Which condition is the most common cause of blindness in adults under 70 in the USA?

• A. Hypertension.
• B. Diabetes mellitus.
• C. Macular degeneration.
• D. Retinal artery occlusion.

Answer: (B)

Chronic high blood glucose from diabetes damages the small blood vessels in the retina, leading to diabetic retinopathy. This process can cause progressive vision loss and, if untreated, blindness. Diabetes is common, so diabetic retinopathy has become the leading cause of blindness in adults under 70 in the United States.

Hypertension can contribute to retinal vascular changes but is not the primary cause of blindness on a population level. Macular degeneration is a major cause of vision loss, but it predominantly affects adults older than 70. Retinal artery occlusion is an uncommon, sudden event and does not account for the majority of blindness in this age group.