Diagnosis; Microscopic examination (part 1)

In a previous article ( Making a Diagnosis ), we established that to make a proper diagnosis, we need to initiate an investigation. One of the investigation options is microscopic examination. We will elaborate on this in this and a subsequent article.

The microscope
Buying a microscope is something you'll hopefully only do once in your life. When making a purchase, it's important to consider several things, and there are "minimum" requirements that a microscope must meet for our purposes.

Monocular or Binocular
First, you'll need to choose between a monocular or binocular light microscope. Simply put, do you choose one with one eyepiece or one with two? In other words, do you prefer to look through the microscope with one eye or both? Both have advantages and disadvantages:

Both microscopes are suitable for the koi hobby; the choice is yours. Don't confuse a binocular microscope with a stereo microscope; the latter isn't suitable for our hobby!

Enlargements
The lens in the eyepiece, the tube you look through, usually has a magnification of 10x. The objectives are usually 4x, 10x, and 40x. This means you can work with magnifications of 40x (10x4), 100x (10x10), and 400x (10x40). Ideally, you use 40x, 100x, and 200x in our hobby. This would mean you could buy an additional 20x objective. At 200x, with a good microscope, all identifiable parasites we might encounter are clearly visible.

Parafocal
Parafocal means that when you change objectives by turning the turret, you'll focus on virtually the same part of your object and only need to turn the focus knob minimally to get a good image. A good microscope has its objectives aligned.

Cross table
A cross-stage is essential for examining your specimen in a structured manner. The cross-stage allows you to precisely navigate your specimen under the lens using two adjustment screws (for left/right and up/down movement). You can imagine how microscopic objects quickly disappear from view when you have to move your slide by hand.

Finally
Some people start with a simple microscope, which can sometimes be bought for as little as eighty euros at Lidl. With practice, you should be able to see everything through it. However, a slightly more robust and therefore more expensive device is much easier to use and prevents you from missing tiny parasites. It's better to invest in a good microscope once.

Author: Joop van Tol (www.koitoday.nl)