Pellucid marginal degeneration

• bilateral asymmetric focal ectasia of the corneal stroma 1-2mm above the inferior limbus b/w 5 & 7 o'clock w/o evidence of scarring, vascularization or lipid infiltration
• progressive ectasia results in the development of ATR astigmatism
• can lead to corneal hydrops
• advanced cases show "kissing doves" or "crab claw" topography with superior flattening and a small island of inferior central flattening