Rapid, Non-Invasive Screening Of Keratitis Based On Raman Spectroscopy.

INTRODUCTION

Keratitis is a common eye condition characterized by inflammation of the cornea, the clear outer layer of the eye. Traditional diagnosis often relies on physical examination and may require additional tests. Raman spectroscopy emerges as a potential tool for rapid, non-invasive screening of keratitis.

Raman spectroscopy is a powerful technique used to analyze the molecular composition of a material. It works by focusing a monochromatic light source, usually a laser, onto the sample. When light interacts with the molecules in the sample, it can scatter in two ways:

1. Rayleigh Scattering: This is the predominant form of scattering, where the scattered light retains the same wavelength as the incident light.
2. Raman Scattering: In a small fraction of scattering events (1 in 1 million photons), the light interacts with the vibrations of the molecules within the sample. This interaction causes a slight shift in the wavelength of the scattered light. This shift, known as the Raman shift, is unique for each type of molecule and acts as a fingerprint of its vibrational energy levels.

By analyzing the Raman shift of the scattered light using a spectrometer, Raman spectroscopy provides detailed information about the molecular composition of the sample.

Figure 2: Principle of Raman spectroscopy.

Application of Raman spectroscopy in keratitis screening:

• Analyzing Tear Composition: Tears contain a variety of molecules, including proteins, electrolytes, and metabolites. These molecules create a unique characterized spectrum when analyzed by Raman spectroscopy.
• Distinguishing Between Healthy and Diseased States: In healthy eyes, the tear composition remains stable. However, when keratitis develops, the tear composition changes due to the body's inflammatory response. Raman spectroscopy can potentially detect these changes in the molecular fingerprint of tears.
• Identifying Keratitis Types: Studies suggest that Raman spectroscopy might be able to differentiate between diverse types of keratitis, such as bacterial, viral, or fungal. This information can be crucial for guiding appropriate treatment options.

Keratitis screening is crucial for early diagnosis, preventing complications, and selecting the right treatment to save vision. Therefore, the Raman spectroscopy is a great technique because it brings some benefits such as:

• Specificity: The unique molecular fingerprint of tears allows Raman spectroscopy to potentially differentiate keratitis from healthy eyes and even identify specific types of keratitis.
• Non-invasive Nature: Tear collection is a painless procedure, eliminating the need for invasive corneal scraping often used in traditional diagnosis.
• Rapid Analysis: Raman spectroscopy analyses can be completed quickly, potentially leading to faster diagnosis and treatment decisions.

Result

Figure 3: Raman spectrum of keratitis and healthy tears in the range of 400 cm^-1 to 4000 cm^-1

Figure 4: Raman spectrum of keratitis tears show peaks at 1005c m^-1, 1155 cm^-1 and 1514cm^-1 that intensity is higher than healthy tears.

In a specific study using Raman spectroscopy analyzed fresh tears from 19 patients with infectious keratitis and 27 healthy individuals. The analysis of the normalized average Raman spectra revealed key differences between the two groups. When focusing on the wavenumber range of 550 cm^-1 to 2000 cm^-1, researchers observed a higher intensity of peaks at 1005 cm^-1, 1155 cm^-1, and 1514 cm^-1 in the keratitis samples compared to healthy tears. While the specific molecules linked to these peaks remain unclear, these findings suggest a potential for Raman spectroscopy to differentiate between healthy and keratitis-affected tears based on molecular composition variations. Further research is needed to interpret the meaning of these peak changes and validate Raman spectroscopy as a diagnostic tool for keratitis.

Measurement system

In the realm of keratitis screening, a powerful combination emerges: the Ocean QEPro spectrometer and a Raman laser light source. Here is how this duo contributes to this crucial diagnostic tool:

Ocean QEPro Spectrometer: This high-sensitivity spectrometer plays a vital role in capturing the Raman signal effectively. Its exceptional ability to detect weak signals ensures that the subtle shifts in light wavelength (Raman shift) caused by tear molecules are accurately measured. The QEPro's wide spectral range allows for a comprehensive analysis of the molecular fingerprint present in the tear sample.

Figure 5: QEPro spectrometer.

Raman Laser Light Source: This focused laser beam serves as the initial source of light that interacts with the tear molecules. The specific wavelength of the laser light is crucial for optimal Raman scattering. Here, a carefully chosen laser wavelength effectively excites the vibrations within the tear molecules, leading to the characteristic Raman shift.

Figure 6: Raman laser light source.

Together, the Ocean QEPro spectrometer and the Raman laser light source form a robust system for keratitis screening. The laser effectively interacts with the tear molecules, inducing Raman scattering. The QEPro spectrometer then precisely captures the resulting weak signal, revealing the unique molecular fingerprint within the tear sample. By analyzing this fingerprint, researchers can potentially detect changes associated with keratitis, aiding in early diagnosis, and potentially differentiating between healthy and diseased states.

CONCLUSION

Raman spectroscopy offers a promising, non-invasive method for the rapid screening of keratitis. By analyzing the unique molecular spectral in tears, this technique can distinguish between healthy and diseased states, potentially identifying specific types of keratitis. The combination of the Ocean QEPro spectrometer and a Raman laser light source enhances the accuracy and efficiency of this diagnostic tool, paving the way for early diagnosis and better treatment outcomes. Further research is needed to fully validate its clinical application.