Page 165 - Flexible Robotics in Medicine

Handheld flexible robot with concentric tubes aiming for intraocular procedures 151

technology, the light intensity limitations of bent light pipes and small gauge sizes can be
overcome [8]. However, flexible light pipes do not exist currently.

One of the issues with light pipes is the potential for retinal phototoxicity to occur when the
macula is exposed to light for prolonged periods of time. Typically, surgeons are
recommended to not expose the retina to light for longer than 13 minutes at a time [6].
With a straight pipe, this would mean removing the light pipe from the eye or shining the
light away from the macula, which could impede the speed of the surgery.

6.1.1.2 Chandelier lighting
One solution to the problem of retinal phototoxicity is to use a different type of light
source. A chandelier type light source reduces the risk of retinal phototoxicity by supplying
wide-angle illumination from farther away. This illuminates the entire retina, albeit with a
lower light intensity compared to light pipes. In addition, the chandelier can be used in a
self-retaining system, which can free up the surgeon’s hand for bimanual operations.
However, a single fiber chandelier system often results in a shadow, and thus a two-fiber
system is usually used. This results in one more sclerotomy to be performed and can cause
issues with glare for the surgeon, often in eyes after fluid-air exchange [8].

6.1.1.3 Infusion cannula
The infusion port is used to keep intraocular eye pressure to ease the surgery.

6.1.1.4 Vitrector
A vitrector is a cutter that is used to perform tissue manipulation. Other tools, such as
micro-forceps, may be used for more specific surgical tasks. Laser probes are used to
facilitate photocoagulation in order to treat things like retinal tears. Unlike light pipes,
however, directional laser probes exist [9,10] (Fig. 6.2). These include two tubes: a rigid
outer tube and a precurved nitinol inner tube. Models of tubes with both a laser and
illumination exist. The curvature of the probe can be adjusted manually by moving the
outer sheath via controls on the grip. Intraocular procedures face similar challenges to

Figure 6.2
Example directional laser probes from Synergetics USA, Inc.