The retina is a thin membrane that lines the bottom of the eyeball and is made up of photosensitive nerve cells: cones and rods:
- The cones are located in the centre of the retina and are responsible for day vision, and visual acuity and allow us to see colours.
- The rods are, for their part, located on the periphery. They are more numerous than cones and much more sensitive to light. They are what allow us to see in the dark. It is also thanks to them that we manage to detect the movements around us.
The stimulation of these photoreceptor cells by light will generate an electric current called a nerve impulse. The latter will be transmitted to the brain via the optic nerve located behind the retina; it is its extension. Arriving at the level of the centre of vision, the brain will analyze it.
According to God Service Eye Clinic Various retinal diseases develop due to retinal disorders and can be severe in some cases, some may even lead to complete blindness as discussed below.
What are retinal diseases?
The main retinal diseases are retinal detachment, age-related macular degeneration, diabetic retinopathy, and retinal vein or artery occlusions. In addition, retinal inflammation and injury may occur.
In children, retinopathy of prematurity and retinoblastoma are important. Hereditary macular degeneration and retinal dystrophies are rarer diseases of the retina.
Retinal detachment
In the case of retinal detachment, the layer containing the sensory cells detaches from the retinal pigment epithelium. This condition is rather rare, but it can have serious consequences. Patients can go completely blind if not treated completely.
The most common causes are degenerative changes in the retina and vitreous humour, which cause tears in the retina. Retinal detachment occurs mainly in the elderly and in cases of high myopia. There is also a familial predisposition.
Retinal split
Retinal splitting (retinoschisis) is age-related splitting in the layers of the retina. Preliminary stages of this disease occur in many older people without causing problems. The changes are not normally located in the centre of the retina, so visual acuity is preserved. A retinal split usually does not require treatment.
Macular degeneration
The aggregation of metabolic products causes damage to the macula which is a place where vision is most correct. This disease can significantly reduce visual acuity. Macular degeneration is common: Almost 10 per cent of people in Germany suffer from at least an early stage of age-related macular degeneration.
Diabetic retinopathy
Diabetic retinopathy is a disease of the retina that appears as a result of diabetes. A large proportion of diabetics develop signs of diabetic retinopathy after many years of diabetes.
The increase in blood sugar in diabetics eventually damages the small blood vessels in the retina. Haemorrhages appear and fats and proteins are deposited in the retina. Fluid collects in the area of the macula (macular oedema). If the retina is heavily damaged, there is a risk of retinal detachment.
The retinal vein or artery occlusion
A central retinal vein occlusion mainly occurs in the elderly. The consequences are moderate to severe vision loss. The occlusion is probably due to sclerotic changes in the vessels.
Blood circulation disorders can also be the cause. High blood pressure and increased intraocular pressure can promote vein occlusion. A retinal artery occlusion can be caused by an embolism.
Retinopathy of prematurity
This disease of the retina is found in children born prematurely. New blood vessels form in the immature retina and insert into the vitreous body. These vessels deform the retina and haemorrhages may also occur.
Traction of the vessels can detach the retina and thus lead to blindness. Premature infants who need to be ventilated are the most affected.
Retinoblastoma
Retinoblastoma is a malignant tumour of the retina and the most common eye tumour in children. It is congenital or develops during the first years of life.
The pupil becomes completely white which means an increase in the growth of the tumour inside. Strabismus can also be a sign of retinoblastoma.
Inflammations and lesions of the retina
Inflammations of the retina can be caused by viruses, borrelies, fungi and small unicellular parasites, Toxoplasma.
Retinal injuries occur, for example, when the eyeball is bruised or when sharp objects, such as splinters, enter the eye.
Hereditary macular degenerations and retinal dystrophies
Hereditary macular degenerations include, for example, Stargardt’s disease and Best’s disease. They often appear in childhood or adolescence, but can also occur later. Retinal changes can affect visual acuity to varying degrees.
In the case of hereditary retinal dystrophies, these are malformations of the cones or the rods. The gradual loss of function of these sensory cells results in progressive deterioration of vision. Retinal dystrophies are incurable.
What are the symptoms of retinal diseases?
Blurred vision, distorted vision and reduced visual field are common symptoms of retinal diseases. Patients sometimes also see flashes of light, black spots, or shadows in their field of vision. Night blindness or sensitivity to light can also be symptoms.
How does the ophthalmologist find retinal disease?
To detect retinal changes, the ophthalmologist must be able to look at the fundus through the patient’s pupil.
This is done using an ophthalmoscope. The doctor places the ophthalmoscope as close to the patient’s eye as possible. A light source from the ophthalmoscope illuminates the patient’s eye. The doctor can thus see through the pupil to the retina.
To be able to accurately assess the retina, the ophthalmologist observes the enlarged fundus using a slit lamp microscope. The slit lamp microscope is a microscope equipped with a lamp that illuminates the eye. During the examination, the patient sits directly in front of the microscope and looks into the device.
What can be the consequences of retinal disease?
In cases of retinal detachment, early diagnosis and treatment are important. In uncomplicated cases, the prognosis is good. As early as the symptoms get detected, the disease can be cured better. But even with early treatment, it takes weeks or months for the retina to recover.
In the case of diabetic retinopathy, early treatment is also decisive. Most of the time, it is then possible to control the disease. However, it can happen that people lose their sight due to the disease.
The prognosis of venous occlusion depends on the degree of damage to the macula and the extent of neovascularization. Often, vision remains limited. Complications can be secondary glaucoma, which can lead to blindness.
In severe cases, retinopathy of prematurity can also lead to blindness in children. But even if the disease could be treated in children born prematurely, sequelae may appear. The consequences can be high myopia or retinal detachment in adulthood.
In people with age-related maculopathy, vision is reduced, but they do not become completely blind. Magnifying visual aids and magnifying glasses can make reading easier.
How are diseases of the retina treated?
In the case of retinal detachment, the treatment depends on the extent of the retinal damage. Small holes and tears in a retina still in place are lasers sclerosced to prevent the retina from continuing to sink in and detach. However, after the complete detachment of the retina, it can’t be treated with laser treatment.
An operation is necessary to reattach the retina to the retinal pigment epithelium. The doctor sews a silicone rubber “lead” on the sclera from the outside. Lead hollows out the wall of the eyeball from the outside and thus brings the pigment epithelium back to the retina.
If this is not enough, for example in the case of retinal detachment over a large area, The eyeball is filled with a silicone gas or oil. The retina is thus pressed from the inside against the wall of the eyeball.
In cases of vascular diseases of the retina, such as diabetic retinopathy and venous occlusion, new vessels of poorer quality form as a result of the vascular injury and often become fragile.
It can also cause retinal haemorrhage. One of the main objectives of the treatment of vascular diseases of the retina is therefore to prevent the formation of these new vessels.
In order to inhibit the formation of new vessels, VEGF inhibitors can be injected into the eye. VEGF (Vascular Endothelial Growth Factor) is the body’s own growth factor that stimulates the formation of new vessels.
Also, the doctor may inject anti-inflammatory steroids into the eye. Laser coagulation also helps fight new vessels and bleeding in the retina. The doctor sclerites the blood vessels using a green laser.
Retinopathy of prematurity is also treated with laser coagulation. In severe forms of the disease with retinal detachment, vitrectomy is required.
Retinoblastoma can be treated by completely removing the eye with the tumour or by chemotherapyand radiation therapy.
Age-related macular degeneration is an age-related phenomenon and can only be treated to a limited extent. When the disease is accompanied by neovascularization of the choroid, VEGF inhibitors are used.