Polarizing Light Microscopes And Its Medical Applications
Although polarizing light microscopes are better known for their use and application in geological sciences, they are also extremely useful in medicine where they can be utilized for both quantitative and qualitative examination and analysis of biological samples. They also offer a stepped-up version of microscopy compared to brightfield imaging or other optical imaging techniques, which usually provide limited visuals of certain specimens. Polarizing light microscopes provide more information regarding details of a specimen, including its color, composition and structure.
How a polarizing light microscope works
To understand how polarizing light microscope is used in medicine, it is important to learn how it works. A polarizing light microscope, as its name implies, uses polarized light. Unlike natural light or non-polarized light, polarized light vibrates in a specific direction while natural light vibrates in all directions. Polarization can occur either in a horizontal or vertical direction. Using polarizing and analyzing filters, certain characteristics of the sample specimen can be observed, which are normally invisible or difficult to discern using normal light or other microscopy techniques.
The use of polarizing light microscope
The first use of early microscopes was mainly for the observation of minute specimens, primarily organisms such as bacteria and protozoa. This helped push the study of organisms and the medical application of microscopes to the forefront of many modern advances. The discoveries performed by Louis Pasteur, for example, were invaluable in proving that numerous infectious diseases were caused mainly by bacteria. Using the microscope, the source of anthrax was also discovered, leading to systematic study of organisms and the application of microscopes in medicine.
One major advantage of using a polarizing light microscope is that it can distinguish isotropic materials from anisotropic materials. Isotropic materials, such as cubic crystals, liquids and gases are not restricted in terms of the vibration of the light passing through. Anisotropic materials, on the other hand, have a broad range of refractive properties. About 90% of solid substances are anisotropic materials.
In medicine, polarizing light microscopes can be used to examine specimen from both synthetic and natural sources. Whether they are fat tissues, muscle tissues, bones, teeth or gout crystals, polarizing light microscopes can be very effective tools for sample identification or analysis. Polarizing light microscopy can make use of reflected or incident light and transmitted light. Reflected light is often required when viewing and studying opaque materials, including biological specimens. This allows the observer to determine the physical and chemical nature of the sample and observe changes that may occur as part of culturing techniques, an important method used for determining the presence of certain strains of bacteria.
Medical uses of the polarizing light microscope
The use of polarized light in order to observe and examine specimens has a natural advantage as applied in medicine, although it is mainly used in petrographic optical observations of rocks and mineral samples. In medicine, polarizing light microscopes may be used in biomedical research, biochemistry, forensic medicine, toxicology and pharmaceutics.
Polarizing light microscope can be an ideal observation tool in medicine because it allows live biological specimens – samples that are not stained with fixative substances. Live biological tissues, when prepared for observation, are often translucent. When other optical microscopy techniques are used, certain characteristics of the specimen get lost and become invisible to the observer. Furthermore, staining the biological specimen also means killing it, not a very helpful technique when used in certain medical applications such as bacteria culturing, for example. Other types of microscopy also cannot provide the kind of viewing contrast that polarizing light microscopes offer.
In dermoscopy, polarizing light microscopes can also be a valuable tool. Live biological sample specimens from excised tissues can be studied using polarized light, allowing physicians and researchers to observe features in clinically non-pigmented samples. Polarizing light microscopes can also be used effectively to perform compositional analysis of cellular structure in conjunction with other microscopy techniques such as brightfield and fluorescence.
Polarizing light microscopes can also help in the diagnosis of certain diseases, including gout, pneumonia and tuberculosis, among others. They can help identify urate crystals, for example, allowing physicians to determine whether a patient has gout or some other forms of metabolic deficiencies based on the observation of samples using polarizing light microscopy. They are also effective in the observation of bacteria culture, where live specimens are required. Polarized light can also be used in skin cancer screening, allowing live epithelial tissues to be assessed in situ and not limiting the number or amount of samples to be used.
Another medical application of the polarizing light microscope is its use in imaging for in vitro fertilization processes. The instrument allows intensified images of fertilized egg cells, where the presence, location and characteristics of certain cellular components may be determined, thus allowing the analysis and evaluation of that egg’s developmental potential.
