Lighted magnifying lamps offer you the ability to view small details effortlessly, and as a result, they are extremely helpful in preventing eye strain and reducing vision fatigue.

However, there are a few factors to consider when choosing the correct magnification to suit your requirements:

 

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Factor 1:

Choosing the right Dioptre (magnification)

You will often see the term ‘dioptre’ used when searching for a magnifier. This quite simply refers to the amount of curvature in the lens. The higher the dioptre value, the greater the curvature of the lens and thus the more powerful the magnification.

You should also note that the greater the curvature on the lens there can be increasing optical distortion at the edges the image. 

Dioptre  value	Magnification  (equivalent)	Objective  size increase
2	1.5x	150%
3	1.75x	175%
4	2x	200%
5	2.25x	225%
6	2.5x	250%
7	2.75x	275%
8	3x	300%
9	3.25x	325%
10	3.50x	350%
11	3.75x	375%
12	4x	400%

 
 

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Factor 2:

Consider the Focal Length (gap between object and magnifier)

This is how close you need to position the magnifier to your object to achieve the focus. The higher the diopter, the shorter the focal length. 

If you need to use instruments under the magnifier, then you need space to work. You would subsequently choose a lower magnification to increase your focal length and to give you additional space to work.


 

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Factor 3:

Understand your Field-of-View (size of area in focus)

The higher magnification (dioptre) the smaller the field of view. This may mean that to complete your task, you might have to reposition your lamp or object multiple times.

 

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Considering these factors, the table below may help to guide you in choosing the most appropriate product for your application. 
 

The exact working distances may depend on lens design and model. 

 

Clinical Task	Recommended Dioptre	Approx. Magnification	Working Distance (Focal Length)	Reason
General skin examination / wound assessment	2–3 dioptres	1.5x–1.75x	13–20 inches (33–50 cm)	Wide field of view and longer working distance for overview tasks
Suturing / minor procedures	4–5 dioptres	2x–2.25x	8–10 inches (20–25 cm)	Good balance of magnification and working room for instruments
Removal of splinters / foreign bodies	5–6 dioptres	2.25x–2.5x	6–8 inches (15–20 cm)	Clear detail with moderate working space
Dermatoscopic / skin lesion assessment	8–12 dioptres	3x–4x	4–6 inches (10–15 cm)	High magnification for fine detail inspection

References:
Daray Medical https://daray.com/pages/dioptre-explained