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Veterinarian Technician May 2012 (Vol 33, No 5)

Clinical Pathology Close-up: Digital Microscopy

by Margi Sirois, EdD, MS, RVT

    Box 1. Benefits of Digital Microscopy

    • Enhanced communication with consultants
    • Improved client education
    • Archiving of images for teaching
    • Legal documentation of a patient’s condition

    Click here for the editor's introduction to this new series.

    Many veterinary practices incorporate digital images of new patients when creating patient records. Veterinary practices also use digital imaging to document specific patient conditions and, increasingly, to obtain images in the radiology suite. Many practices take “before and after” images of patients undergoing dental procedures to provide to clients as visual evidence of treatment. Visual images can be used to help explain concepts or disease conditions to clients, possibly resulting in increased client compliance. Digital images can also be used to share patient information during consultations with other veterinary professionals and to create an image library for teaching purposes. Adding digital photomicrography, also known as digital microscopy, can also enhance a veterinary practice (BOX 1). Photomicrographs of abnormalities seen on blood films or tissue cytology preparations, parasite evaluations, urine sediment evaluations, and similar diagnostic tests can be used to document findings in a patient’s record. This can be especially beneficial for dealing with legal issues that arise from diagnosis or treatment of patients. Photomicrographs can be added to electronic patient records as a simple way to document diagnoses.

    Digital microscopy has become more affordable, even for small practices. Common types of digital systems include those that incorporate a digital microscope, attach to the third eyepiece of a trinocular microscope (FIGURE 1) , or replace one of the eyepieces on a standard binocular microscope. Some systems incorporate a small viewing screen in addition to interfacing with a computer screen or monitor. While it may be possible to obtain an adapter to attach a microscope eyepiece to a standard handheld digital camera for obtaining photomicrographs, some newer cameras cannot be used in this way, and the adapters may be cost prohibitive. Digital microscopy systems may include computer software that allows images to be categorized and archived in standard formats such as jpg, bmp, and tiff. Some of these programs can directly export images to a photo-editing program.

    Most of the systems can capture still images as well as video, which can be played back in real time on a monitor or computer screen. This can serve as a training tool for new staff members, allowing multiple individuals to view microscopic images as a veterinary technician performs a microscopic evaluation. Real-time streaming of images via the Internet may also be possible and can greatly enhance consultations with other veterinary professionals.


    Digital microscopy systems vary in image resolution capability. Resolution refers to the degree of clarity and visible detail in images. Resolution is measured in pixels: the greater the number of pixels, the greater the degree of detail and clarity and the more the image can be enlarged without loss of clarity. The two primary types of digital imaging methods use different types of image sensors. Charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) image sensors vary in the degree of sharpness of the images they produce. CCD cameras are recommended because they tend to provide higher-quality images than a comparable CMOS camera at the same resolution. In addition, a CMOS camera may not allow smooth real-time projection of images. The resolution of an image is limited by the resolution of the output device used, such as the computer screen or monitor used to display the image. Unless publishing the images is a priority, a veterinary practice should choose the highest-resolution camera system within its budget. If the practice wishes to print images to give to clients, a resolution of 2 megapixels is generally sufficient for printing images up to 5 × 7 inches without loss of clarity.

    Types of Systems

    Digital microscopes that incorporate a digital camera and include software to download and save images to a computer are generally compatible with Microsoft Windows operating systems. These integrated systems tend to be much more costly than purchasing a separate camera to attach to a standard binocular or trinocular clinical microscope. However, integrated systems have the advantage of always being ready to capture images, which they generally do quickly. A very busy practice laboratory may find the higher cost worthwhile.

    Various less expensive digital cameras are available to add to a standard clinical microscope for photomicroscopy. Digital cameras that attach to trinocular microscopes are the most efficient. The camera attachment is mounted to the third eyepiece and the system attached to a computer, most often via a universal serial bus (USB) attachment. Other systems contain an integrated media device, such as a secure digital (SD) card, that can be removed to transfer images to a computer. These systems allow veterinary technicians to obtain images quickly in a clinical setting.

    An eyepiece camera that attaches to a binocular microscope usually requires replacing one of the microscope eyepieces with the eyepiece camera to capture images directly on a computer (FIGURE 2). These systems are highly cost effective but tend to be slightly slower than the systems discussed above. With an eyepiece camera system, a veterinary technician would remove one of the microscope eyepieces, attach the camera, and capture an image directly on a computer (FIGURE 3) . The technician would then remove the camera and replace the eyepiece to continue the remainder of the evaluation.


    It is important that microscopes used for obtaining photomicrographs have high-quality optics. The overall quality of digital photomicrographs is greatly influenced by the quality of a microscope’s optics. The microscope should have plan achromatic (flat field) objectives. Many older clinical microscopes use filament light sources (generally halogen or tungsten) and are configured for Köhler illumination. To obtain high-quality images, the microscope must be adjusted to proper Köhler illumination (BOX 2). Without proper illumination and adjustments, the image may appear to be unevenly illuminated, containing bright and dark areas or shadows. Click here for a tutorial on performing adjustments to obtain Köhler illumination. Newer clinical microscopes that use light-emitting diodes (LEDs) tend to produce the highest-quality images due to enhanced color balance and greater stability of light output. Regardless of the type of microscope used, having it professionally serviced at least annually is essential.

    Box 2. Steps for Köhler Illumination

    1. Secure a slide on the microscope stage.
    2. Adjust the light source to approximately half its total brightness.
    3. Place the 10× ocular lens in position.
    4. Verify that the eyepiece is at the correct interpupillary distance and is focused.
    5. Use the coarse adjustment knob to focus on the specimen (FIGURE A) .
    6. Close the field diaphragm and condenser until a small ring of light is visible through the specimen in the field of view.
    7. If needed, adjust the condenser screws until the light is centered in the field of view (FIGURE B) .
    8. Open the diaphragm until the circle of light just touches the edge of the circumference of the field of view.
    9. Adjust the condenser until the light is in sharp focus. If this makes the image darker, adjust the brightness to compensate.
    10. Repeat this procedure for each ocular objective.


    Digital microscopy can greatly enhance practice recordkeeping and can become a valuable tool for client education and staff training. While image resolution is an important factor, choosing a system that allows simple image acquisition, storage, and management may be more important.


    Here are additional tutorials on obtaining high-quality digital microscope images:


    NEXT: Editorial: Introducing Clinical Pathology Close-up


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