The Evolution of Loupes in Dental Hygiene

Although the first dental-operating microscopes were commercially available in 1981, they were slow to be accepted.¹ More recently, however, a 2019 survey of US dentists who graduated dental school during or before 1995 reported dental loupes as one of the most important innovations in dentistry over the past 30 years.² Dental loupes are telescopes mounted into glasses. The telescopes, or oculars, are the magnifying lenses that are mounted in or on the glass or plastic carrier lenses. Important customized features include a clinical working distance, inter-pupillary distance, and the horizontal convergence angle. Comparative product features include field of view, depth of field, and the optical grade of the glass used in the oculars.³

Although the primary reason for clinicians to seek the aid of a loupe is a desire for improved visual access, there have been a subsequent significant number of studies that have determined a positive relationship between dental loupe use and reduction of musculoskeletal disorders among dental professionals.^3,4 Additional studies have demonstrated improved procedural outcomes and increased performance by dental students when using loupes.^5,6

Traditionally, magnification loupes have been divided into two classifications based upon their design and construction techniques.³ Galilean loupes usually have two lenses, one objective convex and one concave eyepiece, whereas Keplerian (or prismatic) loupes can have two or more lenses, all convex, and include a prism between the lenses. The lenses in Keplerian loupes are also generally a higher magnification power when compared with the Galilean loupe lenses. Due to the prisms, Keplerian loupes provide a greater depth of magnification, a wider field of view, and a longer working distance. Galilean loupes, on the other hand, are smaller and more lightweight.³ The oculars for both Galilean and Keplerian loupes are generally mounted into the lower third of the lens carriers to achieve the steepest angle of declination possible. This positioning also allows the user to have visual contact with the patient or nearby surroundings simply by moving the eyes upward. Galilean loupes have proven suitable for first-time users and practitioners with a preference for direct vision.³

Now that clinicians have spent more time integrating loupes into their work, there is a growing number of second-generation loupe users who are making upgraded purchases and seeking advanced features. Many purchasers today show interest in increased magnification, lightweight frames, edge-to-edge clarity, and customizable declination angles. Although an increased magnification power provides a longer working distance, it also results in a smaller field of view and limited depth of field. This option may require more time for clinicians to adjust to and therefore may be more difficult for first-time users.

The newer loupe options entering the dental market, which offer more advanced features, have been designed to improve upon the Keplerian or prismatic loupe designs. These include deflection loupes, also referred to as ergonomic prism loupes, which have an internal optical design similar to that of a single reflex camera. The camera design uses a roof pentaprism in order to allow the photographer to see the image through the lenses right-side up.⁷ This roof prism is able to reflect light through two faces that meet at a 90° angle and, therefore, can flip the image to appear upright.⁸

Ergonomic prism loupes profess superior optical quality, an expanded field of view when compared with Galilean loupes, reduced eye strain, and a design that enables a neutral posture working position. The customizable position of the oculars allows for a forward, neutral direction for one's eyes, rather than a downward direction. This, in turn, reduces the strain put upon the head, neck, shoulders, and cervical spine. Comparative data reviewed by the author indicates that a deflection loupe is approximately a third heavier in weight, due to its specific design and construction. However, this increased weight may not be as important or noticeable as it was in previous loupe designs because the operator is positioned in a proper neutral posture. The design also allows for a higher magnification capacity.

Although some users have indicated a difficult adjustment period when switching to deflection loupes, operators who are accustomed to performing direct vision procedures appear to have less of an adjustment period. The lengthier adjustment period may be explained by the position of the oculars when mounted in the middle of the frame directly level with the pupils. In this position, the user must turn the head to the side, upward, or downward in order to have eye contact with the patient or view other objects, such as the instrument tray. Keep in mind that these additional head movements can cause a feeling of displacement or vertigo for a newer user.

Ultimately, no matter how good a product design appears to be, it can always get better. As dental practitioners, we need to seize the best designs available but continually demand improvement.

Cindy Purdy, RDH, BSDH, CEAS
Registered Dental Hygienist
Certified Ergonomic Assessment Specialist
Founder
THRIVE! Wellness and Therapeutic Summit for Dental Professionals