PubMed · 9818321
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I Kremer, M Blumenthal. 1998. Focal or diffuse PTK?. https://doi.org/10.1016/s0886-3350(98)80149-1
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PURPOSE: To describe a new surgical technique for posterior corneal transplantation. METHODS: An elderly patient had painful, pseudophakic bullous keratopathy with low visual potential. Through a 9.0-mm scleral tunnel incision, a midstromal pocket was dissected across the cornea, and a posterior lamellar disk 7.0-mm in diameter, which consisted of posterior stroma, Descemet membrane, and endothelium, was excised. A similarly shaped donor posterior disk was implanted in the recipient opening without suture fixation, and the scleral incision was sutured. RESULTS: Throughout the postoperative period, the posterior corneal transplant remained clear and in position. Three months after surgery, the "suture-in" astigmatic error was 3.5 diopters. Pachymetry measured 0.44 mm. CONCLUSION: Posterior lamellar keratoplasty may be a new surgical approach with which to manage corneal endothelial disorders.
BACKGROUND: The measuring value of intraocular pressure (IOP) in non-contact-tonometry (NCT) depends on IOP and is additionally highly influenced by the biomechanical parameters of the cornea. These parameters (especially corneal thickness) differ among several patients. It is desirable to characterize this influence and to correct the measuring value during the IOP measurement. The new tonometer consists of an air pulse applicator generating an air pulse with a rampshaped rising and a sharp decay after switching off and a Michelson-type laserinterferometer for detecting the corneal movement during the air pulse application and the oscillation after switching off the air pulse. METHOD: The method was tested with a mechanical phantom eye. The pressure inside the chamber of the phanton is adjustable. Measuring surfaces, which have to simulate the shape and the elastic properties of the cornea, are made of soft silicon rubber and fabricated with different thicknesses. RESULTS: Measurement results show that both the rise of the corneal deformation and the damped oscillation (frequency and damping) depend from material thickness and internal pressure of the phantom eye. CONCLUSION: Thus a characterization of the influence of the mechanical properties and a determination of a corrected IOP-value are possible. The task at present is the investigation and formulation of the mathematical dependences.