What to look for in surgical telescopes
Dr. Craig C. Callen has been using magnification in his practice for more than 25 years. He outlines the 12 most important benefits of surgical telescopes.
Craig C. Callen, DDS
I have been using magnification in my practice for more than 25 years. I would not think of looking in a patient's mouth without my surgical telescopes. I just cannot see adequately without them!
Lately, I have been reading a number of articles about choosing the right surgical telescopes. My purpose here is to introduce you to enough information (and provide references for more) so that you can make an informed buying decision about the type of telescopes you will choose ... and not be swayed by hype and misinformation.
I have always had bad posture. I can remember my Mom telling me over and over to stand straight and get those shoulders back. I was shy and tall (always in the back of the line according to height), and I suppose that is why I became round-shouldered. I have made the mistake over the years of compromising my optimum working position to the needs of the magnification equipment. I have been in some really crazy positions for prepping teeth. As a result, I am victim - as are many dentists - to back problems. Insurance companies tell us that back-related problems account for many disability claims.
I have always found the focal length of my telescopes to be the most critical measurement. Not so, according to an article published in the July 1999 issue of the Journal of the American Dental Association (Vol. 130) titled "Declination Angle and Its Role in Selecting Surgical Telescopes," by Rucker, Beattie, McGregor, Sunell, and Ito. "A surgical magnification device must accommodate the user's anatomical and physiological needs, not vice versa. The technology of optical devices is sophisticated enough to permit clinicians to work without compromise, but they must choose these devices carefully. Any optical system that does not support the anatomical and physiological requirements for balanced posture - and, as a result, forces compromise of a clinician's declination angle - is likely to be a literal pain in the neck, head, and/or back."
The authors go on to say, "In general, the farther a clinician is forced to tip the head forward and downward to see through telescopes, the greater the risk of strain to musculature of the head, neck, and shoulder areas. On the other hand, a certain degree of forward and downward tipping of the head minimizes the strain on the eye musculature, which accompanies any extreme downward casting of the eyes. The optimal declination angle, then, represents a balance between the extremes of eye strain (when there is no downward tipping of the head) and neck strain (when there is no declination of the eyes). This balance is critical. The optimal declination angle is defined as the angle between the physiological support line of a clinician's spectacles-mounted system and the actual line of sight chosen by the clinician."
When clinicians understand the important benefits (i.e., both visual acuity and ergonomic) of surgical telescopes and are ready to make a selection, they must consider at least 12 important factors:
- Magnification power
- Image quality
- Optical coatings (antireflective coatings)
- Working distance
- Depth of field
- Interpupillary distance
- Convergence angle
- Field of view (magnified view, magnification scotoma, and normal peripheral view)
- Declination angle
- Frame design
- Color and style of frame
When selecting a pair of telescopes, clinicians often consult colleagues who are familiar with surgical telescopes and who carefully study various manufacturers' sales literature. However, sales pitches frequently are misleading and colleagues only have experience with a limited number of surgical telescope brands. Therefore, to select a proper pair of surgical telescopes, the clinician must clearly understand the 12 aforementioned selection criteria. More simply, these criteria can be classified into two major categories: (1) optical-performance and cosmetic-appearance factors and (2) ergonomic factors.
Optical performance and cosmetic appearance
Magnification power, image quality, optical coatings, and frame color and style are optical-performance and cosmetic-appearance factors. Most dental procedures can be performed with 2x to 4x power. As the working distance increases, higher magnification power is required to see the same degree of detail. For example, taller clinicians need higher magnification power. Generally, the magnification-power level is a personal preference, depending on the precision necessary for the procedure and the clinician's desired comfort level.
The majority of major brands use similar quality lenses and optical coatings, so their image qualities are almost equivalent if the two oculars are precisely aligned. The convergence angle of certain brands of telescopes is not fixed and often is easily misaligned. As long as clinicians deal with the major brands, the magnification power is the only optical factor that they really have to ponder. The most commonly used magnification power is 2.5x for both dental and medical procedures.
Once clinicians become familiar with lower magnification power, many decide to work with higher magnification power. As the magnification power increases, the depth of field will decrease, so it becomes more difficult to hold images steady. In addition, the higher the power, the larger the magnification scotoma (the blind zone between the magnified central view and the peripheral unmagnified view). Cosmetic factors such as frame color and style are personal and can be easily decided.
Working distance, depth of field, interpupillary distance, convergence angle, field of view (magnified vision, scotoma, and peripheral vision), declination angle, weight, and design of frames are ergonomic factors. Since the optical performance of major brands of telescopes is similar, these ergonomic factors should be the major selection criteria when choosing surgical telescopes. Ergonomic factors greatly affect the productivity, quality of care, and well-being of the clinician today and in the years to come.
The three basic ergonomic guidelines for selecting proper surgical telescopes are:
1. They are comfortable to wear.
2. The working range of the optical system does not force clinicians to compromise their optimal working distance.
3. The declination angle of the telescopes must be adaptable to the needs of the clinicians for different clinical procedures, not the reverse. The clinician's head/neck and back should maintain a neutral position.
The newer designs of "headlights" are much lighter and more clinician-friendly. Most are easy to adapt to the telescopes and do not add excessive weight. The illumination provided by these new systems is far superior to anything you have experienced before. Most clinicians quickly become addicted to using them.
Some of the illumination systems are universally adaptable to all telescope systems. These systems are generally available in two types:
1. Lights mounted to headbands
2. Lights directly mounted to the surgical telescope-mounting fixture
The separate headband-mounted light is heavy and cumbersome and easily misaligned with the clinician's line of sight. A light clipped directly onto the telescope becomes an integral part of it, and the illumination direction will stay in line with the clinician's line of sight.
Final factors to consider
So, you are convinced this is something you should do and are ready to look for some surgical telescopes. Here are final factors to consider:
- Flip-up or fixed? I prefer the flip-up style, so I can move the telescopes out of the way when not needed.
- They should be easy to clean with sealed lenses that can be immersed for disinfecting.
- A protective lens is especially important if you are using air abrasion in your office.
- The telescope should be fully adjustable.
- Add an external light source that clips onto the telescope, and you will flood the clinical field with more light than you have ever seen before. Then, you can eliminate the expensive fiber-optic systems from your handpieces.
Surgical telescope systems should be properly fitted by competent company representatives and should be guaranteed.
By now, if you are not convinced of the benefits of intraoral magnification with surgical telescopes, you either have the eyes of Superman or you don't know what you're missing!