Working Distance The working distance is distance at which a loupe will focus. The working distance must be equal to the distance from the loupe lens to the top of your subject. Each loupe has a defined working distance, but the working distance you require will depend upon your height, posture and table height. It is best to determine your desired working distance, and then choose a set of loupes that will meet your criteria. You can measure your actual working distance or use the table at left to get a rough idea.To measure your working distance, sit or stand in a comfortable position with your back straight. Do not lean forward too much. Measure the distance from your eyes to the top of your subject. Usually, your working distance will be close to what is shown in the table. 504053 — 4.5x Binocular Loupe MICRODISSECTION, MICROSURGERY Field of View The area that is in focus when viewed through the loupes is the field of view. The longer the working distance of a loupe, the greater its field of view will be. Likewise, the lower the magnification factor, the larger the field of view. This tradeoff must be considered carefully when choosing loupes. When using a Galilean loupe the center of the image is clear, but the outer rim of the image is blurred. The prism loupe image is sharp to the very edge of the field of view. Depth of Field Like the field of view, the depth of field is directly related to the working distance and magnification factor. The depth of field is the amount of depth that is in focus when viewing the subject through the loupe. Greater depth of 504040 — 3x loupes flip up to allow use of prescription lenses (installed by user’s ophthalmologist). 504038 — 2.5x Binocular Loupe BINOCUlAR lOUPES PART # 504050 504029 504055 504052 504053 504054 504038 504056 504037 504038 504039 504057 504058 504040 504059 504060 PRISM ✔ ✔ ✔ ✔ ✔ ✔ POWER 3.5x 3.5x 4.0x 4.0x 4.5x 4.5x 2.5x 2.5x 2.5x 3.5x 2.5x 3.0x 3.0x 3.0x 3.5x 3.5x WORKING DISTANCE 34 cm 50 cm 34 cm 50 cm 34 cm 50 cm 35 cm 50 cm 34 cm 50 cm 34 cm 34 cm 50 cm 50 cm 34 cm 50 cm field is preferred, because you can see deeper into the subject without repositioning. For greater depth of field, choose a loupe with a longer working distance or a lower magnification factor. chose a magnification factor of 5.0x to 6.0x. Higher magnification loupes can be used in place of a surgical microscope, if desired. Interpupillary Distance The distance between the pupils of your two eyes is your interpupillary distance. For the sake of comfort when focusing, your loupes must fit your eyes. You optometrist can give you an exact measurement. WPI loupes are adjustable so that you can set your loupes to an interpupillary distance that suits you. Magnification The size of the image viewed through the loupe is determined by the amount of magnification, which is a personal preference. Higher magnification provides a larger image, but it also means a reduced field of view and depth of field. Generally speaking, for simple surgical cases or for beginners in training, 2.5x or 3.0x magnification is sufficient. When a more delicate or complicated procedure is required, choose a magnification factor of 3.5x to 4.5x. If you are working on a tiny area or are conducting a microsurgery, TTL 504037 — 2.5x loupes clip onto the user’s glasses. World Precision Instruments UK: Tel: +44 (0)1462 424700 • wpiuk@wpi-europe.com www.wpiinc.com Germany: Tel: +49 (0)30-6188845 • wpide@wpi-europe.com US: Tel: 941-371-1003 • sales@wpiinc.com 31