5/8/2023 0 Comments Pellucid marginal degneration![]() ![]() Studies have shown that the degradation of stromal collagen in KC is accompanied by the altered expression of cytokines, matrix metalloproteinases (MMPs MMP-1, -3, -7,- 9, -13) with their inhibitors (tissue inhibitor of metalloproteinases-1 (TIMP-1)) and growth factors (epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) as well as nerve growth factor (NGF)). However, a recent review by Galvis and colleagues has suggested that ectatic disorders are partly inflammatory conditions.īiomarkers in the tear film have been studied in more depth in patients with KC but no studies have been reported for PMD. Īll histopathological studies of PMD and KC have noted the absence of inflammatory cells, and corneal ectatic disorders are generally believed to be non-inflammatory diseases with a multivariable origin. Furthermore, crescentic wedge resection in PMD can also be a treatment. In advanced cases, both ectasias can be treated with penetrating or deep anterior lamellar keratoplasty, but the technical disposal is different (graft size, position). Intracorneal ring segment implantation is widely used in KC, but may not be applicable in true PMD. In progressive cases, collagen cross-linking could be effective in both disorders. In the early stages of both conditions, the management is most commonly non-surgical: KC is typically managed with rigid-gas permeable (RGP) contact lenses, whereas early cases of PMD are typically managed using spectacle lenses alone. The adequate therapy depends on the stage of the ectasia. The clinical significance of distinct PMD compared to KC is that the clinical continuum and treatment modalities-including the surgical interventions for these two entities-are different. It is important to note that PMD is not associated with vascularisation and lipid or iron deposition. ![]() PMD is usually discovered in the later decades of life (between the second and the fifth) compared to KC. Pellucid marginal degeneration is often misdiagnosed and is often confused with inferior keratoconus. In early cases of PMD, the cornea may look relatively normal and, in severe cases, PMD (end-stage ectasias with large corneal scarring) may be difficult to differentiate from KC. ![]() It is not known whether PMD and KC are distinct diseases or whether they represent different clinical presentations of the same underlying disease process. Pellucid marginal degeneration (PMD) is a very rare peripheral thinning disorder of the inferior (in atypical cases of the superior ) cornea, while keratoconus (KC) is the most common primary corneal ectatic disease that gives rise to a cone-shaped cornea. The rate of progression among the various ectatic entities is different and is associated with an increase in the spherical component of the refraction and irregular astigmatism with consequent deterioration of visual acuity, furthermore also results in the inducement of significant higher-order aberrations (HOAs), which contribute to a poorer retinal image quality, resulting in decreased visual acuity. They are characterized by progressive deformation of the corneal architecture-including corneal thinning at different locations-depending on the type of the ectasia. Corneal ectatic disorders have considerable importance in public health. ![]()
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