Our eyes help us to recognize the world around us. They also make us aware of danger. Suddenly losing one's vision can be a scary experience.
Sudden blindness requires urgent medical attention as this is often due to a serious condition. If delayed, damage could be irreversible. Early intervention and treatment may help preserve sight and limit worsening of the condition. People describe it as a gradual fall of a gray-black curtain or blurring, fogging or dimming of vision.This can last from a few minutes to hours and sometimes with multiple reoccurrences.
A sudden loss of vision can occur in one or both eyes and can be total or partial.
What Are The Causes of Sudden Vision Loss?
A number of causes have been identified. Some are serious and can lead to permanent loss of sight or even risk to life.
1. Retinal Detachment
The retina is a thin layer lining the back of the eye, which helps us to see clearly. It is made up of cells that help in the transmission of signals to the brain which interprets the information to produce an image.
The retina is described as detached when it pulls away from its attachment in the eye or becomes loose. This is a medical emergency as delayed treatment may result in permanent loss of sight.
Conditions like uncontrolled diabetes and trauma to the eye can lead to this condition.
2. Giant Cell Arteritis (GCA)
In this condition, there is inflammation of the blood vessels which are around the scalp, with the most affected vessel being the artery on the side of the head. It is commonly seen among the elderly and patients usually complain of headaches and pain when chewing.
This condition can also cause blindness in both eyes. Any visual problem in a person with GCA is an indication for prompt medical review and intervention.
3. Dry Eye Disease
A number of people have a problem with tear production. They do not produce enough tears to keep the eyes properly lubricated. This is a serious problem as if left untreated can cause scarring of the cornea, through which light enters the eye, resulting in permanent loss of vision.
4. Vitreous Haemorrhage
Between the lens of the eye and the retina, there is a space called the vitreous humour. This space of filled with a clear gel that provides nutrition for the eye and maintains the pressure within the eye.
Due to certain risks, there may be leakage of blood into this space. This leads to blockage of light entering into the eyes, resulting in blurred vision or the sudden appearance of specks within your visual field.
5. Cataracts
This is when there is cloudiness of the lens of the eyes. In this case, the lens of the eye can no longer receive light into the eyes. It is common in old age. 
Other symptoms a person may experience are a reduction in both close and far vision that cannot be corrected with the use of glasses. People also complain of difficulty reading in low light.
6. Underlying Medical Conditions:
Medical conditions such as stroke could cause sudden loss of vision if it involves the area of the brain that controls eyesight. Serious medical conditions such as brain tumour and increased pressure within the skull can also cause sudden loss of vision.
How Is It Managed?
The sudden loss of one's vision is a medical emergency. To establish the cause, an eye examination, and tests to assess brain function will be done.
Other tests like brain scans and blood tests may also be done to identify the specific cause.
Some of the questions you will be asked to help determine the cause will include your age, when the problem started, how it has changed over time, how many times you have experienced it, whether it is worsened by anything at all, and presence of other symptoms like headache, history of trauma to the eye, or any previous eye surgery.
You will ideally be assessed by an eye specialist. 
The treatment depends on the cause and its severity. It may include eye drops, medications or even surgery.
Summary
Our eyes are important organs with which we see the world around us. Damage to the eye can be serious and irreversible. It is therefore important to see an eye specialist immediately you begin to have visual problems as early treatment will improve the outcome.
