A fixed and dilated pupil is an uncommon postoperative complication after penetrating keratoplasty (PK) for keratoconus. Although the clinical features have been well described, the precise aetiology is uncertain. We performed anterior segment fluorescein angiography in the early postoperative period on three patients who developed fixed, dilated pupils after apparently uncomplicated surgery. All of the eyes had severe iris ischaemia. A possible role for a postoperative rise in intraocular pressure in the aetiology of this syndrome is discussed.