Non-ablative ultra-pulsed laser interaction with intraocular lenses for refractive power modification

Session Details

Session Title: Cataract
Session Date/Time: Saturday 16/02/2019 | 08:30-11:00
Paper Time: 10:12
Venue: Hall Trianti

First Author: K.Bacharis GREECE
Co Author(s): E. Drakaki  G. Kareliotis  E. Chalkiadaki  I. Sianoudis  M. Makropoulou  A. Serafetinides  

Abstract Details

Purpose:

The aim of this work is to present our experimental efforts on laser induced refractive power modifications of intraocular lenses (IOLs). For non-invasive interventions on implanted IOLs, after cataract surgery, the most appropriate laser system must ensure both efficiency and safety. For that, nondestructive photorefractive alterations of IOL must be induced by focusing the laser beam at fluence below the damage threshold while the defocused beam shining the retina should not overcome the maximum permissible exposure levels. In our work, the relevant physico-chemical background of the focal length alteration of an IOL through refractive index tuning will be outlined.

Setting:

The presenting author or any co-author has no financial interest in the subject matter or has no received money from any mentioned company.

Methods:

Laser - IOL interaction experiments were performed in laboratory on commercially available IOLs, as well as on contact lenses and PMMA plates, applying different laser radiation parameters. The laser source was a pulsed laser (Ti:Sapphire laser) at λ= 800nm, pulse width tp=48 fs, frequency=85 MHz and mean power P= 360 mW. The morphology of the ablated IOL and PMMA surface and quantitative measurements of the refractive index were examined at various settings of laser pulses, different focal length and laser fluencies, with the help of a spectra refractometer (Metricon) and Digital abbe refractometer (Kruss Optronics) in constant temperature.

Results:

The experimental results of the modification of the refractive power values of intraocular lenses after fs laser irradiation show small differences in the measured refractive index. However, according to literature, about 0.3 to 2.5 diopters correspond to 1% change of refractive indexes. The effect of lens and PMMA material’s surface morphology after exposure to NIR fs laser radiation was also investigated by SEM examination, demonstrating no visible surface damages, as it was expected, because we used non-ablative laser parameters. We hypothesize that the laser interaction with IOLs depends on both optical and physico-chemical material properties.

Conclusions:

Our first preliminary results indicate a small modification of the refractive index of the polymeric ocular lenses and PMMA plates. The exact mechanism for photo-induced modification of refractivity must be further elucidated, before any attempt to translate this research into in vivo and, furthermore, to clinical applications. Moreover, the hypothesis that the underlying mechanism is a cross-linking procedure involving a photo-induced photochemical process and the possible role of hydrophilicity must be further studied.

Financial Disclosure:

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