What is macular edema and what causes it?
Macular edema is edema of the central retinal zone (yellow spot, or macula) responsible for central eyesight. The macula is located opposite the eye pupil, slightly higher than the area where the eye is connected to the optical nerve. Macula got its second name (yellow spot) owing to high concentration of a yellow pigment in its cells. The retina in the central macular zone is very thin, and it contains a lot of photoreceptors, or cone cells sensitive to light that form the central vision; this is the area of the highest visual acuity. Cone cells enable people to see well ad daylight and distinguish between colours. Therefore, macular pathologies may considerably decrease visual acuity.
Macular edema is not a separate pathology, but rather a manifestation of certain eye pathologies and conditions: diabetic retinopathy (a condition when retinal vessels are damaged due to diabetes), eye injuries or consequences of surgeries, uveitis (choroid inflammation), or occlusion of retinal veins. Occlusion of retinal veins is one of the most dangerous eye pathologies that may cause irreversible loss of vision. Unfortunately, the diagnosis “occlusion of retinal veins” has become much more frequent over the past decades.
Occlusion of retinal veins is a blockage of retinal veins and capillaries. It is often caused by essential hypertension and atherosclerosis.
Factors contributing to macular edema:
- age over 40-50 years;
- diabetes mellitus;
- hyperlipidemia (abnormal lipid and cholesterol revels in a patient`s blood);
- hypodynamia (low physical activity);
- increased intraocular pressure;
- concomitant inflammatory diseases;
- increased blood viscosity;
- congenital or acquired thrombophlebitis.
The thrombus hampers blood supply in the vessel. There is no blood outflow from the veins and capillaries. Blood gets into the retina, which causes its thickening. This results into edema.
As a result of thrombosis, the tissues surrounding the affected area develop ischemia, or a decrease in blood hemoglobin. In order to fight this lack of oxygen, the organism produces new blood vessels. However, all these new vessels have pathologically thin walls that conduct the liquid part of the blood into the retina. If an abnormal vessel`s wall is ruptured (e.g. in case of increased blood pressure), blood gets into the retina. Consequently, the affected area is extended. The edema prevents the retina from performing its main function of providing good peripheral vision. If macular edema is not eliminated in a timely manner, eyesight may be lost forever.
Symptoms of macular edema:
- blurred vision;
- distorted images: straight lines appear to be wavy or curved;
- the image has a pink hue;
- increased sensitivity to light;
- a cyclic decrease in visual acuity may occur at certain time of the day (usually in the morning);
- differences in light perception, although very rare, may occur during the day.
Diagnostics and treatment of macular edema
Apparent macular edema may be diagnosed by an ophthalmologist during examination with a slit lamp. Unfortunately, treatment at this stage will not always bring positive results; it requires a lot of time and effort.
The disease at its early stages, or susceptibility to the disease, may be diagnosed during optic coherence tomography (OCT). Ophthalmologists at the EXCIMER Clinic recommend people with predilection to thrombosis in retinal veins and capillaries to undergo a regular OCT examination. This is the only way to diagnose macular edema at its early stages and to take urgent measures for resolving it.
The EXCIMER Clinic has a new generation optical coherence tomographic scanner RTVue-100 (Optovue, USA). The OCT scanner RTVue-100 produces two- and three-dimensional images of the retina and the optic disc structures, which enables specialists to reveal pathologies at their early stages.
The most efficient method of fighting most retinal pathologies (retinal separation, rupture, or dystrophy) is laser coagulation. However, this method is not indicated to patients with macular edema because laser rays may damage the yellow body. Macular edema requires conservative treatment, which implies the use of various anti-inflammatory drugs (injections, tablets, eye drops). Multiple clinical trials proved that drugs containing synthetic analogs of glucocorticosteroids (hormones generated by the adrenal cortex) are highly efficient. In order to achieve the best result, they are injected right into the vitreous body. Yet, despite higher efficiency of these hormones compared to other drugs (eye drops or tablets), the treatment effect did not last long in many cases because if the drug is injected traditionally, its actual substance is completely consumed. The new drug Ozurdex, used for treatment in the EXCIMER Clinic, offers an innovative approach to treating macular edema.
What is Ozurdex, and how does it work?
Ozurdex is a drug used for treating macular edema caused by occlusion of the central retinal vein or its branches. Ozurdex is an implant that is injected into the vitreous body. Unlike traditionally used injections, the highly efficient glucocorticosteroid dexamethasonum, introduced in the innovative way, is released in small portions. This new technology of drug injection considerably increases the treatment effect`s duration.
Ozurdex has many ways of action. It not only eliminates macular edema, but also fights with its underlying reason – occlusion of retinal veins. Ozurdex has a powerful anti-inflammatory effect. As a result of treatment with Ozurdex:
- inflammatory mediators (prostaglandins) that cause macular edema are blocked;
- thrombuses are dissolved (fibrin deposits are frozen), and venous and capillary blood flow is resumed;
- walls of pathological blood vessels and capillaries are strengthened;
- new blood vessels with high wall penetrability are not formed.
Ozurdex: duration of the treatment effect
The implant`s treatment effect is retained during 90 days after its introduction. Only one Ozurdex injection is enough for a 6 months therapy. As a rule, the zone of ischemic lesion in an eye affected by macular edema extends far beyond the macula lutea. Therefore, laser coagulation along the borders of the affected zone is possible after the Ozurdex implant has been introduced. In most cases, a single Ozurdex injection is enough to eliminate macular edema after laser coagulation has been performed.
Clinical trials of the Ozurdex implant have demonstrated its efficiency according to the following parameters:
- retinal thickness in patients on the 90th day after a single Ozurdex injection was 3 times lower than before, a decrease from 600 micron to 240 micron (normal value 220 micron);
- visual acuity in a considerable number of patients increased from 5% to 55% within 90 days;
- the implant prevents loss of vision as a result of macular edema.
The EXCIMER Clinic guarantees high quality, efficiency, and reliability of treatment with Ozurdex. Treatment with the Ozurdex implant in the EXCIMER Eye Clinic adheres to all the necessary safety and sterility standards. Prior to treatment, the patient undergoes a compulsory diagnostic examination of eyesight. The examination results help the doctor to evaluate the patient`s visual system and to decide whether s/he needs treatment with Ozurdex.
- sensitivity to the drug`s active agent or its additive agents;
- active or suspected ocular or perocular infection;
- viral diseases of cornea and conjunctiva, including active epithelial herpetic keratitis;
- serum sickness;
- fungal diseases;
- advanced stage of glaucoma;
- age below 18.
Caution is needed in case of the following conditions:
- herpetic eye infections;
- pregnancy and lactation;
- aphakia (absence of the eye lens);
- special precautions should be taken by patients taking anticoagulants (drugs preventing blood clotting) or antiaggregants (drugs decreasing coagulability).