**Core Concept**
Corneal endothelial cell count is a critical parameter in assessing the health and functionality of the cornea, particularly in cases of corneal transplantation or diseases affecting the corneal endothelium. The corneal endothelium is a single layer of cells lining the posterior surface of the cornea, playing a vital role in maintaining corneal hydration and transparency.

**Why the Correct Answer is Right**
The corneal endothelial cell count is typically measured using a technique called specular microscopy, which involves examining the corneal endothelium under high magnification. This allows for the accurate enumeration of endothelial cells and assessment of their morphology. Specular microscopy provides a direct visualization of the corneal endothelium, enabling the measurement of cell density, cell size, and other relevant parameters. This information is essential for diagnosing and monitoring conditions such as Fuchs' endothelial corneal dystrophy, pseudophakic bullous keratopathy, and corneal graft rejection.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe a method for measuring corneal endothelial cell count. While optical coherence tomography (OCT) can provide information on corneal thickness and morphology, it is not a direct measure of endothelial cell density.

**Option B:** This option is incorrect as it is a type of imaging modality that can provide information on corneal structure and morphology, but it is not specifically designed for measuring endothelial cell count.

**Option C:** This option is incorrect as it refers to a surgical procedure used to correct vision problems, but it is not a method for measuring corneal endothelial cell count.

**Clinical Pearl / High-Yield Fact**
A normal corneal endothelial cell density is typically greater than 2500 cells/mm^2, and a significant decrease in cell density can indicate endothelial dysfunction or disease. This information is crucial for ophthalmologists and corneal specialists to make informed decisions regarding patient care and treatment.

**Correct Answer:** C. Specular microscopy.