de Freitas Carolina P, Cabot Florence, Manns Fabrice, Culbertson William, Yoo Sonia H, Parel Jean-Marie
Ophthalmic Biophysics Center, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miami, Florida, United States Biomedical Optics and Laser Laboratory, Department of Biomedical Engineering, University of Miami College of Engineering, Miami, Florida, United States.
Ophthalmic Biophysics Center, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miami, Florida, United States Anne Bates Leach Eye Hospital, Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
Invest Ophthalmol Vis Sci. 2015 Jan 27;56(2):1222-7. doi: 10.1167/iovs.14-15822.
To assess if a change in refractive index of the anterior chamber during femtosecond laser-assisted cataract surgery can affect the laser beam focus position.
The index of refraction and chromatic dispersion of six ophthalmic viscoelastic devices (OVDs) was measured with an Abbe refractometer. Using the Gullstrand eye model, the index values were used to predict the error in the depth of a femtosecond laser cut when the anterior chamber is filled with OVD. Two sources of error produced by the change in refractive index were evaluated: the error in anterior capsule position measured with optical coherence tomography biometry and the shift in femtosecond laser beam focus depth.
The refractive indices of the OVDs measured ranged from 1.335 to 1.341 in the visible light (at 587 nm). The error in depth measurement of the refilled anterior chamber ranged from -5 to +7 μm. The OVD produced a shift of the femtosecond laser focus ranging from -1 to +6 μm. Replacement of the aqueous humor with OVDs with the densest compound produced a predicted error in cut depth of 13 μm anterior to the expected cut.
Our calculations show that the change in refractive index due to anterior chamber refilling does not sufficiently shift the laser beam focus position to cause the incomplete capsulotomies reported during femtosecond laser-assisted cataract surgery.
评估飞秒激光辅助白内障手术过程中前房折射率的变化是否会影响激光束聚焦位置。
使用阿贝折射仪测量六种眼科粘弹性装置（OVD）的折射率和色散。利用古尔斯特兰德眼模型，当OVD充满前房时，用折射率值预测飞秒激光切割深度的误差。评估了由折射率变化产生的两种误差来源：用光学相干断层扫描生物测量法测量的前囊位置误差和飞秒激光束聚焦深度的偏移。
在可见光（587nm）下，所测量的OVD的折射率范围为1.335至1.341。重新填充后的前房深度测量误差范围为-5至+7μm。OVD使飞秒激光焦点偏移范围为-1至+6μm。用密度最大的化合物的OVD替代房水会在前房产生13μm的预测切割深度误差。
我们的计算表明，前房重新填充引起的折射率变化不会使激光束聚焦位置发生足够大的偏移，从而导致飞秒激光辅助白内障手术中报道的不完全撕囊。
