Changes of Axial Length After LASIK Surgery: A 3-Year Follow-Up Study Yoshinori Nakai, Osamu Hieda, and Shigeru Kinoshita Department of Ophthalmology Kyoto Prefectural University of Medicine Kyoto, Japan

Background Corneal epithelium over-formation (change of thickness) Regression can occur after LASIK surgery even without obvious complications during or after the procedure. Corneal epithelium over-formation (change of thickness) Forward displacement of the posterior cornea Lens stiffening Axial length elongation? Lohmann CP. Regression after LASIK for the treatment of myopia: the role of the corneal epithelium. Semin Ophthalmol. 1998;13:79-82. Spadea L. Role of the corneal epithelium in refractive changes following laser in situ keratomileusis for high myopia. J Refract Surg. 2000;16:133-9. Kozak I. Changes in central corneal thickness after laser in situ keratomileusis and photorefractive keratectomy. J Refract Surg. 2003;19:149-53. Ciolino JB. Changes in the posterior cornea after laser in situ keratomileusis and photorefractive keratectomy. J Cataract Refract Surg. 2006;32:1426-31. Seitz B. Posterior corneal curvature changes after myopic laser in situ keratomileusis. Ophthalmology. 2001;108:666-72; discussion 673.

Purpose To investigate the changes of axial length and corneal curvature after LASIK surgery. Subjects 544 eyes（286 cases: 147 males, 139 females）of Japanese patients who were followed up for 3 years postoperatively. Mean patient age: 37.4 years（range: 20-72 years）

Methods Axial length was determined by ultrasound A-mode (TOMEY) and IOL-Master® (Zeiss). Corneal curvature was determined by ARK-700A® (NIDEK). A comparative study was then made between higher myopia（≤-6.0D）and low-moderate myopia（-6.0D<）.

Mean of Preoperative DATA UCDVA: 0.05; CDVA: 1.3 Spherical Equivalent (S.E.): -6.0(±2.8)D Axial Length: 26.09(±1.3)mm Corneal Curvature: Kw42.8(±2.4)D; Ks44.1(±2.5)D; Kave.43.4(±2.4)D ≤-6.0D: 146 cases, 276 eyes A-mode: 133 cases, 254 eyes IOL-Master ®: 13 cases, 22 eyes -6.0D<: 140 cases, 268 eyes A-mode: 131 cases, 248 eyes IOL-Master ®: 9 cases, 20 eyes

Examinations Axial length elongation Changes of corneal curvature Postoperative to 3-Years Postoperative UCDVA and CDVA Spherical Equivalent (S.E.) Axial Length Corneal Curvature (Kw, Ks, Kave.) Correlation between Regression (Changes of 1-Year to 3-Years Postoperative) and… Axial length elongation Changes of corneal curvature Patient age at the time of surgery

Visual Acuity

Spherical Equivalent (S.E.) * （D） * ** * ** * p<0.001 ** p<0.01

Axial Length (A-mode) * （mm） ** * p<0.01 ** p<0.05

Axial Length (IOL-Master®) ** ** ** * p<0.01 ** p<0.05

Corneal Curvature ≤-6.0D >-6.0D （D） （D） * * * * * * * * * ** * * * * p<0.01 ** p<0.05

1- and 3-Year Postoperative Changes Post 1Y Post 3Y S.E. -0.44(±0.76) -0.60(±0.90) AL 26.84(±1.22) 26.84(±1.16) Kave. 38.55(±1.56) 38.67(±1.58) -6.0D< Post 1Y Post 3Y S.E. -0.13(±0.36) -0.19(±0.42) AL 25.44(±0.96) 25.48(±1.02) Kave 40.40(±1.57) 40.44(±1.61) P<0.01 P<0.05 Correlation with Regression (P value) ≤-6.0D P value AL 0.516 Kave. <0.001 Y.O. 0.456 -6.0D< P value AL 0.078 Kave 0.793 Y.O. 0.690

Summary Regression had occurred by the end of the 3rd postoperative year. Axial length had elongated approximately 0.1mm by the end of the 1st postoperative year. A significant correlation was found between regression and changes of corneal curvature in cases of higher myopia (≤-6.0D).

Conclusion Not only changes of corneal curvature but also the elongation of Axial Length might have to be considered as the reason for regression after LASIK surgery. The findings of this study might need to be compared to further investigations involving the measurement of more cases by IOL-Master®.