CDST_LT: Maintenance of the microscope

Regular cleaning of microscope is essential to ensure that it is optimally functioning. Cleaning is important to remove dirt, lens immersion oil and ensure disinfection. It involves cleaning the lenses, the body, the stage of the microscope and the light source. The microscope needs to be cleaned daily and the lenses need to be cleaned after each use.

Materials used for cleaning:

1. Lint free cloth
2. Lens paper
3. Lens cleaning solution
4. 70% ethanol
5. Detergent solution

Procedure for Cleaning Different Parts of the Microscope

1. The eyepiece shades, stage, focusing knob and nose piece are commonly touched during microscope operation, so these parts and the body of the microscope must be cleaned first to remove any stains with a neutral detergent /solution recommended by the manufacturer.
2. To clean the microscope eyepiece, objective lens, surfaces of the condenser and the light exit glass, moisten a lens paper with 1 to 2 drops of lens cleaning solution and clean the lens/ glass with a circular/spiral motion (as shown in the figure below).
   • Dry with a clean, dry piece of lens paper.
   • Use the Spiral Wiping Technique: Wipe from the center to the periphery in a circular motion.
   • The oil immersion lens should be cleaned after each use to ensure that immersion oil is not left on the surface.
3. The microscope surface and parts (except the lenses) need to be disinfected using 70% ethanol.

Figure: Cleaning of Lenses using the Spiral Wiping Technique. Source: How to Clean the Microscope

Important Considerations for Cleaning Microscopes

• Do not blow air to remove the dirt.
• Do not wipe the lens with an ordinary cloth. All the lenses should be cleaned with dry lens paper/lint-free cloth. 
• Never use spirit or alcohol or xylene to clean the lenses as these can damage them.
• Avoid using organic solvents that may damage plastic parts.
• Whenever possible, use the cleaning fluid recommended by the manufacturer.

Resources

• Laboratory Diagnosis of Tuberculosis by Sputum Smear Microscopy, GLI, 2013.
• Module for Laboratory Technicians, CTD, 2005.
• How to Clean and Sterilise Your Microscope, Olympus, Life Science Solutions, 2020.

Assessment

Proper handling, maintenance and storage of the microscope are essential for proper functioning and life of the microscope.

The microscope should be placed and stored preferably in a box in a dry, dust-free and vibration-free environment, which is specially built in the laboratory (as shown in the figure below).

Figure: Storage of microscope in a wooden box; Source: Laboratory diagnosis by sputum smear microscopy

Important considerations for the storage of microscope

• When the microscope is not being used/ stored overnight, it should be covered or kept in a storage cupboard/box to keep it free from dust.
• Avoid exposing the microscope to direct sunlight.
• Avoid exposing the microscope to moisture as humidity may allow fungus to grow on the lens and cause rusting of the metal parts.
  • The stored microscope must be kept warm with a light source to prevent growth of fungus. A bulb holder for a 15-watt bulb should be fixed on the rear wall of the storage cupboard, such that the microscope does not contact the bulb while storing or removing the microscope. The bulb should remain on when the microscope is stored inside the box
  • An alternative may be to place plenty of dry blue silica gel into a shallow plate and place it in the box when the microscope is kept in it. Silica gel is blue in colour when it is dry, but when it becomes wet /absorbs moisture it turns pinkish. As soon as the silica gel becomes pink, it should be changed or heated until it turns blue again and then be reused.

Resources

1. Laboratory Diagnosis by Sputum Smear Microscopy.
2. Module for Laboratory Technicians.

Assessment

Removable parts in a microscope that need replacement include objectives, eyepieces, light bulbs, fuses. In case of repair/ technical support, only competent agency that handles maintenance of instruments should be contacted. Laboratory personnel should never attempt to dismantle any part of the microscope for repair.

Some of the common technical problems encountered, their likely causes and solutions are given in the table below.

In case, the viewing field is still dim and cloudy, consider the following possible causes and contact the competent personnel for cleaning/ repair:

• Massive growth of fungus on the lenses or prisms due to storage in a high-humidity environment
• Penetration of immersion oil between the lenses of the objective
• A damaged objective (as a result of careless focusing, dropping, rough changing of slides).

Resources

1.    

Module for Laboratory Technicians

2.    

Laboratory diagnosis by sputum smear microscopy

Assessment

The binocular microscope requires considerable care in its use, regular cleaning, and protection from dust and fungal growth.

Annual maintenance of a microscope includes:

1. Checking for broken or damaged parts and ensuring that the lenses, mirrors and other light-conducting surfaces are clean.
2. Cleaning the lenses first for dirt with a blower brush, then wiping with lens solution on a lens paper/ 70% alcohol on the lens paper.
3. Removing eyepieces or objectives from their fixation holes for cleaning.
4. Properly cleaning the lower lens of the condenser after removal from its fixing.
5. Cleaning the slide holder after removing from the mechanical stage.
6. Cleaning for any deposition of immersion oil and fungal growth on the prisms in the binocular tube and eyepieces
7. Changing electrical services including bulbs and fuses.
8. Greasing/ lubrication of movable parts.

National Tuberculosis Elimination Programme (NTEP) has earmarked INR 2000 for Annual Maintenance [AMC] per binocular microscope including spare parts and repairs.

Resources

1. Module for Laboratory Technicians.
2. Laboratory diagnosis by sputum smear microscopy.
3. Norms and Basis of Costing.

Assessment