A 68-year-old Indian male smoker presents with sudden-onset central vision loss and metamorphopsia over 2 weeks. Fundoscopy reveals a grayish-green subretinal membrane with surrounding subretinal fluid and lipid exudates at the macula, against a background of drusen. SD-OCT confirms the presence of subretinal fluid and a hyperreflective lesion. The pathological process marked **B** in the diagram accounts for which of the following clinical realities in age-related macular degeneration?

Question

Accepted Answer

B. Although it represents only 10–15% of all AMD cases, it causes >90% of severe vision loss from AMD and is the leading cause of legal blindness in adults over 65 in developed countries. ## Why option 1 is correct

The structure marked **B** — wet (neovascular) AMD with choroidal neovascularization and subretinal fluid — is the exudative form of AMD. Despite accounting for only 10–15% of all AMD cases, it causes >90% of severe vision loss from AMD and is the leading cause of legal blindness in adults over 65 in developed countries (AAO PPP 2024; CATT Research Group NEJM 2011). This disproportionate impact reflects the aggressive nature of CNV-driven disease: the fragile neovessels leak serum and blood, creating subretinal/intraretinal fluid, lipid exudates, and hemorrhages that rapidly destroy the foveal photoreceptors and lead to a disciform fibrovascular scar with permanent central vision loss. The patient's presentation—sudden metamorphopsia, central scotoma, and SD-OCT evidence of subretinal fluid with hyperreflective CNV—is pathognomonic for this entity.

## Why each distractor is wrong

- **Option 2**: Wet AMD accounts for only 10–15% of all AMD cases, not 50%. The majority of AMD patients have dry (non-exudative) disease with drusen and geographic atrophy. Wet AMD is the minority form but causes the majority of vision loss.
- **Option 3**: Wet AMD is defined by choroidal neovascularization—abnormal new vessels arising from the choriocapillaris that breach Bruch's membrane. It is not caused by lipid accumulation alone; the hallmark is new vessel formation with leakage. This describes dry AMD pathology, not wet AMD.
- **Option 4**: Wet AMD is a rapidly progressive disease. Metamorphopsia is the earliest symptom and signals acute CNV activity. Without prompt anti-VEGF therapy (loading dose of three monthly injections), vision loss is severe and irreversible. Amsler grid monitoring alone is insufficient; SD-OCT and anti-VEGF treatment are the standard of care.

**High-Yield:** Wet AMD = 10–15% of cases but >90% of severe vision loss; CNV is the pathognomonic lesion; anti-VEGF therapy (bevacizumab, ranibizumab, aflibercept) is the standard of care since 2006.

[cite: AAO Preferred Practice Pattern — AMD 2024; CATT Research Group NEJM 2011]

Answer

A. It is caused exclusively by lipid accumulation beneath the retinal pigment epithelium and does not involve new vessel formation

Answer

C. It occurs in approximately 50% of all AMD patients and is the most common form of AMD presenting with drusen

Answer

D. It progresses slowly over 10–15 years and rarely causes central vision loss if detected early with Amsler grid monitoring alone

Explanation

Why option 1 is correct

Why each distractor is wrong

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