Chemical basis for alteration of an intraocular lens using a femtosecond laser.

Josef F Bille,Hans-Robert Volpp,Abdelmoutalib Laghouissa,Marcus Motzkus,Johann Engelhardt,Zhongxiang Jiang,Ruth Sahler

doi:10.1364/boe.8.001390

Abstract

The chemical basis for the alteration of the refractive properties of an intraocular lens with a femtosecond laser was investigated. Three different microscope setups have been used for the study: Laser Induced Fluorescence (LIF) microscopy, Raman microscopy and coherent anti-Stokes Raman Scattering (CARS) microscopy. Photo-induced hydrolysis of polymeric material in aqueous media produces two hydrophilic functional groups: acid group and alcohol group. The spectral signatures identify two of the hydrophilic polar molecules as N-phenyl-4-(phenylazo)-benzenamine (C18H15N3) and phenazine-1-carboxylic acid (C13H8N2O2). The change in hydrophilicity results in a negative refractive index change in the laser-treated areas.

Highlights

The use of the femtosecond laser to create refractive index change in various materials has been studied for years
The detailed views of the strip imaged by Laser Induced Fluorescence (LIF) in Fig. 4(a) and Fig. 4(b) shows the creation of hydrophilic areas exactly where the rings are located on Fig. 4(a)
The Refractive Index Shaping (RIS) treatment (see e.g. Fig. 1(a)) uses a femtosecond laser to change the hydrophilicity of the targeted area, which allows a change in the refractive index, e.g. a negative refractive index change in the laser treated areas

Summary

Introduction

The use of the femtosecond laser to create refractive index change in various materials has been studied for years. Ohmachi et al (1972) showed a refractive index change of 0.056 in glass using a femtosecond laser [1]. Ding (2006) used a femtosecond laser to obtain a refractive index change of up to 0.06 in hydrogel polymers [2]. Different theories regarding femtosecond laser material interactions which affect the refractive index change have been offered. The Rochester Group hypothesized that the light from the femtosecond laser induced crosslinking within a hydrophilic material and created an increase in the refractive index [3]. Takeshima et al (2004) believed the refractive index change in glass was caused by local heat effects from phase separation [4], while Katayama (2002) proposed that all changes resulted from either: i) crosslinking, ii) phase separation, or iii) decomposition [5]

Methods

Results

Conclusion