The effect of the local anaesthetics oxybuprocaine (OBu) and tetracaine (Tetra) and the preservatives chlorhexidine (CH) and benzalkonium chloride (BAK) on corneal epithelial permeability was studied by fluorophotometry in normal human eyes. Five instillations of one drop ophthalmic solution of the compounds were administered to one eye at 2-minute intervals; a control solution was instilled into the fellow eye. The increase in corneal epithelial permeability, expressed as the permeability ratio between the treated and control eye, was not significant after instillation of the anaesthetics. The preservatives and the combination OBu + CH increased corneal epithelial permeability significantly (P less than 0.05). OBu + BAK and Tetra + BAK increased permeability to a far greater extent (P less than 0.005).
Mersilene (polyester monofilament) seems to be suitable for penetrating keratoplasty because it is strong, shows no degradation by ultraviolet light, is insoluble, so that it can be left in situ, and offers the possibility of regulating postoperative astigmatism by suture adjustment. In 12 patients penetrating keratoplasty was performed with the combined interrupted/running suturing technique, using eight interrupted nylon 10-0 sutures and one running Mersilene 11-0 suture. The results were compared with those of 25 patients in whom eight interrupted nylon 10-0 sutures and one running nylon 11-0 suture were used. Six months after penetrating keratoplasty, no differences could be found between the two groups in keratometric astigmatism, visual acuity or slitlamp findings. In three patients postoperative adjustment of the running Mersilene suture reduced astigmatism by 50, 90 and 100% respectively. In an animal study the behaviour of Mersilene in the cornea was evaluated by slitlamp examination, histology and electron-microscopy. The tissue response to Mersilene was minimal. Considering the resemblance to nylon in clinical findings, minimal tissue response, lack of biodegradation and possibility of regulating postoperative astigmatism by suture adjustment, Mersilene seems to be a suitable material for penetrating keratoplasty.
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