What is the difference between dry and wet AMD?

Dry AMD involves gradual breakdown of the RPE and photoreceptors, with drusen deposits, progressing slowly over years. Wet AMD involves abnormal blood vessel growth beneath the retina that leaks fluid and blood, causing rapid vision loss. Dry is more common (85-90%) but wet causes 90% of severe vision loss.

Does AMD cause total blindness?

AMD typically does not cause total blindness. It affects central vision (reading, driving, face recognition) but usually preserves peripheral vision. Patients maintain navigational ability and can function independently in many activities, though central tasks become increasingly difficult.

What is the Amsler grid used for?

The Amsler grid is a screening tool consisting of straight lines with a central fixation dot. Patients look at the dot and note any distortion, waviness, or missing areas in the surrounding lines. Distorted lines (metamorphopsia) can indicate wet AMD. Patients at risk are often given a grid for daily home monitoring.

Macular Degeneration for ABO

What Is Macular Degeneration?

Age-related macular degeneration (AMD) is a progressive disease affecting the macula, the central area of the retina responsible for sharp, detailed vision. It is the leading cause of central vision loss in people over age 50 in developed countries. AMD affects the ability to read, drive, and recognize faces while typically preserving peripheral vision.

Types of AMD

Dry AMD (Non-Exudative) - 85-90% of cases

Dry AMD involves the gradual breakdown of photoreceptors and the retinal pigment epithelium (RPE) in the macular area. Characteristics:

Drusen: Yellow deposits beneath the RPE, visible on examination
RPE changes: Pigmentary irregularities, atrophy
Geographic atrophy: Advanced dry AMD with well-defined areas of RPE and photoreceptor loss
Slow progression over years

Wet AMD (Exudative/Neovascular) - 10-15% of cases

Wet AMD involves the growth of abnormal blood vessels (choroidal neovascularization, CNV) beneath the retina. These fragile new vessels leak blood and fluid, causing rapid damage:

Sudden onset of distorted or blurred central vision
Metamorphopsia: Straight lines appear wavy or bent
Central scotoma: A blind spot in central vision
Can cause severe vision loss within weeks if untreated

Dry AMD is more common but progresses slowly. Wet AMD is less common but far more aggressive and is responsible for 90% of severe vision loss from AMD. Dry AMD can convert to wet AMD at any time, which is why monitoring with the Amsler grid is important.

Risk Factors

Age: Risk increases significantly after age 55
Smoking: The strongest modifiable risk factor (2-3x increased risk)
Family history: Genetic component is significant
Race: More common in light-skinned populations
UV exposure: Cumulative light damage over time
Cardiovascular disease: Shared risk factors with atherosclerosis

Symptoms and Detection

Early AMD may have no symptoms. As it progresses, patients may notice:

Difficulty reading or doing detailed work
Need for brighter light
Blurred or dark area in central vision
Distortion of straight lines (metamorphopsia) - a hallmark of wet AMD

The Amsler grid is a simple screening tool: a grid of straight lines with a central dot. Patients with AMD may notice wavy, distorted, or missing areas in the grid.

Treatment

Dry AMD: No cure. AREDS2 supplements (vitamins C, E, zinc, lutein, zeaxanthin) may slow progression. Lifestyle modifications (stop smoking, UV protection, diet).
Wet AMD: Anti-VEGF injections (ranibizumab, aflibercept, bevacizumab) are the standard treatment. These drugs block the growth factor that stimulates abnormal blood vessel growth. Monthly or bimonthly injections can stabilize or improve vision in many patients.

Low Vision Aids for AMD Patients

As an optician, you may help AMD patients with low vision devices:

High-add reading glasses: +4.00 D or higher for magnification
Handheld magnifiers: For spot reading tasks
Stand magnifiers: For sustained reading
Telescopic systems: For distance tasks (bioptic driving in some states)
Electronic magnifiers (CCTV): Provide high magnification with adjustable contrast
Tinted lenses: Amber or yellow tints to enhance contrast

AMD patients often benefit from high-contrast filters and increased illumination. When dispensing to an AMD patient, suggest anti-reflective coating (reduces glare), photochromic lenses (adapts to lighting), and possibly a yellow or amber tint for indoor use to enhance contrast. Task-specific lighting recommendations are also valuable.

Telling an AMD patient they will go completely blind. AMD affects central vision but typically preserves peripheral vision. Patients retain navigational ability and independence in many activities. While central tasks become difficult, total blindness from AMD alone is rare.

Key Takeaways

AMD affects the macula, causing central vision loss while preserving peripheral vision
Dry AMD (85-90%) progresses slowly; wet AMD (10-15%) can cause rapid severe loss
Smoking is the strongest modifiable risk factor
Wet AMD is treated with anti-VEGF injections; dry AMD with AREDS2 supplements
Low vision aids (magnifiers, high adds, tints) help AMD patients maximize remaining vision