There is a need for precise visual functional analysis that parallels and complements the advance technologies employed in ophthalmic surgery. An instrument is needed which can be coupled to the surgical device which allows precision assessment of vision in some sub portion of the cornea, the entire area of surgical intervention, and the entire cornea. A device is proposed for inclusion which allows (1) monitoring and control of fixation during surgery and visual assessment, (2) precision alignment of the corneal surgical area and the eye lens with the point of fixation (using an achromatic axis), (3) focusing, locating, adjusting, and monitoring an aperture image in the surgical plane, (4) provision of any desired test of vision, and (5) measurement and correction of refractive error and certain aberrations as often as required. The utilization of the hyperacuity paradigms as part of the test battery are also suggested. These can be highly precise reliable benchmarks for characterizing refractive surgery. Hyperacuity testing is well suited for analysis of visual performance in relation to keratorefractive surgery because the procedure is highly resistant to optical image degradation and requires a higher-order analysis by the visual system. The uses of hyperacuity techniques are discussed. These techniques allow assessment of vision through cloudy, distorted, or absorbing optical media, and it is possible to separate quantitatively optical from neural decrements in visual performance. These techniques allow fine detection and measurement of distortion and metamorphopsia. Hyperacuity is also used for precision alignment of the optical elements of the eye and the fovea.