Sudden loss of vision may indicate stroke

Has your vision blurred off late? Are you ignoring it thinking it might be a temporary inconvenience? Think again. A person experiences a mini stroke also known as transient ischaemic stroke, before suffering from a stroke. The symptoms and the underlying causes are same in both cases, but not permanent in case of TIA, which disappears in few minutes or hours. The patient experiences loss of vision in one eye after TIA, and can gradually lose vision completely.

Vision loss happens when the blood vessel supplying oxygenated blood from the eyes and brain gets blocked. A blockage in the vessel can initially manifest as transient or complete vision loss. The other disorders that can accompany are damage to the eye nerve and a part of the brain that processes the eye signals, thus resulting in stroke.

Symptoms

The nerve fibres in the eyes cross over each other, which means that the left eye is controlled by the right side of the brain and vice-versa. Any loss of vision in the left side of the visual field of each eye is an indication of stroke or lesion on the right side of the brain.

Multiple patterns of visual field loss are a signal of multiple strokes and can affect central, peripheral or both vision. The following symptoms with the eyesight and vision are sufficient to confirm an upcoming stroke:

* Sudden decrease in vision is caused by the damage to the tissues and nerve fibres that transmit signals from the eyes to the brain. As the transmitting distance is longer, the blood flow can be disrupted at any point, causing sudden blurriness or decrease in vision.

* Double vision occurs when the damage is caused to the nerves that are responsible for movement and alignment of the eyeballs. This not only lead to vision defects, but also problems in decision making, judgements, logical reasoning and processing complex information.

Let's look at the types of vision loss:

Hemianopia: Here, half of your line of vision is affected and you may also experiences blindness. Decrease in the ability to see properly in the right vision field is an indication of stroke.

Quadrantanopia: Here, the loss of vision is limited to quarter of the visual field.

Scotoma: The area of vision loss is smaller compared to the other two, but the spotty vision signals stroke on the opposite side of the brain.

Tunnel vision: This is an indication of a bilateral stroke affecting both the halves of the visual fields. The connected nearby areas in the cortex disrupts the blood supply causing loss in peripheral vision.

Treatment

Every minute that the stroke goes untreated, the average patient loses 1.9 million neurons. Golden hour of stroke is the first six hours. Medications prevent the extension of the blood clot in the area, taken along with blood thinners. But for some patients whose condition keeps deteriorating, an emergency procedure to open up the blood vessel is required to restore the blood flow.

Dr Vipul Gupta
(The author is director, Neurointervention, Artemis - Agrim Institute of Neurosciences)