Age-related macular degeneration, also known as age-related macular degeneration, mostly occurs in people over 45 years of age, and its prevalence increases with age, and the prevalence of people over 50 years of age accounts for 15.5% in recent research, which is one of the important eye diseases causing blindness in the elderly.
1.Risk factors of age-related macular degeneration
According to the research of some famous epidemiological groups in the United States and Australia, the risk factors for age-related macular degeneration are as follows: age, diet, light exposure, smoking history, hypertension, family history, hypercholesterolemia, difference in gender and race (more Caucasians), and history of cardiovascular disease, etc.
2.Etiology
Its cause is still unclear, but it is generally believed to be related to genetics, chronic photodamage, malnutrition, systemic diseases such as cardiovascular system and respiratory system, and other environmental factors.
3.Typing
(1) Dry age-related macular degeneration: also called non-exudative age-related macular degeneration or atrophic age-related macular degeneration, which means no bleeding in the macular area, accounting for about 80%–85%.
(2) wet age-related macular degeneration: also known as exudative age-related macular degeneration, refers to the presence of neovascularization and hemorrhage, accounting for about 15%.
4.Pathogenesis
With ageing, retinal pigment epithelial dysfunction, the retinal pigment epithelial cells accumulate material, extracellular matrix abnormally gathered in the basement membrane, between the pigment epithelium and Bruch’s membrane many eosinophilic material accumulation formed vitreous warts. The vitreous warts may cause different degrees of degeneration, hyperplasia or atrophy of the pigment epithelium, Bruch’s membrane and optic cells; the permeability of Bruch’s membrane to nutrients is altered, thus causing the retinal pigment epithelium to respond to metabolic disorders, resulting in atrophy of the retinal pigment epithelium, Bruch’s membrane and choroidal capillaries, which slowly develops into atrophic age-related macular degeneration (or dry macular degeneration); also It can also cause collagen thickening in Bruch’s membrane and post-elastic layer rupture, resulting in choroidal capillaries entering the subpigment epithelium or subneuroepithelium through the fissure of Bruch’s membrane, forming choroidal neovascularization. Due to the structural characteristics of neovascularization, leakage and hemorrhage are bound to occur, forming exudative age-related macular degeneration or wet-type age-related macular degeneration.
5.Fundus performance
(1) Dry age-related macular degeneration: It occurs mostly in the elderly over 50 years old, with slow onset, and the patient’s visual acuity decreases unconsciously, and there may be visual distortion, and the degree of both eyes is similar, so it is easy to be mistaken for “aging” of the eyes. As the outer layer of the retina, pigment epithelium, Bruch’s membrane, choroidal capillaries and other layers gradually atrophy and degeneration, yellowish-white round-like vitreous warts of different sizes can be seen in the posterior pole of the fundus in the early stage of the disease, which can be fused, pigment epithelial hyperplasia or atrophy, loss of central concave light reflection, pigment disorder in the posterior pole, and further emergence of a map-like atrophy area with clear borders. In the advanced stage, the choroidal capillaries in the area are atrophied, and the exposed choroidal vessels can be seen.
(2) Exudative age-related macular degeneration: The clinical manifestation is sudden loss of vision in one eye, distortion of visual objects or the appearance of central dark spot, and the other eye may show symptoms after a longer period of time. Subretinal hemorrhage and exudation in the posterior pole of the eye, in which grayish-yellow lesions are sometimes visible, i.e., they may be neovascularization. The hemorrhage is located under the neuroepithelium or pigment epithelium, the latter being dark red or even black with a slightly red margin, while there may be superficial bright red hemorrhages, sometimes with vitreous warts visible nearby, and the lesion area may be elevated. Fluorescence angiography in the early stage appears to have a clear border of highly fluorescent neovascular form, called typical neovascularization, and in some patients there is no clear border, called occult neovascularization, which rapidly leaks fluorescein, its border is unclear, and the late stage of angiography is still relatively highly fluorescent. Indocyanine green angiography is more useful to show the morphology of choroidal neovascularization. If a large number of superficial hemorrhage can enter the vitreous, resulting in vitreous accumulation of blood, the fundus cannot be peered into. In time, the hemorrhage in the macular area is mechanized, forming a disc-shaped scar, and the central visual function is completely lost.
6.Treatment
(1) Atrophic age-related macular degeneration: There is no exact treatment.
(2) Exudative age-related macular degeneration: The purpose of treatment is to close the choroidal neovascularization under the retina, and the neovascularization located 500um away from the central recess can be closed by laser to prevent further development. However, it cannot prevent recurrence, so close observation is still needed after photocoagulation. 1990s vitreous surgery was used to successfully remove subretinal neovascularization, but due to the damage of retinal pigment epithelial cells and optic cells, the visual function failed to improve after surgery, and failed to prevent vision loss compared with the observation group, and there were obviously more complications of surgery.
a. Photodynamic therapy (PDT) The use of photosensitizers that specifically bind to choroidal neovascularization endothelial cells and are activated by certain wavelengths of light irradiation to produce photo-oxidation reactions that kill endothelial cells, thus achieving the effect of destroying choroidal neovascularization, has been widely used. However, the lesion still has the possibility of recurrence, and long-term clinical follow-up is still pending to observe the efficacy.
b.Trans-pupillary thermotherapy (TTT) The essence is thermal therapy, using the 700-900nm infrared laser or near-infrared laser penetration deep, less damage to other tissues, especially the neuroepithelium, to close the choroidal neovascularization.
c, anti-VEGF drug therapy Mainly used in ophthalmology are bevacizumab (bevacizumab) and ranibizumab (ranibizumab), which have been successfully treated in the clinic this year for exudative age-related macular degeneration, which is a significant achievement.
7. Prevention
The occurrence of macular degeneration may be related to the toxic accumulation effect of light, so light damage should be avoided, and light-blocking glasses should be worn for activities under strong light. In recent years, the application of laser treatment of vitreous warts to prevent further evolution of age-related macular degeneration has been reported, further observation of the efficacy is needed.