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Magnification and illumination.

I can remember seeing my first pair of loupes back in the mid-eighties. I had just returned to private practice after having spent a number of years living and working in Germany. I knew that my dentist employer was sort of a dental "nerd" when it came to trying new techniques and technologies. I figured that these new hornrimmed glasses with the telescopic eyepieces were just another passing gadget that would soon find their way to the lab bench along with the other "convention special" purchases. I didn't have the slightest interest in even trying out his new magnifiers. Besides, they were hardly the fashion statement I was interested in making.

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Fast forward to 2010, and I cannot imagine working without my loupes and headlight. After getting my first pair of loupes about 10 years ago, I have never looked back to my pre-magnification days. Adding a headlight several years ago has solved a career-long battle with shadows and constant overhead light adjustments. I rely on my loupes and light for even my youngest patients. Not only do I have increased clarity in my vision (think of the difference between looking at a small object with a high-quality magnifying glass), but I also have improved my ergonomics. The musculoskeletal benefits of working with loupes have been addressed frequently, but have you ever kept track of the number of times you reach up to adjust your light while treating a patient or over the course of a day?

Focusing your light directly on the working area without the need for any overhead adjustments will save you time and reduce eyestrain and musculoskeletal stress. Once you make the decision to convert, you won't know how you practiced without these indispensable pieces of equipment. Today's clinician has many options when looking at magnification and illumination systems. To evaluate which product best suits your individual needs, it is helpful to be familiar with a few basic design features. Let's start with magnification.

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When you think of magnification, the first thing that usually comes to mind is the power, or the size, of the image viewed through the lens. Rather than looking at the image size, the first characteristic to evaluate should be the resolution, or clarity, of the image. Resolution is determined by the quality of the optical design and the precision lenses used in the product. Just imagine comparing the resolution from a child's set of plastic binoculars to a top-of-the-line pair from a specialty shop. The difference is in the lens.

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The next feature to consider is the width of field, or the size of the viewing area. Dental hygienists are accustomed to looking at the whole mouth or arch, so the field width should accommodate this need. Restorative dentists, on the other hand, often focus on a single tooth in their work and may choose a narrower field width with a higher power of magnification. The key point to remember is that as the magnification power increases, the field width decreases. Loupes offering magnifications between 2.0 to 2.9 power have a field width between four and five inches, making them ideal for dental hygienists. The resolution and field width should work together to provide optimal viewing clarity.

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A third feature to consider is the depth of field, or the range of focus, which determines how much movement you can have while still maintaining focus with your loupes. While depth of field is influenced by outside factors such as the finishing on the lenses, lighting and the eyes' ability to focus, the typical depth of field is four to five inches.

Once you have made the decision to purchase loupes, you will have to decide whether you want your lenses to be "flip-up"--mounted outside of the eyeglass frame--or "through-the-lens"--mounted into the eyeglass lens. Before deciding on which version to purchase, it is important to understand a few basic optical rules. (1) When telescopic lenses are manufactured, they are polished to a specific optical center, matching the clinician's unique interpupillary distance, The interpupillary distance is, as the term implies, the distance between the pupils. When the eyes converge from working at a distance to focus on close work, a new functional interpupillary distance is established. Through-the-lens designs set the telescope lenses to the functional interpupillary distance, thus guaranteeing correct optical positioning and reducing eyestrain. In contrast, flip-up lenses are not surfaced to match the individual's functional interpupillary distance and require manual adjustments for proper function. Clinicians may be attracted to the flip-up option due to the versatility offered by not needing to remove the loupes for activities not requiring magnification. Provided that the carrier lenses are non-prescription, flip-up loupes can also be shared amongst multiple clinicians, making them a cost-effective investment in some clinical settings. (2) A third option is a "through-the-flip" loupe with the telescope lenses mounted into the carrier lens connected by a hinged attachment to the eyeglass frames. The whole unit can be flipped up, enabling the clinician to perform tasks and communicate with patients without removing the frames.

Clinicians using prescription glasses may have the lenses for the loupes made according to their own eye prescription. It is recommended that clinicians have a current eye examination and prescription prior to having the custom loupes manufactured. Some loupe manufacturers also feature custom inserts or lenses fabricated with filters and opaque side shields designed for laser use, thus eliminating the need for additional eye protection.

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The working distance is calculated by measuring the distance from the eye to the working area. Working distances will vary according to the individual and should be measured with the clinician seated in an ergonomically correct position. Some manufacturers use pre-set ranges for working distance while others offer a custom option. (1) The correct working distance ensures improved ergonomics and reduced musculoskeletal strain due to improper posture. The declination angle is formed by the line of sight in neutral eye position and the actual line of sight made by the declined eye as the operator focuses on the work area. Declination angle plays a critical role in managing head and neck fatigue, Properly set, the declination angle ranges between 20 and 25 degrees and will allow the operator's head and neck to stay in a neutral position. (3)

Additional features to consider include the overall weight of the loupe and the style and fit of the frame. Flip-up loupes are typically heavier than through-the-lens models due to the additional hardware needed to mount the telescopes. Each manufacturer should provide the weight of the loupes in the product specifications. Frame style, aside from being a dental hygiene fashion statement, plays an important role in overall fit, durability and comfort.

Fortunately, dental hygienists have many options when considering loupes. Purchasing decisions should be based on the best product to meet your specific needs and budget. Many manufacturers offer payment and extended service plans, discounts and trial options to consider before making your decision.

Once you have your loupes, it is time to look at the world of illumination. Lighting options available today continue to evolve and improve with new technologies.

As recently as 2007, the brightest light available was a fiber-optic version requiring the clinician to be connected via a fiber-optic cable to a light box positioned on the counter While the light was powerful, the cable proved restrictive and the replacement bulbs were costly. Light-emitting diode (LED) technology has made significant advancements in the health care field. The LED is actually a solid state device, not a bulb, and has a life expectancy of about 50,000 hours. Just divide a 40-hour work week into 50,000 hours and you will see how many years the LED will last (about 15 years)

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Before shopping for a headlight, consider the basic specifications to look for in the product. Footprint, brightness and weight vary depending on the light. The diameter and shape of the light is the footprint cast by the light. The intensity of the light, or brightness, is measured in foot candles. Some models feature varying degrees of brightness. The weight of the light varies and should be added to the overall loupe system to determine the impact on operator comfort. Light color is a product feature, with white light the desirable color. Some lights come with removable filters to prevent the premature curing of composite and sealant materials. The new generation of LED lights are fully portable, battery-powered devices. Weight, size, run and charging time of the battery must be taken into consideration when selecting an LED light. Battery current output refers to the percentage of light output over the duration of the battery charge time. Some lights rapidly diminish in intensity as the battery charge depletes, while other lights remain constant and give a warning signal as the charge is depleted. Some units provide multiple batteries for a continuous back-up power supply. Questions regarding battery specifications should be incorporated into the overall decision-making process regarding any headlight purchase.

Magnification and illumination have the potential of becoming standard of care for the delivery of dental hygiene services. Many dental hygiene programs now require that students purchase and use magnification from their very first day in pre-clinic. (4) Clinicians working with magnification and illumination report improved visual acuity for a full range of intraoral procedures in addition to extra-oral activities including radiographic interpretation and instrument sharpening. (5) Reduction in musculoskeletal injuries contributes to a long and healthy career as a dental hygienist. The answer to the question of whether or not to invest in your own health and the health of the patients you care for should be clear!

References

(1.) Murphy PJ. There is more to optical magnification than meets the eye. Library of Congress Catalog Number TX4-931-034. 1999.

(2.) Daniels AH. Visual acuity-surgical loupes: which one to choose. J Practical Hyg 2005; April: 27-8.

(3.) Nield-Gehrig JS, Goucher J. Fundamentals of periodontal instrumentation, 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2004: 11-15

(4.) Maillet JP, Millar AM, Burke JM, et al. Effect of magnification loupes on dental hygiene student posture. J Dent Educ 2008; 72(1): 33-44.

(5.) Syme SE, Fried JL, Strasser HE. Enhanced visualization using magnification systems. J Dent Hyg 1997; 71(5): 202-6.

Cathy Draper, RDH, MS, graduated in 1975 from Foothill College and completed her MS in dental hygiene at the University of Michigan in 1978. She has practiced dental hygiene in Germany as well as in California. She currently splits her time between private practice, teaching at Foothill College and volunteering as a library reference associate at Stanford Hospital.

By Cathy Draper, RDH, MS
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Title Annotation:technology update
Author:Draper, Cathy
Publication:Access
Geographic Code:1USA
Date:May 1, 2010
Words:1781
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