Refractive change in the adult rabbit eye after corneal relaxation with the femtosecond laser.
BACKGROUND
A new procedure to correct myopia that does not disturb the cornea in the optical zone and avoids injuring the corneal epithelium could be a key advance in corneal refractive surgery. The aim of this study is to observe the refractive change in the adult rabbits undergoing femtosecond laser-assisted multilayer intrastromal ablation in the mid-periphery of the cornea without injury of epithelium.


METHODS
The right eyes of 8 New Zealand White adult rabbits were used for the experiments. A 60-kHz femtosecond laser delivery system was used, and three lamellar layers of laser pulses were focused starting at a corneal depth of 180 μm and ending at 90 μm from the surface, with each successive layer placed 45 μm anterior to the previous layer. In the interface of the applanation contact lens cone, a 6-mm diameter aluminum circle was placed at the center to block the laser, limiting ablation to the mid-periphery of the cornea. The laser settings were as follows: spot/line separation, 10 μm; diameter, 8.0 mm; energy for ablating the stroma, 1.3 μJ. An authorefractor was used to assess the manifest refraction.


RESULTS
Mean spherical equivalent (SE) (mean ± SD, SD: standard deviation) was significantly increased at postoperative week 1 (1.67 ± 0.26 D, p < 0.0001), month 1 (1.65 ± 0.23 D, p < 0.0001), and month 3 (1.60 ± 0.22 D, p < 0.0001) compared to baseline (0.68 ± 0.27 D). Mean spherical equivalent showed no significant change between postoperative week 1 and month 3 (p = 0.1168).


CONCLUSIONS
Femtosecond laser-assisted multilayer corneal intrastromal ablation in the mid-periphery may cause a consequent hyperopic shift with no refractive regression.
Department of Ophthalmology, Putuo Hospital, Shanghai University of Chinese Traditional Medicine, No, 164, Lanxi Road, Shanghai (200062), China. zzyly818@sina.com.
Zhen-Yong
ZY
Zhang
Matthew R
MR
Hoffman
Xing-Tao
XT
Zhou
Ye
Y
Xu
Xing-Ru
XR
Zhang
Ren-Yuan
RY
Chu
Chong-Da
CD
Chen
D000704:Analysis of Variance; D000818:Animals; D003315:Cornea / Q000503:physiopathology*; D048988:Corneal Surgery, Laser / Q000379:methods*; D019781:Corneal Topography; D004195:Disease Models, Animal; D054018:Lasers, Excimer; D011817:Rabbits; D012029:Refraction, Ocular / Q000502:physiology*