The present invention contemplates a new and improved wavefront aberrometer attachable to an ophthalmic microscope. The present invention also contemplates implementation of a long working distance and a large measurement range into the wavefront aberrometer. The present invention further contemplates to make it quick and easy to insert the wavefront aberrometer and to move it away from the working space of the ophthalmic microscope. The present invention still further contemplates implementation of a keratometry measurement to monitor the corneal status at the time of wavefront power measurement.