**Core Concept:** Corneal transplantation, also known as keratoplasty, is a surgical procedure to replace a damaged or diseased cornea with a healthy cornea from a donor.

**Why the Correct Answer is Right:**

The correct answer is **D.** Corneal preservation in organ culture. In this method, the cornea is placed in a specialized culture medium that provides a controlled environment for tissue preservation and regeneration. This allows the cornea to remain viable and functional until it is ready for transplantation.

**Why Each Wrong Option is Incorrect:**

A. **Corneal preservation in formalin:** Formalin is a fixative used for preserving tissues, but it is not suitable for corneal preservation as it causes severe alterations in the corneal structure and function.

B. **Corneal preservation in saline solution:** Saline is a physiologic solution, but it is not specifically designed for corneal preservation. This method may not maintain the corneal tissue's viability and functionality adequately for transplantation.

C. **Corneal preservation in dry storage:** Dry storage is not a suitable method for corneal preservation, as it does not maintain the cornea's integrity and functionality, making it unsuitable for transplantation.

**Clinical Pearl / High-Yield Fact:**

During organ culture, the cornea is placed in a special medium, such as the O'Sullivan's culture medium, which provides essential nutrients, oxygen, and growth factors to maintain the corneal tissue's viability and functionality. Organ culture allows for long-term preservation of the cornea, enabling its transplantation when needed.

**Correct Answer:** D. Corneal preservation in organ culture.