Trauma to the eye, which usually is easily diagnosed, varies from a ruptured globe to hyphema, cataract, dislocation of the lens, angle recession, vitreous hemorrhage, retinal detachment, commotio retinae, and choroidal ruptures. All of these conditions can be seen and easily identified by the ophthalmologist. Trauma to the head or eye can also cause loss of vision or field without any of the above-mentioned defects. The diagnosis and management of these cases is more difficult.
The trauma that causes optic nerve disease most commonly is a frontal blow in which the force is concentrated in the area of the optic canal. This has been demonstrated by using holographic interferometry to demonstrate the surface perturbations caused by a frontal bone blow. The cause is obvious when optic canal fractures are seen on the CT image. However, most patients do not show fractures, and another mechanism of visual loss must be postulated. One theory is a vascular one. In the area of the optic canal, there are small penetrating arteries from the ophthalmic artery that enter the nerve at a right angle. The nerve does not lie loosely in the canal but has septal attachments, particularly superiorly. This fixation of the nerve, arteries that enter at right angles, and concentration of frontal traumas to the canal area probably combine to cause the optic nerve damage. These penetrating arteries may rupture, causing ischemia, or they may hemorrhage, causing compression in the limited space of the canal. A greater hemorrhage in the orbit, as we occasionally see after retrobulbar anesthesia, rarely causes any loss of vision, perhaps because the nerve is coiled somewhat, is more mobile, and can be displaced rather than compressed against the bony optic canal.
There is a controversy about how to handle patients with trauma-induced visual loss. Most ophthalmologists treat them conservatively with cautious observation, with or without steroids to reduce the swelling, which may compress the nerve In the canal. Others, like Fukaclo, believe a more aggressive surgical approach, particularly by the transsphenoidal route, is the best mode of treatment. Fukado's series of 750 cases of decompression of the optic nerve head is larger than any other and includes a large number of canal fractures. None of his patients with immediate blindness improved with conservative treatment; 28 of these were then surgically treated, and 7 improved. His successful visual results with this operation have not been shared by others with equal surgical experience: Another frequent consideration in these cases is the general neurologic condition of the patient and the associated trauma. Many of these cases involve vehicular accidents or severe blows on the head from a fall or falling objects. These patients may be in an intensive care unit with multiple services looking after multiple problems, ranging from possible ruptured viscus, unconsciousness, and other fractures. Although a transsphenoidal surgical approach is less traumatic than an intracranial approach, these are not the best patients for general anesthesia. This is particularly true when the visual results of surgery are still open to question. I prefer to observe and treat such patients with large doses of steroids, which will also help with any other intracranial swelling.
Some trauma patients appear to have full vision initially and then lose it sometime afterward. Admittedly, assessing the degree of vision is not easily done during the initial management of a patient with life-threatening problems. Nonetheless, some trauma patients experience a loss of vision that appeared to be present at the initial examination, a few hours or days after their injury. At this point, one thinks of compression by swelling or hemorrhage, which could be relieved by unroofing the canal and decompressing the nerve. This scenario suggests that the nerve was not irretrievably damaged at the initial injury and can be retrieved by prompt surgical intervention. This conclusion is still an open question, and all the diagnostic skills at hand are required to decide which patients have the greatest chance of a surgical success.
Another form of trauma that we have seen is chiropractic manipulation. Frumkin described four cases of Wallenberg syndrome from chiropractic neck manipulation. We have seen several Homer syndromes and one case of a carotid dissection with subsequent embolic infarction of the ipsilateral optic nerve.
Recent studies by Spoor suggest that megadose use of steroids makes a significant difference in the recovery. This is based on the work of Braughler, who postulated different mechanisms for megadose steroids and regular-dose steroids. The results are also better the sooner the steroids are instituted after the traumatic incident. This makes sense, since prolonged compression of the nerve by edema and associated vascular compression in ischemia will only increase nerve damage. Spoor's series showed improvement in 70% of 21 patients; an impressive number, even if some would have improved without therapy. Most series have a very dismal outlook for any improvement in untreated cases. Lessell's review in 1989 can attest to that fact. Of 25 patients, only 5 spontaneously improved, and 2 of 6 patients with no light perception had minimal improvement; 4 were treated with a routine dose of steroids, and 1 improved; 4 were treated with steroids and optic canal decompression, and 3 improved. In a more recent study by Joseph, 11 of 14 patients treated with dexamethasone and a transethmoidsphenoid decompression of the optic canal improved, with no operative morbidity or mortality.
Chronic increased intracranial pressure is a well-known cause of optic atrophy and vision loss. This sequela can occur with chronic pressure resulting from pseudotumor cerebri more frequently than was previously suspected. It also can occur with a failed shunt put in place for that problem or others, such as hydrocephalus. Although the loss of field and vision often is slow, it can also be abrupt, so cautious observation of chronic increased intracranial pressure is not always safe. Rapid loss may be due to interference of blood flow to the optic nerve and the occipital lobe or to herniation of the parahippocampal gyrus through the tentorial notch with damage to the lateral geniculate body.
If the involvement of the visual system is anterior (e.g., in the optic nerve), then there may be no changes in the sensorium to guide clinical judgment. If the involvement is posterior with compression of the posterior cerebral artery and ischemia to the occipital cortex, it may cause a decrease in vision and/or fields. The same area of compression may also extend caudally, affecting the reticular formation and midbrain and resulting in changes in the sensorium.
Constant and cautious observation is required in managing patients with chronic increased intracranial pressure and shunts. No examination of these patients is the final one.
Central Serous Retinopathy
Central serous retinopathy is an idiopathic detachment of the sensory layer of the retina. A casual observer may miss the retinal findings and diagnose optic nerve disease. The diagnosis is best made with use of the indirect ophthalmoscope and fundus contact lens. A fluorescein angiogram can then confirm the diagnosis. An increase in VEP latency and the presence of an APD are usually associated with optic nerve dysfunction. However, Folk and his coworkers have demonstrated that patients with central serous retinopathy may also have an increase in VEP latency, color defects, and a relative afferent pupillary defect. The fundus appearance should serve as adequate evidence to differentiate optic nerve disease and central serous retinopathy. However, a resolved case of each may leave some doubt as to the correct diagnosis. Defects of color vision and VEP latency may remain after both entities resolve. The presence of an APD is a much more likely residual of optic nerve disease than of central serous retinopathy. The relationship between final visual acuity and the VEP latency is much more significant for optic nerve disease than central serous retinopathy.
Paget's disease is a progressive disease of the skeletal system in adults. Roentgenograms of affected individuals typically have a cotton-wool appearance because of irregular laying down of abnormal bone and resorption of normal bone. The more activity there is in this disease, the more positive is the scan, because of increased uptake in the hyperactive bone. The usual cause of decreased vision in Paget's disease is optic nerve compression in the canal. Another cause that has been postulated is a steal phenomenon of the nearby neural structures such as the optic nerve or eighth nerve from the hypervascular bone. Other ocular signs with this disease are exophthalmus, angioid streaks, glaucoma, corneal opacities, and extraocular muscle palsies.
The medical treatment of Paget's disease is administration of calcitonin, which decreases the vascularity and is aimed at decreasing the steal phenomenon. Surgical treatment is directed toward relieving direct pressure on the optic nerve.