Eye bleb. Eye of an elderly patient with a bleb above the iris. An eye bleb is an elevation of the membrane (conjunctiva) that covers the surface of the eye. In this case the bleb has become opacified (white). This patient's bleb occurred as a result of a trabeculectomy, an operation where a flap is cut in the white of the eye to relieve fluid pressure inside the eye. The appearance of an opaque bleb is a late complication of this operation.