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Static cyclotorsion measurements in the Schwind Amaris laser

Session Details

Session Title: New evaluation tools in refractive surgery

Session Date/Time: Sunday 06/10/2013 | 08:00-09:30

Paper Time: 09:12

Venue: Forum (Ground Floor)

First Author: : D.Fahd LEBANON

Co Author(s): :    E. Jabbour   S. Fahed           

Abstract Details

Purpose:

To assess efficacy and repeatability of static cyclotorsion correction (SCC) measurement on the Schwind Amaris Excimer laser platform in patients undergoing refractive surgery and to compare the results of treating astigmatism with and without SCC.

Setting:

Ophthalmic Consultants of Beirut, Lebanon. Private practice.

Methods:

Prospective study of 80 eyes of 40 patients undergoing LASIK or t-PRK (between May and July 2012) for correction of myopic astigmatism followed up for at least 3 months postoperatively. On the day of planned surgery, all patients had iris registration in the sitting position on the Keratron Scout Optikon 2000 Corneal Wavefront Analyzer (Schwind Eye-Tech Solutions). Proper chin and shoulder positioning were confirmed. All eyes then had 2 or 3 sets of 5 measurements by the Schwind Amaris laser (Schwind Eye-Tech Solutions) while the patient is lying on the laser bed: before and after speculum placement, and after flap lift (in the eyes undergoing LASIK). Variables studied include: percentage of "no catch", repeatability and accuracy of different measurements, as well as visual outcome at 3 months-postoperatively. Astigmatism calculation was done using the polar method of vector analysis.

Results:

Average age: 23.67±4.19years. Male:female ratio: 0.53:0.47. Mean preoperative spherical equivalent was -3.79±2.85D, with a mean cylinder of +1.62±1.11D. Mean measurement time was 13.1sec/measurement and 3.6min/set. Percentage of measurements with "no catch" was 63.8%, 14.9%, and 26.9% pre-speculum placement, post-speculum placement, and post flap-lift, respectively. Percentages of eyes that had "no catch" were 37.5%, 8.5%, and 12.5% pre-speculum placement, post-speculum placement, and post flap-lift, respectively. In eyes with positive SCC, the mean SCC was +4.30° pre-speculum placement, +4.90° post-speculum placement (p=0.706), and +2.05° post flap-lift (p=0.203). In eyes with negative SCC, the mean SCC was -4.34° pre-speculum placement, -3.22° post-speculum placement (p=0.304), and -2.80° post flap-lift (p=0.138). The percentage of eyes that had a cyclotorsion ?±2°, was 41% pre flap-lift and 67% post flap-lift. Significant cyclotorsion (?±5°) was seen in 13% and 18% pre and post flap-lift. In the eyes in which SCC was used, the mean cylinder preoperatively was +1.53D@1° and +0.34D@3 postoperatively. In eyes where SCC was not used, preoperative cylinder was +1.86D@-1° and +0.23D@7° postoperatively. Residual astigmatism postoperatively was not statistically different between both groups (p>0.05). Postoperative cylinder was ?1D in 7.2% of eyes when SCC was used and 18.2% of eyes when SCC was not used (p>0.05).

Conclusions:

Measurement of cyclotorsion using SCC in the Schwind Amaris Excimer laser is easy and useful. It does not delay surgery significantly, despite the fact that it is not always feasible. There was no statistically-significant correlation between measurements taken pre- and post-speculum placement, and post-flap lift. When the cylinder was significant the residual astigmatism correction was better when SCC was used.

Financial Interest:

NONE