What makes an eye blind

Doctor's letter : Retinal detachment

EXPLANATION The retina is indispensable for seeing: Here the incident light is bundled and creates an image that is transmitted to the brain via the optic nerve. If the retina becomes detached from the inner wall of the eye, sensory cells die because they are then no longer adequately supplied with food and oxygen. Then it is important to reattach the retina as soon as possible, because this ophthalmological emergency leads to blindness if left untreated.

Every year around 30,000 people in Germany have to go to hospital to have a retinal detachment or tear treated there. The vast majority of patients are over 50 years of age.

SYMPTOMS "When the retina is detached, patients often perceive lightning bolts, shadows or even swirling spots in front of their eyes that are reminiscent of a swarm of mosquitoes or soot rain," says Joachim Wachtlin, chief doctor of the eye department at the Sankt Gertrauden Hospital in Wilmersdorf.

If the retina is detached at the point of sharpest vision (macula), humans can only distinguish between light and dark images. As a rule, patients already complain of deficits in their visual field.

Causes Tiny holes in the retina that almost completely line the inner wall of the eye can cause the retina to peel off. Often these holes are less than a millimeter in size. They arise when the vitreous humor, a gelatinous substance that fills the eyeball, pulls away from the retina. The resulting pull on the retina can cause tears and holes. Eye water, a liquid that circulates in the eye, can collect under the damaged points and thus push the overlying retina away from the inner wall of the eye.

Especially nearsighted people with a power of more than minus three diopters are at risk because their retina is thinner than that of other people. The sensitive tissue can also tear from bruises from the outside - for example when footballs or champagne corks pop unchecked on the eye.

In addition to injured and nearsighted people, diabetics also suffer more retinal damage than other people. Because their blood vessels tend to grow uncontrollably into the vitreous humor. When these pathological vessels shrink, scars can occur, which in turn can lift the retina, which only adheres slightly to the inner wall of the eye, from the inner wall of the eye or tear holes in it.

DIAGNOSISThe ophthalmologist diagnoses the disease by examining the fundus. He must clarify whether the point of sharpest vision on the retina, the macula, is affected by the detachment or not. To do this, the ophthalmologist looks deep into the patient's eyes with the help of a bright lamp and a magnifying glass. As a result, on the one hand, the veins in the bright red retina become visible, which supply the tissue with oxygen. On the other hand, the possibly detached areas of the retina are visible, for example in the form of white spots under the healthy bright red.

At these points, the highly sensitive nerve cells can no longer be adequately supplied with blood. "Once sensory cells have died, they no longer grow back," says chief physician Wachtlin. The patient can then go blind.

Depending on the severity, doctors may have to treat the retinal detachment within just a few days after the examination. If the point of sharpest vision has not yet been removed - and thus the chance of a complete restoration of 100 percent visual acuity is greatest - the patient is often operated on within a few hours in order to take advantage of the opportunity.

THERAPYThere are various surgical techniques that are usually performed under general anesthesia. The position and the degree of detachment are decisive. If there are only holes in which the retina has not yet detached, they are usually closed with a laser or a cold pen. This is to prevent the skin from peeling off at all.

If a detachment already exists but not yet advanced, surgeons treat it externally. In doing so, they dent the eye glass body with silicone strips or a seal that is sewn on. As a result, the retina rests against the choroid and continues to be supplied with blood.

In the majority of cases, however, retinal detachment has progressed by the time the symptoms appear. Then the retinal surgeons operate inside the eye. Before treating the retinal detachment, the specialists have to remove the vitreous humor that caused the retinal hole - they call this method a vitrectomy. “The vitreous body is important for development in childhood. But adults don't actually need it any more, ”says chief physician Wachtlin. In old age, the gelatinous mass can even impair vision.

The surgeon follows the procedure with a microscope over the anesthetized patient's diseased eye. This is a matter of millimeters, because he has to work with his instruments in a tiny area. He sits close to the patient's head on an operating chair that is equipped with special armrests for precision work. The patient's eye is opened wide by a metal spring.

During the operation, the assistant's eye is therefore repeatedly moistened with a protective gel to keep it from drying out.

The surgeon uses three small metal tubes about half a millimeter thick that are inserted through the conjunctiva into the eyeball. The surgeon now has access to the inside of the eye through these tubes in order to carry out the operation with special tools. One of these tools, a so-called vitreous cutter, shreds the gelatinous vitreous and sucks it off. The vitreous humor that fills the inner space of the eyes consists of 98 percent water. Each eye contains around milliliters of this substance.

Once the vitreous humor has been removed, the surgeon replaces it with a heavier liquid - doctors call it decalin. It is reminiscent of the consistency of olive oil. This pushes the detached retinal tissue firmly back against the inner wall of the eye.

The surgeon then takes a laser or cold pen with which he freezes the wall of the eye from the outside point by point for seconds to minus 68 degrees. “We use this to specifically trigger inflammation,” says Joachim Wachtlin. The retina will later become scarred without complications. The scars anchored the retina, which can then attach itself again in peace.

At the end of the operation, Wachtlin exchanges the heavy liquid again, this time for a gas mixture that remains in the eye after the operation and can initially cloud the patient's vision. After about two weeks, however, the natural eye water completely replaces the gas mixture - the vision clears up.

This procedure does not always go without complications. There are the following risks during the operation: New retinal holes can appear while the vitreous humor is being removed. Infections, bleeding and increased intraocular pressure are possible after every eye operation, but fortunately very rare, says Joachim Wachtlin.

Problems can arise later even after successful interventions. According to experts, those who have been operated on have an increased risk of having a retinal detachment again. Nevertheless, there is no alternative to surgery and without an operation there is a risk of blindness.

The lenses of the eyes affected by retinal detachment or surgery often became cloudy as a result. A cataract develops (see page 30). Then an artificial lens has to be used, which is why it often makes sense to combine these two operations at the same time, says Wachtlin.

The editors of the magazine "Tagesspiegel Kliniken Berlin 2016" compared the Berlin clinics that treat this disease. For this purpose, the treatment numbers, the hospital recommendations of the outpatient doctors and the patient satisfaction were compiled in clear tables in order to make it easier for the patient to choose a clinic. The magazine costs 12.80 euros and is available in the Tagesspiegel shop.

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