What is the difference between dry and wet AMD?

Dry AMD (non-neovascular) involves drusen accumulation and gradual RPE cell death leading to geographic atrophy. It progresses slowly and accounts for 85 to 90% of AMD cases. Wet AMD (neovascular) involves abnormal blood vessel growth from the choroid, which leaks fluid and blood under the macula, causing rapid central vision loss. Wet AMD accounts for 10 to 15% of cases but is responsible for the majority of severe vision loss. Both forms can coexist in the same eye.

What is metamorphopsia and what causes it in AMD?

Metamorphopsia is the visual symptom where straight lines appear wavy, distorted, or bent. In wet AMD, fluid accumulating under or within the retina lifts and distorts the photoreceptors. Because the photoreceptors are physically displaced from their normal positions, the visual map they send to the brain is distorted, causing straight lines to appear curved. Metamorphopsia detected on Amsler grid testing is a classic warning sign of wet AMD or conversion from dry to wet AMD.

How often should AMD patients monitor with the Amsler grid?

AMD patients with intermediate or advanced dry AMD, or treated wet AMD, should check the Amsler grid daily, one eye at a time, at a consistent viewing distance of about 14 inches with their reading glasses on. Any new distortion, new blurry or dark area, or change from baseline should prompt an urgent call to the office rather than waiting for the next scheduled appointment. Early detection of wet AMD conversion allows for earlier treatment and better visual outcomes.

What is optical coherence tomography (OCT) and why is it essential for AMD management?

OCT is a non-invasive imaging technique that produces high-resolution cross-sectional images of retinal layers, similar to an ultrasound but using light. In AMD management, OCT detects subretinal fluid, intraretinal fluid, pigment epithelial detachments, and neovascular membranes, which are the hallmarks of wet AMD activity. OCT guides treatment decisions: the presence of fluid indicates active disease requiring injection, and resolved fluid supports extending the injection interval. It is performed at virtually every AMD follow-up visit.

Age-Related Macular Degeneration (AMD) for the CPO Exam

Q: What are AREDS2 vitamins and who should take them?

AREDS2 vitamins are a specific supplement formulation (500 mg vitamin C, 400 IU vitamin E, 10 mg lutein, 2 mg zeaxanthin, 80 mg zinc oxide, 2 mg cupric oxide) proven to reduce the risk of progression from intermediate AMD to advanced AMD by approximately 25%. They are recommended for patients with intermediate AMD (large drusen) or advanced AMD in one eye. They are not recommended for early AMD and do not help patients who have not developed intermediate AMD.

Age-related macular degeneration (AMD) is the leading cause of permanent central vision loss in adults over 65 in the developed world. It affects the macula, the central retina responsible for sharp, color, and detail vision. As a CPO, you will assist with AMD monitoring and treatment in virtually every ophthalmic practice that sees older patients.

Understanding Dry AMD

Dry AMD (also called non-neovascular or atrophic AMD) accounts for approximately 85 to 90% of all AMD cases. It is characterized by the accumulation of drusen, yellowish deposits between the retinal pigment epithelium (RPE) and Bruch's membrane. Drusen are classified by size:

Small drusen (less than 63 microns): Common with normal aging, low risk of progression.
Intermediate drusen (63 to 125 microns): Moderate risk of progression to advanced AMD.
Large drusen (over 125 microns): High risk; indicates intermediate AMD.

As dry AMD advances, the RPE cells gradually die, leading to geographic atrophy (GA), well-defined areas of RPE and photoreceptor loss. Geographic atrophy progresses slowly and causes gradual central vision loss. There is no treatment that reverses geographic atrophy, though research is ongoing.

The AREDS2 (Age-Related Eye Disease Study 2) vitamins, a specific formulation of antioxidants and zinc, have been shown to reduce the risk of progression from intermediate AMD to advanced AMD by approximately 25%. They do not treat early AMD or restore lost vision.

Understanding Wet AMD

Wet AMD (neovascular AMD) accounts for only 10 to 15% of cases but is responsible for the majority of severe vision loss from AMD. It occurs when abnormal new blood vessels (choroidal neovascularization, CNV) grow from the choroid through Bruch's membrane under or into the retina. These abnormal vessels are fragile and leak fluid and blood, causing rapid damage to the macula.

Symptoms of wet AMD include:

Sudden distortion of straight lines (metamorphopsia)
A dark or blurry spot in central vision
Colors appearing washed out or dim
Rapid change in vision over days to weeks

Any AMD patient who reports new distortion or sudden worsening of vision must be seen urgently, within 24 to 48 hours if possible. Wet AMD can cause irreversible central vision loss rapidly if untreated. Never schedule these patients for a routine follow-up appointment without informing the physician first.

The Amsler Grid

The Amsler grid is a simple monitoring tool for AMD patients. It consists of a grid of horizontal and vertical lines with a central fixation dot. The patient covers one eye and looks at the central dot, reporting any distortion, wavy lines, blurry areas, or missing areas in the grid. AMD patients should check their Amsler grid daily at home and contact the office immediately if they notice changes. The CPO may administer and document Amsler grid testing at office visits.

Treatment: Anti-VEGF Injections

Wet AMD is treated with intravitreal injections of anti-VEGF agents (bevacizumab, ranibizumab, aflibercept, faricimab) that block vascular endothelial growth factor, the protein driving abnormal vessel growth. Injections are given every 4 to 12 weeks, often on a treat-and-extend protocol where the interval between injections is gradually extended based on response. Anti-VEGF treatment can stabilize and, in many patients, improve vision, but requires long-term ongoing therapy.

Dry AMD with geographic atrophy now has approved treatments: complement inhibitors (pegcetacoplan and avacincaptad pegol) delivered by intravitreal injection to slow GA progression.

The CPO Role in AMD Care

Obtain and document best-corrected visual acuity at every visit.
Administer and document Amsler grid testing.
Assist with OCT (optical coherence tomography) imaging to assess fluid and drusen.
Prepare patients for intravitreal injections and assist post-injection care.
Educate patients about home Amsler grid monitoring and the importance of reporting new symptoms promptly.
Discuss AREDS2 vitamin supplementation for eligible patients.

Key Takeaways

Dry AMD (85-90% of cases) is characterized by drusen and slowly progressive geographic atrophy; AREDS2 vitamins reduce progression risk.
Wet AMD (10-15% of cases) causes rapid central vision loss from choroidal neovascularization; treated with anti-VEGF intravitreal injections.
New metamorphopsia or sudden vision change in an AMD patient is urgent; notify the physician immediately.
The Amsler grid is the primary home monitoring tool; abnormalities require prompt evaluation.
OCT is the key imaging modality for detecting and monitoring subretinal and intraretinal fluid in wet AMD.