Macular degeneration is prevalent among millions of people across the globe. There are two primary forms: wet and dry macular degeneration. While both types may lead to vision loss, they differ in their root causes, symptoms, and treatment approaches.
We are here to explain the types of macular degeneration - their similarities, differences, risk factors, symptoms, diagnostic methods, and management.
Understanding the Macula Anatomy
Before going into the specifics of wet and dry macular degeneration, let's take a look at the anatomy of the macula. That's how you can understand how it functions and how macular degeneration affects vision.
The macula is a small, highly sensitive area in the center of the retina at the back of the eye. Macula is responsible for sharp, central vision. It allows us to see fine details, read, recognize faces, and perform tasks requiring visual acuity.
Layers of the Retina
The retina is a thin layer of tissue lining the back of the eye. The retina contains photoreceptors (cells), which are responsible for converting light into electrical signals. The signals are then transmitted to the brain for interpretation as vision.
Simply said, the retina has several layers, each with specific functions:
Outermost layer of the retina contains the photoreceptor cells - rods and cones. Rods are responsible for vision in low-light conditions, while cones are responsible for color vision and visual acuity.
Inner layers process and transmit visual information between photoreceptors and the optic nerve.
Ganglion cell layer contains the cell bodies of ganglion cells, which form the fibers (axons) of the optic nerve to the brain.
Structure of the Macula
The macula is located near the center of the retina and is approximately 5.5 millimeters in diameter. The high density of cones in the macula, particularly in the fovea, enables us to perceive colors and details with exceptional clarity.
Fovea is a small depression in the center of the macula where visual acuity is highest. It contains a high concentration of cones and is responsible for precise, color vision. When we look directly at an object, its image falls on the fovea, allowing us to see it with the greatest clarity.
Macular pigment is a yellow pigment of the macula, composed of lutein, zeaxanthin, and meso-zeaxanthin. The pigment protects the retina from damage by blue light and oxidative stress.
Wet Macular Degeneration
Wet macular degeneration, also known as neovascular AMD, occurs when abnormal blood vessels grow under the macula.
These blood vessels are fragile and prone to leaking fluid and blood into the retina, contributing to scarring and rapid vision loss.
Wet AMD typically progresses more rapidly than dry AMD and can cause severe vision impairment.
Symptoms of Wet Macular Degeneration
Wet macular degeneration symptoms are:
Sudden or gradual loss of central vision
Distortion of straight lines
Difficulty reading or recognizing faces
Appearance of dark or blank spots in the central vision
Wet Macular Degeneration Risk Factors
The exact cause of wet macular degeneration remains unclear, though several risk factors may contribute:
Aging
Genetics
Smoking
Hypertension
History of UV light exposure
People with a family history of age-related macular degeneration are at a higher risk of developing wet AMD.
Wet Macular Degeneration Diagnosis
The way eye doctors diagnose wet macular degeneration is through an eye exam.
Visual acuity tests, dilated eye exams, optical coherence tomography (OCT), and fluorescein angiography are part of the examination process.
The evaluations assess the extent of retinal damage and detect abnormal blood vessel growth. Once the eye doctor knows these things, they can determine the best individual treatment approach.
Wet Macular Degeneration Treatment
Anti-VEGF therapy is the primary approach for patients with wet macular degeneration. The therapy includes anti-VEGF drug injections directly into the eye. The drug blocks the action of the vascular endothelial growth factor, responsible for abnormal blood vessel growth.
Alternative treatment modalities include photodynamic therapy (PDT) and laser therapy, although these are less common today.
Dry Macular Degeneration
Dry macular degeneration (non-neovascular AMD), occurs due to the gradual breakdown of cells in the macula and the accumulation of small deposits (drusen).
Unlike wet macular degeneration, dry AMD progresses more slowly. We tend to associate it with a milder form of vision loss.
Symptoms of Dry Macular Degeneration
Dry macular degeneration symptoms include:
Blurry or distorted central vision
Difficulty reading or performing close-up tasks
Appearance of yellowish deposits in the macula (seen during eye exam)
Dry AMD may progress asymptomatically for years before causing a noticeable loss of vision.
Dry Macular Degeneration Risk Factors
Some of the risk factors are similar to wet macular degeneration, while others differ:
Aging
Genetics
Smoking
Obesity
Cardiovascular disease
Unbalanced diet (low in antioxidants and omega-3 fatty acids)
Diagnosis of Dry Macular Degeneration
Similar to wet AMD, dry macular degeneration is diagnosed through an extensive eye exam.
The exam consists of visual acuity tests, dilated eye exams, and OCT imaging. As well as evaluation of drusen formation in the macula.
Dry Macular Degeneration Management
There is no cure for dry macular degeneration so far. Further research is on the way.
Dry macular degeneration treatment focuses on managing symptoms, slowing down disease progression, and preventing vision loss.
The approach may insist on lifestyle modifications. For example, smoking cessation, maintaining a healthy diet rich in antioxidants and omega-3 fatty acids, and regular eye exams to monitor disease progression.
RELATED: Eye Conditions from Old Age
Similarities Between Wet and Dry Macular Degeneration
Despite their differences and being distinct forms of the same condition, wet and dry macular degeneration share some commonalities in terms of risk factors, symptoms, and the disease process.
1. Age-Related Condition
Both wet and dry macular degeneration are primarily age-related conditions. The risk of developing the disease increases with getting older. While the disease may occur in younger individuals, the common diagnosis occurs in people over the age of 50.
2. Genetic Factors
Genetics also contribute to both types of macular degeneration. Individuals with a family history of the disease are at a higher risk of developing macular degeneration themselves. The onset of AMD is linked to several genes, although the precise genetic mechanisms are still not fully understood.
3. Lifestyle Factors
Smoking, obesity, poor diet, and long-term exposure to UV light increase the likelihood of both wet and dry macular degeneration. Smoking, in particular, can exacerbate inflammation and oxidative stress in the retina, worsening the condition.
4. Gradual Symptoms Onset
Both wet and dry macular degeneration trigger changes in vision occurring slowly over time. In the early stages, individuals may not experience any noticeable symptoms. That's why undergoing regular eye exams is important to detect macular degeneration in its earliest stages.
5. Central Vision Impairment
The predominant symptom of both types of macular degeneration is the deterioration of central vision. As the disease progresses, central vision loss may become more apparent and seriously impact an individual's quality of life.
6. Damage to the Macula
Both wet and dry macular degeneration involve damage to the macula. In dry macular degeneration, we notice the accumulation of drusen (yellowish deposits) and the gradual breakdown of cells in the macula. In wet macular degeneration, abnormal blood vessels grow beneath the macula, leading to fluid and blood leakage, scarring, and vision loss.
Resources:
Age-Related Macular Degeneration (AMD), National Eye Institute
Checked by Atanas Bogoev, MD.