Sudden Loss of Vision in One Eye or Both – Why Does It Happen?

Sudden loss of vision in one eye or both represents a huge problem that should not be ignored under any circumstances. See why.

Without a doubt, sight is one of the most used senses. Therefore, vision loss represents a serious problem that drastically changes life. Do you want to know what are the causes and symptoms of this problem? Keep reading and we will explain it to you.

First of all, for there to be a decrease in visual acuity, any of the means involved must be affected. In this sense, partial or total blindness will occur when there is a problem with the cornea, the lens, the retina or the optic nerve.

Causes of sudden loss of vision in one eye or both

When we refer to partial blindness we are talking about those people who, despite having a considerable loss of their vision, are still able to distinguish certain shapes, lights and shadows. The sudden loss of vision in one eye or both can mean partial blindness. In this way, there is no complete loss of vision, but its use is difficult.

Depending on its origin, this type of blindness can be chronic or acute. Let’s look at the most common causes of a sudden loss of vision in one eye or both.

Cornea lesions

Any injury to the surface of a tissue will generate a scar and the cornea is no exception. This scar eliminates the transparency of the cornea, which prevents light from reaching the retina, causing a decrease in visual acuity.

Injuries to the cornea can have a variety of origins, from severe infections to direct trauma. Any stimulus that can damage the cells of the same to a considerable depth will be able to generate partial blindness.

The visual field affected will vary according to the location and size of the scar. In this sense, there is no specific presentation pattern. However, the following symptoms may occur:

  • Blurred vision: or an area of ​​black or cloudy vision.
  • Pain: itchy in the affected eye.
  • Crying eyes.
  • Red spots.
  • Gritty sensation: like having something embedded in the eye.


Another of the most common causes of partial blindness is cataracts. These are opacities in the lens, which is the eye’s main means of refraction. This opacity prevents the light from hitting the retina in an adequate way, thus generating partial loss of vision.

In most cases they appear due to degeneration of the lens or due to some injury to it. According to various studies, cataracts represent the cause of 47.9% of blindness in older adults.

Among the main symptoms reported by people with cataracts are blurred, cloudy or cloudy vision, faded colors and the inability to see well at night. They also report lights that look very bright or have a halo around them, as well as double vision.

Retinal problems

The retina is the part of the eye responsible for translating the light signals directed by the lens for the brain to process. So any injury to it can cause loss of vision.

In most cases, retinal problems are caused by faulty capillaries, which will leak fluid into the tissue. In this way, among the most common causes we can find the following:

  • Diabetic retinopathy.
  • Blockage of arteries or veins in the eye.
  • Tear of the retina.
  • Partial retinal detachment.
  • Hypertensive retinopathy.

On the other hand, there is another type of retinal injury that is not related to the presence of fluids. An example of this is macular degeneration, in which the center of the retina begins to deteriorate, causing blurred vision or a blind spot in the visual field.

Finally, various infections by fungi, parasites or bacteria can seriously injure it. Such is the case of ocular toxoplasmosis, very common in immunosuppressed people.

Optic nerve problems

The optic nerve is in charge of transmitting all the information captured by the retina to the brain, which is why it is also an essential part of vision. In general, problems related to this structure affect one or more visual fields.

In most cases, they happen due to glaucoma. This is a common disease that generates an increase in intraocular pressure that affects the nerve. In this sense, it is unable to transmit signals adequately, making vision difficult.

However, there is another series of conditions that can cause partial blindness affecting the optic nerve, such is the case of optic neuritis or inflammation of the nerve. Furthermore, we indirectly have the effect of cerebral vascular events (CVD) or tumors in the central nervous system.

It is important to clarify that the symptoms of optic nerve injuries can vary depending on their etiology. However, people often have rapid vision loss, red saturation in one or more visual fields, double vision, and eye pain.

Causes of total blindness

On the other hand, we have total blindness. This occurs when a person is not able to distinguish between lights and shadows. The situations that can cause total loss of vision may be the same as those that cause partial blindness, however, at this point they are in their terminal stage.

Trauma or serious injury

When the trauma is very serious and affects the cornea in its entirety, total blindness can be generated. One of the most common causes of these types of injuries is chemical burns.

However, not only injuries to the cornea are capable of affecting visual acuity. A trauma to the head or eyeball, whether penetrating or blunt, can damage the optic nerve and retina.

Complete retinal detachment

We have mentioned partial retinal detachment as a cause of partial blindness. However, if you don’t treat it in time, it can progress and become a total detachment, preventing vision.

In most cases, it occurs due to the presence of fluid in the back of the retina. This will separate the tissue from the eyeball, interrupting the blood supply, causing ischemia and death of the area.

Although it may be asymptomatic and painless at first, some people may have the following symptoms:

  • Appearance of spots in sight.
  • Sudden lights in all visual fields.
  • Blurry vision.
  • Abrupt loss of peripheral vision and then central vision.

End-stage diabetic retinopathy

Diabetic retinopathy is one of the complications of diabetes mellitus. It affects the capillaries of the retina, which will filter liquid into it and favor the deposit of substances. Also, some healthy blood vessels may become clogged.

In the initial stages of the disease, partial blindness can be generated, however, if it is allowed to progress, it causes total loss of vision. This is because in the last stage, new blood vessels with very thin walls are generated to try to irrigate the tissue adequately. These new capillaries are prone to rupture spontaneously and cause retinal hemorrhage


A rare cause of vision loss is endophthalmitis. It is an infection inside the eye and you should always consider it a medical emergency.

This infection is due to, in large part, the entry of external microorganisms after eye surgery or injury. However, it can also be caused by an internal septic infection that has affected the eye.

Among the symptoms that people with endophthalmitis present, severe eye pain with redness of the eyes and the appearance of a yellow, white or purulent discharge inside the eyeball stand out. There’s also inflammation of the eyelids.

Vascular occlusion

All blood vessels in the body are prone to clogging. When those of the retina or optic nerve are occluded, there may be painless loss of vision.

In the event that the affected blood vessel is the central retinal artery or the optic nerve artery, there will be an inadequate blood supply to the tissue. This will cause insufficient supply of oxygen, so it could be infarcted and permanently damaged.

On the other hand, when there’s damage to the central vein of the retina, there will not be adequate blood drainage. This will cause waterlogging, that is, an excessive accumulation of fluids in the tissue, which will lead to blindness.

When to see a doctor for vision loss?

Vision loss, whether in whole or in part, should always be considered a medical emergency. On many occasions, it may not be accompanied by pain, although this does not indicate that it is less serious and, therefore, it should never be ignored.

For this reason, it is imperative to go to a specialist as soon as possible so that he or she performs the relevant tests and arrives at an accurate diagnosis. Many of the causes only allow a short period of time before the damage is irreversible.

It is important to clarify that when you cannot reverse vision loss, you must change your lifestyle. Fortunately, today there are many ways that visually impaired people can carry out their daily activities without inconvenience.

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