Surgery – Truss – Pad
Patent
1988-07-23
1990-05-15
Green, Randall L.
Surgery
Truss
Pad
128646, 128648, 128652, A61B 316
Patent
active
049248677
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to a tonometer of the non contact type for measuring the intra-ocular pressure of an eye.
BACKGROUND TO THE INVENTION
British Patent Specification No. 2175412 describes an improved from of non contact tonometer and methods of use.
It is an object of the present invention to provide an improved pneumatic feed for delvering pulses of air to an eye under test in such a tonometer.
It is a further object of the invention to provide an improved form of construction of the optical and pneumatic systems incorporated in the tonometer previously described.
SUMMARY OF THE INVENTION
According to the present invention there is provided a tonometer for measuring the intra-ocular pressure of an eye in which a pulse of fluid is projected towards the cornea of the eye to distort the corneal surface by the pressure of the pulse, the distortion in the corneal surface being detected by a change in the reflection of light directed onto the cornea characterised by:
(1) a constant volume chamber forming part of a fluid delivery system,
(2) inlet means by which fluid under pressure can be supplied to the chamber when a fluid pulse is required,
(3) lens means fixed in the chamber wall for directing light toward an eye under test, and
(4) a tube which extends coaxially through the lens means and has a section which protrudes internally into the chamber where it is closed-off but includes a plurality of apertures in the interally protruding wall section to permit the controlled passage of fluid from the chamber into the tube.
The invention removes the criticality of the length of the tube protruding into the chamber (sometimes called the plenum chamber) and represents a distinct advantage over previously known arrangements in which it has proved necessary to adjust the length of the tube protruding into the plenum chamber so as to obtain optimum reproducability as between one air pulse and another during successive tests.
Preferably the chamber forms part of a housing which includes a first section which extends between the lens at the one end and a viewing eyepiece at the other and may accommodate a source of illumination, and an optical focussing and reflecting system.
The housing may include a second section within which the source of illumination is located.
The housing may include a third section containing the fluid inlet means and the light detection means.
Preferably one part of the housing, comprising the said third section and a portion of the first section of the housing leading from the third section to the apertured lens, is separated from the remainder of the housing by means of a semi-reflecting mirror fitted so as to represent a fluid-tight seal between the said one part and the remainder of the housing.
Typically at least a part of the wall of the housing is comprised of a printed circuit board forming at least a light tight seal with the housing, and electrical components required to be located within the housing are mounted on regions of the printed circuit board which communicate directly with the interior thereof.
The apertured lens means conveniently comprises a pair of aligned centrally apertured plano-convex lenses and the tube extends through the aligned apertures in the lenses, and a mask which determines the light pattern which is to form the final image on the light detection means is formed on one of the plane surfaces of the lenses.
The mask preferably comprises two slit like windows symmetrically arranged relative to the central opening and bounded by an opaque surround.
The invention will now be described by way of example, with reference to the accompanying drawings in which:
FIG. 1 is a side view of a hand held tonometer constructed in accordance with the invention;
FIG. 2 is a front view of the tonometer of FIG. 1;
FIG. 3 is a rear view of the tonometer shown in FIG. 1;
FIG. 4 is a perspective view showing the hand held tonometer installed in a base unit adapted to be placed on a horizontal surface such as a desk;
FIG. 5 is a perspective view of the
REFERENCES:
patent: 3832890 (1974-09-01), Grolman et al.
patent: 4386611 (1983-06-01), Kantorski et al.
patent: 4724843 (1988-02-01), Fisher
Fisher John
Little Mervyn A.
Matthews James R. A.
Green Randall L.
Keeler Limited
Shay Randy
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