A non-powered, hand-held ophthalmic instrument intended for qualitative assessment of the curvature of the anterior surface of the cornea, typically to detect astigmatism during ophthalmic surgery (e.g., changes induced by sutures during corneal transplantation). Also referred to as a Maloney keratometer, it is in the form of a hollow cylinder or cone with internal concentric rings designed to be held on the cornea, whereby the distorted reflection of the rings on the corneal surface of the patient is indicative of astigmatism. This is a single-use device.