Eye Structures Involved In Contusion Ocular Injury

Contusion simply means any mechanical injury resulting in hemorrhage beneath unbroken skin. In the eye, contusion injury may result from a variety of causes, e.g. flying blunt objects (for example a squash ball), falling objects, the individual falling, explosions or compressed air accidents, fluid under pressure escaping from burst pipes, or water jets from fire hoses.

The resultant ocular damage is due to a wave of pressure traversing the fluid content of the eye. As the fluid is incompressible the blow will act as an explosive force in all directions from the centre outwards, resulting in the ocular contents being flung against their outer coat. The globe expands around the equator to take up a vertically oval shape. The effects of contusion on the various structures are numerous and will now be discussed sequentially.

The Eyelids and Orbit

Eyelids~black eye

Fortunately, the eyes have their own natural defense: they are deeply set in bony orbits and have a fast blink reflex. Hence, the eye often escapes damage and the orbits and lids take the force of the blow. This frequently results in the appearance of a 'black eye'. Due to the vascularity and loose connective tissue structure of the lid, oedema and subcutaneous hemorrhages are common and usually occur rapidly after trauma.

Hemorrhages may also spread under the conjunctiva, resulting in the lids being swollen and tightly shut. To examine the eye, the lids may need to be opened forcibly. A 'black eye' may spread to the other eye within 24 hours as a result of subcutaneous blood infiltration. The swelling and discoloration of the skin normally resolve within two weeks.

In more severe cases the hemorrhages may be due to intracranial damage. Such hemorrhages become apparent after 12-24 hours, which is the time it takes for the blood to seep to the eyelids and forehead. This is a serious condition and X-rays must be taken to see whether there are fractures of the orbital bones.

Photo Credit: www.medscape.com

Ptosis

Trauma to the upper lid may cause it to 'droop', which narrows the palpebral aperture. This is known as ptosis and may be caused by the lid being oedematous. In more severe cases there can be damage to the third cranial nerve, which supplies the levator muscle or detachment of the muscle itself; the latter case will require surgery. Occasionally a 'partial protective' ptosis or a tendency for the lid to close will develop if there is an irritant causing discomfort and photophobia.

Ectropion

Damage to the lower lid may result in ectropion, a condition in which the lid margin turns away from the eye. This prevents the tears from draining properly through the puncta. Instead they flow down the cheek (epiphora) and can cause skin sores.

Fractures of the orbit

These can occur directly from a blow to the orbit or indirectly from radiating skull fractures. These injuries may also be associated with other facial fractures, head injuries, or severe lacerations. Not surprisingly, the most common fracture affects the lateral wall of the orbit. The zygomatic bone and arch of the lateral wall may be fractured, resulting in depression of the lateral canthus and flattening of the check bone.

Recommended: Anterior Segment Damage In Contusion Eye Injury

Fractures of the floor of the orbit may occur after a heavy blow and are known as blow-out fractures. The blow increases the intraorbital pressure, which causes the very thin bone of the maxilla to collapse into the maxillary sinus and the orbital contents then prolapse into the antrum. Elevation of the eye will be defective because the tissues surrounding the inferior rectus and inferior oblique muscle become trapped in the fracture.

Double vision will also be present in one or more directions of gaze. The herniation of the orbital contents results in a sinking or recession of the eye within the orbit (enophthalmos) with a narrowing of the palpebral fissure. There will also be loss of feeling on the same side of the face due to damage of the intraorbital nerve. Surgery, if required, should be carried out fairly promptly (within a week or two), before fibrous tissue has a chance to form. It will involve the insertion of a plate over the damaged orbital floor.

Damage to the nasal bone, ethmoidal sinuses and the medial wall is often apparent by the presence of air creptitus. Blowing the nose should be avoided, as air is forced under pressure into the soft tissue of the eyelids and surrounding skin, which results in swelling. As this can provide a route for the spread of infection, a course of systemic antibiotics is usually given.

Fractures of the superior orbital rim generally result in diplopia due to damage of the trochlear of the superior oblique muscle. This damage will be permanent unless there is early repair.

Inferior orbital rim damage is shown by ptosis or ectropion of the lower lid and by anesthesia of infra-orbital nerve distribution. It is often associated with diplopia and hypotropia. Whenever a fracture is suspected, X-rays should be taken.