Porcine corneal opacity reversibility assay

Porcine corneal opacity reversibilitThe Porcine Corneal Opacity Reversibility Assay (PorCORA) evaluates recovery of ocular irritation in excised, cultured, porcine corneas. Like the Draize rabbit eye test, substances are applied directly to the corneal surface and then corneal recovery is evaluated over a period of 21 days.  Corneal injury and reversibility are determined by scoring the area of sodium fluorescein (NaFL) stain retention 1, 2, 3, 7, 10, 14, and 21 days post-exposure.  NaFL retention is a well-characterized indicator of tissue damage and, more specific to the cornea, loss of the surface epithelial layer integrity.  The endpoint of this assay is a time to corneal recovery score (days).  A test substance can therefore be characterized as causing reversible or irreversible corneal damage.  Re-epithelialization is the primary method of corneal healing. Because this multi-layered epithelial process is driven by replenishment of cells from the corneal periphery, a replacement test using whole, intact corneas is critical to an accurate assessment of corneal recovery and reversibility. In addition, the PorCORA air-interface culture technique is imperative for maintenance of normal in vivo corneal physiology. PorCORA has been developed for the purpose of replacement of the reversibility component of the Draize rabbit eye test.  In combination with in vitro tests that quantify the severity of ocular injury and vascular effects, PorCORA could replace in vivo ocular irritation tests.