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Posterior Cornea (posterior + cornea)
Selected AbstractsOn the compensation of horizontal coma aberrations in young human eyesOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 3 2008Fan Lu Abstract The nature of the compensation of horizontal coma (Z31) between optical elements of the human eye has been studied and the compensative mechanism has been attributed to a passive process linked to angle kappa of the eye. We measured the horizontal coma in the anterior cornea, the whole eye and the internal optics for 221 young subjects. Thirty-three eyes with minimum angle lambda and 53 eyes with relatively large angle lambda were selected from these eyes to test the hypothesis that horizontal coma compensation is linked to angle kappa. Significant horizontal coma in the anterior cornea was observed for the group with minimum angle lambda in both the right (,0.12 ± 0.07 ,m) and left eyes (0.12 ± 0.10 ,m), and this was well compensated by the internal optics so that the level of horizontal coma in the whole eye over a 6-mm pupil size was very low (,0.05 ± 0.07 ,m for OD and 0.02 ± 0.08 ,m for OS). The horizontal coma in the anterior cornea was significantly correlated to the horizontal coma in the internal optics for both the right and the left eye. The results suggest that there is another source of horizontal coma, in addition to that linked to angle kappa, in the anterior cornea, and also a new compensative mechanism to balance the corneal coma, perhaps in the posterior cornea or the lens. [source] Grafting of the posterior cornea.ACTA OPHTHALMOLOGICA, Issue 5 2000Description of a new technique with 12-month clinical results ABSTRACT. Purpose: To describe the technique of grafting only the posterior cornea and to report 12-month clinical results. Method: A two-layer technique with an anterior recipient flap created by a microkeratome and a posterior penetrating donor graft allows for a watertight wound closure and at the same time a peroperative correction of astigmatism. Four eyes (3 patients) were followed for 12 months. Results: The surgical technique could be completed in all cases without complications. The postoperative course was uneventful. The intrastromal absorbable sutures disappeared spontaneously and completely. Graft thickness showed the expected 6-month minimum while recipient flap thickness remained constant. After 1 year endothelial cell densities were 1200,2300 cells/mm2. Confocal microscopy showed activated keratocytes in the flap and quiescent keratocytes in the donor tissue by one year. The anterior chamber depth was normal in all cases. The optical quality of the cornea was studied by automatic keratometry and keratoscopy (TMS). The obtained optical properties were not optimal. Conclusions: The developed novel technique gives a better wound closure and a complication free postoperative course. It may allow for better control of postoperative astigmatism. In order to disseminate the use of the technique, eyebanks should supply posterior corneas to the surgeon. [source] | ||||||||||