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Microtip Cryoextractor Bond Strength
NOTES, CASES, INSTRUMENTS MICROTIP CRYOEXTRACTOR BOND STRENGTH C. RICHARD HULQUIST,
til the ice bond failed. The weights used were 10, 20, 50, 100, 200, 500, and 1,000 g.
M.D.
RESULTS
Los Angeles, California
At either temperature, adhesion failed in the majority of lenses in the mid-range of the various weights tested (Table 1). Twenty grams of weight was always held, so either temperature should be adequate for the 17.6 g of force Cherednichenko2 found necessary for an average extraction. Fifty grams of weight was always held at the warmer temperature, a fact which might be considered for future miniaturized tip de signs. The results obtained by the two tempera tures were very simi lar, as shown by the comparison curves in Figure 2.
With line-connected cryoextractors, the bond strength is greatest when the tip is ap plied prior to freezing.1 This method might safely allow the use of a very small tip, which would provide greater visibility and maneuverability. In the study reported here, the limits of bond strength were determined for a miniaturized line-connected cryoextractor. MATERIAL AND METHODS
The Dynatech vitreous probe (EY 10290) is 1 mm in diameter (Fig. 1). It is de signed to operate with carbon dioxide or nit rous oxide at 650 to 675 pounds of pressure. I used carbon dioxide, which produced —38° C at the tip. Tests were also made at — 22°C ; paradoxically, because of efficiency factors, this temperature was obtained with the max imum carbon dioxide cylinder pressure of approximately 810 pounds. The manufac turer does not recommend such use clini cally. One hundred lenses, freshly extracted during cataract procedues, were refrigerated in lens culture medium until they were used. Fifty lenses were tested at each probe tem perature in a manner outlined in detail in an earlier report. 1 Before the procedure, a plas tic disk with a 1.1-mm central hole was slipped onto the probe shaft. Then the tip was applied to the lens at room temperature, freezing was continued for 30 seconds, and weights were hung from the plastic disk un j
Reprint requests to C. Richard Hulquist, M.D., Suite 812, 10921 Wilshire Boulevard, Los Angeles, California 90024.
SUMMARY
A line-connected cryoextractor, 1 mm in diameter, was ap plied at room tempera ture to 100 lenses, freshly extracted in cataract procedures. Thirty seconds of. freezing was carried out at - 2 2 ° C in 50 lenses and — 38°C in another 50. Adhesion was tested in each lens against weights from 10 to 1,000 g. This microtip provided a bond strength able to support at least 20 g of weight, and it per Fig. 1 (Hulquist). mitted better visibility One-mm diameter mi and maneuverability crotip probe. than a larger tip.
158
VOL. 76, NO. 1
NOTES, CASES, INSTRUMENTS TABLE 1
CATARACT BOND STRENGTH FOR MICROTIP PROBE
Maximum Weight Held (ing) 10 20 50 100 200 500 1000
No. Lenses
159
DOWNWARD ROTATION O F T H E GLOBE USING CORNEAL TRACTION SUTURES SAMUEL W. COHEN,
M.D.
-22°C
-38°C
Brooklyn, New York
0 0 6 23 20 1 0
0 2 13 23 12 0 0
To avoid the disadvantages of a superior rectus muscle suture, I have been using two 7-0 black silk corneal sutures for the past 18 months in all types of intraocular surgery. The sutures are placed just inside the corneoscleral limbus at the four- and eight-o'clock meridians. In this position one avoids the area of the corneoscleral incision. A bite of 2-3 mm on each side ensures good traction. A hemostat clamped to the two sutures rotates the globe inferiorly, giving the striking ap pearance of a parachute coming down (Fig. 1). In addition to traction, the sutures may
TIP TEMPERATURE
[ -ZZ'C \ -38'C
100
öl
3f o 8«
20
SO
100
200
500
1000
GRAMS OF WEIGHT APPLIED TO ICE 8ON0
Fig. 2 (Hulquist). Microtip cryoextractor ad hesive strength curves for two temperatures.
ACKNOWLEDGM ENTS
The lenses were obtained from the eye operating rooms at Jules Stein Eye Institute and St. Vincent's Hospital, Los Angeles. The cryoextractor was pro vided by the Dynatech Cryomedical Company. REFERENCES
1. Hulquist, C. R. : Cryoextraction adhesion pa rameters. Am. J. Ophth. 73:10, 1972. 2. Cherednichenko, V. M. : A study of the strength of Zinn's ligaments with the use of an electronic cryoextractor-dynamometer. Vestn. Oftal. 81:56, 1968. Fig. 1 (Cohen). Right eye in downward traction, using two 7-0 silk corneal scierai sutures at the four- and eight-o'clock meridians. Reprint requests to Samuel W. Cohen, M.D., 522 Ocean Avenue, Brooklyn, New York 11226.
til the ice bond failed. The weights used were 10, 20, 50, 100, 200, 500, and 1,000 g.
M.D.
RESULTS
Los Angeles, California
At either temperature, adhesion failed in the majority of lenses in the mid-range of the various weights tested (Table 1). Twenty grams of weight was always held, so either temperature should be adequate for the 17.6 g of force Cherednichenko2 found necessary for an average extraction. Fifty grams of weight was always held at the warmer temperature, a fact which might be considered for future miniaturized tip de signs. The results obtained by the two tempera tures were very simi lar, as shown by the comparison curves in Figure 2.
With line-connected cryoextractors, the bond strength is greatest when the tip is ap plied prior to freezing.1 This method might safely allow the use of a very small tip, which would provide greater visibility and maneuverability. In the study reported here, the limits of bond strength were determined for a miniaturized line-connected cryoextractor. MATERIAL AND METHODS
The Dynatech vitreous probe (EY 10290) is 1 mm in diameter (Fig. 1). It is de signed to operate with carbon dioxide or nit rous oxide at 650 to 675 pounds of pressure. I used carbon dioxide, which produced —38° C at the tip. Tests were also made at — 22°C ; paradoxically, because of efficiency factors, this temperature was obtained with the max imum carbon dioxide cylinder pressure of approximately 810 pounds. The manufac turer does not recommend such use clini cally. One hundred lenses, freshly extracted during cataract procedues, were refrigerated in lens culture medium until they were used. Fifty lenses were tested at each probe tem perature in a manner outlined in detail in an earlier report. 1 Before the procedure, a plas tic disk with a 1.1-mm central hole was slipped onto the probe shaft. Then the tip was applied to the lens at room temperature, freezing was continued for 30 seconds, and weights were hung from the plastic disk un j
Reprint requests to C. Richard Hulquist, M.D., Suite 812, 10921 Wilshire Boulevard, Los Angeles, California 90024.
SUMMARY
A line-connected cryoextractor, 1 mm in diameter, was ap plied at room tempera ture to 100 lenses, freshly extracted in cataract procedures. Thirty seconds of. freezing was carried out at - 2 2 ° C in 50 lenses and — 38°C in another 50. Adhesion was tested in each lens against weights from 10 to 1,000 g. This microtip provided a bond strength able to support at least 20 g of weight, and it per Fig. 1 (Hulquist). mitted better visibility One-mm diameter mi and maneuverability crotip probe. than a larger tip.
158
VOL. 76, NO. 1
NOTES, CASES, INSTRUMENTS TABLE 1
CATARACT BOND STRENGTH FOR MICROTIP PROBE
Maximum Weight Held (ing) 10 20 50 100 200 500 1000
No. Lenses
159
DOWNWARD ROTATION O F T H E GLOBE USING CORNEAL TRACTION SUTURES SAMUEL W. COHEN,
M.D.
-22°C
-38°C
Brooklyn, New York
0 0 6 23 20 1 0
0 2 13 23 12 0 0
To avoid the disadvantages of a superior rectus muscle suture, I have been using two 7-0 black silk corneal sutures for the past 18 months in all types of intraocular surgery. The sutures are placed just inside the corneoscleral limbus at the four- and eight-o'clock meridians. In this position one avoids the area of the corneoscleral incision. A bite of 2-3 mm on each side ensures good traction. A hemostat clamped to the two sutures rotates the globe inferiorly, giving the striking ap pearance of a parachute coming down (Fig. 1). In addition to traction, the sutures may
TIP TEMPERATURE
[ -ZZ'C \ -38'C
100
öl
3f o 8«
20
SO
100
200
500
1000
GRAMS OF WEIGHT APPLIED TO ICE 8ON0
Fig. 2 (Hulquist). Microtip cryoextractor ad hesive strength curves for two temperatures.
ACKNOWLEDGM ENTS
The lenses were obtained from the eye operating rooms at Jules Stein Eye Institute and St. Vincent's Hospital, Los Angeles. The cryoextractor was pro vided by the Dynatech Cryomedical Company. REFERENCES
1. Hulquist, C. R. : Cryoextraction adhesion pa rameters. Am. J. Ophth. 73:10, 1972. 2. Cherednichenko, V. M. : A study of the strength of Zinn's ligaments with the use of an electronic cryoextractor-dynamometer. Vestn. Oftal. 81:56, 1968. Fig. 1 (Cohen). Right eye in downward traction, using two 7-0 silk corneal scierai sutures at the four- and eight-o'clock meridians. Reprint requests to Samuel W. Cohen, M.D., 522 Ocean Avenue, Brooklyn, New York 11226.