What did the pellucid marginal degeneration of the cornea?
The pellucid marginal degeneration (or pellucid marginal degeneration) is always bilateral corneal pathology (right eye and left eye are achieved fairly symmetrically). It is accompanied by an arch located in the lower part of the cornea which then protrude forward, over a lower peripheral corneal thinning area.
The thinning is commonly observed in the lower quadrant of the cornea, and is fairly characteristic of this condition. In very advanced forms, this thinning is visible in less than the biomicroscope (slit lamp review). The cause of this condition is unknown. In some case, the notion of repeated eye rubbing is found.
Unlike Keratoconus, the corneal "protruding" tends to occur rather 'above', and not inside, the area of maximum thinning; the resulting deformation evokes a 'casesure' of the corneal curvature. The degree ofastigmatism armature is variable but it can reach values above 20 D. The degree of myopia is usually lower than in case of Keratoconus (see also:) OPD and pellucid marginal degeneration)
The prevailing direction of the topographic cylinder (astigmatism induced by the toricite of the cornea) is reversed (branch known as "against the rule") because the vertical meridians are a flattening marked next to the box corresponding to the pupil of entry. The lowest corneal power therefore lies in a central vertical corridor, and the highest power zone stretches along the inferior cornea on both sides of the flattened vertical portion, with a curved direction characteristic (appearance in wings of mill).
Pellucid marginal degeneration may be related to Keratoconus in terms of the physio-pathogenesis, not by common biomechanical factors that govern the location of the ectasia. As with Keratoconus, there is Vascularity or lipid deposits within the corneal tissue. The pellucid degeneration is a contraindication to the realization of a LASIK.
In this context, the use of the optical product is important to help differentiate between Keratoconus and pellucid degeneration, topographic aspects specular earlier ("aspect in Gallic mustache), although features, are not specific. Here is an example of map topographic and tomographic of horny affect EU of pellucid marginal degeneration (reverse astigmatism corrected at 6 D in the glass bezel).
Pellucid marginal degeneration is usually diagnosed later in life that of Keratoconus, usually between 40 and 60, when patients consult for a loss of Visual acuity due to a reverse astigmatism partially irregular, and a corneal topography is performed. It is possible that pellucid marginal degeneration begins earlier over the existence, but is revealed only to the 4th or 5th decade, to share the importance taken by reverse astigmatism. Non-surgical management of the D.M.P. (adaptation of rigid lenses) continues to occupy a prominent place in the management of this condition. Surgery often comes with a mediocre best corrected Visual acuity and a follow-up extended (at least 8 years old). The cornea transplant should be considered only for the case where the strain is extreme: his achievement is difficult due to the lower corneal thinning.
Any topographic aspect wing' mill', or "crab claws" is not synonymous with pellucid marginal degeneration. Evidenced by this case of dystrophy of Cogan, where irregularities in the epithelial surface created a previous topographic pattern that evokes that of a DMP. There is however no less corneal thinning; on the contrary, there are certainly Hyperplasia with irregularity of the epithelial sheet.