Bullous KeratopathyDefinition: Bullous keratopathy is a swelling of the cornea due to endothelial damage.
Incidence/Prevalence: Bullous keratopathy is most common in older people. Bullous keratopathy occurs after cataract surgery, its incidence has decreased since the advent of intraoperative viscoelastic agents that protect the corneal endothelium and the decreased use of iris plane and anterior chamber intraocular lenses. A review at the University of Toronto indicate that pseudophakic bullous keratopathy is the 3rd leading indication of penetrating keratoplasty. (
Maeno et al.) In our material it is the most common diagnosis for corneal button specimens.
Etiology: Often the cause of bullous keratopathy is loss of endothelium from a malpositioned intraocular lens (pseudophakic bullous keratopathy). There is failure of the corneal endothelial cell layer to perform its normal pump function. The pumping failure can occur either because the cells themselves do not function normally or because the absolute number of endothelial cells has decreased below a critical level necessary to maintain corneal clarity. In addition retrocorneal fibrous membranes arise from uneven internal wounds and compromise the endothelium.
Clinical Presentation: Bullous keratopathy occurs most commonly after cataract removal. Bullous keratopathy is characterized by the formation of fluid-filled blisters on the surface of the cornea. The blisters rupture, causing pain, often with a foreign body sensation and impairment of vision. The diagnosis is made from the typical appearance of a swollen, cloudy cornea with blisters on the surface. Pachymetry will confirm a thicker cornea.
Histopathology: The changes observed include desquamating epithelial cells from the anterior surface (arrow 1),
separation of epithelium from Bowman's layer creating the bullous detachment (number 2). There are hydropic changes (tiny bubbles) within the epithelium giving them less apparent staining (arrow 3). Bowman's layer is irregularly thinned probably related to the bullae (arrow 4). The stroma shows areas devoid of keratocyte nuclei and irregular lamellae (number 5), features indicative of scarring. The endothelium is markedly attenuated; there are fewer endothelial cells than normal. Here we find only a single endothelial cell in this view (arrow 6). Additional findings that may be seen include a thickened and redundant epithelial basement membrane. In general the key finding is a paucity of endothelial cells, and those cells remaining are flattened and attenuated. Descemet’s membrane is usually intact, except in cases triggered by a retrocorneal fibrous membrane.
Treatment: Bullous keratopathy is treated by reducing the amount of fluid in the cornea. Hypertonic eye drops can be used to draw the fluid out. Occasionally, soft contact lenses can be used to decrease discomfort. If vision is insufficient for daily activities or discomfort is significant, corneal transplantation may be indicated.
Compare to the normal cornea by clicking here.
