Background/aims: Scant consideration has been given
to the variation in structure of the human amniotic
membrane (AM) at source or to the significance such
differences might have on its clinical transparency.
Therefore, we applied our experience of quantifying
corneal transparency to AM.
Methods: Following elective caesarean, AM from areas
of the fetal sac distal and proximal (ie, adjacent) to the
placenta was compared with freeze-dried AM. The
transmission of light through the AM samples was
quantified spectrophotometrically; also, tissue thickness
was measured by light microscopy and refractive index by
refractometry.
Results: Freeze-dried and freeze-thawed AM samples
distal and proximal to the placenta differed significantly in
thickness, percentage transmission of visible light and
refractive index. The thinnest tissue (freeze-dried AM) had
the highest transmission spectra. The thickest tissue
(freeze-thawed AM proximal to the placenta) had the
highest refractive index. Using the direct summation of
fields method to predict transparency from an equivalent
thickness of corneal tissue, AM was found to be up to
85% as transparent as human cornea.
Conclusion: When preparing AM for ocular surface
reconstruction within the visual field, consideration should
be given to its original location from within the fetal sac
and its method of preservation, as either can influence
corneal transparency
