A hyperacuity testing instrument is adapted to evaluate visual function by selectively changing the relative position of two spots or points of light that function as visual stimuli for observation by a patient. The instrument includes a laser that emits a single beam of light that is split into two beams when it passes through a bi-prism. The beams of light are visually shown as two spots on a display screen for recorded perception by a patient. A rotary adjustment selectively varies the rotational positions of the spots relative to each other whereas a linear adjustment selectively varies the separation gap between the spots. The recorded data enables a surgeon to determine whether corrective surgery to remove an ocular media opacity will, in fact, improve vision, i.e., the test procedure "penetrates" the opacity to assess visual function at the retinal-neural level.

An improved visual field testing device is disclosed. The device is a modification of an automatic Goldmann-type perimeter device which permits operation by the physician or technician.

A first light is moved and illuminated by an x-y plotter mechanism on a rear projection screen under computer control so as to be continuously fixated by an eye of a test subject. The computer also causes one or ones of fixed-position second lights, typically sixteen in number positioned in a regular array, to momentarily illuminate at various times corresponding to various positions of the moving first light. The test subject indicates detection or non-detection of the momentary illuminations to the computer by voicing the numbers "1", "2", "3", etc. From successive illuminations and test subject responses the computer is able to survey the entire visual field of each subject's eye in all directions. The surveyed visual field is plotted on graph paper with the same x-y plotter mechanism that is otherwise and at other times used for moving the first light source.

A perimeter has a predetermined index to be projected onto a fundus of an eye to be examined and an index projection imaging optical system which can form an intermediate image of the index in front of the eye. An optical system as being at least a part of the index-projection imaging optical system, is movable to displace the position of the index image on the fundus of the eye. The index-projection imaging optical system has an image forming section which moves the intermediate image in the direction of the optical axis.

An automatic perimeter automatically presenting stimuli in a plurality of conditions, in which the presentation of stimuli can be readily stopped by an operator during the presentation, and an accurate examination of eyesight is carried out in accordance with eliminating the few latest perception signals before the stimulus presentation is stopped during an examination of eyesight.