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Corneal measurment apparatus and a method of using the same

Corneal measurment apparatus and a method of using the same description/claims

The present invention relates to corneal measurement apparatus, and a method of corneal measurement, and more particularly to an apparatus and method for projecting a plurality of slits of light for performing corneal measurements.

Ophthalmologists and optometrists would like to have an accurate representation of subjects' eye. Such representations include, for example, one or more of a representation of a subject's corneal anterior surface, posterior surface, and corneal thickness and density, as well as anterior chamber profiles. This information may be used to prescribe contact lenses and eye glasses, and to reshape the cornea by surgical procedures or to perform other surgical procedures. Since it is not comfortable to measure these data with physical contact, remote sensing techniques are preferably used to perform the measurements. A device that measures only the front surface of a cornea is commonly referred to as corneal topographer, a device that measures the front and back surfaces, and the stroma of the eye is referred to as a corneal profiler, and a device that measures anterior chamber profiles is called an anterior chamber analyzer.

One common technique for obtaining corneal measurement information includes projecting narrow bands of light (commonly referred to as slits or slit beams) onto a patient's cornea at multiple locations across a cornea. For each of the slits, after the light in the slit has been scattered by the cornea, an image of the light is obtained.

To project a slit of light, an aperture of appropriate shape and size, and a lens are placed in the path of light from a light source such that the light passing through the aperture forms a slit of light on a subject's cornea. Typically, to project slits at each of multiple locations across the cornea, a single aperture is translated such that the light passing through the aperture at selected times forms the multiple slits. One example of such a corneal measurement apparatus is presented in U.S. Pat. No. 5,512,966 to Snook.

A problem with such apparatus is that it is difficult to accurately position an aperture to form each of the slits, and over time (after many patients) it is difficult to know the position of the slits accurately so that an accurate recreation of a cornea can be obtained.

Aspects of the present invention are directed to an apparatus for measuring a subject's cornea, comprising (A.) an illumination projection subsystem comprising a light source, (B.) a mask subsystem disposed in a path of light from the light source, comprising (i) a first slit mask defining a plurality of apertures, (ii) a second slit mask defining a selection aperture, (iii) a translation apparatus adapted to translate the second slit mask, the translation apparatus and the second slit mask being configured and arranged such that by translating the selection aperture, portions of the light can be selectively transmitted through ones of the plurality of apertures toward the cornea, sequentially, (C.) an imaging element configured and arranged to image the plurality of apertures onto the cornea, and (D.) an image capture subsystem arranged to capture images of the portions of light after the light impinges on the cornea.

In some embodiments, the corneal measurement apparatus, further comprises (E.) a second illumination projection subsystem comprising a second light source, (F.) a second mask subsystem disposed in a path of second light from the second light source, comprising (i) a third slit mask defining a second plurality of apertures, (ii) a fourth slit mask defining a second selection aperture, (iii) a second translation apparatus adapted to translate the fourth slit mask, the second translation apparatus and the fourth slit mask being configured and arranged such that by translating the second selection aperture, portions of the second light can be selectively transmitted through each of the second plurality of apertures toward the cornea, and (G.) a second imaging element configured and arranged to image the second plurality of apertures onto the cornea, the image capture subsystem arranged to capture images of the portions of second light after the light impinges on the cornea.

In some embodiments, the second slit mask is disposed upstream of the first slit mask. In other embodiments, the illumination projection subsystem is configured and arranged to project light from the light source through each of the plurality of apertures defined in first slit mask without moving the illumination projection subsystem. The light source may comprise at least one LED arranged to project light in the path of light. 14. In some embodiments, the light source comprises at least one LED. And in some embodiments, the light source consists of only a single LED (e.g., a high power LED).

In some embodiments, the corneal measurement apparatus further comprises a condenser lens configured and arranged to gather light from the light source and project the light in the path of light. The imaging element and condenser lens may configured and arranged to operate as a condenser-projector system. The imaging element and the first slit mask may be disposed in a Scheimflug arrangement to obtain a plane of slit images at the cornea.

In some embodiments, the plurality of apertures is disposed in a single plane. The plurality of apertures may be formed on a single substrate. The plurality of apertures may be defined by openings in an opaque layer deposited on the substrate.

The corneal measurement apparatus may further comprise an image processing subsystem coupled to the image capture subsystem, the image processing subsystem being adapted to convert the images into a single representation of the cornea. The corneal measurement apparatus may further comprise a subject positioning apparatus adapted to maintain the subject's cornea in a location.

Another aspect of the invention is directed to a method of facilitating measurement of a subject's cornea, comprising (A.) providing a plurality of apertures, (B.) projecting light toward the plurality of apertures, (C.) translating a selection aperture while maintaining the plurality of apertures in fixed locations to selectively transmit a portion of the light toward the cornea, the portion of the light passing through the selection aperture and a selected one of the plurality of apertures and (D.) imaging the portions of light after the light impinges on the cornea.

In some embodiments, the light passes through the selection aperture prior to passing through any of the plurality of apertures. In some embodiments, the step of projecting light comprises projecting light from at least one LED. The method may further comprise processing the images to convert the images into a single representation of the cornea.

Illustrative, non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which the same reference number is used to designate the same or similar components in different figures, and in which:

FIG. 1 is a schematic plan view of an example of a corneal measurement apparatus according to aspects of the present invention;

FIG. 2 is an expanded plan view showing further details of one arm of the corneal measurement apparatus of FIG. 1;

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