Posterior Segment Damage In Contusion Eye Injury

Damage to the posterior segment may initially be obscured from direct view by a hyphaema. The damage that may occur to the retina after contusion includes the following:

1. Oedma, macula cysts and holes, necrosis, atrophic retinal changes;
2. Vascular changes~hemorrhages (embolism, thrombosis, aneurysm);
3. Tears of the choroid and retina;
4. Retinal detachment.

Oedema, cysts holes and necrosis

The retina may appear milky-white within a few hours of the trauma and vision will be reduced. Commotio retinae is the term used to describe oedema of the retina; it is transient and reversible. The oedema usually subsides within four days and vision returns to normal.

In some cases vision may be permanently impaired due to the development of pigmentary changes at the macula or to the formation of a macula cyst or hole. In severe injuries intraretinal hemorrhages or hemorrhages into the anterior vitreous from the pars plana region may occur.

Vascular changes

Eyes with pathologically altered blood vessels, e.g. with hypertension, arteriosclerosis or diabetes, are particularly vulnerable to hemorrhages. These hemorrhages may be retinal, subretinal, preretinal or into the vitreous. They may cause a sudden and profound loss of vision and leave the site of retinal pathology obscured from view.

Tears

Although the choroid is firmly attached to the sclera, choroidal tears are common and generally occur between the disc and macula or temporal to the macula. They are cresentic, vertical and of variable length; they may be single or multiple. Hemorrhages into the choroid, subretinal space or the retina itself may occur after such tears. These hemorrhages are usually absorbed, leaving yellowish grey lesions in the choroid. The tears affect vision only if they are between the disc and macula. Choroidal detachment does not occur unless trauma is combined with decreased intra-ocular pressure. This allows fluid to pass into the suprachoroidal space, facilitating the detachment.

Recommended: Eye Structures Involved In Contusion Ocular Injury

Retinal detachment

This is the separation of the retina from the pigment epithelium, which may occur gradually or suddenly. In cases of a gradual detachment, the individual may be unaware of the condition but such symptoms as floaters and photopsia (light flashes) due to vitreous traction on the retina may be experienced. Typically, if the retinal detachment occurs shortly after trauma, a peripheral retinal tear is found, frequently in the upper temporal region. People with predisposed factors, such as myopia, peripheral retinal degeneration and aphakia, where there are areas of retinal weakness, are more prone to retinal tears and hence detachments.

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Nervous Supply

The innervation to the eye may be affected after a contusion injury. Contusion of the infra-orbital nerve will lead to decreased sensitivity or anesthesia of the skin in the area of distribution of the nerve. The infra-orbital nerve is damaged most frequently after a sharp blow.

The innervation to the extra-ocular muscles, which are responsible for eye movements, may also be affected. Horizontal double vision may occur due to sixth cranial nerve damage but fortunately recovery is complete in most cases. If the fourth trochlear nerve is involved it gives rise to vertical double vision. 

Trauma to third cranial nerve may result in mydriasis, ptosis, double vision, lack of addiction and loss of accommodation. Traumatic hyperopia, due to the loss of accommodation, may be temporary or permanent. Myopic changes, which occur more commonly, are generally due to ciliary muscle spasm caused by irritation to the nerve or the muscle fibres. Myopic shifts in the order of 1-6D may occur but in most cases they are transient and the refraction returns to normal within about a month.