The quality of loupe system can summarize by some 4 visual characteristics: Magnification,              Field of view, Resolution and Field depth. Besides, design, weight and angle of declination are also important to make the loupe comfortable.

What is the advantage of wearing loupes?

Most of the dentists suffer from chronic back and neck pain. Incorrect working posture makes neck and shoulder tense and the related tension induces headaches. By the loupes dentists can improve posture and ergonomics especially for prolonged surgeries. Loupes help to have ideal posture and also improve the vision during the surgeries.  

Specifications:

-          Magnification power

Magnification power is the ability of loupe system to increase an image size (not the clarity of the image). 

The level of the magnification is often based on personal preferences. But choosing the lowest comfortable magnification level provides the widest field of view.  

The most common magnifications are 2.5x and 3.5x.

Though increased magnification provides a more detailed working site, there are some downsides like Smaller field of view and darker field of view because of decreased light entrance.

The most common magnification for loupes in different dental fields are:

•          General dentistry, dental hygiene, Implantology : 2.5X, 3.0X,3.5X.
•          Endo, Crown and bridge work: 3.5X, 4.0X
•          Lab Work, technician: 4.0X, 5.0X, 6.0X

There are two terms "Galilean" and "Prismatic" refers to magnification. Galilean means, lower magnification loupes and Prismatic means 

high magnification loupes which are more expensive.

-          Working distance

The working distance refers to the distance between your eyes, and the area you are working on.

You can measure this when you are in your normal working position. Be comfortable while your back is straight, do not lean forward or backwards too much. Perhaps you could ask someone to help you.

-          Field of View

The field of view is the area that is visible and in focus while looking through the loupes.

A larger field of view is preferred as there is a larger area visible through the loupes and there is less need to move your head around. The size of the field of view changes with the working distance.

Simply stated; a loupe with a longer working distance will have a larger field of view and vice versa.

All comfort loupes utilize high performance lens systems that provide an extra wide field of view (up to 125 mm)

-          Depth of  Field (Range of maintained focus)

The depth of filed is the depth of the area that is visible and in focus, while looking through the loops.

This determines how much you can lean in, or lean back, while wearing your loupe, and still maintain focus of the entire viewing field. Field depth is dependent on the available lighting, the optical design, the magnifying power, and the eye’s ability to focus.

A higher depth of field is preferred, as there is a deeper area visible through the loupes, making it easier to work without losing focus as you move your head.

The size of the “depth of field” corresponds directly to the “working distance”.
Simply stated: A loupe with a longer working distance, will have a larger depth of field, and vice versa.

The size of the “depth of field” also corresponds directly to the magnification factor.
Simply stated: A loupe with a lower magnification factor, will have a larger depth of field, and vice versa.

All Comfort Loupes utilize high performance lens systems that provide an extra-large depth of field.

-           Resolution

Resolution relates to the clarity of the image through the field of vision. It is the synergistic specification to field of view. 

The most common signs of poor quality loupes are low resolution, chromatic aberration and spherical aberration. Resolution is defined as an optical system's ability to form distinguishable images of objects separated by small distances, or to recognize fine detail.When comparing different loupes, look at the testing objects and select an area of tiny details that can only be seen with magnification.

Chromatic aberration refers to color distortion. Because each color has a different wavelength, uncorrected optics cause the various wavelengths to focus at different points in space. The first color that generally comes out of focus is blue; when looking at black lines on white paper, poor quality loupes will display a blue haze just to the side of the black lines.

Spherical aberration refers to the flatness of the image. When viewed through loupes, an object that exhibits spherical aberrations would appear to be curved or spherical. The lines would not be straight.

Viewing colorful or complex objects such as anatomical models or the inside of your hand does not give you the opportunity to evaluate loupes for their true optical performance, as you are not trained to see the differences on such complex images. A simple piece of graph paper, however, can reveal the difference between mediocre and high quality loupes.

-          Angle of Declination:

Angle of declination is the most important specification for the ergonomics of wearing loupes. A correctly set angle of declination makes dentist look down the optics rather than bend her/his neck towards the working site.

The steeper the angle of declination, the less need of bending neck.

-          Weight:

Weight is an important factor when choosing a new loupe.

Light weight loupes are more comfortable, and in the long term, will reduce tension and strain.

Ultra light weight loupes, offer the maximal comfort.

 All loupes utilize extremely light weight materials.

-          Design:

Newer loupes are available in plastic sports frames, reducing the weight and improving the aesthetics of the loupes.

Older style frames however tend to be, so it might be something to factor in when considering the longevity of loupes. 

-          Prescription Lenses:

. If you use glasses with prescription lenses, it is important that you have the option of fitting your loupes frames with the correct prescription. Otherwise, the loupes will not perform according to specifications. The standard frames, can easily be fitted with prescription lenses by your optician. Loupes are also available in a "clip-on" option, which can be clipped on to your regular glasses.

TYPES OF LOUPES

FLIP UP LOUPES

Flip up loupes have the optics attached to a moveable arm, and can be manually adjusted to suit anyone.

Advantages

• Much cheaper (£100-500+)
• Easily flipped up when not required (good for communicating with the patient)
• Better resale value
• Easier to add prescription

Disadvantages

• Heavier
• Smaller field of view

THROUGH THE LENS (TTL) LOUPES

TTL loupes have the optics built into the glasses, with the specifications (such as inter-pupillary distance) customised to your eyes.

Advantages

• Lighter weight
• Wider field of view (as the optics are closer to the eyes)
• Optics will always be in the right position

Disadvantages

• Much more expensive (£1000s)
• Cannot be moved from the view, so more difficult to communicate with the patient
• Poor resale value (as only suited to the clinician they are set to)