Nonresonant Raman spectroscopy of isolated human retina samples complying with laser safety regulations for in vivo measurements.

Clara Stiebing,Martin Jahn,Amanda J Kiliaan,Michael Schmitt,Laurin Ginner,Rainer A Leitgeb,Robert Kleemann,Antonia Lichtenegger,Wolfgang Drexler,Iwan W Schie,Jürgen Popp,Izabella J Jahn,Florian Knorr,Nanda Keijzer

doi:10.1117/1.nph.6.4.041106

Abstract

.Retinal diseases, such as age-related macular degeneration, are leading causes of vision impairment, increasing in incidence worldwide due to an aging society. If diagnosed early, most cases could be prevented. In contrast to standard ophthalmic diagnostic tools, Raman spectroscopy can provide a comprehensive overview of the biochemical composition of the retina in a label-free manner. A proof of concept study of the applicability of nonresonant Raman spectroscopy for retinal investigations is presented. Raman imaging provides valuable insights into the molecular composition of an isolated ex vivo human retina sample by probing the entire molecular fingerprint, i.e., the lipid, protein, carotenoid, and nucleic acid content. The results are compared to morphological information obtained by optical coherence tomography of the sample. The challenges of in vivo Raman studies due to laser safety limitations and predefined optical parameters given by the eye itself are explored. An in-house built setup simulating the optical pathway in the human eye was developed and used to demonstrate that even under laser safety regulations and the above-mentioned optical restrictions, Raman spectra of isolated ex vivo human retinas can be recorded. The results strongly support that in vivo studies using nonresonant Raman spectroscopy are feasible and that these studies provide comprehensive molecular information of the human retina.

Highlights

Vision impairment is a frequently occurring condition in people over 50 years of age and experiences a steady increase in prevalence due to an aging society and population growth.[1]
We demonstrate to the best of our knowledge for the first time the applicability of nonresonant Raman spectroscopy on isolated ex vivo human retina complying with international laser safety regulations for the permissible excitation power
In contrast to previous studies, ours was able to obtain a comprehensive overview of the macromolecular information of human retinas

Summary

Introduction

Vision impairment is a frequently occurring condition in people over 50 years of age and experiences a steady increase in prevalence due to an aging society and population growth.[1] the World Health Organization states that around 81% of occurrences could be avoided if diagnosed and treated early.[2] Especially, retinal diseases such as diabetic retinopathy, glaucoma, and age-related macular degeneration (AMD) are leading causes of vision impairment in high-income countries.[3] new approaches in ophthalmology are aiming at early diagnosis of retinal alterations. Typical diagnostic methods in the clinical environment range from direct fundus examination, i.e., the rear inner eye surface, by ophthalmoscopy to highresolution optical imaging, to fluorescence-based angiography and optical coherence tomography (OCT). OCT is routinely used in ophthalmology, due to its three-dimensional sectioning of the retina, allowing evaluation of subtle morphological changes in the underlying structure. OCT tomograms are recorded using laser interferometry by measuring the path

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