A transient pressure wave created in photoablation-based laser corneal refractive surgery propagates along the optical axis of the eye from the cornea toward the fundus. Along its path, it is attenuated, reflected several times at tissue interfaces, focused due to the spherical shape of the cornea, and partially phase-converted to a tensile wave after passing the acoustic focus. Employing the numerical acoustic eye model, the dynamics of the acoustic focusing is described in detail. The simulated pressure waveforms are first validated against the existing measurements. Then, the calculated full pressure fields are used to obtain the extreme values of the pressure amplitude at every point within the eye over the whole timespan of interest. Over these pressure maps, various threshold contours obtained from the existing literature are superimposed to help ophthalmologists investigate the consequences of acoustic focusing within the human eye during laser keratorefractive surgery. The comparison indicates that the simulated negative peak pressure values used in the contemporary broad beam and flying spot laser-assisted in situ keratomileusis/photorefractive keratectomy treatments exceed some of the reported threshold values. The critical volume where the thresholds are surpassed is located near the lens-vitreous boundary and extends to the retina for wide beams. The photoablation-induced pressure wave focusing is, therefore, a mechanism that needs to be researched carefully and included in the list of potential risks accompanying refractive laser surgery.
| Funder: | ARRS - Slovenian Research Agency |
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| Project number: | P2-0263, P2-0270, P2-0392, L2-6780, L2-8183, L2-9240, L2-9254 |
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| Name: | Mehanika v tehniki, Proizvodni sistemi, laserske tehnologije in spajanje materialov, Optodinamika, Hibridni ps laser velikih moči, Ultrakratki laserski pulzi na zahtevo, Prostorsko in časovno oblikovanje laserske svetlobe za minimalno invazivne oftalmološke posege |
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