Soft tissue specimens shrink during fixation, dehydration and critical point drying when prepared for scanning electron microscopy (SEM). This can cause serious artifacts not only in 'compact' tissues but especially in hollow structure, like the eye, where the chambers are lined by delicate layers such as the corneal endothelium. In this study various glutaraldehyde and formaldehyde fixations at different concentrations with or without 5% sucrose were tested. Dimensional as well as morphological changes of rabbit corneal endothelial cells were evaluated. The mean surface diameter and area of rabbits' central corneal endothelial cells were measured first in vivo by specular microscope. Thereafter the same corneas were fixed in 9 different solutions and processed for scanning electron microscopy. The surface structure of the same endothelium was then photographed with SEM. The cell dimensions were remeasured. According to our results 1.25% or 2.50% glutaraldehydes without sucrose gave the best surface preservation and caused the least shrinkage.
Using a scanning electron microscope, we have studied the healing of the posterior corneal surface after a small perforating trauma. Both corneas of adult guinea pigs were perforated with a needle and studied at various time intervals during recovery. Thirty minutes after the perforation the wound was sealed with a fibrous plug. Leukocytes adhered to the wounded area from the first day of healing on, but usually most of them disappeared after the third day. Fibroblast-like cells were present during the entire healing process from the first day on. Endothelial cells at the margin of the wound lost their hexagonal shape and began to slide over the plug. In 7 days the wound was completely covered by irregularly arranged endothelium. The endothelial cells did not reach their regular arrangement during the 14-day follow-up period.
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