Folds, breaks, or thickening of Descemet's membrane.Diffuse corneal thinning, most severe peripherally.Fleischer rings, Vogt striae, and anterior stromal scarring are not typical, but Descemet membrane thickening and folds are common. Corneal topography and tomography as well as pachymetry can then be utilized to demonstrate diffuse corneal steepening and thinning. Finally, evaluation of the optic disc, macula, retinal vessels, and peripheral retina should be completed after pupillary dilation. Gross examination followed by slit lamp biomicroscopy should then be performed to evaluate the anterior segment. Measurements of pupillary reaction, ocular motility and alignment, as well as intraocular pressures should be documented. Physical examination begins with an assessment of visual acuity followed by retinoscopy and refraction. Rarely, they may present with an episode of severe eye pain due to corneal hydrops or corneal rupture. Patients usually present with a stable or worsening bilateral visual impairment that cannot be properly corrected with spectacles or contact lenses. Keratoglobus is not associated with atopic disease.Īn effective means of prevention has not been discovered. The pathophysiologic mechanism is unknown, but keratoglobus may be associated with a defect in collagen synthesis or degradation. Meghpara et al found similar alterations in expression of Sp1 and a1-PI in patients with keratoglobus. This leads us to believe that the underlying cause of corneal thinning in noninflammatory corneal ectasias may be due to alterations in the stromal degradation. Sp1, a transcription facter known to suppress a1-PI promoter activity, has been found to be elevated in these same patients. Various publications have demonstrated decreased levels of alpha1-proteinase inhibitor (a1-PI) within the stroma of keratoconus patients. In an attempt to uncover the mechanism behind the noninflammatory corneal ectasias, specific gene products have been investigated. Additional findings include central epithelial hyperplasia, neovascularization and scarring of the stroma, disruptions in Descemet's membrane, as well as thickening of Descemet's membrane. Despite this thinning, stromal lamellar organization remains unchanged from its normal configuration. Keratoglobus characteristically exhibits diffuse stromal thinning as well as focal disruptions in Bowman's layer which are most severe in the peripheral cornea. Unlike other noninflammatory corneal ectasias such as keratoconus, eye rubbing has not been designated a risk factor. However, associations between keratoglobus and disorders such as Ehlers-Danlos type VI, Marfan syndrome, and the blue sclera syndrome indicate that the etiology may result from defects in collagen synthesis. It is associated with vernal keratoconjunctivitis, dysthyroid ophthalmopathy, and chronic marginal blepharitis. The acquired form presents in adulthood and may evolve from preexisting cases of pellucid marginal degeneration or keratoconus. The congenital form is present at birth and is associated with Ehler-Danlos type VI, Leber congenital amaurosis, and the blue sclera syndrome.
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