a streamlined cataract knife

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1040 NOTES, CASES, INSTRUMENTS apt to be troublesome. In this test, the cross-cylinder axes must be placed ex- actly at 45 degrees to the test-cylinder axis and in this fixed position the cross cylinder must be twirled through ex- actly 180 degrees. If a change of axis is indicated and the test cylinder rotated, say, 10 degrees, the cross cylinder must be realigned to the new position of the test cylinder and similarly rigidly held and twirled through 180 degrees. With the mounted cross cylinder this procedure is easily carried out. The cross cylinder is accurately lined up on its own axis scale where it stays fixed in position during the twirling. It is quickly rotated and set in any new position as required by a change in the test-cylinder axis. The automatic stop always assures a rota- tion of exactly 180 degrees. Dr. Edward Jackson and other out- standing ophthalmologists have repeatedly referred to the cross cylinder as one of the most useful devices for subjective test- ing. Yet it is a fact that the cross cylinder is relatively little used. I believe this is due, in part at least, to the gap between the theoretical excellence of cross cylinder tests and the practical difficulties in apply- ing the tests. The device here presented does not introduce any new cross-cylinder tests. It is designed primarily to bridge the gap, to some extent at least, between the theoretical precision and the practical application of these really worthwhile tests. 37 West Ninety-seventh Street. A STREAMLINED CATARACT KNIFE CHARLES NELSON SPRATT, M.D. Minneapolis, Minnesota For more than three quarters of a century the Graefe knife has been the instrument of choice with the majority of surgeons in making the- cataract sec- tion. A number of years ago I felt that this instrument could be improved. In making the section for the removal of cataract with the narrow knife, the iris may be injured by falling against its edge, due to the escape of aqueous. In many models of the instrument the point is rather blunt and more force is required in making the incision than is desirable. Fig. 1 (Spratt). Streamlined knife, showing cross section and straight back. The two lower figures show the difference in level of the counter puncture made by this knife as com- pared with that made by the Graefe knife. The counter puncture is not directly op- posite the puncture and often results in off-axis astigmatism. The Beer knife with the wedge-shaped blade, in contrast, prevents the escape of aqueous. The straight back of the blade allows the point of the knife to make the counter puncture at the same level as the puncture. This instrument, however, is clumsy, and the point, forming an angle of 30 degrees, is too blunt for easy pene- tration of the cornea.

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Page 1: A Streamlined Cataract Knife

1040 NOTES, CASES, INSTRUMENTS

apt to be troublesome. In this test, the cross-cylinder axes must be placed ex­actly at 45 degrees to the test-cylinder axis and in this fixed position the cross cylinder must be twirled through ex­actly 180 degrees. If a change of axis is indicated and the test cylinder rotated, say, 10 degrees, the cross cylinder must be realigned to the new position of the test cylinder and similarly rigidly held and twirled through 180 degrees.

With the mounted cross cylinder this procedure is easily carried out. The cross cylinder is accurately lined up on its own axis scale where it stays fixed in position during the twirling. It is quickly rotated and set in any new position as required by a change in the test-cylinder axis. The automatic stop always assures a rota­tion of exactly 180 degrees.

Dr. Edward Jackson and other out­standing ophthalmologists have repeatedly referred to the cross cylinder as one of the most useful devices for subjective test­ing. Yet it is a fact that the cross cylinder is relatively little used. I believe this is due, in part at least, to the gap between the theoretical excellence of cross cylinder tests and the practical difficulties in apply­ing the tests. The device here presented does not introduce any new cross-cylinder tests. It is designed primarily to bridge the gap, to some extent at least, between the theoretical precision and the practical application of these really worthwhile tests.

37 West Ninety-seventh Street.

A STREAMLINED CATARACT KNIFE

CHARLES NELSON SPRATT, M.D. Minneapolis, Minnesota

For more than three quarters of a century the Graefe knife has been the

instrument of choice with the majority of surgeons in making the- cataract sec­tion. A number of years ago I felt that this instrument could be improved.

In making the section for the removal of cataract with the narrow knife, the iris may be injured by falling against its edge, due to the escape of aqueous. In many models of the instrument the point is rather blunt and more force is required in making the incision than is desirable.

Fig. 1 (Spra t t ) . Streamlined knife, showing cross section and straight back. The two lower figures show the difference in level of the counter puncture made by this knife as com­pared with that made by the Graefe knife.

The counter puncture is not directly op­posite the puncture and often results in off-axis astigmatism.

The Beer knife with the wedge-shaped blade, in contrast, prevents the escape of aqueous. The straight back of the blade allows the point of the knife to make the counter puncture at the same level as the puncture. This instrument, however, is clumsy, and the point, forming an angle of 30 degrees, is too blunt for easy pene­tration of the cornea.

Page 2: A Streamlined Cataract Knife

NOTES, CASES, INSTRUMENTS 1041

Many years ago I stopped making the incision at the limbus with the small con-junctival flap and changed to the pocket-flap operation with suture introduced be­fore making my section. At about this time I ground the cutting edge of a Beer knife to one half its width, reducing the angle of the point from 30 to 15 degrees. The back of the knife remains in a di­rect line with the handle. The blade is 30 to 32 mm. long, 4.5 mm. wide, and 0.7 mm. thick. On cross section the blade is streamlined so that it effectively blocks the corneal wound.

Similar knives with a point of 15 de­grees have previously been described by

Jackson, Pinto, Ridley, Taylor, Ramsey, and others.

The advantages of this knife are : (1) the cutting edge being straight can be more easily sharpened; (2) the needle­like point penetrates the cornea with the slightest pressure; (3) the straight back, continuous with the handle, causes the counter puncture to be made in a hori­zontal plane and thus oblique astigmatism is avoided; (4) the knife being wedge shaped in both cross section and length plugs the incision of the puncture and counter puncture, thus preventing loss of aqueous and injury to the iris.

1231 Medical Arts Building.