SEM of corneal endothelium and Descemet’s membraneeter (30.0 ± 8.0 nm: mean ± SD, calculated on allprepared specimens) (Fig. 5a), whereas in the uncoated specimen, it showed a felt-like appearance withfibrous structures of approximately 15 to 20 nm indiameter (Fig. 5b).
On the other hand, the stromal surface of themembrane with platinum coating in a surface tension specimen was composed of relatively illbalanced, larger-sized granular substances of approximately 26 to 78 nm in diameter (50.0 ± 12.8
nm: mean ± SD, calculated on all prepared specimens) (Fig. 6a), whereas in the uncoated specimen,
it showed a felt-like appearance with fibrous structures of approximately 30 to 50 nm in diameter,
which were thicker than that on the endothelial side(Fig. 6b).

Fig. 4. Low-magnified SEM image of Descemet’smembrane (DM) exfoliated from the stroma (ST) by thesurface tension. Bar = 1 µm.

Discussion
The undulation of the basal surface of the endothelium observed by TEM (Fig. 1) is supposed to correspond to small wrinkles on the basal surface of theendothelium observed by SEM (Fig. 3a). Smallopenings on the basal surface of the endothelium observed by SEM (Fig. 3a, arrows) are thought to correspond to orifices of pinocytotic vesicles beneaththe basal cell membrane of the endothelium observed by TEM (Fig. 1). Pinocytotic vesicles are supposed to be concerned with the active pumping action of the endothelium, by which intracorneal fluid
is pumped out into the anterior chamber when thefluid volume is increased.
In TEM images, the border between the stromaand Descemet’s membrane is less distinct than thatbetween the endothelium and the membrane, because of the presence of collagen fibrils within thestromal side of Descemet’s membrane (Hogan et al.,
1971; Komai et al., 1990). The present TEM study
demonstrated the binding between the stroma andthe membrane by the collagen fibrils (Fig. 1).
According to the three-dimensional observation of the basal lamina in pancreatic acinar cells,
cardiac muscles and blood capillaries, each basal
lamina consisted of globular materials of various
sizes which were attached to or buried in a flat mesh-Fig. 5. SEM images of the endothelial surface ofDescemet’s membrane with platinum coating in a surface tension specimen (a) and without coating in a heating specimen (b). The metal-coated Descemet’s membrane is composed of fine granular substances, whereas
the uncoated Descemet’s membrane shows a felt-likeappearance with fine fibrous structures. Bar = 100 nm.

33

K. Sasaki et al.

work composed of fine filaments and amorphous substances (Sawada, 1981). In this study, Descemet’smembrane with platinum coating in the surface tension specimen consisted of fine granular substances
as observed by Sawada (1981) (Figs. 5a and 6a).
However, the size of the granular substances obviously differed between the endothelial and stromalsides. These results suggest that their native sizes
also differ between the two surfaces.
Descemet’s membrane was mainly composedof type VIII collagen, partly by type IV and barely
by type VI collagens (van der Rest and Garrone,1991). Marshall et al. (1993) demonstrated, in an

immunoelectron study, that type VIII collagen wasabundant in the stromal side of Descemet’s membrane and type IV collagen was rich in the endothelial side. They also showed that collagen types
V and VI were present in the corneal stroma and its
transitional zone to Descemet’s membrane, for adhering the stroma to the membrane.
Our observation of Descemet’s membranewithout metal coating clarified that its endothelial
surface was composed of felt-like fine filamentous
substances (Fig. 5b), whereas the stromal surface
was composed of thicker fibrous structures (Fig. 6b).
These results may reflect a difference of the collagen types between the two surfaces of the membrane.

Acknowledgments: We express our sincere thanks toProfessor Yoshitsugu Inoue, Division of Ophthalmology
and Visual Science, Department of Medicine of Sensory
and Motor Organs, School of Medicine, Tottori University Faculty of Medicine, for his generous help. We arealso indebted to Mr. Hitoshi Osatake (Division of Morphological Analysis, Department of Functional, Morphological and Regulatory Science, School of Medicine,
Tottori University Faculty of Medicine) for his technicalhelp.
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34

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Received March 3, 2004; accepted March 31, 2004
Corresponding author: Akihiko Tamai, MD35