What is AMD or macular degeneration of the eye?

Macula –  is responsible for a central vision. If we compare the human eye with a camera, then the macula is the most sensitive part, like a film. Thanks to the macula, our eye is capable of:

  • read and write
  • recognize faces and colors
  • distinguish between small objects and details

Age-related macular degeneration (AMD) or macular degeneration of the eye is the most common cause of irreversible loss of central vision among elderly patients. The main diagnostic methods are ophthalmoscopy with an enlarged pupil, color photography, fluorescence angiography and optical coherence tomography. These investigations allow you to confirm the diagnosis and propose treatment. The treatment is carried out with the help of food additives, intravitreal injections of anti-VEGF drugs, laser photocoagulation, photodynamic therapy, and devices for visually impaired people.

AMD is the most common cause of irreversible loss of vision in the elderly. It is more common among the Caucasian-white population.

Etiology

The following risk factors are distinguished:

  • Age
  • Genetic predisposition (for example, pathological complement factor H)
  • Family history
  • Smoking
  • Cardiovascular diseases
  • Arterial hypertension
  • Obesity
  • Exposure to sunlight
  • Diet with reduced intake of omega-3 fatty acids and dark green leafy vegetables

Pathophysiology

There are two forms of this disease:

  • Dry (non-exudative or atrophic): all AMDs begins as a dry form. About 85% of patients with AMD have a dry form of the disease.
  • Wet (exudative or neovascular): a wet form of AMD develops in 15% of patients.

Despite the fact that only 15% of patients suffering from AMD, it develops into a wet form of the disease, 80–90% of significant loss of vision are caused precisely by the wet form of AMD.

The dry form of AMD causes changes in the retinal pigment epithelium, which are usually visible as dark point foci. The retinal epithelium pigment has an important function to maintain the normal state and functioning of cones and rods. The accumulation of metabolic products from rods and cones can lead to the formation of drusen, which appear as yellow spots. Zones of chorioretinal atrophy (often referred to as geographical atrophy) occur in more advanced cases of dry AMD. In that cases, a protruding macular scar (disk-shaped scar) does not form, there is no edema, hemorrhage or exudation.

The wet form of AMD occurs when new abnormal blood vessels develop under the retina in a process called choroidal neovascularization (abnormal formation of new blood vessels). Edema of the optic disc or local hemorrhage in this area can lead to its elevation and local detachment of the retinal epithelium pigment. After the time, untreated neovascularization leads to the formation of a disk-like scar under the macula.

A photo of a retina affected by a wet form of age-related macular degeneration (AMD). This image shows calcified Druze, subretinal bleeding, a choroidal neovascular membrane (black from old blood and fibrosis) and xanthophyllum pigment spots.

Clinical manifestations

Dry AMD

The loss of central vision occurs during years and is a painless process. Most patients has a vision which is maintained at a sufficient level to read and drive. In the late stages of the disease, blind spots (scotomas) can occur in the central part of the visual field, sometimes growing to large sizes. The damage is usually bilateral.

Changes in ophthalmoscopy are as follows:

  • Changes in retinal pigment epithelium
  • The appearance of nodules
  • Formation of chorioretinal atrophy zones

Age-related macular degeneration – nodules are subretinal deposits. In the image they are yellow. nodule is one of the signs of age-related macular degeneration

 

Wet AMD

The wet AMD is characterized by rapid, usually within a few days or weeks, loss of vision. The first symptom is usually visual impairment, such as central blind spots (scotomas) and impaired perception of the shape and size of objects (metamorphopsia). Peripheral and color vision, in fact, do not suffer, however, the patient may develop almost complete blindness of the affected eye (visual acuity <20/200), especially in the case of untreated AMD. The wet form of AMD usually affects only one eye, so the symptoms are one-sided.

Changes in ophthalmoscopy are as follows:

  • Subretinal fluid, which is manifested by local elevation of the retinal epithelium pigment
  • Retinal edema
  • Gray-green hypopigmentation focus under the macula
  • Exudates in or around the optic disc
  • Detachment of retinal pigment epithelium (visualized as a zone of retinal elevation)
  • Subretinal hemorrhage in or near the optic disc

Diagnostics

  • Ophthalmoscopy
  • Color fundus photography
  • Fluorescence angiography
  • Optical coherence tomography

Ophthalmoscopy reveals both forms of the disease. Visual impairment can be detected using the Amsler grid (Definition of the field of view). If clinical examination data proposes a wet form of AMD, color photography and fluorescence angiography are performed. Angiography visualizes choroidal neovascular membranes and reveals areas of geographical retinal atrophy. Optical coherence tomography can detect the presence of intraretinal or subretinal fluid, as well as evaluate the effectiveness of the therapy.

Treatment

  • Nutritional supplements for dry high-risk AMD or single-sided wet AMD
  • Intravitreal anti-VEGF drugs or laser treatment for wet AMD
  • Supportive measures

Dry AMD

Damage caused by dry AMD is irreversible. Patients with multiple nosen, pigment changes and/or geographic atrophy, the risk of advanced AMD can be reduced by 25% by daily use of the following supplements:

  • Zinc oxide 80 mg
  • Copper 2 mg
  • Vitamin C 500 mg
  • Vitamin E 400 IU
  • Lutein 10 mg / zeaxanthin 2 mg (or beta-carotene 15 mg or vitamin A 28000 IU for patients who have never smoked)

For current and former smokers, beta-carotene may increase the risk of developing lung cancer. Recent studies have shown that the use of lutein in combination with zeaxanthin is comparable in efficacy with beta-carotene. Therefore, such substitution should be considered with current or former smokers. The content of zinc in supplements increases the risk of hospitalization for the treatment of urinary tract disorders. Some patients taking beta-carotene also have yellowed skin. Reducing cardiovascular risk factors, as well as regular meals with a high content of omega-3 fatty acids and dark green leafy vegetables slow down the development of the disease; however, recent large studies have not shown that supplementation with omega-3 fatty acids reduces disease progression.

Wet AMD

Patients with single-sided wet AMD should take daily dietary supplements recommended for dry AMD, to reduce the risk of AMD-induced loss of vision in the other eye. The choice of treatment tactics depends of the size, location and type of neovascularization. Intravitreal injections of anti-VEGF drugs (ranibizumab, bevacizumab or aflibercept) can significantly reduce the risk of vision loss and improve vision near one third of patients. In a small group of patients, laser photocoagulation of pathological vessels outside the central fossa can prevent significant loss of vision. Under certain conditions, photodynamic therapy, a form of laser therapy, is also effective. Corticosteroids (eg, triamcinolone) are sometimes injected into the eye with anti-VEGF drugs. Other treatments, including transpapillary thermotherapy, subretinal surgery, and operative macular translocation, are applied quite rarely.

Supporting measures

Patients with a significant decrease in central vision are recommended to use magnifying glasses, reading glasses, large computer monitors and telescopic lenses. There are also special computer programs that can increase the font size or read the text aloud.