Résumé
AIM: To investigate the difference between anterior corneal astigmatism axis and total corneal astigmatism axis, and the related factors.?METHODS: The anterior corneal astigmatism axis and total corneal astigmatism axis in 789 patients(1141 eyes) of China Medical University Eye Hospital were detected by Petacam and recorded the corresponding age, value of astigmatism, anterior chamber depth, corneal thickness, refraction of cornea and anylized statistically.?RESULTS:We found age was positively correlated with the difference of the anterior corneal astigmatism axis and total corneal astigmatism axis(r=0. 139, P<0. 001). The value of astigmatism was negatively correlated with the difference of the anterior corneal astigmatism axis and total corneal astigmatism axis(r=-0. 293, P<0. 05). The anterior chamber depth was negatively correlated with the difference of the anterior corneal astigmatism axis and total corneal astigmatism axis ( r=-0. 067, P<0. 05). And the corneal thickness, refraction of cornea was not significantly correlated with the difference of the anterior corneal astigmatism axis and total corneal astigmatism axis.?CONCLUSION: There is significant difference in the anterior corneal astigmatism axis and total corneal astigmatism axis, and is positively correlated with age, and is negatively correlated with value of astigmatism and the depth of anterior chamber.
Résumé
Objective To investigate the spherical diopter and astigmatism change of humans at sitting and supine position.De- sign Prospective case series.Participants 96 eyes of 52 patients (spherical diopter from-2.50 D to-10.00 D,astigmatism diopter from -0.75 D to-4.50 D) were selected.Methods The subjects were examined with NIKON portable retinomax at sitting and supine posi- tion,respectively.Main Outcome Measures The spherical diopter,cylinder diopter and axis change were analyzed statistically.Re- sults Spherical diopter at supine position (-5.31?3.43 D) was a little higher than that at sitting position (-5.27?3.24 D) statistically(P= 0.25),and cylinder diopter at sitting position (-2.27?1.24 D) and at supine position (-2.35?1.19 D) was no statistically difference (P= 0.20).The axis of astigmatism changed from-16?to +18?.Axis change was within 2?in 52.1% eyes,6?-10?in 5.2%,over 10?in 3.1%. The change of axis rotation tended to counter-clockwise in the right eye and clockwise in the left eye.Conclusions Eye rotation at sit- ting and supine position may cause the astigmatism axis change.It may be one of the main factors affecting the results of LASIK.
Résumé
PURPOSE: To evaluate the presence, degree and direction of ocular cyclotorsion in eyes undergoing laser in situ keratomileusis (LASIK). METHODS: We measured the presence, degree and torsional direction of 161 eyes of 88 patients who underwent LASIK for myopic and hyperopic astigmatism with LADARVision 4000 excimer laser (Alcon Summit Autonomous). Preoperatively, each eye was marked at the 3, 9-o'clock conjunctival area with marking pen under the slit lamp observation with a horizontal beam while the patient was seated upright. After lifting of corneal flap and acquiring of LADARVision4000 auto-tracking system, the presence and torsional direction was confirmed on the computer monitor and the rotational deviation degree was measured from horizontal reference line by software program built in laser computer system before the laser exposure. RESULTS: There was a cyclotorsional deviation in 144 eyes (89%). The counter-clockwise rotation was shown in 99 eyes (69%) and clockwise rotation in 45 eyes (31%). Mean ocular torsional misalignment was 3.8 +/- 2.9 degrees (right eye; 4.7 +/- 2.9 degrees, left eye; 3.5 +/- 2.4 degrees). 85 eyes (53%) had a torsional deviation less than 4 degrees and 5 eyes (3%) had a deviation greater than 10 degrees. CONCLUSIONS: A misalignment of astigmatism axis caused by ocular cyclotorsion was known as a reason of astigmatism undercorrection during LASIK. Thus, preoperative marking on conjunctiva and cyclotorsional axis alignment before laser treatment may reduce the incomplete astigmatism correction in LASIK.