The expansion of the cornea of fresh enucleated bovine eyes was tested by means of double-exposure holographic interferometry. The tissue was subjected to small increases in intraocular pressure. First preliminary results indicate that each bovine cornea has its own special elastic expansion which appears in different fringe pattern.
Int roduct ionFor the exact planning of corneal surgery a lot of information should be given to the surgeon. Besides the radius of curvature an.d th.e thickness of the cornea, the elastic expansion of thecornea might be of special interest. Holographic interferometry is accepted as a non-invasive means of structural analysis .In our experiments double-exposure holographic interferometry was applied for displacement measurement of the cornea.
Material and MethodsIn the preliminary study the expansion of the cornea of fresh enucleated bovine eyes was investigated by double-exposure holographic interferometry. The optical system for recording is shown in fig. 1. The laser beam is delivered by an Argon-laser with 514 nm wave length (Spectra Physics). The time between two exposures was 3-5 sec., the exposure time was 50 ms.
Concepts including the length of T-incisions are mainly based on empirical evaluation of the surgeons. We report on a holographic iiiterferometric study of the effects of straight T-incisions of 5niiii, lOnuiii and l5niiii length using double-exposure holographic interferoiiietry. A new classi flcation of the central holographic i nterterometric fringe pattern mci iiding cross-like, parallel and convex fringes allows an objective qualitative analysis of 48 holographic interferogranis of the corneas of six bovine eyes. The intraocular pressure is 1 34OPa with lOPa and 2OPa pressure increase. 'I-incisions of 5iiuii length of incision (incision depth 95 %) change the holographic interferometric fringe pattern completely. An increase to I 0mm length of incision results iii a change of holographic fringe pattern in 50% of the cases. \Vitli 15mm length of incision only two types of holographic interferometric fringe pattern of the cornea can be seen: parallel fringes atid irregular fringes indicating an instal)ility of the cornea. This iiiight he a reason for paradox flattening of tile cornea in tile unincised meridian.
In order to investigate the effects of 193nm excimer laser radiation on comeal wound healing 5bovine comeas were treated with subablative and ablative 193nm Excimer laser radiation, by simple light exposure and mechanial ablation of the corneal tissue or not treated. The comeas were metabolically labelled with a [35S]-labelling reagent. The proteoglycans were then extracted and radioactivity was measured with a liquid scintillation spectrometer. Corneas after ablative 193nm excimer laser radiation and after mechanical ablation had less radioactivity incorporated but had also less comeal tissue.
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