Noninvasive metabolic analysis of preserved rabbit cornea
K. Tsubota, R. A. Laing, K. Chiba, L. A. Hanninen and K. R. Kenyon
Department of Ophthalmology, Boston University School of Medicine, MA 02118.
With the method of corneal redox fluorometry, the autofluorescence of
reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) in rabbit
corneal endothelium was measured as a function of storage time in
McCarey-Kaufman (MK) medium and K-Sol medium. Measurements were started
immediately after preparation of the corneal button, and the corneas were
followed up for up to three weeks of storage. In both media, the PN/Fp
ratio of the endothelium initially increased slightly in the first or
second day and then began to decrease toward a level lower than baseline.
This initial increase is possibly a result of an adaptive mechanism. The
PN/Fp ratio maintained itself in the range of baseline values up to one
week in MK medium but not in K-Sol medium. With scanning electron
microscopy, the surface of the membrane and cell border were maintained for
a three-week preservation period, and no apparent differences were found
between the corneas stored in the two media. With transmission electron
microscopy, the intracellular organelles appeared almost normal through one
week of preservation in corneas stored in either media. During weeks 2 and
3, however, intracellular edema with increased endothelial thickness became
prominent in the corneas stored in both media. Although no visual
difference in the morphological features of the endothelium was apparent
between corneas stored in either medium, computer-assisted morphometric
analysis showed a statistically significant increase in the coefficient of
variation of mean cell area for the corneas preserved in K-Sol medium but
not for those preserved in MK medium.
