There are many different types of microscopes used in modern pathology laboratories and research departments around the world, these typically include stereo, compound, digital, and pocket microscopes as well as electron, and fluorescence microscopes.
Light Microscopy is the corner stone in all laboratories as it provides substantial magnification, enabling the professional to observe the specimen as required and with ease.
How does light microscopy work?
As the name suggests light is the principal behind these types of microscopes, and the size of the image seen is determined by the angle of light entering the eye. Therefore a glass lens is used as it slows the light causing the wavelength of the light to become shorter and as a result light bends (refraction), the amount bent is called the refractive index.
The lens within the light microscope serves to focus light rays at a specific place called the focal point, this is the distance between the center of the lens and focal point is the focal length. The strength of the lens is related to focal length as the shorter the focal length, the greater the magnification.
Normal light microscopy is called bright field, however there are also specialist types of light microscopy methods called dark-field microscopy, phase-contrast microscopy, polarised light microscopy as well as fluorescence and stereo microscopy.
Types of Light Microscopes
The Compound Microscope
The compound microscope is a light microscope that utilizes photons (light) and lenses to magnify the object under observation. It differs from other types of microscopes as it utilizes multiple lenses and can achieve a high magnification typically reaching 1000x magnification. The lenses are called the eyepiece lens and the objective lens.
Compound microscopes have many uses in modern laboratories, for example in pathology departments they are commonly used by physicians to observe patient specimens e.g. tissues and cells and to look for cellular changes that could help to diagnose or screen for diseases such as cancer.
The Stereo Microscope
A stereo microscope is another common microscope found in laboratories, yet due to its low magnification has limited use. Stereo microscopes are typically below x100 magnification, yet they allow specimens to be viewed in three dimensions.
They are commonly used in tissue inspection and microsurgery.
The Electron Microscope
The electron microscope is an extremely powerful microscope capable of magnifications of x1,000,000 and resolutions of about 2 nm. They utilize the same principles as the light microscope, yet instead of a light source, a beam of electrons is used.
In laboratories they are used by highly trained professionals to investigate and observe various markers of cell differentiation to identify tumours types, and in renal disease, to monitor disease progress.
They also have a critical role in the diagnosis of renal disease and a range of other conditions. Additionally they are often used for micro-organism identification.
The fluorescence microscope utilizes fluorescence and phosphorescence to observe and study various molecules of interest. The specimen absorbs the light then re-emits it with a longer wavelength, this is usually achieved by attaching fluorchromes to the tissue or biomolecule of interest. A flurochrome or fluorophore is a fluorescent chemical that can re-emit light when light is “excited”.
This results in biomolecules that can easily be observed and tracked under the microscope, this is commonly used to confirm the presence of certain proteins e.g. growth factors important in the treatment of particular types of cancers.