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Vector analysis of astigmatism before and after excimer laser treatment

Session Details

Session Title: Surface Ablation I

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

Paper Time: 08:36

Venue: Main Lecture Hall (Ground Floor)

First Author: : A.Biscevic CROATIA

Co Author(s): :    M. Bohac   I. Dekaris   N. Gabric        

Abstract Details

Purpose:

To compare the outcomes of astigmatic Laser in Situ Keratomileusis (LASIK) procedures according to two different platforms using J0, J45 and S vector analysis.

Setting:

Specialty Eye Hospital "Svjetlost", Zagreb, Croatia

Methods:

Patients with myopic (i) or mixed (ii) astigmatism underwent unremarkable LASIK using either Wavelight Allegretto IQ 400Hz (group I: i, n=127 ii, n=61 ) or Schwind Amaris 750S (group II: i, n=118 ii, n=110) laser platforms. The preoperative and postoperative sphere [S], negative cylinder[C] and axis [ų] of subjective refractions were subjected to vector analysis by calculations of the standard J0 (=cos [4?(ų-90)/360]xC/2), J45 (=sin[4?(ų-90)/360]xC/2) and S2 (=S+C/2). The pre-and post vectors were compared using standard t test and linear regression.

Results:

Reporting the key results, A) there was no significant difference between myopic (i) and mixed (ii) astigmatic groups for the mean J0, J45 & S2 values before and after surgery. B) J0 and S2 very significantly reduced after LASIK in (i) & (ii) for both platforms (p<0.001) but not for J45. C) Pooling the data, mean (±sd) values for J0, J45 & S2 were pre-op, 1.301 (0.802), 0.028 (0.732), -4.21 (2.06) and post-op, 0.079 (0.244), -0.027 (0.120), -0.41 (0.54). D) There was a weak association between individual pairs of pre-and post- J0 & J45 values. There was no significant difference between the outcomes of the two platforms.

Conclusions:

Both Wavelight Allegretto 400Hz and Schwind Amaris 750S showed excellent results for treating patients with astigmatism, regardless whether it is mixed or myopic astigmatism, because of the highly significant fall in values of J0 and S2 vectors. The J45 did not reduce significantly possibly because of low number of eyes with oblique astigmatism. There was no genuine difference between groups treated on two different laser platforms according to the vector analyses.

Financial Interest:

NONE