is embryonal type.

• Paralysis of opposite lateral rectus muscle is often the first sign of involvement of contralateral cavernous sinus.

• The earliest clinical feature of orbital extension of the basal cell carcinoma of the eyelid is diplopia.

• Carotid angiography is the investigation of choice in carotico-cavernous fistula.

• The first sign of cavernous sinus thrombosis is restriction of ocular movements.