Corneal stroma

The corneal stroma is the thick, transparent middle layer of the cornea, which is the clear, dome-shaped surface that covers the front of the eye. The stroma accounts for approximately 90% of the cornea's thickness and plays a crucial role in maintaining the cornea's transparency and refractive power.

Structure

The corneal stroma is composed primarily of collagen fibers, which are organized into parallel lamellae. These lamellae are interwoven in a manner that provides both strength and transparency. The collagen fibers are predominantly type I collagen, with smaller amounts of type V and type VI collagen.

Keratocytes

Embedded within the stroma are specialized cells known as keratocytes. These cells are responsible for maintaining the extracellular matrix and play a role in the repair and regeneration of the corneal tissue. Keratocytes are flattened cells that lie between the lamellae of collagen fibers.

Extracellular Matrix

The extracellular matrix of the corneal stroma is rich in proteoglycans, which are essential for maintaining the spacing between collagen fibers. This precise spacing is critical for the transparency of the cornea. The main proteoglycans found in the stroma include keratan sulfate and dermatan sulfate.

Function

The primary function of the corneal stroma is to provide structural support to the cornea while maintaining its transparency. The unique arrangement of collagen fibers and the presence of proteoglycans ensure that the stroma remains clear, allowing light to pass through to the retina.

Refractive Power

The corneal stroma contributes significantly to the eye's refractive power. The curvature and uniformity of the stroma help focus light onto the retina, which is essential for clear vision.

Pathology

Several conditions can affect the corneal stroma, leading to vision impairment.

Keratoconus

Keratoconus is a progressive disorder characterized by thinning and cone-shaped protrusion of the cornea. This condition affects the structural integrity of the stroma, leading to distorted vision.

Corneal Edema

Corneal edema occurs when there is an accumulation of fluid within the stroma, often due to endothelial dysfunction. This can result in a loss of transparency and blurred vision.

Corneal Scarring

Injury or infection can lead to scarring of the corneal stroma, which disrupts the regular arrangement of collagen fibers and results in opacity.

Clinical Significance

Understanding the structure and function of the corneal stroma is essential for diagnosing and treating various corneal diseases. Surgical procedures such as corneal transplantation and laser-assisted in situ keratomileusis (LASIK) involve manipulation of the stroma.

See Also

• Cornea
• Keratocyte
• Collagen
• Proteoglycan

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