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S Barbero, S Marcos, L LLorente; Optical Changes In Corneal And Internal Optics With Cararact Surgery . Invest. Ophthalmol. Vis. Sci. 2002;43(13):388.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate changes in the optical aberrations of the different ocular components induced by cataract surgery : 1) Possibilities of aberrometry to measure aberrations through a cataract. 2) Measurement of optical aberrations of the implanted intraocular lens (IOL) in vivo. 3) Measurement of corneal aberrations due to the surgical incision. Methods: Corneal and total aberration measurements were performed on 8 eyes (mean age: 73.11 std=10) before surgery and then ≷3 months after surgery (2 eyes). Surgical technique was phacoemulsification, with a 4.2-mm incision, with implantation of a 6-mm acrylic foldable IOL (Acrysof, Alcon). Total aberrations were measured with Laser Ray Tracing (sequentially scanning the pupil with a 786-nm laser diode and collecting the corresponding aerial images). Corneal aberrations were obtained from videokeratographic corneal elevation maps. Pupil size was 5 mm. Wave aberrations were computed from spot diagrams and fit by Zernike polynomial expansions. The optical quality was assessed by the Root Mean Square wavefront error (RMS). The wave aberration for the internal optics was computed as the difference of total and corneal wave aberration Results: 1) Reliable aberration measurements were obtained in 7 of the cataract eyes, for which the measured spot diagram was repetitive and reproducible from wave aberration estimates. 2) Mean total RMS wavefront error (for 3rd order and higher aberrations) was 0.660.20 µm before surgery and 0.54±0.09µm after surgery. These values are higher than 0.20.04µm for a control group of 15 young eyes (age= 293.7, spherical error <4.5 D). 3) Post-operative mean internal RMS wavefront error (3rd order and higher) was 0.8 0.48µm, as opposedto 0.240.14µm in young eyes. 5) Corneal astigmatism increased with surgery by a factor of 1.35 (std=0.72) and for 3rd order terms by 2.99 std=0.42). Conclusion: 1) Aberrations can be measured through cataracts only in some eyes. Opacities may deflect the beams, producing irregular spot diagrams. These results only account for low order aberrations, and not for scattering. 2) The presence of internal aberrations post-surgery can be due to IOL aberrations, tilt or decentration, or posterior corneal surface changes due to corneal incision. 3) Corneal incision produces significant changes in corneal astigmatism as well as in higher order aberrations.
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