Cataracts are classified by age, location, stage of development, and:

• A. etiology
• B. color
• C. breed
• D. gravity

Answer: (A)

The main idea is that cataracts are categorized not only by when they appear, where they are in the lens, and how advanced they are, but also by what causes them. Etiology, or the cause, is a standard additional dimension of classification. It covers congenital or hereditary cataracts, diabetic or metabolic-related cataracts, traumatic or inflammatory/infectious causes, radiation exposure, and drug- or nutritional-related cataracts. Knowing the cause helps with prognosis, management decisions, and identifying any associated systemic issues. Color describes appearance but isn’t a formal classification axis, while breed isn’t relevant to humans and gravity isn’t used in cataract classification.