anatomy and diseases of the orbit

Anatomy and diseases of the orbit

Anatomy of the orbit:

It is pyramidal in shap- the base is represented by the orbital margin and the apex by the optic foramen. The walls of the orbit are:

1)Roof2)Medial wall3)Lateral wall4)Floor

It has 3 openings:1)Optic foramen transmitting optic nerve and ophthalmic artery.

Anatomy of the orbit

2)superior orbital fissure transmitting 3rd,4th,6th cranial nerves and branches of ophthalmic division of 5th cranial nerve ,superior ophthalmic vein .

3)inferior orbital fissure – transmitting the zygomatic nerve, infra orbital nerve etc.

From the surgical point of view there are 4spaces.

1) the subpetiosteal space between the bones of the orbital wall and the periosteum .

2)The peripheral space between tha periosteum and the extraocular muscles,which are joined by fascial connections .

3) Central space or muscle cone – a cone shaped raea enclosed by muscles .4)Tenon s space around the globe .

Orbital cellulitis:

Definition : Inflammation of the cellular tissue of the orbitEtiology: 1) It is due most frequently to extension of Inflammation from neighbouring parts , especially the para nasal sinuses (ethmoid etc .) teeth in children , orbital periostitis .2) Deep injuries especially those with retained foreign body .3) septic operation , particularly enucleation of eye ball4)Facial erysipelas 5)Metastasis in pyaemia 6) extension of Inflammation in panophthalmitis ,dacryocystitis .

Orbital cellulitis

Symptoms: 1-constitutional symptoms-high fever, vomiting , violent pain in the orbit.2- vision may be effected .in some cases it may be reduced owing to optic neuritis .3-diploppia 4-cerebral symptoms such as convulsions may be added.Signs:It is usually unilateral :1-Lid swollen , oedematous2-Conjunctiva – ciliary and conjunctival congestion chemosis of conjunctiva .

3-Proptosis and marked limitation of movement of eyeball.4-After sometime pus appears at a certain part of the skin of lids (usally below supra orbital margin ) and perforates or less frequently it may empty into the superior fornix. After evacuation of pus ,pain subsides.5-Fundus may be normal or may show picture of papilloedema or optic neuritis- blurred disc margin ,hyperaemia of the disc etc.

Differential diagnosis:

Orbital cellultisPanophthalmitisCavernous sinus thrombosis

(1) Unilateral UnilateralInitially unilateral but soon becomes of intercavernous communications.

(2) Vision not affected in early

stage.

Complete loss vision from the

onset.

Vision not affected in early

stage

(3) Cornea, AC are normal.

Cornea may show perforated ulcer whole eyeball full

of pus.

Corneal insensitive.

(4) Pupil normal.Cannot be seen.Semidilated and fixed.

(5) Marked limitation of movement of eyeball.

Partial limitation of movement of eyeball.

Marked limitation of movement of eyeball.

(6) No oedema over mastoid region.

No oedema over mastoid region.

Oedema over mastoid region due thrombosis of emissary vein.

(7) Consitutional symptoms _ fever

MildSever, patient may be in cornea.

(8) Prognosis of vision and life good.

Prognosis of vision poor, life good.

Prognosis of life serious.

Complications :

1-Thrombosis of central retinal vein.2-Cavernous sinus thrombosis.3-Due to exposure of cornea _ ulcer develops ,

perforation of ulcer leads to panophthalmitis .4-Purulent meningitis, cerebral abscess.5-Optic atrophy.Treatment:

1-General treatment by antibiotics – chloromycetin 250 mg q.i.d. injection crystalline penicilline 5 -10 lakhs q.i.d.

2-Analgesics / antipyretic tab. Paracetamol .

3-Hot fomentation.4-Peripheral surgical space – opened by an incision through the skin at the orbital margin .This operation is to be undertaken only when the pus is pointing under the skin .5-Cause and source of infection (paranasal sinuses ets. )should be determined and treated .

Cavernous sinus thrombosis:

Etiology :This may be due to extension of thrombosis from

various sources. The anatomy of the venous channels which communicate with the cavernous sinus is of great importance in this connection.

Infection may occur via :1-Orbital veins as in erysipelas , furuncle of

face and orbital cellulites .2-Infective condition of mouth , pharynx , ear

, nose and accessory sinuses.3-Metastases as in pyaemia.

Cavernous sinus thrombosis

Symptoms :1-There is severe supra orbital pain owing to involvement of the branches of the ophthalmic division of the 5th cranial nerve.2-Constitutional symptoms – high grade fever , vomiting .3-Vision may not be affected in early stage; later it may be reduced owing to optic neuritis.4-Cerebral symptoms may be severe and patient may be comatose.Signs:Initially it may be unilateral later it becomes bilateral.This is because the cavernous sinus of one side communicates with that of the other by 2 transverse sinuses . The first sign is often paralysis of the opposite lateral rectus.1- The lids are oedematous and swollen. In addition there is oedema over the mastoid region behind the ear due to thrombosis of emissary vein.

2) Congestion and chemosis of conjunctiva. 3) Proptosis and limitation of movement (due to involvement of 3rd,4th and 6th cranial nerves) 4) The cornea is insensitive due to involvement of 5th cranial nerve. 5) The pupil is semidilated and fixed due to the involvement of 3rd cranial nerve. 6) Fundus examination shows typical picture of papilloedema or papillitis.Differential diagnosis : Refer orbital cellulitis.

Treatment : 1) Massive doses of intravenous antibiotics 25 mega units of penicillin, methicillin, oxacillin, cloxacillin. 2) Anticoagulants – heparin, dicoumarol.

Proptosis (exophthalmos)

Proptosis (exophthalmos) :

Abnormal protrusion of the globe is called proptosis orexophthalmos. It is due to many causes, among which increasein the orbital contents is the most important. Accurate estimatesof the amount of proptosis can be obtained by special mechanicaldevices known as exophthalmometer e.g. Hertel`s exophthalmometer. Causes of unilateral proptosis: I) Inflammatory causes: 1) Orbital cellulitis 2) Panophthalmitis

3) Dacryoadenitis 4) Pseudo-tumour

II) Cysts and tumours of orbit :

1) Dermoid cyst , parasitic cyst 2) Benign tumour-haemangioma 3) Malignant tumour – rhabdomyosarcoma , lympho- sarcoma, adenocarcinoma of lacrimal gland. 4) Tumour of optic nerve-glioma 5) Tumours extending from the eye ball – retinoblastoma, malignant melanoma of choroid. 6) Tumours extending from the cranium - meningioma of sphenoid ridge. 7) Tumours extending from paranasal sinuses – like maxillary antrum, and from nasopharynx. 8) Metastases from carcinoma breast, cervix, thyroid.

III) Traumatic 1) Retrobulbar haemorrhage IV) Vascular 1) Varicosity of orbital veins – causes intermittent proptosis. 2) Carotico cavernous fistula

Causes of bilateral proptosis: 1) Endocrine exophthalmos – both thyrotoxic and thyrotrophic. 2)Cavernous sinus thrombosis. 3) Leukaemia 4) Developmental anomalies of the skull and orbit as in oxycephaly. 5) Hand – Schuller Christian disease.

Causes of pulsatng proptosis:

1) Carotico – cavervous fistula – there is communication between the internal carotid artery and cavernous sinus. 2) Von – Reckling-hausen`s disease or neurofibromatosis: due to erosion of the roof of the orbit the cerebral pulsations are transmitted to the orbit.

ENDOCRINE EXOPHTHALMOS :

Graves` disease : It is well recognised that exophthalmos with the associated ocular manifestations and the general signs of hyperthyroidism may appear together or separately or vary independently. They can be considered as 2 aspects of one disorder – Graves` disease : 1) Hyperthyroidism or the general thyrotoxic component. 2) Ophthalmic form which may be a) Thyrotoxic exophthalmos b) Thyrotrophic exophthalmos.

Graves` disease

Etiology : 1) Hyperthyroidism is caused by an increase in the circulating level of thyroid hormone. a) Auto – immune disease : LATS may be an antibody to some thyroid antigen and the reaction with the latter may trigger of the thyroid over activity. b) Genetic factor 2) Ophthalmic features : The ocular manifestation do not respond satisfactorily to antithyroid drugs, radioactive iodine or thyroidectomy like the general features of hyperthyroidism.

Cross reaction between thyroid and eye muscle antigens with subsequent infiltration by lymphocytes and inflammatory edema is believed to be responsible for exophthalmos.

Thyrotoxic exophthalmos thyrotrophic

or progressive exophthalmos or Malignant exophthalmos exophthalmos

1) most commonly seen in . ..Most commonly seen in hyperthyroid patients euthyroid (normal thyroid) patient.

2) lid retraction due to… …. lid retraction seen ina) overaction of L.P.S initial stage .later this (levator palpebrae superioris) is replaced by sewllingb) overaction of Muller's of eye lids and even muscle. Ptosis. Rim of sclera seen above The cornea ,it becomes wider As the eyes are depressed (lid lag) Von Graefe's sign.

3) no chemosis of conjunctiva ...chemosis of conjunctiva.

4) exophthalmos mild or …severe and asymmetrical moderate symmetrical and irreducible on pressure. reducible on pressure.

5) ophthalmoplegia slight ….external ophthalmoplegia Weakness of convergence may occure. (Mobius sign) .

6) Fundus-normal . …May show papilloedema, Optic atrophy.

Treatment :

• Hyperthyroidism1. Medical – carbimazole , methyl or propyl

thiouracil2. Radioactive iodine.3. Surgical –subtotal thyroidectomy

• Ocular features1. 0,7% methyl cellulose drops to protect the

cornea2. Guanethidine (adrenergic blocking agent)

drops3. Lateral tarsorrhaphy in case of lagophthalmos

to protect the cornea from exposure keratitis.4. Radiotherapy to orbit.5. Systemic cortico steroids in some cases of

malignant exophthalmos.

Enophthalmos

Abnormal retraction of the eye ball is called Enophthalmos . it is rare.Causes of Enophthalmos:blow out fracture of orbithorner's syndrome due to paralysis of cervical sympathetic.Duane's retraction syndrome due to muscular facial anomalies of lateral and medial recti.

Enophthalmos