Abstract: An apparatus for assessing the visual field of a patient is disclosed which utilizes a virtual image of a visual stimulus. The disclosed apparatus includes a light pattern generator which generates a visual stimulus, such as a moving fixation target, and an optical assembly which produces a virtual image of the visual stimulus projected a distance in front of the patient's eye. During measurement of the patient's visual field, the patient observes the virtual image of the visual stimulus. A centration illumination source, such as an infrared laser, also illuminates the patient's pupil with an infrared beam, which is then scattered off the patient's iris. In operation, the apparatus monitors the patient's fixation on the visual stimulus by tracking the movement of the patient's pupil using the scattered infrared image. When the center of the pupil image moves beyond a predefined threshold, a lost of fixation is indicated, from which the patient's visual field can be assessed.

Abstract: A novel psychophysical visual test is proposed for testing a person for glaucoma, and based on the discovery that a frequency doubling phenomenon is produced by isoluminent color visual stimuli. More specifically, it is proposed to construct a visual stimulus for which alternating colors in a grating pattern is the only basis for producing the frequency doubling phenomenon. That is, the colors are of the same luminance or intensity level, i.e., isoluminent, but each grating or pattern alternates from one color to another. Preferably, the colors are complementary color pairs, such as blue and yellow.

Abstract: A technique for evaluating the topography of a cornea in which a virtual object of a keratoscope pattern isured. The topography system includes a structured light source to create the keratoscope pattern or another diagnostic pattern, an optical assembly to focus the created pattern upon or behind the cornea, and for capturing the image reflected off the patient's eye and directing the reflected image toward an imaging system for processing. Light emitted by the light source is preferably not in the visible range, to minimize discomfort to the patient. Since the topography is evaluated with a projected virtual image, there is no nose or brow shadow, thereby allowing better corneal coverage. The optical system includes an aperture stop which is preferably conjugate with a point behind the corneal surface approximating the center of a normal cornea. Thus, wide angle capture is achieved as reflected rays reaching the imaging system appear as if they originated at the center of the cornea.

Abstract: The present multi-functional, visual test instrument is realized by integrating miniature, close-proximity displays, such as LCDs, with viewing optics, which is constructed in the form of preferably a unitary housing. In a preferred embodiment, the multi-functional, visual test instrument includes two viewing assemblies, and displays, which are all enclosed in the housing that is slidably or pivotally attached to a movable mount, such as a slit lamp base. In operation, various optical test objects or stimuli are viewed by the patient on the displays through the viewing assemblies. The shape, size, speed, frequency, location, color, contrast and intensity of the test objects or stimuli are computer generated. A hand operated switch, mouse, joystick, or other input means, may be used for the patient to respond to the observed test objects or stimuli.