Abstract
Purpose: :
To examine the effect of pressure and length of cutting pass on the accuracy of Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) lenticle creation.
Methods: :
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.
Results: :
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.
Conclusions: :
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.
Keywords: cornea: clinical science • transplantation