Macular Degeneration, generally called Age-related Macular Degeneration (AMD), is an eye condition that causes gradual loss of central eyesight.

AMD targets Macula, a specialized area located in the central part of the retina at the back of the eye.

Macula is responsible for providing sharp, detailed, and central vision, which is essential for reading, recognizing faces, and driving.

The degeneration of the Macula can result in blurriness, distortion, or gradual decline of vision in the direct line of sight.

It is a primary cause of vision impairment, particularly among older age groups.

This comprehensive article explores the causes, symptoms, risk factors, and various treatment options for Macular Degeneration.

What is Macular Degeneration

Let’s first understand what Macula is.

Simply put, Macula is part of our eye that powers clear, sharp, and detailed sight of objects directly in front of our eyes (also called visual acuity), both near and far.

The Macula contains a high concentration of light-sensitive cells called cones responsible for color vision and visual acuity.

Unwanted alteration in the natural state and structure of the Macula is known as Macular Degeneration. 

This degeneration can occur in various ways depending on the type of Macular Degeneration, which we will discuss later in this article.

It is a progressive condition that leads to blurry, distorted, dark, or empty areas in straight-ahead vision and difficulties with color perception.

The rate of deterioration varies from person to person and with age.

On a global scale, age-related macular degeneration (AMD) is the third leading cause of blindness, following Cataracts and Glaucoma.

Over time, individuals with AMD experience a gradual deterioration of vision, which can impact either one or both eyes.

Fact:
Macular Degeneration doesn’t cause complete blindness. Peripheral vision, which refers to the ability to see objects located off to the sides, remains intact.

Causes/Risk factors

The most significant predictor of AMD is advanced age, especially in individuals who are over 50 years old.

AMD is a widespread condition that impacts approximately 8.7% of the world’s population and is estimated to affect 288 Million people by 2040.

A systematic analysis of studies identified several factors with varying degrees of risk associated with AMD.   

Primary Causes

The strongest risk factors and primary causes behind AMD include:

Age

AMD is more prevalent in individuals over the age of 50. As the name suggests, it is primarily associated with the aging process.

Genetics

Macular degeneration (MD) is a condition with a strong genetic component, meaning it is highly heritable.

The likelihood of MD occurring in siblings of an affected individual is three to six times higher compared to the general population.

Smoking

Numerous studies have identified smoking as a significant factor in the development of AMD.

Smoking is thought to cause oxidative stress and inflammation, ultimately leading to macula damage.

Smoking can damage the blood vessels in the eyes, reducing blood flow and oxygen supply to the macula.

This scarcity can contribute to the development and progression of the disease.

It is important to note that ex-smokers, too, are at risk of developing AMD.

Research has shown that the risk of AMD remains higher for ex-smokers than for individuals who have never smoked.

The elevated risk of developing late age-related macular degeneration (ARMD) persists for up to 20 years after quitting smoking.

Cataract Surgery

Nuclear Cataract
Cataract Surgery

The analysis of studies revealed that past cataract surgery is a significant risk factor for the development of AMD.

Secondary causes

Elevated BMI, a previous history of cardiovascular disease, and Hypertension have shown notable and moderate levels of association as risk factors for the development of AMD.

Individuals with a history of cardiovascular disease may face twice the risk of developing AMD compared to those without such a history.

Tertiary causes

Gender, ethnicity, Diabetes, and history of cerebrovascular disease pose a risk for AMD, though not severe.

The prevalence of age-related macular degeneration is slightly higher among individuals of Caucasian descent than those from other ethnic backgrounds.

Stages of AMD

AMD can vary in its progression and impact from person to person. It’s categorized into three distinct stages.

Early-stage

Symptoms are hardly noticeable in Early AMD, making it difficult to diagnose.

In this stage, medium-sized yellow or white deposits, called Drusen, start to build up beneath the macula.

Vision loss is not yet noticeable.

Intermediate

Deposition of comparatively larger drusen and damage to the retinal pigment epithelium (RPE) may be observed.

In this stage, too, individuals may not experience any noticeable symptoms.

However, some might observe mild manifestations such as slight blurriness in their central vision or challenges with seeing in low-light situations.

Late-stage

Late-stage AMD is this condition’s advanced and severe form.

People experience significant vision loss in this state, which often necessitates advanced treatment methods to manage or decelerate its progression.

Geographic atrophy (dry AMD) or choroidal neovascularization (wet AMD) characterizes late-stage AMD.

Symptoms

While one may not experience symptoms in early-stage AMD, mild symptoms start becoming visible in later stages.

A few symptoms that one may experience as AMD progresses are:

Blurred or distorted central vision

Blurry vision
Blurry vision (hazy vision)

Objects may appear fuzzy, hazy, or distorted, making it difficult to see fine details.

Loss of central vision

A gradual or hurried loss of up-front vision may affect activities like reading, driving, and recognizing faces.

Dark or empty areas in the central vision

You may notice dark spots or gaps in your central vision, making seeing objects directly in front of you challenging.

Difficulty with color perception

Colors may appear less vibrant or washed out, and it may be challenging to distinguish between certain shades.

Straight lines appearing wavy or crooked

Straight lines may appear distorted or bent, which is known as metamorphopsia.

Decreased contrast sensitivity

It may become harder to distinguish between objects that have similar shades or colors.

Warning:
Early AMD is asymptomatic. If AMD exists in your family, regular eye checkups are vital to the early detection and prevention of the condition.

Types of Macular Degeneration

AMD manifests in two primary forms: dry AMD and wet AMD.

Dry (Atrophic) Macular Degeneration

In dry age-related Macular Degeneration, the retina develops small white or yellowish deposits known as drusen, which form beneath the macula.

Drusen comprises various components, including lipids (fats), proteins, and cellular waste products.

Specifically, drusen contain extracellular material, such as lipids and proteins, that accumulate between the Retinal Pigment Epithelium (RPE) and Bruch’s membrane, a layer beneath the retina.

The exact composition of drusen can vary, and their presence is a hallmark characteristic of AMD.

As drusen accumulate, they can disrupt the macula’s normal functioning, leading to its gradual deterioration over time.

Wet (Exudative) Macular Degeneration

Wet age-related macular degeneration (AMD) is an advanced stage of AMD that can result in swift and severe vision impairment.

Unlike dry AMD, where the drusen deposits build up, wet AMD is characterized by the development of abnormal blood vessels beneath the macula.

In the case of wet AMD, these abnormal blood vessels, known as choroidal neovascularization, can release fluid and blood into the macula, damaging the delicate retinal cells responsible for central vision.

This leakage can lead to sudden and significant vision loss, distortion, and a decline in the ability to perceive fine details.

Wet vs. Dry Macular Degeneration

Dry Macular Degeneration
Dry Macular Degeneration

The primary difference between the two is characterized by the kind of deposits/substance accumulated near Macula, leading to degeneration.

In dry AMD, small white or yellowish deposits, called drusen, form on the retina beneath the Macula, causing it to deteriorate or degenerate slowly.

In wet AMD, abnormal blood vessels grow and tend to break, bleed and leak fluid which causes damage to the Macula.

After some time, a scar overlies the entire Macula causing severe loss of central vision.

Dry AMD progresses much more gradually than wet AMD and is less likely to cause vision loss or other vision problems.

Dry AMD is also significantly more prevalent than wet AMD and is considered the milder form of the condition.

The onset of vision loss is more rapid in wet AMD when compared to dry AMD.

Approximately 11 million individuals, accounting for around 85% of all cases of AMD, are estimated to have dry AMD.

On the other hand, about 1.5 million people, representing approximately 15% of all cases of AMD, are affected by Wet AMD.

Around 10% of individuals diagnosed with dry ARMD develop Choroidal Neovascularization (CNV), a defining characteristic of wet AMD.

Most people with advanced AMD have a wet form of the condition.

Wet macular degeneration generally exhibits a more rapid progression in comparison to Dry Macular degeneration.

Any stage of dry AMD can turn into wet AMD — but wet AMD is always a late stage.

Diagnosis

A comprehensive eye examination is usually required to diagnose AMD.

In the preliminary examination, the doctor will first inquire about your symptoms, previous eye issues, and overall health conditions during the exam.

The doctor may then apply dilating eye drops to your eye to enlarge your pupil to observe the internal components of your eye using a specialized lens.

Depending upon the symptoms, the doctor may consider performing the following tests.

These tests aid in assessing the severity and extent of the disease and determining the most suitable treatment approach.

Diagnosing DRY AMD

The progression from dry to wet AMD can occur rapidly, and if left untreated, it can result in severe vision disability within a short period.

Dark Adaptometer Test

Dark adaptation testing is a diagnostic procedure that evaluates the retina’s function in individuals with AMD.

It measures the eyes’ ability to adjust to low-light conditions after exposure to bright light.

This test assesses how well the visual system adapts to changes in lighting, which AMD can influence.

Ophthalmoscopy

The doctor will then assess your central vision.

To check for signs of AMD, such as drusen (yellowish-white spots under the retina), the doctor may perform an Ophthalmoscopy to examine the interior of your eye.

Ophthalmoscopy is a diagnostic technique used to inspect the back part of the eye, known as the fundus, which encompasses the retina, optic disc, choroid, and blood vessels.

Amsler grid test

In addition, an Amsler grid test can identify signs of AMD, where the patient may observe distorted grid lines or a blank spot or hole on the grid.

Optical Coherence Tomography (OCT)

OCT, in particular, now plays a crucial role in diagnosing AMD.

OCT is a non-invasive imaging process that uses light waves to capture high-resolution cross-sectional images of tissues in the body, in this case, of the retina or macula.

Contrast Sensitivity Test

AMD may result in a loss of contrast sensitivity, making contours, shadows, and color vision less vivid.

The loss in contrast sensitivity can be quickly and easily measured by a contrast sensitivity test like Pelli Robson.

Diagnosing Wet AMD

In addition to the tests mentioned above, the diagnosis of wet AMD may involve the inclusion of the following evaluations:

Preferential hyperacuity perimetry(PHP)

Perimetry visual field test equipment
Perimetry visual field test equipment

PHP is a test that detects drastic changes in vision.

It involves the stimulation of the macula with distorted patterns of dots and the patient’s identification of where in the visual field this occurs.

Angiography

In wet macular degeneration, angiography can visualize the leakage of the bloodstream behind the macula.

Fluorescein angiography allows for the identification and localization of abnormal vascular processes.

These tests help locate leaky blood vessels and assist in treatment planning.

Treatments

The stage of AMD determines the most suitable treatment approach.

In general, treatment for AMD typically centers around restraining the advancement of the disease.

It is strongly advised to eliminate risk factors, with quitting smoking being of utmost importance, at all stages of the disease.

While there is currently no known cure for AMD, there are available treatments that can help mitigate symptoms and slow down the progression of the disease.

Let’s look at ways to treat the two kinds of AMD.

Dry AMD treatment

Dry AMD, which does not involve CNV, currently lacks effective treatments.

Nonetheless, there are measures and techniques that can be employed to enhance and maximize the remaining vision.

Age-Related Eye Disease Studies (AREDS and AREDS2) suggest that a combination of vitamins and minerals could decelerate the advancement of intermediate dry AMD to an advanced stage.

The supplements consist of Vitamin C, Vitamin E, Lutein, Zinc, Copper, and Zeaxanthin.

The above combination of supplements has been shown to decrease the likelihood of developing AMD and its related visual impairment by up to 25%.

This initial version of these supplements(AREDS) included the antioxidant Beta-carotene, which poses an increased risk of lung cancer for current and former smokers.

In the updated version(AREDS2), Zeaxanthin and Lutein serve as antioxidants instead, and smokers can opt for this one.

The management of advanced-stage AMD depends on the presence of Choroidal Neovascularization (CNV).

Wet AMD treatment

Laser Vision Surgery
Laser Vision Surgery

In the case of wet AMD, where CNV is present, it is managed using Vascular Endothelial Growth Factor (VEGF) inhibitors or anti-VEGFs.

Wet AMD is typically treated with medicine injected into the eye to prevent blood vessel growth.

This medicine is known as anti-vascular endothelial growth factor (anti-VEGF).

Although this treatment can’t cure AMD, it can stop or slow the progression.

Sometimes vision even improves again during treatment.

Ranibizumab, Aflibercept, Brolucizumab, and Faricimab are VEGF inhibitors approved for treating choroidal neovascularization (CNV) in wet AMD.

These medications are intravitreal injections, which means they are directly injected into the eye.

Pegaptanib and Aflibercept are also approved antiangiogenic drugs for the treatment of neovascular AMD.

Photodynamic therapy(PDT) and Laser Therapy were also used earlier in treating AMD.

Laser therapy involves heating and destroying abnormal blood vessels with laser beams.

PDP applies a combination of medication and laser beams.

However, PDT and Laser Therapy are rarely used nowadays as they have proven less effective and have more side effects than anti-VEGF therapy.

In some exceptional cases – and if no other treatment has helped – abnormal blood vessels may be removed surgically.

Also Read: If you want to know about medication for this condition, read Macular Degeneration Medication: What are the Available Options?

Risks associated

The primary adverse impact of vision impairment resultin