Magnification Alternatives: Seeing is Believing, Part 1

In part one of this 2 part series, I will discuss basic factors for why magnification alternatives might be considered by all practitioners regardless of age or visual acuity, as well as looking at resolution of the native human eye, the Magnification Continuum, and an overview of magnification alternatives in private practice. Part 2 will look at the advantages of using telescopic loupes in dentistry, and conclude with the 4 advantages of using the operating microscope in dentistry.

INTRODUCTION
In the last 2 decades, technology has changed dentistry in nearly all areas, including armamentarium, materials, and techniques.^1-5 Patients are living longer and want to maintain their dentition throughout life. In addition, patients are now more knowledgeable about options for improving their smile cosmetically and replacing missing teeth through dental implants. Technology has given clinicians marvelous new options to create healthy and attractive smiles as long as microscopic attention to detail in both the use of materials and the techniques necessary to provide excellence are observed. Clinicians must now focus on how to provide dentistry that is not only functional but aesthetically exceptional, keeping with the principles of minimal or, in some cases, no intervention at all.^6-8 The rise in technological advances in dentistry, combined within increased expectations and demands from patients for long-lasting “invisible white restorations,” can create challenges for even the most detail-oriented dentists.^9-11
The increasing demand by today’s dental patients for these aesthetic, conservative, and durable restorations requires that the clinician be able to visualize the operating field in much greater detail. The field of medicine has long advocated the use of magnification for aiding in delicate procedures. Medical disciplines such as otolaryngology, neurology, and more recently, acute care, have embraced magnification for surgery as well as delicate procedures such as reanastomoses of severed appendages. Our medical colleagues have relied upon enhanced visual acuity to improve treatment outcomes for many years.^12-18
The use of magnification by general dentists in dentistry has been slow in its growth. The concept that magnification was mainly needed by “mature” practitioners whose eyesight was failing, was generated for many of us in dental school.19 During our education, some of the instructors wore magnification of some sort and, many times in the 1980s, it was simple single lens clip-on magnifiers. After the age of 45 years, presbyopia (the inability to focus sharply on close objects) occurs naturally. In order to see objects that are closer than 6 m clearly, the ciliary muscles of the eye must contract or relax to change the ocular lens thickness.²⁰ With time, through deterioration of the muscles of the eye and a loss of elasticity of the lens of the eye, it becomes more difficult for many dentists older than age 45 years to focus on close objects. Despite this fact, it is interesting to note that many dental faculties and dental hygiene schools are currently requiring their youthful students to purchase magnification as part of their armamentarium, since it is now understood that magnification can help improve ergonomics and treatment outcomes.^21-22 Further, it has been understood that magnification can be a useful tool during the teaching process itself,²³ and, although there are some issues in getting all faculty members to embrace the value of magnification,²⁴ a growing number of dental schools and dental hygiene programs are embracing magnification as being an important in the education process in dentistry.^25-26
The use of surgical telescopes (loupes), from a rarity to the norm in general practice, increased dramatically from 1980 to 2001. In the author’s home province of British Columbia, the percentage of clinicians using any form of magnification rose from 20% in 1986 to 75% in 2000.^27-28 During the past decade, the growth of high levels of magnification (dental operating microscopes) has continued to climb in endodontics. In 1999, one survey found 52% of endodontists had access to and used an operating microscope, and most of the time it was used for difficult treatments where high levels of magnification were required, such as separated instruments, root-end preparations, and root-end fillings.²⁹ In 2008, a similar survey found that 90% of endodontists in the United States had access to and used the operating microscope in their practice, in a similar fashion to the study from 1999, but with a greater number using it for locating canal orifices.³⁰ So, it appears that there is a growing interest in all levels of magnification. This article will discuss reasons for incorporating magnification into your practice, and the alternatives, benefits, and challenges that exist in this journey.

Resolution of the Human Eye and Visual Information
Carr,³¹ in his landmark article, cited research from the medical literature which showed that the human eye, when unaided by magnification, has the ability to resolve or distinguish 2 distinct lines/objects that are separated by a minimum distance of 200 µm (0.2 mm). When these lines or objects are closer together than 200 µm (0.2 mm), the human eye will see them as a single entity.

Figure 1. The 2.5x flip-up loupes.	Figure 2. The 4.5x through-the-lens (TTL) loupes with headlight.

When we add magnification to the equation, the clinician is able to see in much greater detail than what is possible with the eye alone. For example, 2.5x magnifiers (such as entry level telescopic loupes, as shown in Figure 1) improve the resolution of the human eye from 200 µm to 80 µm, and medium range magnification of 4.5x (Figure 2) telescopic loupes improve the resolution of the human eye to 44 µm, or 0.044 mm (Table 1).
Baldessara et al³² concluded that a skilled, trained clinician with a sharp, new explorer could determine marginal gaps in the range of 35 µm to 50 µm. It is therefore possible to conclude, that at levels above 4x to 6x magnification, the dependence on tactile cues (using explorers) might be replaced with a greater reliance on visual cues. It is interesting to note that a dental operating microscope at 20x power will provide a resolution of 10 µm (a human hair is approximately 50 µm in width).
Some clinicians are surprised as to how much more they “see” when they increase the amount of magnification they are using. The amount of visual information that is provided to the clinician is in fact the area of the surgical site (x axis times y axis) and is indicative of the power of increasingly higher levels of magnification. Table 2 and Figure 3 show the impact that higher levels of magnifiers have on the amount of visual information that is provided.
On closer inspection, one can see that increasing magnification from 2x loupes to 4x loupes will not just provide double what you can see, but in fact provides a 4-fold increase in the amount of visual information available. Correspondingly, when an operating microscope is used at 12x magnification, then the amount of visual information provided is 24x what is seen with 2x loupes. As the clinician begins to understand how seeing better may mean better treatment outcomes, routine use of magnification in daily practice becomes a necessity, not a luxury.

Magnification Alternatives
There are 3 basic magnification systems available in dentistry for surgical telescopes; these include single lens, Galilean loupes, and prismatic (Keplerian) loupes.²⁰
Single lens loupes (Amsted) are the simplest form of magnification and are low-powered, clip-on magnifying lenses that attach to glasses or a headband. They are inexpensive solutions, but have limited magnification (up to about 3x), and limited depth and diameter of field of vision.
Galilean loupes are used for 2x to 2.5x magnification in that they use 2 or more lenses to focus the image. The systems are more expensive than single lens loupes and although the level of magnification is limited, the depth and diameter of the field of view as well as the resolution of the image are improved (Figure 1). Often this level of magnification is desirable for someone just beginning a journey into magnification, as it is easier to learn to use, lighter in weight, and does not require additional illumination in most instances.
Finally, prismatic (Keplerian) loupes have multiple lenses (around 5 as well as 2 prisms) to focus the image and give greater clarity. The price is more expensive to make these, and the lenses are larger and heavier, resulting in a smaller depth of field as the magnification increases (Figure 2).
When choosing loupes, a clinician should look at the magnification of the system and choose one that initially will provide the greatest chance of adaptation (ie, 2x to 3x loupes is the most often suggested initial magnification). In addition, one should also consider the field width, depth of field, as well as whether he or she would like to flip up the loupes for an unmagnified assessment of the field of view. These “flip-up” loupes typically are bulkier and heavier than their through-the-lens (TTL) counterparts and can easily go out of adjustment; this can affect the view that you have (double image), and also your posture. The ability of TTL loupes to be mounted directly into a prescription lens does necessitate repair anytime that the prescription changes. Furthermore, TTL loupes can only be mounted at an angle up to about 45° (called the declination angle) from horizontal. The heavier the Keplerian loupes are, the greater is the tendency for the loupes to want to ride down the nose; and the greater is the need for a strap that fits tight around the back of the head to hold the loupes tight.

Figure 3. The relationship between magnification and the amount of visual information seen by the retina.

Figure 4. The Magnification Continuum, as proposed in 2001 by the author.

Figure 5. The 2013 version of the Magnification Continuum.

The ideal working distance is an important consideration when purchasing a new set of loupes, and can be adjusted with most systems. The working distance variation can be set for operators who like to lean closer to the operating field (near focal distance), all the way up to those who like to sit upright and at a further distance away from the surgical site. Under ideal circumstances, the latter situation (sitting in a more upright fashion) is better from an ergonomic standpoint as the operator will have less fatigue in both the lower (back) and upper spine (neck and shoulders). It is nearly impossible for any set of loupes to achieve a straight forward vision (as can be obtained with the operating microscope), and, if neck and back pain are severe for a dentist or a hygienist, an operating microscope may lessen the severity of the pain if the microscope is properly adjusted.

Magnification Continuum
In 2001, I described the term Magnification Continuum to try to define the growing number of magnification users who were progressing through increasing powers of magnification.³³ Through personal experience derived from my lectures and discussions with other dentists, I had discovered that a growing number of clinicians were using magnification routinely in their dental practice. Some of these clinicians were just beginning their journey into enhanced visual acuity, while others had been using loupes for many years. In fact, it was not uncommon to hear of dentists who had several different sets of magnifiers ranging from low-level 2.0x to 2.5x loupes through to 6x loupes with a headlamp. In many instances, with experienced clinicians, there seems to be waves of progression forward to higher and higher levels of magnification throughout time. It seemed that, as the appreciation for the value of magnification matched the level of expertise with the increased level of magnification being used, clinicians would often look to add a new magnification to their armamentariums. In addition, some clinicians were opting to use dental operating microscopes that had multiple levels of magnification (2x to 20x power). These clinicians were often focusing on disciplines such as endodontics or cosmetics, where magnification and illumination could help with details such as discovery of pulpal anatomy, or with nuances in preparation design and marginalization; details that could enhance the final treatment aesthetically, as in the case of cosmetic dentistry (Figure 4).

Twelve years after this initial idea surfaced, the author has revised his original concept to include 2 to 3 phases of magnification progression (Figure 5). The entry-level power of 2.0x to 2.5x magnification is what many dental hygienists and dental students are still being exposed to during their education. This lower-level-magnification introduction is also the suggested starting point for many more-experienced clinicians looking for a solution for presbyopia, to improve clinical results, and/or to aid with neck and back pain. During this initial phase, the clinician will encounter a learning curve (A, Figure 5) that often takes from a week to a month. During this period, the clinician will at times fluctuate among using the loupes for endodontics, cosmetics, root tip extractions, crown preparations, or other procedures, but may also provide treatment without them. After one or 2 more periods of sustained use with shorter learning curves (B, Figure 5) ,the clinician will use them full-time for most procedures and, at times, question how he or she ever did dentistry without magnification!
It is with regular use and time that the clinician may eventually seek out higher powers of magnification (C, Figure 5) and at this point enter into one’s second and eventually even third set of loupes. Initially some practitioners may envision using only the new medium powered loupes (eg, 3.5x magnification) for endodontics or during difficult to visualize procedures (D, Figure 5), and they may then fluctuate between the low and medium powers as the procedure dictates. With time, dentists may then reach a period where they are seldom using the lower power and using only the more recent purchase (E, Figure 5). At times, clinicians will choose another higher magnification again and, in addition, incorporate a headlamp (often needed above 3.5x mag); now they will have 2 to 3 different sets of loupes with a headlamp (F, Figure 5).
If the clinician enjoys endodontics and wants multiple powers of magnification (without changing loupes) and coaxial shadow-free illumination while, at the same time, easing documentation of procedures, a dental operating microscope (Global Surgical, Carl Zeiss Meditec, Leica Microsystems, or Seiler Precision Microscopes, for example), or heads up display system (MagnaVu [Magnified Video Dentistry]) offer the ultimate in higher levels of magnification.
These systems involve a new learning curve, requiring that the clinician learn how to reposition the patient or the patient’s head. In addition, these systems require a greater dependence on indirect vision (intraoral mirrors) in both arches in order to optimize the view. This contrasts with positioning in loupes-based dentistry, where the operator frequently must reposition while the patient remains stationary (G, Figure 5). This learning period can be anywhere from a month to a year, depending on the dentist. However, the operator will eventually learn how to use all magnifications of the system from low to high power. After several phases of using the lower powers of the microscope only (H, Figure 5), the clinician will learn how to operate throughout the ranges of magnification. In time, he or she will be able to work comfortably at most of the magnifications available, as dictated by the procedure, patient, and the challenges thus created for the clinician (I, Figure 5).

Figure 6. Loupes vision versus microscope vision. Slide courtesy of Dr. David Clark, Tacoma, Wash.	Figure 7. The author progressed from 2.5x flip-up loupes (SurgiTel) to 3.5x flip-up loupes (Keeler Instruments) and, eventually, to the 4.5x extended field of view TTL loupes (Designs for Vision).

There is always a price to be paid for the increased amount of visual information that is provided by higher levels of magnification. Although the amount of visual information continues to increase, the value of the clinical information provided is maximized at around 20x magnification. The depth of field, clinically, and the difficulty of the finite motor movements necessary to work at 20x make this power the approximate upper level of clinically valuable magnification. Stabilization of the gross motor joints (elbows and shoulders), through the use of a microsurgeon’s chair, allow for improved control of the micromotor muscles and joints (fingers and wrists). Tibetts and Shanelec34 showed, in working with high levels of magnification (20x power), that clinicians were able to learn how to shrink their movements from one to 2 mm (1,000 to 2,000 µm) increments to 10 to 20 µm (10 to 20/1,000th of a mm) movements at a time. Therefore, it is useful to appreciate that the limitation to precision of treatment is not in the hands…it is in the eyes.³⁴
It is interesting to note that even though the magnification continuum for many clinicians may consist of 3 phases, some clinicians may never see the need to proceed past an entry-level set of loupes. However, others will jump from low power to a microscope, without using a medium level of magnification. On rare instances, a practitioner will actually not be able to become proficient with low-power loupes, instead immediately jumping into a microscope. This can be because of the ergonomic value of the scope to sit upright, relieving back and neck pain; or due to the stereoscope vision that provides easier eye accommodation (for some clinicians) than that found with the convergent vision of loupes (Figure 6). The Magnification Continuum is simply a concept to describe the process that many clinicians progress through when they begin to grasp the value of the magnification for improving their work and if properly aligned for their ergonomic posture.

Figure 8a. Microscope (Global Surgical) capable of providing 6 different magnifications (2.1x, 3.2x, 5x, 8x, 13x, and 19.2x). A simple one-chip medical-grade cube camera (black square on right) provides video so that patients can see in real time during exams and procedures.	Figure 8b. The G6 Operating Microscope (Global Surgical), with HD digital video camera on left and a digital single lens reflex camera on right side of microscope.
Figure 9a. Microscope-centered operatory.	Figure 9b. G6 Dental Operating Microscope and “microsurgeon’s” chair being used for restorative dentistry in the operatory.

Figure 10. The Magnification Continuum, showing the operator moving from the naked eye on the left to the operating microscope on the right. In this case, note the improved posture allowed with increasing levels of magnification; the longer working distance provides a more neutral and balanced posture.

The author has progressed through entry-level loupes, 3.5x and 4.5x loupes (Figure 7), and, for the last 16 years, has completed almost 100% of any clinical work through the operating microscope (G6 Microscope [Global Surgical]) (Figures 8a to 9b). In the author’s current office, all 9 operatories have a microscope available for all procedures. Furthermore, all the operatories have been designed to function ideally with the microscope as the centerpiece visually, ergonomically, and functionally. The increasing ability to see with higher levels of magnification (Figure 10) has correlated with an ability to sit upright as the operator had the loupes adjusted properly (focal distance). In addition, as the clinician switched from flip-up loupes to TTL loupes (TTL loupes have a higher declination angle), to an operating microscope, true neutral and balanced posture was achieved.

IN SUMMARY
Magnification should be considered a must for all dental practitioners, regardless of age or visual acuity. The native resolution of the human eye limits our ability to visualize the details that are so crucial to delivering clinical excellence. Many dentists have moved beyond entry-level loupes to higher levels of magnification, and we are now seeing operating microscopes becoming more popular.
In the second part of this article series, we will explore the advantages of using telescopic loupes. It will conclude with the 4 advantages of using operating microscopes in the daily practice routine.

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Dr. van As graduated from the faculty of dentistry at the University of British Columbia, Vancouver, Canada, and was an assistant clinical professor there from 1989 to 1999. His memberships include, but are not limited to, the British Columbia Dental Association, the Canadian Dental Association, the Academy of Microscope Enhanced Dentistry, the Academy of Laser Dentistry, and the American Academy of Cosmetic Dentistry. Dr. van As has built a high-tech, high-touch, full-time dental practice where the entire dental team is committed to using the latest technologies available to provide the highest level of clinical excellence in dentistry. He has lectured internationally and provided hands-on workshops, as well as publishing internationally, on multiple topics involving dental lasers and microscopes. He is an active member on many Web forums dealing with lasers and microscopes in general practice, acts as a consultant for many high technology companies, and is a reviewer of articles for dental magazines. Dr. van As was distinguished with the Leon Goldman award in 2006 for worldwide clinical excellence in laser dentistry and has been one of Dentistry Today’s Leaders in Continuing Education since 2012. He can be reached at glennvanas@mac.com or at drvanas.com.

Disclosure: Dr. van As has received honoraria from Global Operating Microscopes and equipment from Surgitel Loupes.