Abstract: A field test apparatus is disclosed which is interactive both in the automated positioning of trial lenses (used to correct the patient's focal distance to the tester hemispherical projection screen) as well as providing automatic gaze direction determination through automated video surveillance of the patient's eye. A moveable trial lens holder is provided. This trial lens holder is remotely moveable horizontally and vertically and carries light sources for illuminating the eye preferably in the infrared spectrum at oblique angles preferably towards the center of the eye from the periphery of the trial lens holder. In the gaze direction determination system, a gaze direction determination infrared source--preferably on the surface of the screen near the center of the screen--generates a gaze direction determination reflection on the cornea of the eye--this reflection being near the apex of a normal spherical cornea.

Abstract: Badal optics are disclosed in which an aperture array at an optical system under test is interrogated for the deflection of light between a detector array conjugate with the aperture array of the optical system under test being examined. Excursion is measured in a plane normal to the axis of the Badal optics instead of observing towards and away image focus along the axis of the Badal system. In the case of an objective refractor, the eye is illuminated at the retina with a test spot, preferably light in the infrared. An image of a detector array is relayed by a relay lens through the Badal optics to the cornea of the eye, the lens under test. Light emanating from the test spot on the retina passes through the eye lens at the at the image of the detector array. This light undergoes excursion in accordance with the power of eye lens under test at each aperture of the detector array.

Abstract: Adaptions of lensmeter optical trains are disclosed for enabling the measurement of contact lenses without the interference of spherical aberration from the highly meniscus lens formats of contact lenses. A generic system of measurement of the contact lenses when off of the eye is introduced by having light incident to or passing from the suspect contact lenses at an approximate aplanatic condition of the contact lens. The approximate aplanatic condition is determined by taking the average power of the posterior and anterior surfaces of the contact lenses for the general population--approximately 8 mm, assuming an index of refraction of approximately 1.5--calculating the aplanatic condition for such a "surface," and having light incident on the lenses for the interrogation of the lenses approximate the aplanatic condition.

Abstract: In an automated lensmeter, provision is made for estimating dispersion when high index glasses are utilized with lenses having relatively large diopter prescriptions and for eliminating error due to spherical aberration when determining the power of contact lenses. For estimation of dispersion--typically required for optical corrections in the range of 10 diopters--two discrete color light sources are used for optical measurement of the power of the suspect lens. As a result of the obtained power difference resulting from the differing colors used, dispersion can either be estimated and referenced back to a generally accepted standard or a look-up table can be utilized to identify the specific glass class or even specific glass type being measured. In the case of the measurement of power of contact lenses, differing points of measurement through the suspect contact lenses are made. Effects of possible dispersion are ignored and differences in lens power determined with different radii of measurement.

Abstract: An objective refractor having no moving parts is disclosed. The refractor, which can be either a hand held or table mounted instrument, includes a reference array and an interrogating array projected onto the eye fundus. The reference array is projected from light sources and the interrogating array is projected to light detectors. Both the reference array and the interrogating array are projected onto the fundus of the eye through preselected spaced apart regions of the eye lens. The movement of the reference array with respect to the interrogating array is observed. By the expedient of making at least two sequential observations utilizing at least three separate regions of the eye lens, the amount of relative pattern displacements can be reduced to a requisite optical prescription for the eye.

Abstract: A prior art ultrasonic eye measuring device is fitted with pinhole optics. A fixation target is provided with the pinhole optics. The instrument is used to measure the dimension of the eye typically preparatory to cataract surgery. In use of the instrument, the patient has the cornea anesthetized. The patient is thereafter told to fixate on the spot of light leaking from the pinhole optics as the eye examiner brings the instrument into contact with the cornea of the eye. The point source of light approaches the eye. As it approaches, the point source increases in size. When the light source becomes sufficiently large, the fixation target becomes visible. Upon touching of the instrument to the eye, ultrasound measurement of the dimension of the eye preferably along the visual axis occurs. By the expedient of aligning the interrogating ultrasound axis to the line of sight of the fixation target, measurement of the visual axis length of the eye occurs.

Abstract: In an instrument having an interrogating optical beam for the measurement of various optical properties of the eye, a detector is disclosed for triangulating the towards and away distance of the eye from the objective of the measurement equipment thus utilizing the beam for serendipitous purpose of ranging. A photosensitive detector having two photosensitive elements is placed in a plane which includes the optical axis of the interrogating instrument and the detector. The detector is mounted towards the eye with the division between the two photosensitive surfaces normal to the plane including the interrogating optical beam and the detector. Typically, the detector has line of sight off axis with respect to the interrogating beam and intersects the axis at the preferred position for eye placement. An imaging lens relays a conjugate image of the detector to that point in space on the optic axis in front of the eye where ultimate placement of the eye for measurement is desired.