PURPOSE To evaluate the leading indications for penetrating keratoplasty (PKP) and their trends in Greece during the period 1982 to 2006. METHODS Retrospective data review of 1,929 patients (2233 eyes) who underwent PKP in the period between 1982 and 2006 at three cornea transplantation units of three hospitals in Greece (Athens General Hospital, Heraklion University Hospital of Crete, and Th...

Purpose: To evaluate the outcomes of secondary Descemet membrane endothelial keratoplasty (DMEK) after failed primary DMEK. Design: Retrospective, interventional case series. Participants: Fifty-five DMEK recipients 42 to 89 years of age. Methods: An initial consecutive series of 1655 DMEK surgeries was reviewed to identify cases of secondary DMEK after failed primary DMEK (n 1⁄4 55). A paired ...

purpose: to determine the indications for penetrating keratoplasty (pk) in iran over an 11-year period. methods: all eye bank records of patients who underwent pk from 1994 to 2004 at ophthalmologic centers throughout iran were reviewed. results: during this 11-year period, a total of 19,668 cases were operated. the most common indication for penetrating keratoplasty was keratoconus (34.5%), fo...

purpose: to report two patients with keratoconus who underwent regrafting to correct anisometropia and high astigmatism after penetrating keratoplasty. patients and findings: the first case is a 34-year-old man with keratoconus who had undergone penetrating keratoplasty. the sutures were removed 6 months postoperatively that led to high hyperopia. regraft was performed considering vitreous leng...

We give a 5-approximation algorithm to the rooted Subtree-Prune-and-Regraft (rSPR) distance between two phylogenies, which was recently shown to be NP-complete. This paper presents the first approximation result for this important tree distance. The algorithm follows a standard format for tree distances. The novel ideas are in the analysis. In the analysis, the cost of the algorithm uses a "cas...

The subtree prune-and-regraft (SPR) distance metric is a fundamental way of comparing evolutionary trees. It has wide-ranging applications, such as to study lateral genetic transfer, viral recombination, and Markov chain Monte Carlo phylogenetic inference. Although the rooted version of SPR distance can be computed relatively efficiently between rooted trees using fixed-parameter-tractable algo...

Supertree methods reconcile a set of phylogenetic trees into a single structure that is often interpreted as a branching history of species. A key challenge is combining conflicting evolutionary histories that are due to artifacts of phylogenetic reconstruction and phenomena such as lateral gene transfer (LGT). Many supertree approaches use optimality criteria that do not reflect underlying pro...

We perform a pruning procedure on a Lévy tree and instead of throwing away the removed sub-tree, we regraft it on a given branch (not related to the Lévy tree). We prove that the tree constructed by regrafting is distributed as the original Lévy tree, generalizing a result of Addario-Berry, Broutin and Holmgren where only Aldous’s tree is considered. As a consequence, we obtain that the “averag...