Dental Loupes | Buyers Guide |
By William Johns-Powell, 5 April 2015.
This article is free from third-party sponsorship.
For those amongst you looking to purchase magnifying loupes you may have discovered there is often confusion and lack of clarity surrounding the subject. This is probably because there is a shortage of literature reviewing dental loupes. Many practitioners do not use loupes, which begs the question why?
I may be so bold as to suggest that every general dental practitioner should be using magnification. If this opinion is too outlandish, please forgive my impertinence. I do not wish to advocate rampant consumerism, this is only a buyers guide! In this article we will cover: different designs, technical specifications and the concerns regarding the Blue Light Hazard associated with LED loupe lights.
Types of Loupes
Flip Up Loupes
Also referred to as front lens mounted loupes; as the name suggests the magnification lenses are separate from the glasses. These can be flipped in and out of position manually.
You can flip them up!
You can change prescription lenses easily and cheaply. For those of you that are already short sighted (1 in 3 of us in the UK) your prescription may change. If however, you have good eyesight this is probably less of a concern but it is always worth visiting optician before buying a pair. My eyesight has altered quite a bit over the last few years and I have had to changed my eyeglass prescription in my loupes twice. (I own the MeridentOptergo flip up loupes - see below).
Some flip up models will allow you to adjust the interpupillary distance for different users, occasionally the working distance can be changed (more on this later).
They may have a narrower field of view, depending on the model. (More on this later).
Can be subject to minor alterations in their position and require manual adjustment. (Some models have more robust lens mounting arms so there are exceptions).
Take a a look at the MeridentOptergo loupes above you will notice they have a thin metal scaffold which keeps the lenses at a specific interpupillary distance (this is personalised when you purchase the loupes). Occasionally I adjust mine as sometimes I feel that they are not in their optimum position. Then again, maybe I am just being a perfectionist.
The Carl Zeiss loupes, worn by the lady above, are an example of a more rigid lens mounting but are heavier. Weight is an important consideration when wearing eyepieces throughout the day. One of my colleagues got the whole shebang, loupes plus the additional light and he gradually discovered they were rather heavy after prolonged use. You can imagine his dismay, he wasted more money than the average student does in the union bar. (For the record, I haven't tried the Carl Zeiss loupes but the weight of the MeridentOptergo loupes do not feel much different to wearing a normal pair of glasses).
Through The Lens (TTL) Loupes
They are at a personalised fixed interpupillary distance.
The lenses cannot misalign.
They generally have a larger field of view as the lenses are closer to your eyes. The field of view is demonstrated by the image below. It will usually be listed on on manufacturers' websites in millimetres, centimetres or inches.
Image (below) - The field of view is represented by the blue circles. The field of view is how much of an object you can see (look at the example with the ruler). Therefore as you go up in magnification the field of view decreases (e.g. instead of seeing most of the ruler you would see a small section of it). To compair the field of view of different loupes they need to be at the same magnification. TTL loupes are said to have a bigger field of view because the lenses are closer to your eyes. A good analogy is to think about looking through a key hole. If you are far away you won't see much throught it (low field of view) but if you put your eye close you can see more (bigger field of view).
They have to be returned to the manufacturer to update the eyeglass prescription; it can be expensive to do this.
Can be heavier than flip up loupes as they need a more rigid frame, although there are many exceptions to this rule.
Before I go on, I would like to stress that I find them very useful in most proceedures in dentistry. I have had mine a few years but I don't use them for denture work or extractions. There is little benefit to using them in these situations because the detail of the magnification is not required. (Often there is a lot of moving about with these procedures which affects your working distance - see below).
They are a great help at spotting, otherwise hidden, white restorations and are helpful in detecting defective restoration margins. Personally, I think the magnification is a good aid in the diagnosis of caries. Most of all, the added detail which the magnification provides allows you to create tooth preps which look like they belong in a hall of fame!
Working Distance and Posture
Working distance is the distance from from what you are looking at to your eye. It depends on many factors: chair height, posture, how you angle the patient, the proceedure and your preference of clinical position. Have a look at the image below.
Left image: This is how I see many practioners operating to get a good access and view. If you work in this position during your working career you are likely to suffer from back/neck problems. A systematic review by Hayes et al (2009) highlighted that back and neck pain are prevalent musculoskeletal problems in the dental profession.
Right image. Angle A - Head tilt angle (the angle between the horizontal and the 'true vision line' - as if you were looking straight ahead). Angle B - The angle of declination (the angle between the 'true vision line' and C (working distance).
Different manufacturers give different values for the angle of declination (this angle is in a direct relationship to the neck tilt angle). The larger the declination angle the less you'll be tilting your head. It is important to note that not all loupes will improve you posture. This aspect is design dependent, it is also reliant on how well they the product is tailored to you.
Firstly, you should take note that magnification is not measured in a standard way. One study examined six loupe manufacturers and found that none of them matched the magnification they advertised. The magnification specified by a manufacturer should be at a personalised working distance.
Typical magnifications are: 2.0x, 2.5x, 3.0x, 3.5x and 4.5x
An important consideration is the optical depth (depth of field); this is this is how much you can change your working distance for the magnified object to remain in focus with minimal distortion. If you move an object too close or too far away from the working distance of the loupes it will go out of focus. This measurement is usally specified by manufacturers.
So what magnification of loupes should you go for? This is really down to personal preference. From what I've read, the common census of opinion is that 2.5x is a good starting magnification; many web articles and journals specifiy that large magnifcations take a bit of practice to get used to but they do allow the user to see in more detail. All the loupes we've seen so far are galliean loupes (these have one convex and one concave lens). Prism loupes (shown in the right image below) are able to go up to much higher magnifcations. However, there are negatives associated with increased magnification.
Disadvantages of high magnifications:
Smaller field of view (More sensitive to minor movements of your head).
A reduction of image brightness (this effect can be lessened by increasing the size of the lenses).
A smaller optical depth.
I have spoken to quite a few people with loupe lighting and the only negative I have heard is to do with the weight. Most people who have it, swear by it. Indeed, lights are popular. As the light is attached to the loupes when you move the illumination moves with you so less fiddling around with the overhead dental light.
The resolution of the lenses is also a consideration. The resolution is how sharp the image is. It is all very well having a high magnification but if the lenses are of poor quality, with a low resolution, it will counteract the benefit of the magnification. My advice is to try different loupes and compare the quality of the lenses.
A literature review published in March 2014 by Stamatacos and Harrison highlighted concerns over the Blue Light Hazard (BLH) associated with this type of lighting. BLH is the potential of retinal damage to occur with high intensities of spectral blue light. Intense blue light at wavelengths 300 - 360 nm is the most damaging. Concerns are present in articles on the web , although not many studies in dentistry have been done. Some are calling for more research.
Why might this be a problem for loupe lights?
Many manufacturers try to create LED lights with a highly intense beam of white light. The trouble is that the spectral blue band is often bigger in comparison with daylight (there is more blue light). Brightness measurements are usually given as 'luminance' or 'radiance' because the definition of these words is dependent on the light reaching the eye from an illuminated source (indirect light).
What should I avoid?
Cool LED lights, some times advertised as 'extreme cool' lights are said to have a much higher blue light emission than that of warmer more yellow lights. Another consideration is if the wavelengths of the light is split up, like the effect observed from shining white light into a glass prism. Reflector optics, like car headlights, often do this. The consequence of splitting wavelengths is that you can get concentrated areas of blue light and the pupil does not react to blue light it only constricts to longer wavelength green light. That's why it is better to have beam uniformity - achromatic lenses produce this.
Should I get one?
You'll have to answer this for yourself. My opinion is that BHL risk in luminance is probably very low; however, more research needs to be done and there needs to be better manufacturer guidance. A brief look a the European directives which products have to pass to obtain a CE mark and I could not find anything in the Medical Devices Directive or the Personal Protective Equipment Directive about BHL. (More about the CE mark below). It would seem senisble for manufacturers to conform to a safe blue light emission band width and intensity.
1. I'll get a cheap pair off the internet because I'm a student.
Sure, by all means go ahead but I have seen some truly awful pairs of loupes and many of them probably do not meet European standards. If the loupes have a CE Mark on then it means the product is approved for sale in Europe and the product meets certain european directives. Why is this important? This means a certain quality is met and the product is safe to use. What you will get with a CE certified pair of loupes is a warranty and a standard of build quality.
"...Yes Prof. Progress, I understand that a part of my loupes is in a patient's lung but how was I to know that my 'Poundsaver Loupes' would fall to pieces?"
The most affordable, high quality loupes we advise is from UK loupes. The company was set up by UK dental students to help students afford a good quality pair of loupes at a reasonable price.
There are other reasonably priced loupes out there but make sure you buy them from a reputible company and that they are CE certified.
2. I'd like to practice without dental loupes so I can do clinical procedures without them; besides my eyesight is good enough.
Let me attempt an argument from common sense to prove that the statement above is illogical. We grant that the clinical procedures we carry out are similar with and without loupes. We grant this because the principles of dental procedures are dictated by clinical theory/guidelines, not the loupes. The only purpose of dental loupes is to improve vision through the use of magnification so more detail is seen. If more detail is seen then small defects can be identified (e.g defects in cavity or crown margins). If you are able to identify these small defects, which cannot be identified without the use of magnification, you will attempt to modify them in order to reach the 'gold' standard set by clinical theory/guidelines. This leads us to the statement that finer manual movements are conducted more often with the use of loupes. We know that if we practice muscle movements more often we get much better at doing them. Thus we reach the conclusion that using loupes must improve the execution of fine muscle movements, more so than by not using loupes. In other words you will learn to be more dextrous if you use loupes.
Now say you forgot your loupes one day, you will see in less detail, you won't pick up on the small defects we mentioned but you will still be able to carry out the clinical procedures because the clinical principles are the same.
 Farook SA, Stokes RJ, Davis AK, Sneddon K, Collyer J. Use of dental loupes among dental trainers and trainees in the UK. J Investig Clin Dent 2013;4:120–3.
 Hayes M, Cockrell D, Smith D. A systematic review of musculoskeletal disorders among dental professionals. Int J Dent Hyg 2009;7:159–65.
 Neuhaus K, Perrin P, Lussi A. Substantial difference between declared and real magnification in medical loupes. Med Instrum 2013;1:2.
 Christensen GJ. Magnification in dentistry: useful tool or another gimmick? J Am Dent Assoc 2003;134:1647–50.
 Stamatacos C, Harrison JL. The possible ocular hazards of LED dental illumination applications. J Tenn Dent Assoc 2013;93:25–9; quiz 30–1.
 Salsberg K. Blue Light Hazard in Dentistry. Oral Health Group. March 3 2014. http://www.oralhealthgroup.com/news/blue-light-hazard-in-dentistry/1002945334/?&er=NA
 Price R. Using LED Lights in Your Office: Are Your Eyes at Risk? Canadian Dental Association: Oasis Disscussions. April 8 2014. http://www.oasisdiscussions.ca/2014/04/08/tho/