BLURRED VISION, BLINDNESS, AND SCOTOMATA

The causes of blurred vision and blindness can best be recalled with the use of anatomy. If the path of light is followed through the eye to the nervous system, the various components of the eye and nervous system that may be involved may be considered in terms of the common diseases that may affect them.

Conjunctiva. Chemical, allergic, and infectious conjunctivitis may cause blurred vision, but it rarely causes blindness. A pterygium may grow across the cornea and impair vision. Trachoma may cause blindness if left untreated.
Cornea. Foreign bodies, keratitis, herpes ulcers, and keratoconus may cause blurred vision and blindness. Congenital syphilis forms an extensive progressive interstitial keratitis. Trachoma may cause corneal ulcers and blurred vision.
Canal of Schlemm. At the angle of the iris and cornea, the canal of Schlemm prompts the recall of glaucoma because obstruction of this area figures so prominently in the pathophysiology.
Iris. Iritis from sarcoid, tuberculosis, histoplasmosis, and other causes is considered here. Iridocyclitis occurs when both the lens and iris are involved.
Lens. The two most common causes of blurred vision, cataracts and refractive errors, are considered here. Cataracts may result from diabetes, myotonic dystrophy, galactosemia, and many systemic diseases. They are also congenital and senile, posttraumatic, and associated with various mental deficiency states. Refractive errors include myopia, hyperopia, and astigmatism. These are usually correctable.
Vitreous humor. Hemorrhages of the vitreous and precipitation of triglycerides (lipemia retinalis) may cause blurred vision.
Retina. Chorioretinitis causes blurred vision and blindness and may result from syphilis, tuberculosis, toxoplasmosis, retinitis pigmentosa, and proliferative retinitis in diabetes mellitus. Retinal detachment may result from all the above. Retinal hemorrhages, exudates of hypertension, diabetes, lupus erythematosus, aplastic anemia, and subacute bacterial endocarditis are all possible causes of blurred vision and blindness.
Retinal artery. Occlusion of the retinal artery is a prominent cause of blurred vision or blindness in older people. Emboli, thrombi, and vasculitis secondary to temporal arteritis are all possible causes of the occlusion. Migraine and birth control pills should be considered, and migraine, in particular, should be a prominent consideration in scintillating scotomata.
Retinal vein. A retinal vein thrombosis is a possibility here. Following the course of the vein, however, one encounters the cavernous sinus, and a thrombosis here may lead to bilateral blurred vision and blindness.
Optic nerve. Papilledema, optic neuritis, and optic atrophy are the most important conditions to consider. The papilledema is usually due to an intracranial space-occupying lesion, but hypertension and benign intracranial hypertension need attention in the differential. Optic neuritis requires the consideration of multiple sclerosis, neurosyphilis, tuberculosis, diabetes mellitus, sinusitis, and lead poisoning. Optic atrophy should suggest syphilis, methyl alcohol poisoning, hereditary optic atrophy, Foster Kennedy syndrome (frontal lobe tumors), and various congenital anomalies. It may be secondary to diseases of the retina. The optic nerve may be severed by an orbital fracture.
Optic chiasma. Pituitary tumors, sphenoid ridge meningiomas, colloid cysts of the third ventricle, aneurysms, and cavernous sinus thrombosis are possible causes. Syphilitic or tuberculosis meningitis may also involve the chiasma, as may the spread of a Schmincke tumor from the nasopharynx. Basilar skull fractures infrequently involve the chiasma.
Optic tract, optic radiations, and occipital cortex. Intracranial hematomas, cerebral thrombi or emboli, transient ischemic attacks (TIAs), aneurysms, cerebral tumors, and abscesses may involve these structures. Certain forms of acute and chronic encephalitis may also involve these areas, causing blurred vision and blindness. Cortical blindness may result from an occlusion of both posterior cerebral arteries at their origin from the basilar artery.


BLURRED VISION, BLINDNESS, AND SCOTOMATA


BLURRED VISION, BLINDNESS, AND SCOTOMATA

Diagnosis
A careful eye examination with magnification and fluorescence to rule out a foreign body and ulcers is essential in the acute case of blurred vision. Ophthalmoscopic examination may reveal optic neuritis or a retinal vein thrombosis. Visual field examination by confrontation may reveal a field defect. If these test results are negative, ocular tension should be checked to rule out glaucoma. A history of migraine, the use of birth control, and alcohol intake must be investigated. If there is headache on the side of the lesion, a sedimentation rate is done, steroids should probably be started immediately, and referral to a neurologist made promptly in case temporal arteritis is possible, especially in the aged. Otherwise, referral to an ophthalmologist is necessary. The ophthalmologist will perform visual field examinations with perimetry, a slit lamp examination, and look for refractive errors. If other neurologic findings are present, a CT scan, skull x-ray film, and spinal tap may be indicated. A neurologic consultant can determine this.

Other Useful Tests

VDRL test (syphilis)
Toxicology screen (drug abuse)
Tuberculin test
Histoplasmosis skin test
Serology for histoplasmosis
Serology for toxoplasmosis
Kveim test (sarcoidosis)
MRI (brain tumor)
Visual evoked potentials (multiple sclerosis)
ANA (collagen disease)
Pituitary function studies
Four-vessel cerebral angiography