Laboratory Studies
No lab studies are available.
Imaging Studies
Specular microscopy has proven to be valuable in identifying the characteristic vesicular changes of the Descemet membrane in patients with PPMD. Typically, the endothelial cell count is only mildly diminished with varying amounts of polymegethism and pleomorphism.
Confocal microscopy has also been used to identify the typical features of PPMD. [7, 8]
On most occasions, PPMD can be clinically diagnosed using slit lamp examination; however, mild cases may require further imaging studies to confirm the diagnosis.
Other Tests
Tonometry is used to measure intraocular pressure, which may be elevated in up to 40% of patients with PPMD.
The secondary open-angle glaucoma that occurs in some patients with PPMD is believed to be due to an abnormality of the trabecular endothelium.
Examination of family members may also be helpful in making the diagnosis.
Histologic Findings
Light microscopy typically demonstrates 4 types of cells: normal endothelial cells, degenerated endothelial cells, fibroblast-like cells, and epithelial-like cells. In 60% of cases, a multilayered endothelium can be identified that has many characteristics similar to that of the epithelium. Immunohistochemical studies have also shown positive staining of the endothelium using epithelial cell markers.
Scanning electron microscopy and transmission electron microscopy of corneal tissue show lamination of the Descemet membrane, fibroblast-like endothelial cells, and microvilli characteristic of epithelial transformation of the corneal endothelium.
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Slit lamp image demonstrates posterior corneal vesicles and opacities in linear bands and other polymorphous configurations typical of posterior polymorphous corneal dystrophy.
