How to Choose Your Magnification Loupes – Part II

This blog post is an continuation of our previous post.

Test the working distance
The working distance refers to the distance between your eyes, and the patient’s mouth. You can measure this while assuming your normal working position, making sure you are: comfortable, that your back is straight, and that you are not leaning forward too much.

Perhaps you could ask someone to assist you in this procedure. You can also use the following overview to help determine the best working distance for your personal needs:

Height:
<170 cm (5ft 7 in) 170-190 cm (5ft 7 in to 6ft 4 in) >190 cm (6ft 4 in)

Sitting:
340 mm (14 in) 420 mm (16 in) 500 mm (20 in)

Standing:
420 mm (16 in) 500 mm (20 in) 550 mm (22in)

Check the 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” also corresponds directly to the magnification factor.

A loupe with a lower magnification factor will have a larger field of view, and vice versa. All loupes utilize high performance lens systems that provide an extra wide field of view (up to 125mm / 4.9 inch).

Check the depth of view.
The depth of field is the depth of the area that is visible as well as  in-focus, while looking through the loupes. A larger depth of field is preferred, as there is a deeper area visible through the loupes. The size of the “depth of field” corresponds directly to the “working distance”.

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.

A loupe with a lower magnification factor, will have a larger depth of field, and vice versa. All loupes utilize high performance lens systems that provide an extra large depth of field (up to 120mm / 4.7 inch).

Test the weight of the loupes.
Weight is an important factor when choosing a new loupe, especially if the loupe is to be used for longer periods of time. Lightweight loupes are more comfortable, and in the long term, will reduce tension and other complications. Ultra light weight loupes, offer the maximal comfort. All loupes utilize extremely light weight materials.

Regarding the Keperlilean loupes, these loupes are heavy. When choosing these, opt for the headband style, which will be comfortable for using a long time.

Operation Loupes and Headlight Were Used as Visual Aids during Cauda Equina Syndrome Operations

Cauda Equina Syndrome (CES) appeared as a postoperative complication in five patients that were operated on for lumbar disc herniation.

The study consisted of a retrospective analysis of records and radiographs in five patients who developed acute cauda equina syndrome after surgery for lumbar disc herniation.

The objective of the study was to postulate as a possible pathophysiologic mechanism the venous congestion caused by preexisting spinal stenosis and to present a management plan: extended decompression within 48 hours.

Cauda equina syndrome is reported as a sequela in 0.2%–1% of the surgeries for lumbar disc herniation. There is, however, no consensus on the possible pathophysiologic mechanism to the complication or to its management.

Methods uses for preoperative investigations consisted of magnetic resonance imaging, or myelography and computed tomography. There was a good correlation between clinical appearance and radiographic findings in all patients. When the complication became apparent in four of the patients, they were investigated with magnetic resonance imaging and reoperated on within 48 hours with wide decompressions.

During the operation, surgical loupes and headlights were used as visual aids. The index operation was reported uneventful in all patients. Postoperative magnetic resonance imaging did not show the cause of the cauda equina syndrome, nor could this be established at the reoperation.

Before surgery, all five patients had preexisting narrowing of the spinal canal. In no case was the lumbosacral disc the index level. Two patients recovered fully, whereas the other three experienced varying degrees of residual symptoms. There was no correlation between the end result and the delay until secondary decompression.

The researchers concluded that relative spinal stenosis may contribute to the development of cauda equina syndrome after surgery for lumbar disc herniation. A venous congestion can be triggered by postoperative edema, leading to nerve root ischemia. The treatment of choice seems to be extended decompression within 48 hours.

(Source: Henriques, Thomas MD*; Olerud, Claes MD, PhD*; Petrén-Mallmin, Marianne MD, PhD†; Ahl, Torbjörn MD, PhD Spine Journal Volume 26 – Issue 3 – pp 293-297)