Sudden Visual Loss - Diagnosis and Treatment

What Is Sudden Visual Loss?

Vision loss is an extremely delicate situation. At one point, the vision is completely normal, and the next second, the individual loses visual input. Individuals get scared and undirectional in any such events, and often ophthalmologists diagnose this as a non-ophthalmologic reason, precipitating from some other underlying conditions. So determining the etiology becomes the prime goal if one wishes to effectively treat, remit, and prevent remission of sudden blindness. This sudden onset of vision loss may be unilateral or bilateral. Binocular vision loss is usually of cerebral origin and respects the vertical midline. Vision loss due to an embolus lasts for a few seconds, whereas visual loss lasting beyond 15 minutes is rare and is usually associated with migraines.

Who Is Susceptible to Sudden Visual Loss?

Transient or sudden loss of vision is reported in about 14 people per 100,000 individuals per annum. The incidence is of a benign nature in individuals below 45 years, with most events being associated with vasospastic (blood flow limitation) or migraines. This vision obstruction is always associated with severe occlusive disorders of the ICA (internal carotid artery), aortic arch, and vertebral occlusion in association with occipital lobe ischemia. Patients with transient blindness and ICA often have other underlying systemic health conditions like atherosclerosis, coronary and peripheral vascular diseases, debilitating history of smoking, hypercholesterolemia (lipid imbalance), and hypertension (increased blood pressure). On the racial predilection front, Black, Chinese, and Japanese report a higher incidence of intracranial occlusive diseases, which can translate to higher vision loss. Sudden vision loss exists with a strong male predilection by a factor of two over females with severe ICA.

What Is the Cause of Sudden Vision Loss?

Sudden vision loss may be caused either due to ocular trauma, vascular occlusion, or problems arising from the retina. Some of the causes of sudden vision loss are:

• Trauma to the eye.

• Blockage to the blood flow to and from the retina.

• Retinal artery occlusion (blockage of the artery of the eye).

• Retinal vein occlusion ((blockage of the vein of the eye).

• Retinal detachment (loss of attachment of the retina from its position).

• Vascular inflammation of the ophthalmic blood vessels.

• Inflammation of the optic nerve.

• Blockage of blood flow to the occipital lobe of the brain.

• Stroke.

• Migraines.

• Embolism.

• Endothelial decompensation (corneal edema)

• Hydrops (stromal edema).

• Giant cell arteritis (inflammation of artery lining).

• Idiopathic causes (unknown causes).

• Fibromuscular dysplasia (narrowing of vessels without inflammation or atherosclerosis).

• Hypercoagulable states (tendency to clot).

Basically, from the reported causes of sudden vision loss, it is clear that the condition arises from ischemia resulting from reduced oxygen and nutrient perfusion. This can result in transient or permanent damage to vision, corresponding to the degree of ischemia.

Some of the variations of ischemia causing vision loss are:

• Transient Visual Obscurations (TVO): These are episodes of visual disturbances lasting for just a few seconds and are closely related to papilledema (optic disc swelling) and increased intracranial pressure.

• Amaurosis Fugax: Short-lived transient attacks of monocular partial or complete loss of vision that can last anywhere between a few seconds to a few minutes.

• Transient Monocular Visual Loss (TMVL) or Transient Monocular Blindness (TMB): This visual loss lasts for a longer period of time (for several minutes).

• Transient Bilateral Visual Loss (TBVL): These episodes of visual loss affect unilaterally or bilaterally, or both cerebral hemispheres.

• Ocular Infarction: This results in permanent loss of vision due to the persistence of ischemia, causing extensive ocular damage.

Transient loss of vision may also result from an embolus that originates from the heart, carotid artery, aorta, or peripheral circulation. Transient monocular vision loss may also arise from arteritis (artery wall inflammation) and also cause end-organ damage.

Transient monocular visual loss may be classified based on origin or pathogenesis:

1. Type 1: Loss of vision in one eye for a few seconds to minutes, followed by complete recovery. This is probably caused due to a dislodged clot (emboli) and ulcerations in the ICA.

2. Type 2: Loss of vision due to hemodynamic instability, occlusion, and low-flow lesions in the ICAs or ophthalmic arteries. Less frequent, more severe, and longer than type 1 with gradual recovery.

3. Type 3: Hypothesized to be occurring due to vasoconstriction or vasospasm (narrowing of the blood vessels in the body or the brain, respectively).

How to Diagnose Sudden Visual Loss?

To accurately differentiate from the differentials, the patients must be questioned thoroughly to obtain a detailed clinical history. The information should include the following:

• Lateralization (monocular or binocular vision loss).

• Horizontal or vertical midline respect.

• Timing and duration of visual loss.

• The pattern of visual loss (altitudinal, diffuse, constricting visual field).

• Provoking factors.

• Associated symptoms like photophobia, headache, or pain.

• History of previous episodes.

• History of any trauma.

• Past history of the eye, including the history of ophthalmic surgery.

The patient must also be enquired about any diagnosed morbidities like atrial fibrillation, thromboembolic disease, hypertension, hypercholesterolemia, diabetes mellitus, collagen vascular disease, hematological disorders, cancer, nicotine use, or drug use.

The ophthalmologist should do an extensive comprehensive eye examination approaching from the anterior orbit to the posterior skull. Some of the parameters of examination that must be included in the study are:

• Best corrected distance visual acuity.

• The reaction of the pupil.

• Intraocular pressure.

• Gonioscopy (assessment of the angle of the eye).

• Color vision.

• Confrontational visual field (to assess for peripheral field visual field cut).

• Extraocular motility.

• Conjunctival injection.

• Conjunctival inflammation.

• Corneal sensation.

• Corneal edema.

• Media opacities.

• Fundus examination to assess optic nerve swelling.

How to Treat Sudden Visual Loss?

The treatment may be clubbed under medical, surgical, and follow-up care.

• Medical Care: Medical care is directed to mitigate the diagnosed etiology or underlying condition. In the case of giant cell arteritis, Prednisone followed by temporal artery biopsy must be performed. With optic neuritis, steroids are prescribed to hasten remission. For arterial occlusions, medical therapy is directed to prevent future ischemic events. Thrombolytics for clot dissolution and other corresponding medications against hypertension, diabetes, and hyperlipidemia should be advised. Drug classes that are usually prescribed include antiplatelet agents, Aspirin, Clopidogrel, or Aspirin-Dipyridamole. Local ophthalmic causes require etiology-directed ophthalmic treatment to prevent further or total visual loss. Glaucomas should be treated with topical intraocular pressure-lowering agents, but the underlying cause must be identified and eliminated.

• Surgical Care: Surgical approaches should be reserved for retinal detachment, globe rupture, and carotid artery stenosis. Carotid endarterectomy is indicated with greater than 70 percent carotid artery stenosis with other risk factors including male gender, age above 75, absence of collaterals on angiography, transient ischaemic attack, vascular disorders, and stenosis between 80 to 94 percent. Central retinal vein occlusion should be surgically managed with radial optic neurotomy, chorioretinal venous anastomosis, vitrectomy, and retinal vein injection with tPA ( tissue plasminogen activator).

• Follow-up Care: Follow-up case consists of regular ophthalmologic consultations and neuroimaging. The prognosis is highly variable and is largely dependent on the nature of the etiology and severity of the symptoms. However, early recognition of the cause and proper therapy can tilt the prognosis balance in favor.

What Is the Differential Diagnosis of Sudden Vision Loss?

• Adult optic neuritis (inflammation of the optic nerve in adults).

• Anterior ischemic optic neuropathy (interruption of the blood flow to the optic nerve head).

• Branch retinal artery occlusion (blockage of the retinal artery branch).

• Branch retinal vein occlusion (blockage of the retinal vein branch).

• Central retinal artery occlusion (blockage of the retinal artery).

• Central retinal vein occlusion (blockage of the retinal vein).

• Childhood optic neuritis (inflammation of the optic nerve in adults).

• Compressive optic neuropathy (compression of the optic nerve).

• Corneal ulcer (ulcers in the cornea).

• Corneal abrasion (abrasion of the cornea).

• Endophthalmitis (inflammation of the intraocular fluids).

• Exudative retinal detachment (fluid accumulation in the subretinal space).

• Giant cell arteritis (inflammation of the arterial lining).

• Acute angle-closure glaucoma (sudden rise of intraocular fluid pressure).

• Globe rupture (trauma causing a momentary increase of the intraocular pressure).

• Hyphema (collection of blood in the anterior chamber of the eye).

• Intraocular foreign body (accidental injury to the eye due to foreign body).

• Leber hereditary optic neuropathy (an inherited form of vision loss).

• Migraine headache (one-sided throbbing headache).

• Papilledema (optic disc swelling).

• Retinal detachment.

Conclusion:

Sudden loss of vision is a symptom of other underlying conditions. Naming the occasional loss and gain of vision as problematic is an understatement, at the very least. Although these episodes do not last more than a few minutes, they are advanced signs of underlying dysfunctions. The only way to prevent the said visual gaps is by taking care of the general health.