Surgery – Instruments – Corneal cutter or guide for corneal cutter
Patent
1992-10-09
1995-08-15
Thaler, Michael H.
Surgery
Instruments
Corneal cutter or guide for corneal cutter
A61B 1732
Patent
active
054415110
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a keratotome for performing arcuate incisions in a cornea in order to correct astigmatism.
BACKGROUND OF THE INVENTION
Astigmatism in an eye is the result of two mutually perpendicular meridians of the anterior face of the cornea not having the same curvature, and a known method of correcting astigmatism consists in forming two incisions in the cornea perpendicularly to the most highly curved meridian, i.e. to the meridian with the shorter radius of curvature, said two incisions being disposed respectively on opposite sides of the optical zone.
Merlin ("Curved keratotomy procedure for congenital astigmatism"; Journal of Refractive Surgery, 1987; 3:92-97) has made arcuate incisions for the purpose of correcting astigmatism, by using a micrometer blade held manually while using visual guidance based on a mark previously made by means of a circular marker.
Nevertheless, it is difficult to make incisions of uniform depth by means of a blade that is merely held in the hand, and this is particularly true when said incisions are situated on a diameter that is small.
As a result, such arcuate incisions are little used.
An object of the present invention is to make it possible to form arcuate incisions that are sufficiently accurate to achieve results regardless of the dexterity of the surgeon.
SUMMARY OF THE INVENTION
The present invention seeks to solve the stated object by mechanical means and, to this end, it provides a keratotome for making an incision in a cornea and comprising, for this purpose, in conventional manner for keratoplasty trephines: including, for application against a cornea, an annular base portion that is circularly symmetrical about the axis of the support and that defines a reference geometrical surface determined by the shape presented by the cornea when the support has its base portion pressed thereagainst; towards the inside of the support relative to the reference surface; support; support; direction, the blade having a sharp tip in a determined direction relative to its longitudinal direction; and including means for displacing the blade in controlled manner in translation along its longitudinal axis relative to the body between a rest position, in which it is set back towards the inside of the support relative to the reference surface, and in which the tip is directed towards said reference surface, and in a cutting position where the tip projects outside from the support relative to the reference surface, in a manner that is offset relative to the axis of the support; angular position and of determined angular length, the support and the body have determining means for determining their relative angular position.
It will readily be understood that such a keratotome makes it possible to make incisions that are exactly in the form of a circular arc, and as a result that relate to a zone in which the cornea is of substantially constant thickness, and also makes it possible, without difficulty, to control two important parameters, namely the angular length of the incision, and the depth of the incision which is adjusted by adjusting the extent to which the tip of the blade projects out from the body, when in the cutting position.
Other characteristics and advantages of a keratotome of the invention appear from the following description of a non-limiting embodiment described with reference to the accompanying drawings which form an integral part of the present description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a keratotome of the invention, half in side elevation and half in section on a plane marked I--I in FIG. 2, and including the relative axis of rotation between the inner body and the outer support, which axis coincides with the visual axis while the keratotome is in use.
FIG. 2 is a fragmentary plan view of the keratotome, i.e. it shows the keratotome as it appears at its end opposite from its base portion, parallel to the axis of relative rotation between the inner body and the outer support and in the direction marked by arrow II
REFERENCES:
patent: 4205682 (1980-06-01), Crock et al.
patent: 4423728 (1984-03-01), Lieberman
patent: 4608977 (1986-02-01), Brown
patent: 4648400 (1987-10-01), Schneider
Arch Ophtalm. vol. 106, Aot 1988, U.S. pp. 1130-1135 Duffey et al.: `paired arcuate keratotomy` voir p. 1134 colonne 2, ligne 46-collone 3, ligne 2.
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