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Pellucid pronounce4/8/2023 ![]() ![]() New Scheimpflug imaging-based devices have shown the importance and usefulness of the pachymetric map for an appropriate diagnosis of PMD. Corneal topographic indices and the classical crab-claw topographic pattern cannot be used as the main tool to distinguish between PMD and keratoconus. Slit-lamp examination is very useful to distinguish PMD from other corneal ectatic disorders with inflammatory nature. PMD usually starts later in life than keratoconus and progresses slower than keratoconus. It is a rare corneal disorder that shares many clinical characteristics with other corneal ectasias, such as keratoconus, keratoglobus or Terrien marginal degeneration. Pellucid marginal degeneration (PMD) is a non-inflammatory ectatic corneal disease characterized by a narrow band of corneal thinning separated from the limbus by a relatively uninvolved area 1–2 mm in width. This is the second study evaluating CXL with iontophoresis in pediatric patients with progressive keratoconus with 18 months of follow-up using two different ways of anesthesia. Transepithelial collagen crosslinking by iontophoresis, unlike other transepithelial techniques seems to halt pediatric keratoconus progression over 18 months. The Kmax remained stable throughout follow-up (p = 0.04). The results showed a stabilization of the refractive UCVA and BCVA as early as the first post-operative month, with a slight improvement over time. 10 males and 3 females with a mean age of 15.4 ± 1.7 years (range 11-18 years) were included. The paired Student t test was used to compare data during the follow-up. Preoperative and post-operative visits at 1, 6, 12, and 18 months assessed the following parameters: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, corneal topography, optical tomography, and pachymetry with Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany), endothelial biomicroscopy (Konan Specular Microscope Konan Medical, Inc., Hyogo, Japan). ![]() Riboflavin solution was administered by iontophoresis for 5 min, and then UV-A irradiation (10 mW/cm) was performed for 9 min. 13 patients (13 eyes) diagnosed with progressive keratoconus underwent corneal CXL with iontophoresis (I-CXL). To evaluate the efficiency and safety of iontophoretic transepithelial corneal crosslinking in pediatric patients with progressive keratoconus underwent general or topical anesthesia in 18 months follow-up. This disorder was more severe in the cornea adjacent to the limbus compared to the cornea further away from the limbus. Our observations of the disorganization and degeneration of CFs suggest that PMD could be related to a disorder in the synthesis of CF. The mean of the minimum CF diameter was 19☓ nm in London Rsin White-embedded tissue. The CFs of the Bowman's layer and the stroma were replaced by very fine microfilaments. The prelimbal region of the PMD cornea had a degenerated Bowman's layer and thin undulating lamellae in the stroma. The lamellae were fused and keratocytes appeared like fibroblast. In the degenerated region of the cornea, the Bowman's layer had been replaced by collagenous pannus and the anterior stroma contained degenerated collagen fibrils (CFs) with very large proteoglycans (462±420 nm(2)). The patients underwent keratoplasty and the excised corneas were processed for light and electron microscopy to study the ultrastructural features.ĭegenerated corneas were observed in the region adjacent to the limbus. The following three patients were diagnosed with PMD corneas: (A) one 41-year-old male, (B) one 56-year-old female, and (C) one 31-year-old male. We report histological and ultrastructural features of three PMD corneas. Pellucid marginal degeneration (PMD) of the cornea is a rare ectatic disorder which typically affects the inferior or superior peripheral cornea in a crescentic fashion. ![]()
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