**Core Concept**
Cataracts are a leading cause of visual impairment worldwide, and understanding their etiology is crucial for ophthalmologists. Age-related cataracts are a type of cataract that occurs due to the natural aging process, leading to the clouding of the lens in the eye.

**Why the Correct Answer is Right**
Age-related cataracts are the most common type of cataract, accounting for approximately 90% of all cataract cases. This occurs due to the progressive accumulation of oxidative damage, protein aggregation, and changes in the lens structure over time. The aging process leads to a decrease in the production of certain proteins, such as crystallins, which are essential for maintaining the transparency of the lens. As a result, the lens becomes cloudy, impairing vision. This is a gradual process that occurs over many years, often starting in the 60s and 70s.

**Why Each Wrong Option is Incorrect**
**Option A:** Hereditary cataracts are a rare type of cataract that is caused by genetic mutations. While they can occur at any age, they are not the most common cause of cataracts.

**Option B:** Diabetes mellitus (DM) can increase the risk of developing cataracts, particularly in patients with poorly controlled blood sugar levels. However, DM is not the most common cause of cataracts.

**Option C:** Traumatic cataracts occur as a result of eye injury, such as a blow to the eye or a foreign object entering the eye. While trauma can cause cataracts, it is not the most common cause.

**Clinical Pearl / High-Yield Fact**
It's essential for ophthalmologists to assess patients for risk factors, such as age, diabetes, and family history, to identify individuals at higher risk of developing cataracts. A thorough medical and ocular history is crucial in the diagnosis and management of cataracts.

**Correct Answer:**
✓ Correct Answer: D. Age related