Selection Guide of Loupes
When we purchase loupes, we should consider several important factors such as loupe mounting styles, magnification power, field size, declination angle, frame design, nose pad options, and maintenance cost. These factors are evaluated based on working distance, working posture (sitting or standing), and facial features such as nose shape.
Selection of Loupe-Mounting Styles
There are two basic mounting styles for ergonomic loupes: customizable FLM (front-lens-mounted) style and custom TTL (through-the-lens) loupes (Figure 1).
1. If you do not know a desirable declination angle for your posture, you may choose the FLM style which allows you to try different declination angles to achieve your best neck posture.
2. If you know a desirable declination angle, you may choose the TTL style, but if your nose is flat, the FLM style may be a better choice to avoid fogging and touching your eyes.
3. If you are experiencing chronic neck pain, you may choose FLM loupes and adjust the declination angle gradually.
Selection of Magnification Power for Your 1st Pair of Loupes
The resolution power of eyes decreases as the working distance increases (Figure #2) and thus the required magnification power increases as the working distance increases. Desirable magnification power for the 1st pair of loupes is decided based on your working distance
- If the working distance is less than 15 inches, 2.5x is a good choice.
- If the working distance is about 16 inches to 18 inches, 3.0x or 3.5x may be selected.
- If the working distance is larger than 19, 3.5x should be selected.
Many dental schools and hygiene schools recommend 2.5x loupes to their students as the 1st pair of loupes because the typical working distance of dental professionals in the past was about 14 inches, but 2.5x loupes are not adequate for students with long working distances.
Field of View and Selection of Loupe Optics
There are two kinds of loupe optics: Galilean loupes and Keplerian (often called Prism) loupes. If you want a larger field of view with high power loupes, you should choose prism loupes which offer a larger field of view than Galilean loupes.
Declination Angle for Safe Neck Posture
Small declination angles will force clinicians to excessively tilt their heads and can create chronic neck pain as a result of using non-ergonomic loupes with small declination angle for an extended period. A safe head tilt angle is one that is less than 20 degrees¹
Warning: Non-ergonomic loupes support human natural behaviors, such as tilting the head to look down rather than rotating eyes downward. Young clinicians may feel comfortable with non-ergonomic loupes because they will not feel the neck pain right away. If you want to protect your neck, you should evaluate your loupes within 45 days.
เพื่อให้แน่ใจว่า Loupe คุณได้รับการออกแบบตามหลักสรีรศาสตร์ คุณควรวัดมุมเอียงศีรษะของคุณ โดยใช้ภาพถ่ายมุมมองแบบ 2 ภาพ ด้านล่าง คุณจะประมาณมุมเอียงศีรษะได้² หากมุมเอียงศีรษะของคุณมากกว่า 20 องศา คุณควรขอให้ผู้ผลิต Loupe ของคุณทำ Loupe ใหม่เพื่อให้มุมเอียงศีรษะของคุณอยู่ต่ำกว่า 20 องศา หากไม่สามารถทำ Loupe ตามหลักสรีรศาสตร์ได้ คุณควรดู Loupe ตัวใหม่ได้แล้ว
Maintenance Cost
The maintenance cost of loupes includes updating prescription (Rx), repairing unbonded loupes, and restoring working distance which can eventually increase due to aging eyes. The accommodation power of eyes decreases, requiring elderly individuals to use reading glasses to read books. Once we start to use reading glasses, the reading Rx changes frequently over time and we have to update Rx.
The maintenance cost of FLM loupes is the lowest because any optical shop can update eyeglass RX. The maintenance cost of TTL loupes is very expensive because updating the Rx of carrier lenses is the same as assembling TTL loupes. Even if you are only updating the Rx inside your loupe optics, this Rx update may take several weeks because your loupes will need to be returned to the manufacturers for the update to be performed. This requires a backup pair of loupes because it is not possible to practice without loupes.
References
- Valachi, Bethany. Practice Dentistry Pain-Free. Portland, Oregon: Posturedontics Press, 2008. https://posturedontics.com/
- Chang, BJ, The Truth about Declination Angle, ErgoPractice News, June 2020
- Chang, BJ, The hidden cost of Non-ergonomic Loupes and Cool/Blue-Tinted LED Headlights, ErgoPractice News, March 2021
Resourced: https://bit.ly/3rjIJUS