macular degeneration

macular degeneration
Name	Macular degeneration
Caption	A fundus photograph showing drusen in dry age-related macular degeneration.
Field	Ophthalmology
Symptoms	Blurred or reduced central vision
Complications	Visual impairment, legal blindness
Onset	Older age
Duration	Chronic
Types	Dry (atrophic), wet (neovascular)
Causes	Aging, genetics, smoking, hypertension
Risks	Age, family history, Caucasian ethnicity, smoking
Diagnosis	Dilated eye exam, Amsler grid, optical coherence tomography, fluorescein angiography
Treatment	Anti-VEGF injections, vitamin supplements (AREDS), photodynamic therapy
Medication	Aflibercept, Ranibizumab, Bevacizumab
Prognosis	Variable; central vision loss can progress
Frequency	Leading cause of vision loss in older adults in the developed world

macular degeneration is a medical condition that results in a loss of vision in the center of the visual field due to damage to the retina. It is a major cause of visual impairment and blindness in older adults, particularly in the developed world. The disease primarily affects the macula, the part of the eye responsible for sharp, central vision needed for activities like reading and driving.

Overview

The macula is a small, highly sensitive area of the retina located at the back of the eye. It is rich in photoreceptor cells, specifically cone cells, which are essential for detailed central vision and color perception. Damage to this region, as occurs in macular degeneration, disrupts the transmission of visual signals through the optic nerve to the visual cortex in the brain. The condition is strongly associated with aging, with the most common form being age-related macular degeneration. Historically, understanding of the disease advanced significantly with the development of imaging tools like optical coherence tomography and contributions from institutions like the National Eye Institute.

Types and classification

Macular degeneration is broadly classified into two main types: dry (atrophic) and wet (neovascular). Dry macular degeneration, accounting for about 85-90% of cases, is characterized by the gradual breakdown of retinal pigment epithelium cells and the accumulation of yellow deposits called drusen beneath the retina. Wet macular degeneration, though less common, is more severe and involves the growth of abnormal blood vessels from the choroid beneath the macula, a process known as choroidal neovascularization. These fragile vessels can leak fluid and blood, causing rapid damage. A rare inherited form that affects younger individuals is known as Stargardt disease.

Causes and risk factors

The exact cause is multifactorial and not fully understood, but aging is the most significant risk factor. Genetic predisposition plays a major role, with variants in genes such as CFH and ARMS2 strongly associated with increased risk. Environmental and lifestyle factors are also critical; smoking is the most modifiable risk factor, doubling the likelihood of developing the disease. Other risks include hypertension, cardiovascular disease, obesity, and a diet low in lutein and zeaxanthin. Demographic factors such as Caucasian ethnicity and a positive family history also increase susceptibility.

Diagnosis

Diagnosis typically begins with a comprehensive dilated eye exam performed by an ophthalmologist or optometrist. Patients may be asked to view an Amsler grid, a pattern of straight lines that can appear wavy or missing if the macula is damaged. Advanced imaging is crucial; optical coherence tomography provides detailed cross-sectional images of the retina, revealing drusen, fluid, or retinal pigment epithelium abnormalities. Fluorescein angiography, which involves injecting a dye into a vein in the arm and photographing the retina, helps identify leaking blood vessels in wet macular degeneration. These techniques are standard in clinics like the Moorfields Eye Hospital.

Management and treatment

There is no cure, but management aims to slow progression and preserve vision. For dry macular degeneration, the Age-Related Eye Disease Study (AREDS) formulations, specific high-dose vitamin supplements containing vitamin C, vitamin E, zinc, and copper, are recommended to reduce risk of progression. For wet macular degeneration, the standard treatment is intravitreal injections of anti-VEGF drugs such as Aflibercept, Ranibizumab, and Bevacizumab, which inhibit abnormal blood vessel growth. Other historical or adjunct treatments include photodynamic therapy with verteporfin and laser photocoagulation. Low vision rehabilitation, involving aids from specialists at institutions like the Lighthouse Guild, is important for managing vision loss.

Prognosis and epidemiology

The prognosis varies significantly between types. Dry macular degeneration often progresses slowly over years, while wet macular degeneration can cause rapid, severe vision loss if untreated. Even with treatment, many patients experience some permanent loss of central vision, impacting quality of life and increasing risk of depression and falls. Macular degeneration is a leading cause of irreversible blindness in individuals over 50 in the United States and Europe. Prevalence increases dramatically with age; it affects about 2% of people aged 50-59 but over 30% of those over 75. Global burden studies, such as those by the World Health Organization, highlight its significant public health impact.

Category:Ophthalmology Category:Blindness Category:Age-related diseases