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Binocular Loupes in Dentistry

 

It becomes increasingly clear that binocular loupes have become a standard of care in dentistry. Today, most dental schools either require that students purchase a pair of loupes or strongly recommend that they do so. Even many hygienist programs suggest that their students purchase loupes.

What has driven this change? To a large degree, it has been the realization that dentists can practice longer and more comfortably if they employ proper ergonomics habits. Studies have concluded that roughly 60% of Canadian dentists, Dutch dentists, Australian dentists, and Thai dentists have reportedly suffered from back or neck pain at some point in their lives.1,2,3 Similar studies also found that nearly 70% of dental hygienists in the state of Minnesota alone have reportedly suffered from similar ailments during their lives.4Since loupes allow the user to observe greater detail while maintaining a set (longer) working distance, the practitioner is forced into better posture, therefore reducing or eliminating neck and back strain. An additional benefit is reduced eye strain when high-quality loupes are used. There are very few dental professionals that cannot benefit from using loupes, both for their personal well being as well as for improved patient outcomes.

So what considerations should one bear in mind when making the decision to purchase a new pair of loupes? The first consideration should always be optical performance. It is also important for the potential buyer to understand how optical performance is determined, and to have an understanding of other factors affecting the selection of loupes:

Field of View – Is it large enough to see the area you are working in (ie, within the oral cavity) while still observing instruments entering your field of view?

Do the optics allow optimal light transmission? Many loupes lose a percentage of light for each optical surface. For example, the four optical surfaces in a Galilean loupe mean a 75% to 80% reduction in light transmission for most loupes. Higher-quality loupes lose approximately 0.3% of light per surface and thus allow 98% light transmission.

Are the optics made of ground glass or molded glass? Ground glass is more precise and free of air bubbles, thus providing a crisper image with no distortion. Molded glass may have a somewhat waved surface, as the molten glass often cools unevenly in the mold. Acrylics are by nature molded and have the same shortcomings of molded glass.

Are the optics achromatically corrected? Few manufacturers use doublet lenses to eliminate chromatic aberration or the “rainbow” effect seen in many loupes, but those that do provide clarity from edge to edge.

Working distance / Depth of focus. It is very important to find a loupe that fits the ergonomically correct distance for you to work. Ultimately, you want to keep your neck and back as straight as possible. Some loupes enable this by offering a greater depth of focus or focal range. A greater focal range also allows you to see the entire oral cavity in focus.

Angle of Declination – The key to eliminating neck and back strain is the ability to keep one’s neck and back straighter in order to maintain proper, upright posture. The most comfortable angles of declination vary based on the anatomy of each user, but typically lie between 35 and 45 degrees. Generally, the only style of loupe that can achieve these angles are the flip up variety , though many of these do not allow for an angle of declination beyond 35 degrees. This may be one of the most important determining factors in finding a loupe to fit you correctly.

Comfort and Protection – It is important to have a frame that wraps the eyes for adequate splatter protection and is adjustable to fit you head and bridge well.

 

Selecting Flip-Up or Through-the-Lens Loupes 

You will also be faced with a decision between loupes with fixed optics known as Through-the-Lens (TTL) loupes or loupes that allow you to flip the optics up and out of the way (flip-up). There are distinct merits to each.

(Continued from page 1 )

 

Through-the-Lens, or TTL loupes, are custom made for the user and the oculars are fitted right into the lens of the spectacle frame. The optics must be placed directly in front of each eye for the operator to have clear binocular images, which means that the manufacturer must take a series of measurements to custom fit the optics. At the same time, any eyeglass prescription that the user may have must be custom ground into the optics. This generally means that the user gets a good quality view, but the loupes may only be used by the person for whom they were measured. It also means that if the practitioner’s prescription changes, the loupes be returned to the manufacturer to be re-ground. This can be a time consuming and costly process. The primary advantage of TTL loupes is that the optics can be mounted closer to the eyes, which for a given optic will provide a larger field of view than if the optics were further away. Through-the-lens loupes are generally more expensive due to their custom nature, and must be removed in order to see well without magnification.

Flip-up optics enable the wearer to flip the optics up for viewing without magnification, as well as self customization. They also allow the user to modify the angle of declination depending on the procedure being performed. It is important for any dental professional to beware of flip-up optics that adjust the pupil setting with a single lever or control knob. Most people are asymmetrical, ie, one eye is often further from the bridge of the nose than the other. Look for a loupe that offers independent adjustment of each ocular. In most flip-up optics, the spectacle frame can have a custom prescription built into it, allowing users with a prescription to see well both with the loupe in the down or viewing position as well as when they are flipped up. This can be an advantage in a busy practice. Some manufacturers even make a prescription insert that can be clipped in and out so the loupes can be used with contacts or shared with other user. This clip-in also makes updating a prescription much easier and less expensive than with a TTL loupe.

Flip-up optics had fallen out of favor to some degree due to weight and field of view concerns. With the advances in light-weight frame and ocular barrel technology, weight has become a nonissue. Field of view is also far less of an issue, as a select few flip-up loupes now offer fields of view that rival or even exceed their TTL counterparts.

 

Conclusion 

First-time users should consider magnifications of 2.5X or less. While loupes are an important part of any modern practice, they take some time to master. Higher magnifications can make this learning curve too steep for the typical practitioner as well as offering too limited a field of view. Expect that it will take you a few weeks to adjust to your first pair of loupes. It is best to begin by using them for five to ten minutes each hour initially, and build the amount of time up from there. For those who have worn bifocals or progressive glasses, you can expect the same kind of adjustment from loupes.

 

References: 

  1. Bassett S. Back problems among dentists. J Can Dent Assoc. 1983 Apr;49(4):251-256. No abstract available.
  2. Marshall ED, Duncombe LM, Robinson RQ, Kilbreath SL. Musculoskeletal symptoms in New South Wales dentists. Aust Dent J. 1997 Aug;42(4):240-246.
  3. Chowanadisai S, Kukiattrakoon B, Yapong B, Kedjarune U, Leggat PA. Occupational health problems of dentists in southern Thailand. Int Dent J. 2000 Feb;50(1):36-40.
  4. Osborn JB, Newell KJ, Rudney JD, Stoltenberg JL. Musculoskeletal pain among Minnesota dental hygienists. J Dent Hyg. 1990 Mar;64(3):132-138.
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