Microscopes are a common instrument used daily in veterinary clinics to view various products (eg, blood, urine, fecal material, fluid aspirates, skin scrapings, ear cerumen). The microscope ocular lenses, objective lenses, stage, and stage clips should be cleaned after each use, and the body of the microscope should be wiped down and inspected at the end of each shift after its last use of the day.
Samples viewed on an improperly cleaned microscope are at risk for contamination, which can lead to false positive results. Because samples may contain transmissible disease organisms, veterinary staff should wear gloves when handling slides, and slides should be disposed of according to practice protocol.
Microscopes in veterinary clinics generally use 10× ocular lenses with 4×, 10×, 40×, and 100× (oil immersion) objective lenses. Objective lenses are housed in a nosepiece that can be rotated to select each lens. Slides are placed on the stage below the objective lens and held in place with metal clips for security.
Examination of Samples
Blood, urine, and fecal material are some of the most common substances viewed under the microscope at a veterinary clinic.
Blood prepared as a smear is stained to view cells.
Stained blood smears must be completely dry before examination under oil immersion.
Fecal material is prepared as a coverslipped wet mount and examined for intestinal parasites using a direct smear or concentration (ie, flotation or sedimention) technique.
Urine sediment is prepared as a coverslipped wet mount and examined to identify cells, crystals, and blood. Staining is discouraged because many of the available stains readily grow bacteria and form crystals that can be misleading when evaluating the sediment.
Solid materials (eg, skin scrapings) are suspended in a small drop of mineral oil on a slide with a coverslip. Skin and ear cytology preparations to evaluate for bacteria, fungi, and cells should be reviewed using the 10× and 40× objectives.
Cleaning the Microscope
The ocular lens, objective lenses, stage, and stage clips should be cleaned after every slide, and the entire microscope should be thoroughly examined and cleaned at the end of the day.
Start by inspecting the cord for damage. To gain access to the objectives for cleaning, lower the stage or raise the arm, depending on the type of microscope being used. Moisten cotton tip applicators with the appropriate cleaning solution and gently clean each objective lens and wipe dry with new lens paper.
Use distilled water to remove water-soluble debris from the microscope lenses and body, and dry with lens paper. Use a solvent such as Windex for nonwater-soluble material. Wipe the eyepiece(s) with Kimwipes.
Look through the eyepiece(s) and rotate each one to ensure that no debris remains on the ocular lens. If it is necessary to remove the eyepiece to clean the inner glass surface, never “probe” into the tube housing; instead, place a lens cap or piece of aluminum foil over the opening while cleaning the eyepiece.
Wipe the entire microscope body, including the light source, with a warm, moist microfiber cloth. Center the 4× objective over the stage, turn the power off, ensure it is dry, and drape the dust cover over the microscope.
Microscopes should be serviced annually by a professional microscopy service, and lenses and bulbs should be replaced as needed.
All veterinary staff responsible for preparing and viewing microscopy samples should be familiar with the different components of the microscope and the viewing requirements for each biologic substance. A well-maintained microscope ensures that samples are free from contamination and results are accurate. Daily cleaning and maintenance also protect the practice’s investment in this valuable resource.