Optics: measuring and testing – Plural test
Reexamination Certificate
1999-12-16
2001-07-03
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Plural test
C356S247000
Reexamination Certificate
active
06256089
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains generally to cells for holding harvested donor tissue samples before they are to be used for transplant surgery. More particularly, the present invention pertains to donor tissue holding cells which allow the tissue sample to be measured and evaluated in the cell for purposes of determining its suitability for transplant surgery. The present invention is particularly, but not exclusively, useful as a donor tissue holding cell which is adaptable for use in optical procedures and techniques to measure and evaluate the suitability of donor corneal tissue for transplant surgery.
BACKGROUND OF THE INVENTION
Specialized organ donor programs have been implemented in the U.S. and other countries with varying degrees of success. Perhaps the most important concern of any organ donor program is the availability of organs. At the next level, however, there is an equally important concern that the donor organ tissue be suitable for the intended use. Specifically, it is necessary for the donor tissue to be suitable for transplant surgery.
In the particular case where the donor tissue is tissue from the cornea of a donor eye, the question of suitability for purposes of transplant surgery is actually two-fold. First, it is necessary for the healthcare professional to assess information about the donor tissue which will assure there is a suitable match between the donor and the recipient. Here, the obvious reason for having a good match is that there will be a more effective surgical outcome with consequent better patient response and recovery. Second, it is also necessary for the healthcare professional to know the precise dimensions and shape (refractive properties) of the eye. Such knowledge not only allows better control of the tissue interface between the donor tissue and the recipient during surgery, it also leads to a better post-surgical visual outcome. Specifically, insofar as the post-surgical visual outcome is concerned, it is important that the necessary refractive corrections provided by the donor corneal tissue be precisely controlled relative to the pre-surgical condition of the recipient.
When assessing corneal tissue for its suitability for transplant surgery, several considerations must be taken. For one, it is important to assess and evaluate the health of the donor tissue. This can be done by evaluating the extent, if any, to which the cornea may have been earlier affected by corneal scarring or corneal disease. It is well known that such an evaluation can be done using optical techniques. Additionally, as another consideration, it is important to assess the material properties of the donor tissue. Specifically, material properties of a cornea such as density, amorphousness, crystallinity, and transparency can affect the suitability of the corneal tissue as a candidate for transplant surgery. It is also well known that such an evaluation can be accomplished using optical interference techniques.
The present invention recognizes that the surgical suitability concerns mentioned above with regard to corneal tissue can be addressed if the donor tissue is appropriately accessible. Appropriate accessibility, however, requires that the donor corneal tissue be properly preserved and that it not be unduly disturbed during evaluation. Further, due to the fact that many material properties involve optical measurements and evaluations of the cornea, accessibility also requires that the donor corneal tissue be appropriately positioned for illumination by light beams and for evaluation by optical detectors.
In light of the above, it is an object of the present invention to provide a sample cell which can be used to image a tissue sample for purposes of screening the sample to identify compromised donor corneal tissue. Another object of the present invention is to provide a sample cell for use in imaging a tissue sample which is adaptable for imaging the sample using both transmitted light and scattered light. Still another object of the present invention is to provide a sample cell for use in imaging a tissue sample which is allows the tissue sample to be measured both for its physical dimensions as well as for its material properties. Yet another object of the present invention is to provide a sample cell for use in imaging a tissue sample which is easy to use, relatively simple to manufacture, and comparatively cost effective.
SUMMARY OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, a sample cell for use in imaging a tissue sample includes a base member which is formed with a pedestal. Further, the pedestal is formed with a base window which acts as a surface for supporting the tissue sample, and the pedestal is formed with a small circular ridge which surrounds the base window (surface) to help maintain the position of the tissue sample on the pedestal. Additionally, the sample cell includes a retainer ring which is engageable with the pedestal, and which acts with the ridge to retain the tissue sample on said pedestal. Importantly, the pedestal and the retainer ring act together to establish a “non-influencing” hold on the tissue sample. Stated differently, the tissue sample is retained, but is not restrained, by the combination of the pedestal and retainer ring.
A housing, which is formed with a housing window, is engageable with the base member to create a vented fluid chamber between the housing and the base member. More specifically, when the housing is engaged with the base member, the pedestal extends into the chamber. Consequently, as the chamber is filled with an appropriate fluid, such as a saline solution, the tissue sample will be bathed in the solution. Also, upon engagement of the housing with the base member, a straight optical path is established through the sample cell which extends sequentially through the base window, the tissue sample, the retainer ring and through the housing window.
A light source is provided for the sample cell of the present invention which is capable of producing a sheared beam of collimated light. Importantly, the light should have a wavelength which will allow the light to pass through the tissue sample, i.e. the tissue sample is effectively transparent to light from the light source. Preferably, the light will be visible light and may include ultraviolet and infrared light. More specifically, this light can be configured as either a first light beam having a substantially circular cross section, or as a second light beam having a slit like cross section. In both cases, the light beam is initially directed along the optical path and through the base window to illuminate the tissue sample. Depending on which light beam is used, however, the light beam will take different paths after it has transited through the tissue sample.
An optical detector, such as a charge-coupled device (CCD), is positioned on the optical path outside the housing window to receive light in the first light beam after is has passed through (transited) the tissue sample on the pedestal. The transmitted light in this first beam can then be used for a wavefront analysis wherein refractive properties of the tissue sample are measured. The same optical detector, or a separate optical detector if desired, can also be used to analyze light of the second light beam after it has passed through the tissue cell.
When light in the second light beam is to be analyzed, the housing of the sample cell will also have at least one side window in addition to the housing window. The side window in this case will be distanced from the main optical path and will be oriented at an angle, &agr;, from the optical axis. Thus, the optical detector will receive the second light beam through the side window after it has been scattered off-axis from the main optical path by the tissue sample. When the slit configuration of the second beam has a length that is about the same as the breadth of the tissue sample, and has a width that is approximately equal to the depth of the tissue sample, the light that is scattered off-axis
Eyetech Vision, Inc.
Font Frank G.
Nydegger & Associates
Stafira Michael P.
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