Orbital complications of endoscopic sinus surgery
Functional endoscopic sinus surgery is known to cause various complications involving the orbit due to its proximity to ethmoidal sinus. Orbit is separated from the nasal cavity by a paper thin bone known as lamina papyracea which can be easily breached during endoscopic sinus surgery.
Various orbital complications of FESS include:
Nasolacrimal duct injury
This complication is usually caused due to inadvertent breach to lamina papyracea. This complication can occur irrespective of the status of Periorbita. It should be borne in mind that the risk of orbital hematoma quadruples with penetration of Periorbita. Ecchymosis can occur due to breach involving the lamina papyracea. This occurs irrespective of breach of Periorbita. Orbital hematoma is commonly due to post septal injury. (The septum is defined as the fibrous membrane that divides the eyelid into anterior and posterior chambers). Orbital hemorrhage is commonly caused due to injury to orbital veins lining the lamina papyracea and rarely due to injuries involving anterior and posterior ethmoidal arteries.
Clinically these two types of injuries can be differentiated by the speed at which the signs and symptoms develop. In cases of injury to ethmoidal arteries the symptoms are fairly rapid. In patients with injury to orbital veins the symptoms are rather slow to develop.
Differences between ecchymosis and orbital hematoma:
Ecchymosis is preseptal accumulation of blood. It is commonly caused due to injuries to angular vessels which commonly occur during infiltration. It is darker than orbital hematoma and is more diffuse. It also produces more lid oedema.
Orbital hematoma is actually post septal hematoma. Orbital / post septal hematoma is characterized by conjunctival chemosis, pupillary changes, mydriasis and proptosis. Proptosis signals increased orbital pressure and eventually it could cause damage to optic nerve.
Orbital hematoma is of two types:
Fast hematoma – arterial in nature (due to damage to ethmoidal arteries).
Slow hematoma – Venous in nature (due to damage to orbital veins).
This is a disaster following FESS. It should be considered as a surgery grossly gone wrong. Blindness could be temporary or permanent.
Is caused by increasing orbital pressure due to orbital hematoma. This increased orbital pressure compromises the vascular supply to the optic nerve which is highly sensitive to ischemia. Studies have shown that increased intraocular pressure gradually returns to normal within a couple of hours. Light perception may not return to normal for several more hours. Pupillary reflexes may take up to 2 days to recover.
In blindness caused by retrobulbar and retro orbital hematoma, the retina can tolerate extreme ocular pressures only for a couple of hours. Intervention if any should take place within this time window. This time limit is true only for venous hematoma. If the hematoma is caused due to arterial bleed, this window gets reduced to half an hour. Any damage to the retina and optic nerve becomes irreversible after this window elapses; hence this “light window” should always be borne in mind before embarking on surgical decompression procedures.
Any complication is better prevented than cured. Patients who undergo endoscopic sinus surgery should be carefully examined for evidence of bleeding diathesis, history regarding intake of aspirin should be sought before surgery. Enquiries regarding pre existent eye problems like diabetic retinopathy and glaucoma should be sought prior to surgery. During surgery it is always better to leave the eyes of the patient uncovered so that early orbital changes like proptosis can be appreciated on the table. The tissues removed should always be deposited in a container containing water. If the tissue floats then it should be considered that it is orbital fat unless proved otherwise.
A right handed surgeon is more prone to cause damage to left orbit because of the anatomical illusion on the left side. The left ethmoidal sinuses are actually more medial than appreciated by the right handed surgeon.
Bulb press test:
This test if performed on a regular basis during surgery will avoid damage to orbit. Nurse is asked to press the eye while viewing endoscopically the lateral nasal wall. Any transmitted movement seen in the area indicates breach to lamina papyracea.
Video clipping shows Blub press test being performed.
In arterial hematoma intervention should be immediate. Intravenous mannitol should be started immediately to reduce intraocular pressure. Mannitol is administered in doses of 1-2 g /kg in a 20% infusion. Orbital massage and administration of heavy doses of steroids can be resorted to. Steroids i.e. Dexamethazone should be administered in doses of 1 – 1.5 mg /kg in divided doses in a day. If not successful then endoscopic decompression of orbit / ligation of bleeding vessels / lateral canthotomy may be resorted to.
In cases of venous bleed, the management regimen is pretty same but surgical urgency is not necessary.
Diplopia – (double vision) this is caused by injury to ocular muscles closely related to the paranasal sinuses. These muscles are the medial rectus and the superior oblique. The medial rectus lies lateral to the Periorbita at the centre of lamina papyracea. This muscle is commonly involved during FESS. The superior rectus muscle is placed high in the orbit just lateral to the ethmoidal roof. Anatomically this muscle is difficult to be reached from intranasally. These muscles may suffer direct injury during surgery / or their nerve / blood supply could be disrupted leading on to dysfunction. Powered instruments used in FESS are more prone to injure the medial rectus.
Unintentional injection of local anesthetics in to the orbit via lamina papyracea may cause transient diplopia due to paralysis of medial rectus.
Nasolacrimal duct injury:
The lacrimal sac and duct lie close to ethmoidal sinuses. This is true in 90% of patients. The agger nasi cells lie adjacent to the sac. The ethmoidal sinus and natural ostium of maxillary sinus lie close to the duct. To avoid damage to the sac and duct, the ethmoidal sinus / natural antrostomy should not be opened anterior to the anterior end of the middle turbinate. Patients with naso lacrimal sac / duct injury suffer from epiphora. Commonly it resolves on its own. If spontaneous resolution fails to occur then DCR should be resorted to.