QUANTITATIVE ANALYSIS OF STROMAL SCAR TISSUE FORMATION IN PHOTOREFRACTIVE KERATECTOMY (PRK)
M. Böhnke, P. Eggli, P. Imesch, K. Vogelberg
Background: PRK may induce stromal scar tissue and increase light scatter. Aim of the study: To perform and compare observations of stromal transparency in normal and PRK treated corneas with various methods.
Materials and methods: In 24 rabbits a PRK of -5D /6mm diameter was performed in one eye. The rabbits were assigned to three treatment protocols. The animals were sacrificed after 4 weeks. The stromal transparency was evaluated in vivo with clinical slit lamp evaluation, confocal scanning slit microscopy, in vitro with photometric evaluation, confocal laser scanning sectioning, and light microscopy.
Results: The slit lamp evaluation yielded differences between the 3 tratment groups in the PRK treated eyes. Confocal microscopy of the living cornea only showed a clear difference to the control corneas. The investigation of excised corneas showed an increased light absorption in the short wave photometric spectra, and an increase of forward and backward light scatter in the confocal laser scan microscope. Light microscopy confirmed the presence od scar formation.
Discussion: The clinical slit lamp evaluation can be supplemented with new methods, which allow for an analysis of stromal transparency changes. The sagittal sectioning with the confocal laser scan microscope has the advantage of combining quantitative with morphologic data.
Dept. of Ophthalmology, University of Bern, CH-3010 Bern