The main characteristic of the vitreous body (glass) is transparency. Diseases affecting the surrounding structures cause its clouding and, consequently, weakening of vision or symptoms such as “threads” and “dash lines” before the eyes. There are several groups of diseases that cause such changes.
Ablation of the vitreous body (lat. Ablatio corporis vitrei):
This phenomenon is typical for people of older age. Namely, the structure of the vitreous changes with age, with the dilution (liquefaction) of its individual parts and the creation of so-called lacunae, as well as the regrouping of the fibrils (threads) of the vitreous. This process is called syneresis (lat. syneresis). Both phenomena lead to the phenomenon of swimming dashes, flies or spiders as people often call them. Such changes in the vitreous also lead to its detachment from the retina, with which it is normally in close contact, whereby the mentioned symptoms intensify. Occasional flashes in front of the eye and blurring of vision are the result of irritation of the retina in the places where it is connected to the vitreous body, and stronger blurring of vision is caused by edema (swelling) of the macular area.
Ablation occurs more often and earlier in myopic people because their eye is more elongated due to anatomical reasons.
Trauma to the eye also causes the aforementioned disorders, which can be complicated by additional bleeding or other more serious consequences.
The ablation of the vitreous body accompanied by the above-mentioned symptoms is not necessary, and in most cases it is not even possible to treat it in an acceptable way. Disturbances in the form of flying dashes can partially disappear spontaneously, and they can also occur in another place. As they are visible only in stronger light, and disappear in weaker light, the most common suggestion to the patient by the doctor is to simply not pay attention to them.
Inflammation:
Inflammation of the eye membranes (uveitis) is characterized by increased leakage of blood vessels of the eye and breakdown of the so-called hematoocular barrier. The aforementioned barrier is an anatomical term for multiple layers of tissue that are structured differently in different parts of the eye, and whose role is to selectively allow certain substances to pass from the blood vessel itself into the eye. Blood and inflammatory cells that due to inflammation pass the hemato-ocular barrier or are formed in the vitreous form clusters that are less transparent than the normal vitreous, so depending on their size and density, they interfere with vision more or less. The symptoms are similar in type to those of vitreous ablation (flies, flashes of light and blurred vision), only they are stronger in intensity. The diagnosis of inflammation can only be made by a specialist doctor, and therapy is determined depending on its type. Today’s therapeutic possibilities are relatively large, and inflammations begin to subside within a few days. In case of severe inflammation, where the retina is significantly threatened and thus the perspective of vision, it is necessary, among other things, to undertake operative treatment. It consists in removing the vitreous (the operation is called vitrectomy) and replacing it with other substances. If this type of treatment is undertaken in time, vision will be preserved to the greatest extent, but if the inflammation affects several surrounding structures, the possible complications and permanent consequences are greater (cataract, glaucoma).
Bleeding:
Bleeding into the vitreous body (lat. haematovitreus) is the most common cause of eye trauma and severe forms of diabetes (diabetic retinopathy).
Eye injuries with or without piercing the eyeball cause a whole complex of damage, including rupture of blood vessels. Bleeding can, depending on the size of the vessel, slowly and very discreetly or almost immediately and completely reduce visual acuity. Similarly, the rupture of weakened blood vessels in diabetic retinopathy causes the same symptoms.
Bleeding in the vitreous is diagnosed based on examination using special lenses and ultrasound. With the aforementioned methods, blood withdrawal or healing can also be monitored.
Regardless of the cause, blood from the vitreous can be spontaneously withdrawn (resorbed), and the cleaning process lasts from several days to several weeks. If there is no significant improvement after that time, it is removed surgically (vitrectomy). With severe diabetic retinopathy, it is possible for the bleeding to recur several times, so regular laser treatment of the fundus of the eye is very important in the prevention of this and other eye complications of diabetes.
Degenerative changes:
In the population, we distinguish a large number of different degenerative changes, but two stand out in terms of their frequency:
Asteroid hyalosis (lat. Scintillatio albescens)
This disease is common in diabetics, although it can also affect other people. It can be bilateral or unilateral. This is about the accumulation of calcium soap crystals in the vitreous, which in most cases do not cause any difficulties with vision, but only when examined, the existence of tiny sparkling white dots in the vitreous is established. Treatment is not necessary.
Scintillating synchysis (lat. Synchysis scintillans)
This disease involves the deposition of cholesterol in the vitreous, which is not directly related to the level of cholesterol in the blood. The patient does not feel any difficulties, and the examination reveals the existence of small, colorful, sparkling dots swimming in the vitreous. Treatment is not necessary.
Literature:
M.Sc. sc. Pavan Dr. Joško, “Eye Diseases”, Zagreb 2003.
