Adjustments to sitting position and the microscope go hand in hand. Whereas in a clinical setting there may be practical limitations on how one can sit and mount the microscope, this tutorial offers scope to learn how to reduce potential discomfort wherever possible. The first step in setting up your workspace should be to assume a physiologically optimal sitting position. Sitting comfortably, without using too much muscle tone to maintain posture, is important in keeping physical exhaustion, tremor and pain to a minimum. Once we have explained what an ergonomic sitting position is, we will demonstrate adjustment of the microscope using a standard laboratory microscope. You may find that the specifics of adjusting your own microscope vary, but the general principles should apply.
Posture and Microscope Adjustment
To begin with, place your feet in front of your chair, approximately shoulderwidth apart. In this position you have three points of balance, providing a maximum of stability and symmetrical muscle tone across your legs and back. Set the height of your chair so that your hip joints are situated at least as high as your knee joints. This tilts your pelvis forward so that you can maintain a natural and ergonomically correct spine position over a longer period with ease. To straighten out your spine and support it with your abdominal muscles, draw your navel inwards towards your spine. Rest your forearms on the table to prevent tiring of your arm and shoulder muscles, leading to large amplitude tremor. Place your hands on the work surface to reduce small amplitude tremor. To achieve an ergonomically correct cervical spine position, push your head upwards to straighten your neck and slightly tilt your chin downwards, as if you were looking down to the ground in the distance. The entire microscope should be mounted to match the sitting position. The eyepieces should be at the correct distance to the operator and at the correct height to meet the eyes. In order to be able to sit straight while still obtaining a sharp image, or if you find you are straining your wrists because they are too low in relation to the workspace, you may need to raise your workspace. To stay comfortable you can role up some towels and place them under your wrists. If you are using your visual aid (eyeglasses/contact lenses), or have no eyesight impairment, set the eyepieces to 0 (zero) diopters. If you have a visual aid, but prefer to work without it, most eyepieces can be set to correct simple myopia, or hypermetropia according to your prescription. Turn on the light source. To keep potentially significant eyestrain to a minimum, use ambient light and keep looking through the microscope with as little interruption as possible, so your eyes do not have to repeatedly adjust to different degrees of brightness. Now set your interpupillary distance. You should obtain one single circular visual field that does not float in front of your eyes. If you experience difficulty in obtaining such a visual field, make sure that the distance between your eyes and the eyepieces is neither too long, nor too short. To keep this distance, you may want to use the shades available on some eyepieces. In order to set the focus in the plane you want to work in, initially set the microscope to its minimal magnification. Adjust the focus using a fine object that provides a good contrast, such as the tips of a microsurgical instrument. Once you have obtained a sharp image, switch to maximal magnification. Proceed with the fine adjustment of the focus. As long as you keep working in the same plane, you can now switch between different degrees of magnification without readjusting the focus. If you enter a different operating plane, you will need to readjust the focus. If you cannot obtain a sharp image at either minimal or maximal magnification, you may have to alter the distance between microscope and work field. When you take a break, turn off the light source to prolong the lifetime of the light bulb and reduce energy expense.
Holding microsurgical instruments
Along with resting your forearms and hands on the table, the way you hold microsurgical instruments can influence precision of movement, as well as the appearance of muscle fatigue and tremor. Most instruments are best held with a three-finger pinch, supporting one arm of the instrument and squeezing the other. This is not only important for precision of your instrument handling, but also to avoid tiring your hand muscles.
Adjusting the resistance of spring handled instruments
To adjust the resistance of spring-handled instruments according to your personal preference, open the spring and bend it to incline or decline its angle.
Pitfalls, tips and tricks
Some of the most common postural mistakes are shown here. These frequently go unnoticed while focusing on the microsurgical tasks themselves. Accustoming yourself to an ergonomic sitting position early on may spare you significant discomfort and pain and aid your overall performance. Keeping your feet shoulder-width apart and your knees extended can be an alternative for a while, but in time pain in the lumbar region may develop. Keeping your feet close together only gives you a two-point support to balance your body on, no matter whether your knees are flexed or extended. Keeping your feet under your chair provides the least support. Keeping your feet on either side of your body, or your legs crossed, bends and twists your spine, and may cause discomfort and pain. Assuming a hyperlordotic or hyperkyphotic position can also lead to discomfort and pain. Resting only your wrists or hands on the table instead of your whole forearms may tire your arm and shoulder muscles and result in large amplitude tremor. If your hands are not resting on the table, smaller amplitude tremor is likely to result. If you still observe some small amplitude tremor even though your hands are resting on the table, rest your fingers upon each other, or try alternative hand positions depending on the operative situation. If even now, you are still experiencing small amplitude tremor, fatigue or cramping in your hands, check if your fingers are in an exhausting position like this one. Tremor that disappears with voluntary movement does not pose a problem. If the eyepieces are set too high or too low, pain may develop in the cervical region. Mounting the microscope too far away from you may make obtaining a clear, circular and large image difficult. If you press your eyes or cheekbones on the eyepieces, you may alter how they are set. Eyestrain or a headache may result. When initially mounting the microscope or adjusting the focus in a different surgical plane, remember to check the curvature of your cervical spine, the height of the eyepieces and the distance between your eyes and the eyepieces.