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L. J. Cervantes, N. Ragusa, C. Y. Shih, I. J. Udell; The Effect of Pressure Variations and Length of Cutting Passes on the Accuracy of Descemet Stripping Automated Endothelial Keratoplasty Lenticle Creation. Invest. Ophthalmol. Vis. Sci. 2010;51(13):774.
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To examine the effect of pressure and length of cutting pass on the accuracy of Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) lenticle creation.
21 pairs of mate corneas were cut using the Moria artificial chamber system with a 300µ head. 12 pairs (24 corneas) were cut using 5 second passes, while 9 pairs (18 corneas) were cut with 10 second passes. The first eye of each pair was cut with a chamber pressure of <65mmHg. The second group, their donor mates, was cut with a chamber pressure of >65mmHg. Chamber pressure was checked with a Tono-Pen prior to the cut. Corneal thickness was measured by ultrasound pachymetry before and after cutting. The variation of the donor cap thickness from the expected 300µ [thicker cap/overcut (+); thinner cap/undercut (-)] was calculated.
Of the pairs cut with 5 second passes, the mean pressure of the <65mmHg group was 39±11 mmHg (range 15-50 mmHg). The mean pressure of the >65 mmHg group was 83±6.5 mmHg (range 69-89 mmHg). In 11 out of the 12 pairs (92%) the resultant donor caps of the <65mmHg group were closer to 300µ than those of the >65 mmHg group (p=0.004). In the <65 mmHg group, the mean difference was +86.5±57.8µ (range +169µ to -6µ). In the >65 mmHg group, the mean difference was +114±55.2µ (range +180µ to +21µ).Of the pairs cut with 10 second passes, the mean pressure of the <65 mmHg group was 34±10 mmHg (range 19-50 mmHg). The mean pressure of the >65 mmHg group was 88±0.9 mmHg (range 87-89 mmHg). In the <65 mmHg group, the mean difference from 300µ was +123µ±42.8µ (range +176µ to +42µ). In the >65 mmHg group, the mean difference was +116±37.1µ (range +178µ to +46µ). The two mean differences were not significantly different from each other.
Donor cornea cuts made with 5 and 10 second passes at pressures above and below 65 mmHg were all associated with a significant amount of overcutting, producing thinner than anticipated lenticles. Cutting with 5 second passes at <65 mm Hg produced significantly more accurate cuts with the 300µ head when compared to longer pass lengths or higher pressures.
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