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A dark‐field ophthalmic contact probe for analysis of aqueous humor (AH) was designed by ray tracing and constructed in quartz glass for experimental use as a prototype probe in a confocal Raman spectroscopic setup. The misalignment tolerance of this probe was theoretically evaluated, whereas the optical performance was experimentally evaluated by a concentration curve of the ocular drug phenylephrine HCl in an artificial eye model. The results indicated a ninefold improvement in misalignment tolerance and a 36‐fold improvement in the signal‐to‐noise ratio at the phenylephrine HCl 1002 cm−1 peak compared with a previous design. The prototype showed a good linear fit with the phenylephrine HCl concentration, with an R2 of 0.996. Phenylephrine HCl concentration down to 0.1% is detectable. [ABSTRACT FROM AUTHOR]

In this report we present a confocal Raman system to identify the unique spectral features of two proteins, Interleukin-10 and Angiotensin Converting Enzyme. Characteristic Raman spectra were successfully acquired and identified for the first time to our knowledge, showing the potential of Raman spectroscopy as a non-invasive investigation tool for biomedical applications. [ABSTRACT FROM AUTHOR]

Purpose: Raman spectroscopy holds potential for the assessment of intraocular pharmacokinetics. Raman spectra of ocular drugs were acquired, to determine the drug-specific Raman signature. The ability of the Raman technique to quantify drug concentrations was also investigated. Methods: The experimental setup was based on a High Performance Raman Module 2500 Raman module, designed for 180° 'backscatter' signal detection in the wavenumber range of 400-1,800 cm−1. Excitation source was a diode laser emitting a beam with a wavelength of 785 nm and a power of 10 mW. Laser light was focused in the sample with a long-working-distance microscope objective (25×/0.50). Samples were measured in quartz cuvettes in 10 sequential measurements, with exposure time 30 s. The total number of measured drugs was 49. To determine whether signal intensity and drug concentration correlate, 2 drugs were diluted in water and measured with 120 s exposure time at different concentrations. Results: An active ingredient-specific Raman signature was detected in 4 glaucoma drugs, 6 mydriatics, 5 antibiotics, 4 anesthetics, 3 anti-inflammatory drugs, 2 types of artificial tears, and 5 other drugs. In 20 drugs, no specific Raman signature was detected. Linear correlation of drug concentration with signal intensity was high ( R2≥0.94). Conclusions: Using low laser powers, Raman signatures for 29 commonly used ocular drugs were detected. Correlation of drug concentration with signal intensity is high, which is essential for monitoring drug concentration in ocular media. The presented results encourage the use of Raman spectroscopy to acquire detailed information on the pharmacokinetics of these ocular drugs. [ABSTRACT FROM AUTHOR]

To obtain a real-time noninvasive analysis of the content of the aqueous humor (AH) in the eye, a confocal dark-field ophthalmic probe was designed and optimized by ray-tracing software. The confocal technique allows Raman spectrometric sampling of the AH with suppressing signals from the surrounding tissues. Dark-field illumination prevents the excitation light to reach the vulnerable retinal tissue directly. In order to evaluate the optical performance and safety of this method, a functional prototyped eye contact probe has been designed and tested on ex vivo rabbit eyes. [ABSTRACT FROM AUTHOR]

Current information about the pharmacokinetics of an ocular drug can only be achieved by invasive sampling. However, confocal Raman spectroscopy bears the potential to quantify drug concentrations non-invasively. In this project, we evaluated the detection and quantification of ocular ketorolac tromethamine levels with confocal Raman spectroscopy after topical administration. Confocal Raman spectroscopy and high-performance liquid chromatography (HPLC) were compared in terms of sensitivity of detection. Enucleated pig eyes were treated with different concentrations of ketorolac. Hereafter, ketorolac concentrations in the aqueous humor of pig eyes were analyzed by confocal Raman spectroscopy and HPLC. Subsequently, twelve rabbits were treated with Acular™ for four weeks. At several time points, ketorolac concentrations in aqueous humor of the rabbits were measured by confocal Raman spectroscopy followed by drawing an aqueous humor sample for HPLC analysis. In ketorolac treated pig eyes, both ex vivo Raman spectroscopy as well as HPLC were able to detect ketorolac in a broad concentration range. However, in vivo confocal Raman spectroscopy in rabbits was unable to detect ketorolac in contrast to HPLC. To conclude, confocal Raman spectroscopy has the capacity to detect ketorolac tromethamine in vitro , but currently lacks sensitivity for in vivo detection. [ABSTRACT FROM AUTHOR]