Central versus peripheral thickness in the human cornea explained.

Area of Science:

• Ophthalmology
• Corneal Anatomy
• Ultrastructural Imaging

Background:

• The human cornea exhibits regional thickness variations, being thicker peripherally than centrally.
• It has been hypothesized that this peripheral thickening is due to a greater number of stromal lamellae.

Purpose of the Study:

• To investigate the anatomical basis for the increased thickness of the peripheral human cornea.
• To determine if increased lamellar number or other factors contribute to peripheral corneal thickening using high-resolution imaging.

Main Methods:

• Human donor corneas were analyzed using light microscopy (LM) and transmission electron microscopy (TEM).
• Stromal regions (central, peripheral anterior, middle, posterior) were imaged to assess thickness, lamellar count, lamellar thickness, collagen fibril diameter, and density.

Main Results:

• Peripheral corneas (536 ± 29 µm) were significantly thicker than central corneas (415 ± 34 µm).
• Lamellar numbers did not differ significantly between central and peripheral regions.
• Peripheral posterior lamellae were ~50% thicker, and peripheral collagen fibril diameters were ~30% larger than central.

Conclusions:

• Peripheral corneal thickening is primarily due to increased thickness of posterior stromal lamellae, not an increased number of lamellae.
• While peripheral collagen fibrils are larger, only posterior lamellae show increased thickness, not anterior or mid-stromal lamellae.