When switching from microscopic to endoscopic (video monitor) viewing, the learning curve is quite steep, due to the following:
• Difference in image composition. Instead of observing the inside of the eye and the intraocular instruments through the microscope's eyepieces, the image is shown on the video monitor.6 This image corresponds to what is found in front of the endoscope's tip inside the eye,7 and the endoscope itself is not visualized.
• Lack of visual feedback of the surgeon's hand motions and the endo-scope's position.
Alternatively observing the video monitor or the microscope-provided image helps with orientation and probe manipulation by allowing identification of anatomical landmarks such as the lens or the optic disc. Switching the view is especially important for the less experienced surgeon.
• Different method of establishing position. Like in B-scan ultrasonography, the endoscope's orientation determines the orientation of the image, e.g., simple rotation of the probe between the surgeon's fingers changes what is up or down.
• Different method of moving along the operative field. This is done no more via directing the microscope along the x-y axis with a foot pedal but by moving the endoscope inside the eye.
6 Once the endoscope is introduced through the pars plana, the surgeon observes the inside of the eye and all intraocular maneuvers on the video monitor, not through the microscope.
7 It is as if the surgeon's very eyes were placed inside the patient's eye.
• Different method of changing the magnification. Bringing the endoscope closer to the target makes the image larger, and vice versa.
• Inability to perform bimanual surgery.8
• Difficulty in dealing with major fresh bleeding if it covers the endoscope's tip.
Endoscope use and especially EAV can be much more difficult in ocular traumatology than for other indications and are best left for the surgeon already experienced in endoscopic and trauma surgery.
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