1. Changes in Posterior Corneal Surface After Laser Surface Ablation for Myopia
Sun Woong Kim, M.D.1, Hae Jung Sun, M.D.1,
Tae Im Kim, M.D.2, Eung Kweon Kim, M.D., Ph. D.2
Department of Ophthalmology, Soonchunhyang University Hospital, Bucheon, Korea 1,
The Institute of Vision Research, Department of Ophthalmology, College of Medicine, Yonsei University, Seoul, Korea 2

2. The authors have no financial or proprietary interest in any materials or methods mentioned.

3. Purpose
To evaluate the changes in posterior corneal surface before and after laser surface ablation using a rotating Scheimpflug camera, the Pentacam (Oculus Inc, Wetzlar, Germany).

4. Methods
30 myopic eyes (14 PRK, 16 LASEK) of 20 patients were evaluated preoperatively and postoperatively (1-6months) with the Pentacam
Main outcome measures
Posterior central corneal curvature change
the average in central 4mm zone in tangential curvature map
Posterior corneal elevation change
determined by subtracting the preoperative elevation data from the postoperative elevation data based on the maximum difference at the center of the difference map
BFS determined by preoperative measures
Anterior chamber depth (ACD) change
determined by subtracting the preoperative central ACD data from the postoperative central ACD data

5. Results Table 1. Patient demographics Sex M : F = 12 : 18 Age
28.43±6.61 yrs
Preoperative SE
-4.80±1.80 D
Ablation depth
58.37±20.83 μm
Follow up period
2.80±1.94 months
SE : Spherical equivalent

6. Results
Table 2. Comparison of changes in posterior corneal measurements
Preop.
Postop.
Difference ∆ P
95% CI
ACD (mm)
3.22±0.22
3.16±0.23
-0.06±0.08
0.000*
0.03~0.08
Posterior elevation (µm)
0.47±4.23
0.551
-1.11~2.05
Posterior curvature (mm)
6.14±0.18
6.12±0.17
-0.02±0.07
0.106
-0.004~0.04
* P < 0.05 by paired t-test

7. Results A paradoxical decrease in ACD was seen after laser ablation.
No significant differences were seen in the posterior curvature after laser ablation.

8. Results
The amount of forward shifting of posterior corneal surface had no correlation with residual corneal thickness or ablation depth (Pearson correlation, P > 0.05)

9. Conclusions
There was no significant protrusion in posterior corneal surface after laser surface ablation.