Maximizing the Depth of Field of Your Loupes

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ErgoPractice News – October 2018

Today, loupes and headlights have become essential for practicing dentistry and surgery. However, a shorter depth of field can make it difficult for some users to use high power loupes.

Controlled by the brain, the eye instantaneously adjusts its focal distance in order to see close or distant objects. Unlike our eyes, loupes have a pre-set focal distance set where we wish to work. We can also see objects clearly within a certain range closer and farther from this point with our loupes (Figure 1). This range is called the depth of field. Outside of this range, objects are out of focus.

In this issue of ErgoPractice News, we will review criteria that impact depth of field and then two options to maximize the depth of field of your loupes. With an optimized depth of field, you may work faster, easier, and more comfortably.

Depth of Field and Age

As we age our eyes change and the minimum distance at which our eyes can focus will increase. This is made apparent by the inability to read the fine print at close distances, requiring reading glasses to adjust. These aging effects may be noticed around 35-40 years of age (Figure 2).

Our eye’s accommodation ability reduces as we age, and so our depth of field will become shorter as we age. Combined with the fact that higher loupe magnifications have the naturally shorter depth of field, this makes it more difficult for clinicians over 40 to use high power loupes.

Depth of Field and Loupe Design

The depth of field which a loupe can provide depends on optical design and assembly methods. Because users cannot adjust proprietary design or assembly technology it is very important to select the loupes with the longest depth of field. It may be difficult to directly compare the depth of field of different brand loupes. For the comparison, you may attempt to compare the same magnifications at the same working distance in the same lighting conditions.

With proprietary optical designs and assembly technology, our data suggests SurgiTel loupes can achieve a greater depth of field across all magnifications, possibly the longest among all brands of loupes available today (Figure 3).

Depth of Field and Lighting

Our eye iris opens and closes to adjust the size of the pupil depending on the brightness of the environment. Under bright light, our pupil size decreases. The smaller our pupil size, the longer our depth of field but with lower perceived detail. A larger pupil size decreases the depth of field but also results in greater perceived detail (Figure 4).

Because of this compromise, those who wish to maximize perceived detail may dim their light to allow their iris to open to increase pupil size, at the cost of depth of field. Those who wish to maximize their depth of field, at the cost of perceived detail, may increase light brightness to close the iris and decrease pupil size.

Be aware, however, lighting that is too bright will blind the eyes reducing image contrast and also potentially damaging the retina. Too bright illumination will saturate the sensitivity of eyes, resulting in loss of detail.

Maximizing the Depth of Field of Your Loupes

In summary, to maximize depth of field one should choose the best available brand and may adjust the lighting intensity. These choices may be even more important to clinicians over 40 who may naturally experience a reduced depth of field.

For more information, or to try different magnification powers and models with different depths of fields in person, contact your local SurgiTel representative at Find a Rep.

References:
  1. Chang, BJ. Choosing Loupes for Dental School: 3 Most Common Myths in the Loupe Industry Demystified, ErgoPractice News, July 2018.