Room setup. (a) Endoscopy unit placed on the opposite side of the surgical microscope in relation to the patient’s bed. The setup should allow the surgeon to quickly switch from the endoscopic view to the microscope view without having to turn much his/her head (b, c)
Focusing the endoscope and determining what is superior and inferior on the monitor screen prior to its introduction into the globe through the sclerotomy can more quickly familiarize the surgeon with controlling the orientation of the intraoperative view, which is crucial for navigating the posterior segment (Fig. 11.2). Since the light source and camera are in the same axis, shadowing is also eliminated and awareness of instruments’ location within the globe therefore relies on monocular clues such as the size of landmarks, intensity of illumination, and changes in focus. Exploring the posterior pole is learned more quickly because of its distinct landmarks and intuitive maneuvering, while viewing anteriorly may require additional learning time.
Focusing the endoscopic image prior to entering the eye. Note fluid coming out of the 23-gauge cannula (slight left)
Orientation inside the eye is probably the most challenging step in learning vitreoretinal endoscopy. The image on the screen can be turned either by turning the endoscopy probe on the surgeon’s hand or by the circulating nurse turning on the orientation knob at the endoscopy console (Fig. 11.3). For this particular reason, we prefer to use the straight probe rather than the curved one (used mostly for endocyclophotocoagulation through the anterior segment of the eye).
Endoscopic orientation. The surgeon can turn the image at his convenience either by turning the endoscope probe on its hand or asking the nurse to turn the focusing/orientation knob on the endoscopy console. Note that on (a), the 25-gauge cannula is inferior. The image was turned to place the cannula on the superior part of the screen (d)
One of the best ways to overcome some of these challenges is initially separate endoscopic visualization from visualization and use of an instrument in the second hand. Using either the 20-gauge or 23-gauge endoscopy probes, the surgeon should initially use the endoscope primarily for illumination and endolaser during routine vitreoretinal cases. These are both steps that the vitreoretinal surgeon is already comfortable performing with a light pipe and endolaser probe. During these cases, the surgeon can quickly switch from the microscopic view to the endoscopic view in order to get used to the manipulation of the endoscopic probe and become more accustomed with visualization through the endoscope. Although the view is somewhat limited through the smaller diameter probe, the 23-gauge endoscope probe increases the ease of use during 23-gauge surgery cases because one can switch the probe from one trocar to another for better visualization of certain areas. But for the first cases, we recommend using the larger probes (19 gauge or 20 gauge) because of its better resolution and illumination capabilities.
The next level of complexity for the surgeon would include beginning to perform endoscopic retinal laser photocoagulation treatment and endoscopic cyclophotocoagulation treatment. The surgeon needs to control the distance of the probe tip from the retina or ciliary body, the power of the laser setting, and the duration of exposure. Utilizing the endoscopic laser for both retinal photocoagulation and cyclophotocoagulation treatment further increases the comfort level with the endoscopic system. Typically, a power intensity of 0.6 W is utilized for retinal laser, and 0.35 W is utilized for endoscopic cyclophotocoagulation treatment.
Once the surgeon has become familiarized with positioning of the endoscope within the eye and viewing in the eye through the endoscope, the surgeon can then introduce an instrument with the second hand that can be operated under direct endoscopic visualization. Some examples of cases where this may be applied are peripheral vitreous base dissections using the vitreous cutter and removal of the capsule from the ciliary processes after pars plana lensectomy using end-grasping forceps.
In cases of clear media, the surgeon can always switch from looking at the screen to looking through the microscope if one becomes disoriented and it helps repositioning your hands and instruments accordingly.
Another exercise that helps understanding the advantages of using endoscopy for peripheral work at anterior retina or ciliary body is flipping from endoscopy to a wide-angle viewing system using scleral depression. Only with time surgeons will appreciate the level of additional benefits you can get using endoscopy to access this region of the globe.
Without a doubt, the efforts spent by a surgeon to become more familiarized and comfortable with the ophthalmic endoscope will pay dividends in more challenging vitreoretinal cases. It should become part of the regular vitreoretinal armamentarium in operating rooms worldwide. For additional information, a basic teaching video is available at http://www.youtube.com/watch?v=n3R1a9SeB8o.
11.3 Small-Gauge Endoscopy
Although a 23-gauge endoscopy probe was introduced in 2008 (OME 230 LA, Endo Optiks, Little Silver, NJ, USA) and a triple-function (video, illumination, and laser) probe has been commercially available in North America since 2011 (OME 230 SMA EA, Endo Optiks, Little Silver, NJ, USA), very little literature is published on this subject . It allows the visualization of the posterior pole up to the ciliary processes and all the way to the posterior surface of the iris, depending on where the surgeon is aiming the probe, the same way as the larger 19/20 g probes do.
There are a few benefits of the small-gauge probe over the larger ones. Because of its reduced diameter (0.56 mm), it fits inside the standard 23-gauge cannulas (Fig. 11.4). This way you can alternate the view provided by this probe by switching hands and using it in any of the three 23-gauge cannulas for better access of the extreme retinal periphery and ciliary body for a more complete removal of all anteriorly located fibrotic membranes or better visibility of both intraocular lens haptics to determine its proper position in the ciliary sulcus. The surgeon can even rotate its seating position from superior to temporal and switch the infusion line from inferotemporal to supero-nasal to allow better access to tissues located around the 12 o’clock meridian. Switching the 23-gauge endoscope probe from one port to another may also allow a more thorough vitreous shaving around the cannula sites.
23-gauge endoscopy probe (left trocar) and 23-gauge vitrector probe (right) under microscope visualization. Note the sequence of endoscopic view progressing inside the valved 23-gauge cannula until reaching the vitreous cavity (bottom)
When used through the 23-gauge valved cannula systems, it also allows for a much better fluidics control during complicated membrane peeling that often can result in bleeding. Hemostasis is much easier in close chamber environment working only through valved cannulas rather than larger gauge leaky incisions without cannulas.
Another important aspect is that you can use in all complicated indications as you would with the larger probes. This is important because after you passed through the learning curve, you can use exclusively 23-gauge probes without much compromise.
For obtaining a better image on the screen when using the 23-gauge endoprobe, although not required, you can have a stronger 300-W xenon light source (standard is 175 W) and a specific adapter for image magnification (600ZMG, Endo Optiks, Little Silver, NJ, USA).
The limitations of this small-gauge probe include the significantly lower resolution of 6,000 pixels (compared to 17,000 pixels on the high-resolution larger probes) and a narrower field of view of 90° (rather than 140° on the 19/20 g probes) (Fig. 11.5) . For these reasons, we recommend the smaller-gauge endoscopy probe only for more experienced surgeons used to vitreoretinal endoscopic surgery.
(a) Endoscopic image of severe anterior proliferative vitreoretinopathy with the 23-gauge endoscope with the standard adapter (300ZMG, Endo Optiks, Little Silver, NJ, USA). (b) 23-gauge endoscope image of residual nuclear material under the iris in traumatic subluxated cataract. Note that the image is almost double the size with the proper 23-gauge adapter (600ZMG, Endo Optiks, Little Silver, NJ, USA); (c) 19-gauge endoscopic high-resolution image of an intraocular lens (IOL) placed in the sulcus in a case of dropped IOL during previous cataract surgery
11.4 Adult Complex Vitreoretinal Cases Indications
11.4.1 Proliferative Diabetic Retinopathy and Neovascular Glaucoma
The endoscope is a valuable ophthalmic instrument that provides a unique and variable perspective into the posterior segment of the eye. This “third eye” view into the vitreous cavity facilitates the treatment of proliferative diabetic retinopathy with anterior pathology such as anterior hyloidal fibrovascular proliferation, fibrovascular ingrowth post-vitrectomies, cases of neovascular glaucoma due to any of the ischemic retinopathies, and placement of pars plana tube shunt (http://www.youtube.com/watch?v=qY5nvKOM_SU).
18.104.22.168 Endoscopic Cyclophotocoagulation
Endoscopic cyclophotocoagulation is achieved using an intraocular endoscopy to directly visualize and photocoagulate the ciliary processes of the ciliary body in order to decrease aqueous production [18, 56]. In the past, cyclodestructive procedures have been used in the treatment of refractory glaucomas,  end-stage glaucomas,  or in combined surgeries with cataract extraction [20, 57]. The indications for ECP have expanded due to the endoscope’s ability to apply mild laser burns to structures, such as the ciliary processes, that are difficult to visualize and treat using other available techniques.
To apply ECP during cataract surgery, the endoscopic probe is inserted transpupillary through the cataract wound. With the aid of a viscoelastic agent, the probe is positioned between the lens and iris. In this position, the endoscopic laser may be applied to about 8 clock hours of the anterior ciliary body. When the laser application is required in more than 8 clock hours, a second limbal wound must be created.
Following pars plana vitrectomy, the endoscope can also be introduced through the sclerotomy. This technique provides nearly full visualization of the ciliary processes, thus allowing for more comprehensive ECP treatment (Fig. 11.6). However, a second sclerotomy located 6 clock hours from the first port is needed in order to treat 12 clock hours with laser. Observational studies have been conducted on patients with neovascular glaucoma that received 12 clock hours of continuous endoscopic laser treatment at 0.35 W . These studies have shown excellent intraocular pressure control with a low rate of postoperative complications.
Endoscopic ciliary body photocoagulation
Vapor bubbles may form if a patient is heavily pigmented, if the laser power is too high, or if the probe is too close to the ciliary processes. This vapor occurs when aqueous is converted into steam. Preventing this vapor formation is a simple but learned technique. Lowering the laser power and/or distancing the probe from the ciliary processes can easily prevent this problem.
22.214.171.124 Panretinal Photocoagulation (PRP)
When inserted through a pars plana sclerotomy, the endoscope allows for a 360° wide field of view of the peripheral retina. A full view of the retina allows for the extension of panretinal photocoagulation (PRP) from the equator out to the ora serrata, areas that are sometimes difficult to treat using standard endolaser techniques (Fig. 11.7). Visualization of the peripheral retina facilitates the thorough application of retinal photocoagulation in severe ischemic retinal vasculopathies. Since some surgeons may wish to avoid the possibility of significant laser burns from the endoscope’s 810 nm diode, an argon laser attachment is available to provide familiar argon green wavelength treatment.
(a) Endoscopic view of aiming beam during panretinal photocoagulation. (b) Note that the laser can be applied on the retinal periphery all the way to the ora serrata
11.4.2 Cornea Opacities and Anterior Segment Disfiguration
The ophthalmic application of endoscopy has two fundamental advantages: (1) circumventing anterior segment opacities and (2) visualizing anterior structures like the ciliary body and sub-iris space. Bypassing anterior segment opacities, endoscopy is a particularly powerful tool in cases where corneal edema or scarring blocks the standard microscopic view (Fig. 11.8). The endoscopic probe’s flexibility allows for rapid changes in perspective and thus provides unique views of anterior structures. These planes of visualization are not available using the traditional techniques of microscopic vitrectomy . The high magnification and wide field-of-view (ranging from 90 to 140°) offered by the endoscope not only increase the safety of surgical procedures but also facilitate the identification of subtle findings like small retinal breaks or holes.
(a) Central corneal scarring from previous penetrating wound. This eye underwent 23-gauge pars plana vitrectomy with endoscopic peeling of proliferative vitreoretinopathy (b) and epiretinal membrane (c) followed by penetrating keratoplasty, secondary intraocular lens implantation, and silicone oil tamponade
126.96.36.199 Indication: Anterior Segment Opacities
Anterior segment opacities present a variety of obstacles during ophthalmic surgery. Unlike many other vitrectomy techniques, endoscopic vitrectomy remains possible despite anterior segment opacities. In fact, small studies report better visual and anatomical outcomes in eyes treated with endoscopy versus other surgical options using temporary keratoprosthesis to increase visualization .
Visualization for vitrectomy is significantly limited in cases when corneal opacities require penetrating keratoplasty or when intraoperative corneal edema progressively worsens the microscopic view (Fig. 11.8). Generally, this issue is addressed by one of the three treatment options: (1) observation of the posterior segment until corneal opacities clear to allow for uninhibited management, (2) combined surgery wherein implantation of a temporary keratoprosthesis allows for conventional pars plana vitrectomy and a permanent keratoplasty is implanted at the end of the case, or (3)  endoscope-assisted vitrectomy, which circumvents anterior segment opacities and may or may not require subsequent keratoplasty. The appropriate intervention plan depends upon the urgency of posterior segment treatment and the prognosis and availability of a corneal graft. The obtainability of corneal grafts in the USA and Canada is a beneficial luxury; many other nations are not afforded the same convenience .
Temporary keratoprosthesis or endoscopy is advisable for urgent cases where observation of anterior segment opacities is unwise. Indications for these techniques include severe endophthalmitis, intraocular foreign bodies, and acute retinal detachment.
Since corneal grafts are not readily available in the majority of the world, the use of a temporary keratoprosthesis can be limited by its requirement of a graft after vitrectomy. In addition, temporary keratoprostheses may require coordination with corneal surgeons. Ocular conditions that preclude this modality include acutely injured globes with severely deformed anterior segments and underlying ocular surface diseases prone to graft failure such as severe autoimmune keratoconjunctivitis.
In addition to its more extensive list of applications, endoscopic vitrectomy has shown improved anatomical and visual outcomes in small retrospective studies. Chun, Coyler, and Wroblewski compared eight traumatic eyes treated with a vitrectomy aided by temporary keratoprosthesis to nine eyes that underwent endoscopic vitrectomy . The outcome measures included time to surgery, surgical time, visual outcome, and a qualitative assessment of postoperative developments. Though the study’s small sample size limits its statistical power, the report indicated that endoscopy cases had significantly shorter time to surgery (median 14 vs 38 days; p = 0.034) as well as significantly shorter surgical time (median 2.9 vs 8.4 h; p < 0.0005). Eyes treated with temporary keratoprosthesis prior to vitrectomy were observed more conservatively, causing a greater time lapse to occur before the decision was made to intervene with vitrectomy. With endoscopic vitrectomy as part of the armamentarium, surgeons may undertake vitreoretinal intervention without hesitation and with less concern for medical management of the anterior segment opacity.
In the above study by Chun et al., many occult retinal tears in the endoscopy group would have progressed to retinal detachment if observed conservatively. Instead, these tears were discovered and effectively treated. Furthermore, the group treated with endoscope-assisted vitrectomy had lower rates of advanced proliferative vitreoretinopathy (PVR) and postoperative retinal detachments, presumably due to its significantly shorter time to intervention and intraoperative detection of small retinal breaks. Conversely, the keratoprosthesis group had a greater number of cases where membrane peeling and perfluorocarbon were employed. The increased rate of membrane peeling and perfluorocarbon use may be attributed to proliferative vitreoretinal proliferation that may have occurred during the significantly greater time that lapsed prior to surgical intervention. The endoscopic group exhibited a trend towards better visual and anatomic outcomes, but this trend was not statistically significant.
188.8.131.52 Indication: Unique Visualization Planes
Endoscopy is also effective for visualizing and manipulating anterior structures including the posterior iris surface, ciliary bodies, pars plana, ora serrata, and peripheral retina (Fig. 11.5). Using an endoscope, variable visualization planes facilitate anterior vitrectomy, membrane peeling, sclerotomy placement, and diagnostic visualization.
Endoscopic visualization of sutured intraocular lenses (Fig. 11.4), sub-iris and ciliary body abscesses, and anterior PVR precludes aggressive scleral depression, which should be avoided in eyes with recent open globe surgery, unstable intraocular lenses, and filtering blebs [38, 46]. The endoscope also provides in vivo perspectives of structures, without the contortion inherent in techniques that require scleral depression. The multiple direct planes of view offered by endoscopy can provide direct visualization of the traction created by anterior PVR, as opposed to the artificially contorted view of scleral depression observed through the surgical microscope. However, the endoscope does offer a relatively modest field of view and a lack of stereopsis, limitations not presented by a conventional coaxial operating microscope .
Creating a sclerotomy is most likely to be performed atraumatically while under direct visualization. In aphakic eyes where the endoscope can be inserted through a limbal incision, sclerotomies can be created under transpupillary visualization  (Fig. 11.9). Complications during the placement of sclerotomies may include ciliary and choroidal hemorrhage or anterior displacement of the vitreous base and retina. Meanwhile, imprecise sclerotomies may result in subciliary, suprachoroidal, or subretinal placement of the infusion line . The intraocular endoscopic view of sclerotomies can prevent such complications.
Patient with severe anterior segment disfiguration. Endoscopic view. (a) 25-gauge sclerotomy was attempted to be placed 3 mm from limbus in this pseudophakic patient. Note that the blade was going to penetrate through the ciliary processes. (b) Blade was retroplaced at 4 mm from limbus, at the anterior pars plana. (c) 25-gauge cannula introduction. (d) Cannula placed without additional trauma to anterior structures
The maneuvers unique to endoscopy also extend a surgeon’s tissue removal capabilities. For instance, even in phakic eyes, the endoscope’s flexibility allows for vitreous removal from sclerotomy sites and from the posterior capsule. The view of subretinal space made possible by the endoscope allows for the performance of tasks, such as removing migrated subretinal perfluorocarbons or silicon oil, that are challenging in traditional vitrectomy. Similarly, the endoscope’s maneuverability allows subretinal bands to be visualized and approached. Maneuvers only possible with an endoscope are of use when preventing retinal slippage during fluid/air exchanges .
Intraocular lens (IOL) sulcus fixation is also another valuable indication for endoscopy . It allows precise placement of IOLs on the ciliary sulcus, avoiding trauma to the ciliary processes and posterior surface of the iris. Appropriate passage of sutures, or placement of forceps or small-gauge cannulas in the sulcus for the newer IOL fixation techniques, is directly visualized (Fig. 11.10). It can also be used as a diagnostic and therapeutic aid in eyes with previous complicated cataract surgery with chronic cystoid macular edema and potentially malpositioned IOL. It provides more reliable information about the IOL haptic position than the current ultrasound biomicroscopy (UBM) images.
Intraocular lens (IOL) fixation using endoscopy. (a) Luxated IOL. (b) Suturing the IOL haptic. 26-gauge needle placement in the sulcus (c) guided by endoscopy (d). (e) Passing the 10.0 prolene needle inside the 26-gauge needle for proper suturing in the sulcus. (f) Centered IOL after scleral fixation. (g) Endoscopic view of IOL haptic sutured in the sulcus. (h–j) Newer sutureless transconjunctival scleral fixation technique using 27-gauge cannulas placed in the sulcus
Finally, the endoscope is a powerful tool in diagnosing cases of severe ocular trauma (Fig. 11.8). When unclear visualization impedes a proper assessment of the viability of the optic nerve and retina, the endoscope’s variable perspective may facilitate the diagnosis and aid in any necessary intervention. In some cases, the endoscopic view could reveal that surgery is futile, thus avoiding any further unnecessary iatrogenic trauma.
11.4.3 Retinal Detachment
184.108.40.206 Primary Retinal Detachment
Vitreoretinal endoscopy can be used for different purposes during primary retinal detachment (RD) repair:
Subretinal Fluid Drainage
Hattori et al.  described a drainage technique using endoscopy to decrease the amount of residual subretinal fluid while avoiding posterior retinotomy and liquid perfluorocarbon (PFC) usage. With endoscopy, the patient’s head can be substantially tilted towards the same side of the retinal breaks allowing for more complete drainage through the primary retinal break without the need for using long silicone soft-tip cannulas in the subretinal space (e.g., Flynn cannula). This technique can also be useful to decrease slippage during fluid-air exchange in giant retinal tear cases.
Often during fluid-air in the presence of intraocular lens (IOL) and posterior capsulotomy, IOL fogging or condensation decreases substantially our view of the retina. Many techniques have been attempted to manage this bothersome obstacle like using humidified air , increasing the anterior chamber temperature , decreasing the temperature of the infused air, dispersive viscoelastic coating of the back surface of the IOL, aiming the infusion line towards the IOL, or simply trying to tilt the eye to allow visualization through the edges of the posterior capsulotomy. But sometimes nothing seems to work well. Sonoda et al.  have described a technique of using the endoscopy probe for direct visualization of subretinal fluid drainage during fluid-air exchange. It can also be used for a more complete PFC removal. The endoscopic view under air is adequate and it bypasses the fogged IOL. It is a valid alternative to keep in mind in this potentially difficult situation.
Finding the Retinal Breaks
The rate of overall undetected preoperative retinal breaks is around 2–7 % . With the current high-technology microscopes and wide-field viewing systems, many of these breaks can be found during pars plana vitrectomy (PPV). Although previous series have shown comparable success rates with either circumferential scleral buckling alone or in combination with PPV for these cases of unseen retinal breaks [45, 53], many surgeons around the world are becoming more and more accustomed to manage primary RD with PPV alone. A recent report by Jackson et al. on 3,403 eyes operated for retinal detachment between 2002 and 2010 showed that almost 80 % had PPV alone as their primary procedure . Using PFC or even injecting subretinal dye may help finding small peripheral breaks. Kita et al.  reported a series of 20 cases of typical primary pseudophakic/aphakic RDs using endoscopy-guided PPV to detect and treat tiny peripheral breaks without the need for PFC, dyes, scleral depression, or anterior segment manipulations such as posterior capsulectomy, pupil stretch, or IOL removal. Using only endoscopy and no other adjuvant, they were able to find and treat the breaks in 95 % of the cases in their series (Fig. 11.11).
Using endoscopy to find retinal breaks. Tiny retinal hole shown by endoscopy (a) responsible for a retinal redetachment not seen during previous surgery using wide-angle viewing system and perfluorocarbon liquid (b)
220.127.116.11 Complex Retinal Detachment
Anterior Proliferative Vitreoretinopathy
Several cases of rhegmatogenous retinal detachment may present with anterior proliferative vitreoretinopathy (PVR) . Cellular proliferation and contraction at the vitreous base may contribute to multiple retinal redetachments and traction on the ciliary body . Anterior PVR is more common in post-trauma, younger patients, uveitis history, and long-lasting RDs. In many of these cases, corneal transparency, small pupil, posterior synechiae, and fibrotic anterior/posterior capsule may decrease visibility and further increase the difficulty of such surgeries. Vitreoretinal endoscopy in this setup is very instrumental because it allows proper visualization of the anterior structures behind the iris and facilitates the removal of some of the fibrotic tissues in this area  (Fig. 11.12).
Endoscopy and anterior PVR. (a) Anterior PVR covering the entire ciliary body in this aphakic eye. Note that the 25-gauge cannula on the left is under the fibrotic sheath. (b) Anterior PVR dissection using the 25-gauge vitrector probe. (c) Anterior PVR peeling with 25-gauge end-grasping disposable forceps. (d) Anterior PVR bimanual dissection
The one important limitation in our instrumentation is that all commercially available vitreoretinal forceps, scissors, picks, and vitrectors have straight shaft. To reach the anterior vitreous base with them is rather cumbersome. Using disposable small-gauge instruments, it allows the surgeon to curve the straight shaft of the forceps or vitrector probes, up to a limit, to try to overcome the anatomical barrier of reaching this area (Fig. 11.13).
Bent 23-gauge vitrector (a) for peripheral proliferative vitreoretinopathy shaving under endoscopy (b)
Another limitation is the fact that the surgeon needs to hold the endoscope probe in one hand so only one hand is free for dissection. We have tried to have the assistant holding the endoscope to allow for bimanual peeling of anterior PVR membranes but this technique is rather demanding and hard to reproduce safely (Fig. 11.12).