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Do Deflection Loupes with Steep Deflected Beam Meet Ergonomic Requirements? (SurgiTel Straight Ergonomic Loupes vs Deflection Loupes)

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Deflection Loupes are not truly ergonomic as manufacturers claimed because they violate both visual and postural ergonomics. Also, magnified vision and peripheral vision are not coaxial. Our conclusion is that “SurgiTel Straight Ergonomic Loupes” is superior to “Deflection Loupes” because of better visual ergonomics, improved postural ergonomics, and increased productivity with a coaxial vision which will be discussed in this article.


Historical Background

Figure 1: PENTAX Deflection Loupes (called PrismVue)

Deflection loupes were first introduced by PENTAX about 15 years ago in Japan and have been sold as the ultimate “PRISMVUE” in several Asian countries (Figure 1). These loupes were sold as ergonomic loupes which allow stress-free parallel viewing, minimizing the risk of strain and eye fatigue. However, these loupes were not accepted well by clinicians because these loupes cannot meet ergonomic requirements.

Recently, deflection loupes were introduced in the US market as “ErgoPrism” loupes by LumaDent (Figure 2) and “Infinity VUE” loupes by Designs for Vision (Figure 3), and in the European market as “ergo” loupes by ADMETEC (Figure 4). These manufacturers are claiming that their loupes are ergonomic loupes as claimed by PENTAX.



Figure 2: LumaDent Deflection Loupes (called ErgoPrism)

Figure 3: Designs for Vision Deflection Loupes (called Infinity VUE)

Figure 4:  Admetec Reflection Loupes (called ergo loupes)


Why are Deflection Loupes Not Truly Ergonomic?

These loupes are not truly ergonomic because they violate both “Visual Ergonomics of Eyes” and “Postural Ergonomics of Neck.” Since magnified field and peripheral field are not co-axial, working with deflection loupes is not natural and requires a long learning curve, reducing productivity.

Ankrum’s article on “Visual Ergonomics in the Office – Guidelines” investigated the effects of gaze (declination) angle of eyes on both accommodation ability and conversion ability.¹ Figure 5 shows that the ideal location of monitor placement is between 15° and 50° below the horizontal eye level which allows users to achieve better accommodation ability and conversion ability. This article concluded that the horizontal viewing angle is not ideal, reducing the accommodation ability (which results in the short depth of field) and reducing the conversion ability (which creates the eyestrain). Therefore, SurgiTel straight ergonomic loupes which support a safe head tilt/neck posture are the better choice.

Figure 5: Ideal Monitor Location vs Gaze (Declination) Angle

“To see the effect of gaze (or declination) angle on accommodation, hold a business card at an arm’s length and at eye level. Slowly bring it towards you until letters start to blur. Without moving your head, slowly lower the card in an arc, keeping it the same distance from your eyes. You will see letters come into focus. Your eyes have improved their ability to accommodate simply by lowering their gaze (declination) angle.”

“To see the effect of gaze angle on your ability to converge, try this next demonstration. With your head erect, hold a pen at arm’s length and at belt level. Gradually bring it towards your nose, following it with your eyes until you can no longer converge accurately, and you see two pens. Without moving your head, try the same test at eye level. Again, notice the distance at which you can no longer converge. Now bring the pen in from an upward gaze angle. As you can see and feel, your eyes converge more easily with a downward gaze angle.”

Reflection loupes with horizontal viewing allow the head and neck only one posture that is both visually and posturally comfortable. It is uncomfortable to keep the same posture for an extended period of time. When users are tired of the head-erect posture, the acceptable alternative postures are limited. Deflection loupes with steep deflection angles often force users to tilt their heads backward. You can easily find that tilting the head backward is uncomfortable. Straight ergonomic loupes allow users to move their necks easily. For postural ergonomics, straight ergonomic loupes are the better choice.

The non-coaxial vision of deflection loupes like microscopes will require a longer learning time and slow down the work speed. For productivity, SurgiTel straight ergonomic loupes are the better choice.

In conclusion, SurgiTel straight ergonomic loupes are the best choice because of superior visual ergonomics, greater postural ergonomics, and improves productivity with the coaxial vision.


Why SurgiTel as Your Partner for Vision Aid Products?

The founding mission of SurgiTel has been to help clinicians practice dentistry and surgery safely by providing ergonomic loupes and eye-safe headlights. As a result of continuous research and development during the last 30 years, SurgiTel can make posture-safe ergonomic loupes for all clinicians with different facial features and can also make the best-LED headlights with the best color accuracy and are the safest illumination for your eyes.

SurgiTel’s free evaluation service can help evaluate your working posture and identify the potential blue light hazard of various brands of LED lights. Click here to schedule a free evaluation.



  1. Ankrum, D. R. Visual Ergonomics in the Office – Guidelines, Occupational Health & Safety, 68, 7, 64-74 (1999)
  2. Chang, B.J. What They Didn’t Teach You About Selecting Loupes in School! – ErgoPractice News, June 2021
  3. Chang. B.J. What They Didn’t Teach You About Dental Lights in Dental School! – ErgoPractice News, May 2021