Abstract
Purpose:
To characterize the structural properties of collagen lamellae in the normal human corneal stroma, we measured the width of the lamellae as well as their angle relative to Bowman’s layer (BL).
Methods:
Eleven normal human corneas (from five women and six men with a mean ± SD age of 58.0 ± 9.4 years and age range of 43 to 69 years) were obtained from an eye bank. The tissue was fixed overnight with 4% paraformaldehyde, and 2-mm-square tissue blocks were excised from the central area of the cornea. The collagen fibers and lamellae of the corneal blocks were visualized by second harmonic generation (SHG) imaging microscopy (Zeiss LSM710NLO and Coherent Chameleon). Optical slices were obtained in 1-μm steps from BL to Descemet’s membrane, and the series of SHG images was subjected to three-dimensional reconstruction. Ten equally spaced points (L1 to L10) of the reconstructed data sets were selected as analysis points for measurement of the width of collagen lamellae and their angle relative to BL with the use of ZEN 2012 software (Zeiss).
Results:
The width (mean ± SD) of collagen lamellae was 3.7 ± 1.1 µm adjacent to BL and increased gradually with progression toward Descemet’s membrane, with values of 7.8 ± 3.4, 14.1 ± 3.4, 27.1 ± 5.8, 34.5 ± 12.8, 46.2 ± 11.9, 58.8 ± 15.0, 66.2 ± 18.0, 87.0 ± 32.7, 109.2 ± 39.7, and 128.6 ± 42.0 µm for L1 to L10, respectively. The angle (mean ± SD) of collagen lamellae relative to BL was 24.4 ± 7.0 degrees at BL and decreased gradually to 11.7 ± 3.7, 8.3 ± 2.4, 6.3 ± 2.3, 5.1 ± 1.4, 4.7 ± 2.0, 4.2 ± 1.6, 3.8 ± 2.0, 3.7 ± 1.9, 3.2 ± 1.9, and 2.4 ±1.8 degrees, respectively, with progression toward Descemet’s membrane.
Conclusions:
Collagen lamellae adjacent to BL are narrow and form a steep angle with BL, whereas they increase in width and their angle relative to BL flattens with progression toward Descemet’s membrane. This three-dimensional arrangement of collagen lamellae may contribute to corneal rigidity and to the stability of the shape of the anterior cornea.
Keywords: 484 cornea: stroma and keratocytes •
519 extracellular matrix •
419 anatomy