Causes of blindness

Synonym

Amaurosis

  • On the one hand, childhood is to be mentioned here, since children can injure themselves so badly by sharp and pointed objects while playing or frolicking around that their eyesight cannot be saved despite immediate help from an eye doctor.
  • The second peak in the incidence of eye injuries is in adulthood, as adults can suffer eye injuries with similar consequences either at work (e.g. construction site) or in a car accident. In addition to eyeball piercings by sharp objects, traumatic causes, burns of the eye by acids or alkalis can also lead to blindness. Besides the hobby (e.g. restoration of old furniture), the most common cause of such injuries to the eye is occupational.

Another common cause of blindness is uveitis.

In most cases, the causes lie in an autoimmune reaction, such as those found in rheumatism or ankylosing spondylitis. The symptoms are usually initially photophobia and tears in the eyes, as well as eye pain and protein leakage. In some severe forms of uveitis, the therapeutic measures taken are no longer sufficient and the patient goes blind.

Chronic uveitis is particularly dangerous because it recurs constantly despite treatment. Furthermore, there is also a risk of blindness in the case of retinal detachment described as retinal detachment. Especially patients with high myopia are at risk for a retinal detachment, because the eye, which is growing more and more elongated, exerts a dangerous pull on the retina.

Patients first describe flashes of light and a so-called sooty rain, which either moves into the field of vision from top to bottom or upside down (small black spots). In the case of a retinal detachment, extreme haste is required, as blindness is imminent. Depending on where and in which context the retinal detachment has taken place, the risk of blindness is higher or lower.

Especially at risk are patients whose retina has already detached a long way and parts of the macula are affected. In this case, saving the eyesight is usually no longer possible despite quickly initiated immediate measures. In all other cases, e.g. if the retina has not yet detached completely and the macula is not yet affected, the eyesight can usually be saved.

For this purpose, the vitreous body of the eye is removed and an oil is filled into the eye. With the filling in, the retina reattaches itself to the back of the eye. Patients with oil usually have blurred vision.

The oil must remain in the eye for several weeks before it can be drained. In developing countries there are other causes of blindness. One of these is cataract, which can be corrected in Western countries through routine surgery.

In countries where there is no public health insurance, however, those affected are often unable to pay for the procedure and have to accept increasing lens clouding (almost 100% of patients in old age). If the lens becomes completely cloudy, one speaks of a matur cataract. It is usually noticed by the observer through the grey to white colored lens.

Patients with a matur cataract are by definition blind, although not irreversible, because a cataract operation performed later on restores the patient’s sight. The main causes of blindness are trachoma, onchocerciasis and keratomalacia. Trachoma is an infectious disease caused by the pathogen Chlamydia trachomatis, which is often transmitted by flies.

The infection usually occurs in early childhood. At first, so-called follicles are formed, which grow in size and eventually burst. They empty secretion with the pathogen into the conjunctival sac.

This results in scarring, entropion (the eyelashes are bent inwards and drag along the cornea), which in turn leads to scratching and finally to scarring of the cornea. In addition, the inflammation can lead to excessive tissue proliferation, which then causes a connective tissue plate with numerous vessels to grow over the cornea, which is then called pannus on the eye. Onchocerciasis occurs mostly in tropical countries and is transmitted by Onchocerca volvulus via the Simulium mosquito.

The disease also known as river blindness affects about 50 million people. 1 million of them are blind. After infection, point cloudiness develops in the cornea, always where cells die off.

During the course of the disease, the number of clouding points can increase so much that the patient can no longer recognize anything.Keratomalacia, another cause of blindness in developing countries, is mainly caused by a vitamin A deficiency in the eye. A deficiency of this type leads to night blindness, and in extreme cases to corneal melting. In Asia, about 5-10 million people, mainly children, suffer from visual impairment due to a vitamin A deficiency.

It is important to first identify the cause of the visual impairment. If a vitamin A deficiency is confirmed, the most effective therapy is a substitution of 200,000 IU of vitamin A (injection into the muscle). Eye drops containing vitamin A can also accelerate the recovery process. In the long term, the patients’ nutritional habits must be changed and made more vitamin-rich so that a deficiency condition does not recur, if possible.