Blood Circulation Disorders
As in all other organs, adequate blood circulation is a prerequisite for a proper function of the eye. The blood circulation of the retina is provided by the central artery. This artery extends through the optic nerve into the eye and is divided into four arteries before entering the eye. Subsequently, it extends further by dividing into the cappillary vessels, which nourish the ganglion cells. Obstruction of the central artery or one of its arms may occur due to numerous reasons, such as general arteriosclerosis. Another hazard occurs as a result of arteriosclerosis in the arteries of the neck; clots may seperate from the artery and reach up to the central artery with the blood flow, obstructing the artery. The same is also true for blood clots coming from the heart. Obstruction of the central vessel may be caused general vasculitis, hypertension, blood coagulation disorders, use of contraceptive pills, hyperviscosity and narrowing of the arteries of the neck. In addition, patients with hypermetropia and glaucoma have a tendency for vascular obstruction.
Obstruction of the central artery is a serious event because a sudden blackout occurs. Suddenly, the retina can not be supplied by nutrients and oxygen, and thus, it can no longer fulfill its duty. Not only central vision, but the whole visual field disappears, yet no pain is felt. Sometimes, blackouts that last for seconds or minutes occur, which are alarming symptoms. The patient should immediately be examined by a physician. Obstruction of the central artery may lead to a mild or very severe loss of visual acuity depending on the degree of obstruction. Accordingly, the symptoms may range from mild loss of visual acuity, mild loss of visual field to sudden blindness, yet no pain is felt. Chronic water accumulation in the middle of the retina (macular edema) may occur as a complication in vascular obstructions and may lead to progressively worsening vision. Another problem is neovascularization, which occurs in the retina and iris when there is insufficent blood circulation in the capillaries. The eye tries to improve the blood circulation with neovascularization. However, these new vessels are weak and may lead to vitreous hemorrhage. Neovascularization in the iris may also occur in the chamber angle and may change the outflow site of the chamber fluid. As a result, glaucoma, which is difficult to treat, occurs (secondary glaucoma). Neovascularization only leads to worsening of the disease.
An opthalmologist can easily assess the retina together with its vessels to see blood circulation disorders with the help of an opthalmoscope, a microscope with a special lens or contact glass. A dye substance test (Fluorescein angiography) is additionally used to give more information.
If the central artery or one of its branches is obstructed, it should be immediately treated by an opthalmologist, who can provide drugs to dissolve blood clots. However, a successful treatment is not possible in many cases. The important point is to control hypertension and eliminate other factors. If the central artery or one of its branches is obstructed, laser treatment is applied in the retina to prevent neovascularization and other complications.