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Table 1 Ophthalmic microendoscope and surgical microscope ophthalmoscopy

From: Endoscopic vitreoretinal surgery: principles, applications and new directions

Microendoscopes Surgical microscopes
Non-stereoscopic imaging: distances to tissue targets are judged by non-stereoscopic cues including tissue target size and structure, motion parallax and changes in tissue color or estimated texture Full stereoscopic imaging: precision of depth judgement depends on the surgeon’s stereoacuity
Larger or smaller fields of view and laser spot sizes are produced by moving the probe tip farther from or nearer to tissue targets, respectively; lens-based microendoscopes currently provide higher resolution images than fiberoptic devices Non-contact ophthalmoscopic lens systems offer wide-field, high resolution imaging; contact systems can increase magnification and resolution in part by eliminating corneal aberration and reflection
Magnification is increased by moving the intraocular probe closer to a tissue target, creating new detail in intraocular optical images and their digital representations on a video monitor (the surgeon increases both ophthalmoscopic image magnification and resolution) Increasing operating microscope magnification can improve visualization of information in an ophthalmoscopic image but it cannot create detail that wasn’t already present in the image (the surgeon magnifies their view of the ophthalmoscopic image without increasing its resolution)
Fine uveovitreoretinal detail undetectable with extraocular ophthalmoscopy can be imaged by moving the microendoscope probe close to a tissue target. Resolution in this ultra-high magnification optical image is reduced when it’s displayed on a digital monitor dependent on multiple factors including vitreous cavity clarity and the number of optical fibers in a fiberoptic image guide (Fig. 2) Visible vitreoretinal tissue detail is limited by optical aberrations in ocular media and ophthalmoscopic lenses and by ocular pathology that interferes with transpupillary ophthalmoscopy. Adaptive optics technology that could correct for ocular media aberrations is not available in contemporary operating microscopes
Images can be viewed on the microendoscope’s dedicated small screen display or larger high definition operating room monitors Images can be viewed through the microscope’s eyepieces. Alternatively, video cameras can transfer bilateral microscope images to heads-up devices such as high definition, three-dimensional monitors