## Core Concept
Keratoconus is a progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape. This alteration in shape can cause distorted vision and increased sensitivity to light. The condition typically starts in late adolescence or early adulthood.

## Why the Correct Answer is Right
The correct answer relates to the characteristics of keratoconus, but without the specific options provided, we'll discuss general principles. Keratoconus involves thinning of the cornea, leading to a conical protrusion, and is associated with progressive myopia and astigmatism. It affects vision by causing irregular astigmatism and myopia.

## Why Each Wrong Option is Incorrect
- **Option A:** Typically, options might include statements about the association with eye rubbing, genetic predisposition, or the presence of conical protrusion of the cornea. Without specifics, we can't directly refute, but generally, statements that are true about keratoconus would relate to its pathophysiology, risk factors (like eye rubbing), and clinical presentation.
- **Option B:** This might relate to a treatment or a characteristic; for example, if it mentions that keratoconus is treated with corneal transplant in advanced cases, this could be true. Incorrect statements would contradict established knowledge, such as suggesting keratoconus is caused by an infectious agent.
- **Option C:** Similarly, this could pertain to clinical features or diagnostic methods. For instance, if an option inaccurately describes a diagnostic criterion, such as stating that keratoconus is diagnosed solely based on symptoms without any diagnostic tools, it would be incorrect.
- **Option D:** This might propose an incorrect association or a false fact about keratoconus, such as suggesting it's more common in older adults or that it's directly caused by vitamin deficiency.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **keratoconus** is often associated with **eye rubbing** and there might be a link with **atopy**. Early detection and intervention, including corneal cross-linking, can help prevent progression. A classic clinical correlation is the **Munson sign**, a V-shaped protrusion of the lower lid when looking down, indicative of the conical shape of the cornea.

## Correct Answer: D.