The best method to evaluate loupes is to look at an object with straight black lines, as below Fig.A. The most common signs of poor quality loupes are low resolution, chromatic aberration and spherical aberration.
Resolution is defined as a 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, as depicted in Fig.B.
Spherical aberration is called to be the flatness of the image. When viewed through loupes, an object that exhibits spherical aberrations would appear to be curved or spherical, as depicted in Fig. B. The lines would not be straight, as in the original (Fig. A) or in the Zeiss loupes image of Fig. C.
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 most people 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.
Other important considerations are light transmission, depth of field and field of view.
Light transmission is important not only for quality of the image, but also for the comfort and safety of your patients. Optimized light transmission means that you can work with less light, reducing your eyestrain while minimizing the exposure of your patient to bright light.
Depth of field is defined as the range that's in focus away from and towards you without moving your head. The ergonomic benefits, or how comfortable the loupes are to wear, of a large depth of field are clear because there is less need to move your back and neck to work effectively.
Field of view refers to the amount of the original object that you can see at one time. Different applications have different needs. A bigger field of view is not always the better choice; for instance, an endodontist might prefer to see only the area of focus, whereas a periodontist would like to see as much of the surrounding area as possible.
Side-by-side comparison is the best method to choose the loupes that are right for you. We are confident that when you look into loupes from us, you'll see why we say the difference is clear. |
