Surgery – Truss – Pad
Patent
1985-08-14
1989-03-28
Freeh, William L.
Surgery
Truss
Pad
128751, A61B 1732
Patent
active
048154636
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to surgical apparatus for radial keratotomy.
By radial keratotomy is intended a surgical method consisting of modifying the curvature of the cornea of an eye by practising on this cornea radial incisions with reference to the optical axis of the eye. This radial keratotomy is particularly used for reducing the curvature of the cornea in a central zone or optical zone of it, either in a manner to adjust for correcting simple myopia, or, when there is simple astigmatism or associated with myopia, respectively in a localised manner corresponding to the most curved meridian of the astigmatism or in a modulated manner, by an appropriate choice of the number and position of the incisions, and of the depth, and of their respective ends towards and away from the optical axis.
For performing this radial keratotomy, various devices have been previously proposed which all use a single knife which the surgeon uses manually for successfully carrying out the different incisions and which differ only by the more or less sophisticated means of guiding of the knife for carrying out each of the successive incisions.
The most simple of these known devices is described in the review "Ophthalmology" of January 1983 (Volume 90-No. 1-PERK Study), and consists of a knife composed of a handle and a sharp blade passing through a guard acting as an abutment foot of the device on the cornea. The size of the projection formed by the blade with respect to the guard can be adjusted by micrometric displacement members, and determines the depths of the incisions; the incisions are made by a rolling turn of this knife, which is displaced the length of a mark previously made on the cornea, for example by means of a device of the type described in the French Certificate of Utility No. 2 490 954 or by the applicant of French Pat. No. 2 530 949, across a central zone and in the direction of the limbus.
The use of such a device leaves much to the manual dexterity of the surgeon, and is characterised by its lack of precision whatever this dexterity, if only because some of the incisions, for example 8 in number, are inconvenient to make since they are situated to the surgeon's left hand. In addition, the time necessary for making the different incisions is sufficient for the lamp of the operating microscope to cause a substantial dehydration of the cornea, with as a result a variation in the thickness of it, difficult to predict and in consequence to take into account progressively as the incisions are made. As a result there is a significant risk that the depth of incision made as a function of the thickness of the cornea in its normal state, transferred by the initial adjustment of the size of projection formed by the blade with respect to the guard, becomes excessive for the last incisions made, culminating in a perforation of the anterior chamber, greatly complicating the operation.
In addition, the making successfully of different incisions in the course of the operation causes loss of rigidity of the cornea, the ocular globe becoming hypotone, so that the last incisions are very difficult to make.
U.S. Pat. No. 4,340,059 describes a very similar device, except that in the place of applying on the eye by the means of a guard forming an abutment foot, the knife is applied on a curvilinear slide carried by a mechanical immobilisation pincer on the eye and intended to be placed in a plane including the optical axis such that the curvature of this slide is homothetic with the natural curvature of the corresponding zone of the cornea. A micrometric adjustment permits adjustment of the depth of incision but the limits of this latter respectively towards and away from the optical axis result from a simple visual control, by reference to a graduation carried by the slide. This device seems at first sight to offer a precision independent to a greater or lesser extent of the dexterity of the surgeon. However, the coercive guiding of the knife in the slide presenting a determined form and occupying a determined position w
REFERENCES:
patent: 4205682 (1980-06-01), Crock
patent: 4246895 (1981-01-01), Rehder
patent: 4340059 (1982-07-01), Marinoff
patent: 4429696 (1984-02-01), Hanna
Freeh William L.
Laboratoire Hydron
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