Gel-modulated photo ablation using noncontact photoacoustic spectroscopy control: a new concept

Benedikt J. Jean M.D.; Thomas Bende

doi:10.1117/12.387534

7 June 2000 Gel-modulated photo ablation using noncontact photoacoustic spectroscopy control: a new concept

Benedikt J. Jean M.D., Thomas Bende

Proceedings Volume 3908, Ophthalmic Technologies X; (2000) https://doi.org/10.1117/12.387534
Event: BiOS 2000 The International Symposium on Biomedical Optics, 2000, San Jose, CA, United States

Abstract

Refractive gels, applied on the corneal surface in situ act as laser beam modulators. Depending upon their surface shape and absorbency, they can be used to reshape irregular surfaces or induce refractive effects. Three gels (Palm I Pallikaris, Greece; Refrax 33, Imperial, USA; Biomask, Maverick USA) have been investigated using Non Contact Photoacoustic Spectroscopy (NCPAS). Their use requires on line detection and monitoring of the ablation process, indicating when the gel is ablated and the corneal tissue is exposed to the incident laser pulse. NCPAS enables this on line control. With the gels in their present form, stable ablation rates where achieved only after 200 - 400 pulses, depending upon the gel. The typical frequency shift of the Fourier -- transformed time signal of NCPAS, observed for different target materials (gels, human, and porcine cornea) allowed the discrimination of the different gels as well as from human and porcine corneal tissue (epithelium and stroma). NCPAS discriminates and identifies even those gels with similar ablation rates, using the typical frequency shift (difference >= 1 kHz). Refractive gels in combination with a powerful on-line control such as NCPAS has a potential to be used as a low cost approach for reducing or minimizing the amount of surface bound corneal optical aberrations; it could thus bypass the complexity and costs of corneal reshaping systems, using topography or wavefront based customized treatment algorithms.

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Benedikt J. Jean M.D. and Thomas Bende "Gel-modulated photo ablation using noncontact photoacoustic spectroscopy control: a new concept", Proc. SPIE 3908, Ophthalmic Technologies X, (7 June 2000); https://doi.org/10.1117/12.387534

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KEYWORDS

Laser ablation

Photoacoustic spectroscopy

Laser vision correction

Cornea

Eye

Natural surfaces

Tissues

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