Purpose To observe the refractive change in rabbits undergoing femtosecond laser-assisted multilayer intrastromal ablation in the mid-periphery of the cornea.
Method The right eyes of 8 New Zealand White 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. A wavefront aberrometer 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).
Conclusion Femtosecond laser-assisted multilayer corneal intrastromal ablation in the mid-periphery may cause a consequent hyperopic shift with no refractive regression. |
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