![]() ![]() Given the corneal thinning and the potential association of eye rubbing with keratoconus and its relationship to PMD, it could be considered to advise patients not to rub their eyes. No preventative strategies exist for PMD. The thin, weakened cornea is hypothesized to protrude as a result of intraocular pressure. The exact pathophysiology of PMD has not been ascertained, but it is thought to be secondary to collagen abnormalities, similar to keratoconus. FLS collagen has also been observed in advanced KC. In cases of acute hydrops, breaks in Descemet's membrane with swelling of the stroma and inflammatory infiltrate is seen. Electron microscopy of the thin regions reveals unusual electron-dense areas of fibrous long-spacing (FLS) collagen with a periodicity of 100 to 110 nm, whereas normal collagen has a periodicity of 60 to 64 nm. Lipid deposits are typically absent and stromal ground substance rich in mucopolysaccharides is present. Classically, PMD is histologically thought to show an area of stromal thinning, normal epithelium, endothelium, and Descemet's membrane, and absent or broken (focal disruption) Bowman's membrane. Histopathologic abnormalities in PMD resemble keratoconus. A recent case showed that PMD was coexistent with corneal plana in an individual with a KERA mutation, thus, potentially implicating KERA in the development of PMD. PMD has no sex or racial predilection, and does not appear to be hereditary, but moderate to high astigmatism has been noted in families with affected patients. PMD typically presents in the second to fifth decade of life. It has not been elucidated whether keratoconus, keratoglobus, and PMD are different diseases or phenotypic variations of the same disease. In series performed in Japan, 17 of 27 cases of unilateral PMD revealed keratoconus or suspected keratoconus in the fellow eye. Ten percent of PMD cases are associated with keratoconus and 13% are associated with keratoglobus. Keratoconus, keratoglobus, and PMD are postulated to be related because these conditions coexist in families. Some people postulate, however, that this prevalence might be underestimated as the condition is often misdiagnosed as keratoconus. PMD, while rare, is the second most common noninflammatory corneal thinning disorder after keratoconus. Also, patients who undergo refractive surgery with PMD can have deleterious results, so it is important to consider prior to refractive surgery. It is important to recognize as it can cause severe deterioration in visual function. PMD is disease of peripheral corneal thinning that is slowly progressive over many years. There is no associated inflammation and the central cornea is of normal thickness. Compare Standard and Premium Digital here.Īny changes made can be done at any time and will become effective at the end of the trial period, allowing you to retain full access for 4 weeks, even if you downgrade or cancel.PMD is uncommon and is characterized by a crescent-shaped band of inferior corneal thinning approaching 20% of normal thickness that is 1 to 2 mm in height, 6 to 8 mm in horizontal extent, and 1 to 2 mm from the limbus. You may also opt to downgrade to Standard Digital, a robust journalistic offering that fulfils many user’s needs. If you’d like to retain your premium access and save 20%, you can opt to pay annually at the end of the trial. If you do nothing, you will be auto-enrolled in our premium digital monthly subscription plan and retain complete access for $69 per month.įor cost savings, you can change your plan at any time online in the “Settings & Account” section. For a full comparison of Standard and Premium Digital, click here.Ĭhange the plan you will roll onto at any time during your trial by visiting the “Settings & Account” section. Premium Digital includes access to our premier business column, Lex, as well as 15 curated newsletters covering key business themes with original, in-depth reporting. Standard Digital includes access to a wealth of global news, analysis and expert opinion. During your trial you will have complete digital access to FT.com with everything in both of our Standard Digital and Premium Digital packages. ![]()
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