SurgiTel Ergo Practice News

Advances in Magnification and Mounting With SurgiTel’s Patented Prism Loupe Technology

ErgoPractice News – February 2014 – Article 2
By Jin Chang PhD

Loupes have become ubiquitous in the practice of dentistry and surgery, and a required tool for the clinician’s best work. They use loupes both to see better and to work with comfortable, ergonomic postures. However, while common low-power loupes  (2.0x to 3.0x) can certainly help clinicians start to work better, they cannot offer users the true benefits of modern magnification. Even without magnification, a clinician can achieve an extremely detailed view, by putting their eyes a few inches away from their target (Figure 1). Not a very useful way to work, however, especially with the disastrous posture this creates. Instead, we use loupes which allow us to see detail from a distance. With loupes, we can work easily and with comfort. To increase perceived detail at our optimum working distance (where we maintain a comfortable and ergonomic posture) we need to increase the magnification. Traditionally, higher magnification has been difficult to achieve without adding far too much weight to be comfortable. Older prism designs were too heavy to wear and were not popular. About fifteen years ago, SurgiTel introduced our first generation of lightweight, lower power loupes. Soon after this, clinicians asked if SurgiTel could do anything about the weight of prism loupes as well. After a period of research and development, we were able to drastically reduce prism weight using technology we have developed and patented.

The First Step of Our R&D Process Was to Identify the Problems With Traditional Prism Loupes

Loupes are built with two monoculars (often simply called “oculars”), which combine to create a binocular system. Binocular vision allows for a greater field of view as well as the ability to perceive depth, which makes your work easier. Oculars are mounted into eyeglasses in a Through-The-Lens (TTL) system, or placed in front of eyeglasses with a Front-Lens-Mounted (FLM) system. The visual quality, or resolution, of loupes, strongly depends on the precise alignment of the two oculars (Figure 2). If the images formed by the two oculars do not overlap precisely, the resolution is reduced and your view is blurry. The misalignment of the two oculars will reduce the resolution of images. If the dipvergence (the misalignment of two oculars in the vertical direction) is larger than the eyes can handle, one will even see double images on top of each other. The higher the magnification, the more precise the alignment needs to be. For example: 8.0x loupes require alignments 4 times more accurate than 2.0x

Why Do Traditionally Designed Prism Loupes Not Perform Well?

Our next step was to survey clinicians to find out exactly how we could better serve their high magnification needs. We identified two main drawbacks to traditional prism loupe designs:

  1. Heavy Weight: Made the loupes nearly impossible to wear for any significant period of time.
  2. Fixed Working Distance: With a fixed working distance, users may have two disadvantages:
    a. Different procedures or different working environments may require different working distances. But because of the fixed working distance in prism loupes, clinicians would have to compromise their working postures. And, in turn, compromising their ergonomic health.
    b. As we get older, the vast majority of us will experience changes in our vision called presbyopia. Presbyopia is often treated with standard reading glasses or sometimes prescriptions. The impact on our loupes is that, as we get older, the working distance of our loupes becomes longer and longer. Since traditional designs cannot allow users to adjust working distance, these loupes need to be eventually remade by their manufacturers.

Why Do Traditionally Designed FLM Loupes Not Perform Well?

Clinicians reported the following two drawbacks of traditional FLM loupe designs:

  1. Difficult adjustment of inter-pupillary distance: There are three ocular mounting methods, for more information read ErgoPractice News October 2013. With sliding arms it is very easy to adjust inter-pupillary distance, but creating arms stable enough to support accurate alignments of two high magnification oculars is very difficult. Traditional FLM prism loupes have used heavy, fixed metal bars or heavy, hinge-type mechanisms. And so, with traditional prism FLM loupes, one cannot hope to be able to adjust inter-pupillary distance easily.
  2. Difficult to Compare Types: Clinicians found shopping for loupes troublesome as no manufacturers offered both FLM and TTL prism loupes. Each manufacturer offered either TTL loupes or FLM loupes. A clinician had to coordinate among several companies just to try both on.

SurgiTel’s Design Approaches for Next Generation Prism Loupes

Based on our survey of clinicians we established the following requirements for our next generation prism loupes:

  1. Must be lightweight
  2. Must feature adjustable working distance
  3. Must offer both FLM and TTL options

In order to reduce the weight, we invented a new compact optical design concept (patented) which allowed us to reduce the length of the oculars and, thus, the weight of the oculars. We first introduced this technology into our line of compact prism loupes (3.5x and 4.5x). Then we introduced our exclusive line of Prism Pro loupes (5.5x, 6.5x, and 8.0x). Then, further miniaturizing lenses and prisms, we introduced a line of Micro prism loupes (3.5x and 4.5x) which are even lighter than most traditional low power (2.0x to 3.0x) Galilean, or “standard-field,” loupes. A comparison of ocular sizes between various prism loupes is shown in Figure 3.

For TTL loupes we designed entirely new frames using sturdy titanium materials; a significant upgrade of the traditional aluminum material. For our FLM loupes we used lightweight composite molds instead of heavy, metal parts for the ocular mounting arms. In order to maintain the stability of sliding ocular mounting arms on a lightweight system, we invented a new rack and arm assembly with stabilizers and components to eliminate dipvergence (patented) (Figure 4).

By using SurgiTel’s interchangeable working distance caps (Figure 5), users may change their working distance for different procedures or to compensate for the changes caused over time by presbyopia.

SurgiTel has made sure to offer prism loupes in both custom FLM and custom TTL loupe options because both types have their unique advantages. SurgiTel’s patented technologies assure both options are significantly lighter weight than traditional models.

TTL Style Versus FLM Style

While TTL loupes can offer a larger field of view to people whose noses are high, custom FLM loupes have several advantages over custom TTL loupes:

  • Declination or “look-down” angle can be customized for different procedures.
  • Field of view can be optimized at any working distance within the depth of field.
  • Optical alignments are not affected by the frame material and thus very lightweight frames can be used.
  • FLM prism loupes can be used with any of our frame lines including our sports frame options, whereas TTL prism loupes are best built with SurgiTel frames designed specifically for TTL loupes (Aero and Ergo titanium frames).
  • Can be used with drop-in laser filters. FLM loupes are the best choice for those frequently performing laser procedures.
  • The user can conveniently change their prescription at their local eye doctor (with Aero and Ergo titanium frames) instead of needing their TTL loupes re-mounted into new lenses.

Note that the field of view achieved with FLM loupes by people with low noses will be similar to what they can achieve with TTL loupes. FLM loupes are the best choice for people with low/medium size noses.

Common Questions

Question: “One manufacturer allows the working distance of each ocular to be adjusted independently by turning the front of the oculars like sport binoculars. Why does SurgiTel use working distance caps instead?”

Answer: We found that it is extremely difficult to fine-tune the same working distance for both oculars using this design. If there is any difference in the settings between the two oculars, the resolution of your image deteriorates. We developed the concept of working distance caps so there is no risk of visual degradation due to asymmetric settings.

Question: “I bought a pair of generic FLM prism loupes at a trade show. I found that the image is dim and my depth perception is lost. Why?”

Answer: The ocular mounting arms of generic loupes are not stabilized and the two oculars are never very well aligned in the vertical direction. This misalignment is called dipvergence. Since the dipvergence is so large, you may see through only one ocular. With half the light, images are not bright. And with only one eye working, you will have trouble perceiving depth which makes your work much harder. High-power loupes must never be mounted onto unstable frames (TTL loupes) or unstable arms (FLM loupes).

Question: “If SurgiTel’s compact line prism loupes and Micro line prism loupes are the same magnifications (3.5x and 4.5x), what are their differences?”

Answer: The main advantage of Micro prism loupes is they are smaller and lightweight. The main advantage of compact line prism loupes is, while larger, they capture more light and may create brighter images (Micro prism loupes create bright images as well, but they may require greater illumination). Users prefer one or the other based on their own personal preferences. Clinicians may try on both and decide which they like more for themselves.

Question: “What magnification powers are popular among restorative dentists?”

Answer: If you have been trained with 2.5x or 3.0x loupes, try 3.5x and 4.5x prism loupes. Dentists report seeing details they had no awareness of when using their lower power models. Once clinicians experience the benefits of upgrading to a higher power magnification, many continue to upgrade to the Prism Pro models (5.5x, 6.5x, and 8.0x). Clinicians who use our Prism Pro line loupes testify that they will never go back to lower power magnification loupes.1

Question: “Which style, FLM or TTL, do you recommend? Why?”

Answer: Both our custom FLM and TTL loupes have their unique features and benefits. Different users find they prefer each type for different reasons. Let’s consider several cases, one may apply to you.

Case I: “Many of my peers are developing chronic neck and upper back pain. How can I prevent this?”

Suggestion: Although we can make TTL loupes with larger declination, or “look-down” angles, your best choice may be the FLM option. FLM models allow you to optimize your declination angle. Be aware, if you have a very high nose bridge your field of view with FLM may be smaller than with a TTL. If your nose is low or medium then your field of view will not be significantly different. Again, there are no frame choice limitations for FLM loupes.

Case II: “I have a high nose bridge and want to have the largest field of view.”

Suggestion: Your best choice maybe the TTL option, but we still recommend trying the FLM option because it may still give you enough field of view and does provide other benefits such as customizable declination angle, flip-up option, and easy prescription change. Our high-power TTL prism loupes should only be mounted on our patented titanium frames (Aero or Ergo frames), but there are no such frame restrictions for FLM models.

Case III: “I have a relatively low nose and want to have the best peripheral vision.”

Suggestion: Your choice is definitely the FLM option. With your facial features, the back of the TTL oculars will be too close to your eyes and there will be a very large blind field (called scotoma) between the magnified and the peripheral fields. (This is because the “case” of the ocular is literally blocking your peripheral view.)

Case IV: “I have an average height nose and want to have all the benefits that loupes can offer.”

Suggestion: Your choice is definitely the FLM option. FLM loupes offer several benefits that are not available with TTL loupes such as a customizable declination angle to achieve the maximum comfort and ergonomics, adjustable inter-pupillary distance to achieve the best field pattern at any distance within the depth of field of loupes, the ability to flip-up for non-magnified view, better peripheral vision, and finally easy prescription update by local opticians. TTL loupes are customized at a fixed set of measurements (fixed working distance, fixed inter-pupillary distance, and fixed declination angle) and do not feature the flip-up option. Any prescription must be updated by the manufacturers.

Note: In the past, the weight of FLM loupes caused issues. But now that SurgiTel FLM loupes are significantly lighter than even traditional TTL loupes, the weight of SurgiTel’s FLM option is no longer an issue.

Over the past twenty years, SurgiTel loupe designs have greatly advanced to serve the demands of clinicians. SurgiTel is uniquely situated to provide higher magnification and greater flexibility than others’ loupes. Other companies may provide higher magnification loupes, but these traditionally-designed models are lacking features offered by next-generation SurgiTel patented loupes which allow for a more comfortable weight along with a stable, quality vision.

To learn more, contact your local representative who can help you decide what will work best for you!

  1. Grayson, George. “Rationale for the Visualization, Diagnosis and Treatment Using SurgiTel Prism Pro Loupes,” September 2013.,.pdf.