Abstract
Background:
3D heads-up visualization systems are aimed to improve the surgical experience by providing high-resolution imaging. Objective of our study is to analyze, over a long-time span, the grade of satisfaction and safety of day-to-day 3D surgery compared to standard surgery and to investigate the technical distinctiveness between the heads-up systems currently in use.
Methods:
In this retrospective observational case series. we reviewed all surgical records of our ophthalmology-dedicated operatory rooms since the arrival of 3D heads-up viewing system, in November 2017. In particular, we compared the procedural complications of 3D-equipped operatory room (3DR) with the standard microscope operatory room (2DR). Moreover, a satisfaction questionnaire was administered to those surgeons shifting on both rooms to test their preferences on seven specific parameters (comfort, visibility, image quality, depth perception, simplicity of use, maneuverability and teaching potential).
Results:
5483 eye surgeries were considered. 2777 (50.6%) were performed in 3DR and 2706 (49.3%) in 2DR. Procedural complication rate was comparable in 3DR and 2DR, also when considering different subtypes of surgery. Twelve surgeons (100% of our surgery team) participated in our satisfaction survey, expressing highest satisfaction score for 3D when applied in retina surgery. For cataract surgery, 3D scored best in all the parameters except for facility in use and depth of field perception.
Conclusion:
Long-term day-to-day use of 3D heads-up visualization systems showed its safety and its outstanding teaching potential in all ophthalmic surgical subtypes, with higher surgeons confidence for retina and cataract surgery.
Keywords
Introduction
Weinstock and Desai 1 reported on the first cases of anterior segment surgery using a 3D heads-up technology. The revolutionary idea was to switch from a traditional surgical microscope to a heads-up vision of a wide-screen monitor. The stereopsis was guaranteed by means of two cameras affixed to the operating microscope sending signals to a central processor. Eckardt 2 reported the first use in retina surgery and then their experience on first 400 vitrectomies, showing promising results. 3 From then on, many papers have been reporting favorable experiences using 3D in different surgeries and various pathologic conditions.4–9 All of them shows, in comparison to standard microscope use, similar surgical outcomes but many important advantages: (1) greater resolution even at highest magnification; (2) panoramic viewing with wider visual field; (3) possibility to reduce significantly the endoillumination power; (4) capability of apply digital filters to the image to enhance visibility of a certain tissue or a dye; (5) a more ergonomic position of the surgeon, not being forced by the microscope eyepieces; (6) outstanding teaching potential driven by the 3D image shared among all the theater staff. Noteworthy, in a satisfaction questionnaire published by Romano et al., 10 3D scored significantly higher than 2D in overall satisfaction and in parameters such as comfort, depth perception, simplicity of use, and teaching.
Here we aim to report on our experience after almost 3 years of day-to-day 3D surgery. As we have had the opportunity to work with different 3D products, we will also review specifications and characteristics of the two main 3D systems commercially available to date. To our knowledge, this is the first report on surgical experience with Zeiss Artevo 800®.
Materials and methods
Patients selection and satisfaction questionnaire
We work in a high-volume center with two ophthalmology-dedicated operating rooms (Room A and B). Rooms A and B share the same daily workload, but room A has been equipped with a 3D system since the 1st of November 2017. All of our 12 surgeons shift regularly and equally on 3D room A (3DR) and standard microscope room B (2DR).
For the present institutional retrospective study, we reviewed and included all the surgical reports of patients undergoing a surgical procedure in the 3DR and 2DR from the 1st of November 2017 to the 1st of March 2020. Type of surgery and procedural complications (defined as all complications occurred during the surgical procedure) were recorded and compared among groups. All data were grouped and treated anonymously, following local privacy regulations. All the procedures adhered to the tenets of the Declaration of Helsinki.
In addition, all of our surgeons filled in a seven-questions satisfaction questionnaire. We used the same parameters published previously by Romano et al. 10 but, differently, we asked to rate these parameters in comparison with the standard microscope surgery, as follows: Better/Worse/The same or Non evaluable (when the surgeon does not perform such a type of surgery).
The questionnaire was proposed for types of surgery where we could provide wide experience (retina, cataract, cornea), plus we introduced the transversal category “trauma” in order to consider the important setting of urgency condition.
3D Heads-up technologies review
Two systems are commercially available for 3D heads-up surgery: Ngenuity® 3D Visualization System® by Alcon (Alcon, Forth Worth, TX, USA) and Artevo 800 System® by Zeiss (Carl Zeiss Meditec, Inc, Jena, Germany).
Ngenuity® has been developed in collaboration with TrueVision company and it is the first system introduced and diffused in ophthalmology since 2010. 1 Zeiss Artevo 800 System® has been introduced in 2019 and, to the time we are writing, there is no literature available.
We experimented both the machines in our daily practice. In particular, we adopted Ngenuity® from November 2017 to January 2020 and Artevo 800® from February 2020 on.
The two systems might seem similar, but actually differ in several aspects of image capturing, processing and rendering.
Image capture
Alcon Ngenuity® is a modular system, composed of a 3D stereoscopic high-definition Image Capture Module (ICM) camera mounted on standard surgical microscope and a mobile workstation. ICM reaches 800 TV lines of resolution, by including a stereo pair of 1-chip cameras and two 3-mega-pixel high-resolution sensors. The camera optics pick up the light from the microscope generating a stereoscopic image, with no need of additional light or energy provided by the system of image capture. The high-resolution sensors are complementary metal oxide semiconductors (CMOS). Compared to standard sensors, CMOS can capture luminosity in a High Dynamic Range (HDR) (i.e. even extreme darkness and brightness), similarly to the range perceived by the human eye. Furthermore CMOS operate high-density integration of logic function on a chip (analog to digital signal conversion rate is of 3 Gb of data/second). The image can be considered as “real-time”, since the time for the ICM to process the captured signal into the onscreen image is, at present, approximately 70 ms of latency.
The amount of light allowed into ICM camera is critical to the depth of field (the increase in the aperture area decreases the depth of field) and can be manually controlled by a specific “Iris Slider”, whose opening should be set between 20% and 60%.
Another advantage is the light levels required to perform surgery. 11 Nonetheless, as the colors rendering is artificial, a white-white balancing before starting surgery is to be regularly performed to obtain realistic colors.
Wide angle viewing system is not integrated and should be added in a modular way. Switching between hybrid and full digital mode requires a separate beamsplitter and manual adaptation of camera settings.
Artevo 800 is by default a digital integrated 3D microscope, optimized for digital visualization performance of the cameras. Ergonomy during acquisition is maximized as the system, including wide-field viewing system and beam splitter, is fully integrated in the microscope head and the surgeon can look even over the microscope head with a reduced “heads-up” angle.
The acquisition core is in the DigitalOptics® microscope, composed of two 3-chip cameras, each with 4K (3860 × 2160 pixel) of resolution. Overall, horizontal resolution is 1000 TV lines. Since the sensitivity of the system is higher than that of human eye, the light intensity required is 10%–20% lower than standard microscope. Remarkably, this is the first heads-up 3D system providing direct color reproduction, thus showing natural colors on the screen.
The contactless viewing system of the fundus is automatically obtained and adjusted with the Zeiss Resight 700, that operate auto-image inversion with InvertertubeTM and integrated focus via Foot Control Panel (FCP).
The acquisition can be obtained in a full digital mode or in a hybrid mode (by using alternatively 3D heads-up or binocular observation). The AutoAdjust TM feature automatically adapts the microscope to changed illumination situation due to beam splitter. Moreover, they relieve the need for a separate keyboard operator, which, on the other hand, is required with Ngenuity®.
Artevo 800 acquisition-to-imaging latency time is below 60 ms.
Image processing (digital visualization)
Ngenuity® image processing is computed by the Embedded Processing Unit (EPU). It is a special computer, integrated onto a mobile cart, containing the proprietary firmware software (TrueWare version 9.5.4®) and specific applications that timely and accurately process the images for storage, manipulation and high refresh rate stereoscopic display (TrueEdit® and TrueMediaTM).
Artevo 800 image processing unit is further compacted and integrated to the monitor cart, with all application included and cable-free attachment aimed to allow larger video displaying and space saving.
Image processing can be optimized by acting on different camera setting, such as hybrid/digital-mode brightness, red/blue amount value (these can also be used as filter options), saturation and light metering.
Image rendering
Alcon Ngenuity® is provided with a 4K (3840 × 2160 pixel of resolution) High-Definition (HD) 16:9 Organic Light Emitting Diode (OLED) 55″ flat panel (LG, Seoul, Republic of Korea), integrated onto the mobile cart. The display receives overlapping images from the EPU and uses passive technology and top-bottom 3D format (with a resolution of 1920 × 1080p for each eye) for 3D imaging.
In detail, the passive technology is a film-type patterned retarder (FPR) technology, which uses a circular polarizer, in order to show a different image for each eye. Left/right polarized glasses allow the left and right images to then be seen by the left and right eyes separately and simultaneously. FPR technology provides imaging on bright screen with less cross-talk, less ghosting, no flickering and less disturbances in case of head tilting than other 3D technologies.
The large 16:9 monitor allows the overlay of key additional information, like imported digital images, intraoperative OCT, cataract assisted functionalities from ORA/Verion or real-time surgical parameters (IOP, infusion pressure, flow rates and laser power) from the DataFusion® software of Constellation Vision System (Alcon).
Artevo 800 relies on a similar 3D passive technology, but it provides a 25% higher resolution on the competitors. The AdVision® software, that integrates overlays such as Callisto data, intraoperative OCT and Phacoemulsification or Vitreo-Retinal surgery parameters. Callisto eye markerless application can provide further cataract assistance functionalities.
Artevo 800 is equipped with circular polarized glasses and Sony LMD-X550MT medical grade 4K (3840 × 2160p) 55″ flat panel in 16:9 format. This technology adds to the former 3D microscopes a significant software improvement, including data transfer speed and cloud connectivity.
Statistical analysis
Data were summarized with the mean ± SD and/or percentage. Statistical calculations were performed with GraphPad Prism version 6.00 (GraphPad Software, San Diego, California, USA). We tested the difference between groups using Chi-squared test, Fisher Exact test, the parametric One-Way ANOVA or Mann–Withney U-test and Kruskal–Wallis test, for the nonparametric variables, as appropriate. All tests were two-side and p-values less than 0.05 were considered significant.
Results
A total of 5483 eye surgeries have been enrolled for this study, divided into 2777 (50.6%) cases performed in 3DR and 2706 (49.3%) cases in 2DR. Surgery types are summarized in Table 1.
Surgery subtypes divided among heads-up 3D room (3D room) and standard microscope room (2D room).
PK: perforating keratoplasty; DALK: deep anterior lamellar keratoplasty; DSAEK: descemet stripping automated endothelial keratoplasty; DMEK: descemet membrane endothelial keratoplasty.
Noteworthy, cataract surgeries were equally distributed into two groups, 1638 (49.8%) and 1648 (50.1%) for 3DR and 2DR, respectively. 3DR presented more retina surgeries, 1059 (65%), than 2DR one, 568 (34.9%). On the other hand, concerning other subspecialties: 26 (7.5%) corneal surgeries have been done in 3DR, while 320 (94.2%) took place in 2DR. Forty-one (33.6%) ophthalmoplasty surgeries have been done in 3DR, while 81 (66.3%) in 2DR. Twenty (7.9%) glaucoma surgeries have been done in 3DR, while 232 (92%) in 2DR. Thirteen (12.7%) strabismus surgeries have been done in 3DR, while 89 (87.2%) in 2DR.
Regarding retina surgery, we recorded six overall procedural complications in 3DR (0.6%) and four (0.7%) in 2DR (p = 0.74). No differences among groups were noted for none of the retina surgery types considered (Table 2). Similarly, also for all the other surgery subtypes we did not record differences in procedural complication rates between 2D and 3D (Table 2).
Procedural complications, defined as all complications occurred during the surgical procedure.
PK: perforating keratoplasty; DALK: deep anterior lamellar keratoplasty; DSAEK: descemet stripping automated endothelial keratoplasty; DMEK: descemet membrane endothelial keratoplasty.
Twelve surgeons (100% of our surgery team) participate in our satisfaction survey (Table 3). Regarding retina surgery, 3D technology scored the majority of preferences over traditional microscope in all the seven parameters. In detail, the 100% of voters indicated a better comfort, visibility and teaching potential. The 90% of voters stated a better image quality with 3D, while only 60% found it easier to use. 3D offered a major depth perception for the 80% of voters and a better maneuverability for the 82% of them.
Satisfaction questionnaire results among our 12 surgeons.
Not all 12 surgeons voted for all four surgery subtypes, as they were requested not to score procedures never performed.
We recorded similar results for trauma surgery (see Table 3 for details). For cataract surgery, 3D scored the majority of voters’ preferences only in comfort, visibility, image quality, maneuverability and teaching potential. For the 67% of voters there was no differences regarding its simplicity of use and for the 33% no differences in depth perception. On the other hand, for the 25% of voters the depth perception was even worse than standard 2D microscope and so was the visibility.
Concerning corneal surgery, 3D was considered better than 2D for visibility (71%), image quality (67%), depth perception (57%) and teaching potential (91%). The 50% of voters found the same comfort and simplicity of use, while the 60% of them felt an equal maneuverability.
Discussion
In this retrospective study we report on our first 2 years of experience using heads-up 3D eye surgery. The overall workload analysis reveals how 3D technology has been mostly used for retina surgery. Such a result is rather unsurprising considering that this viewing system has been developed and commercialized specifically for retina surgery. Interestingly, our data reveal that 3D was the most preferred viewing system in all kind of vitreo-retinal procedures (Table 1). This result is consistent with that recently described by Agranat et al. 12 where they investigate retrospectively one year of 3D experience reporting its use in a wide variety of retinal procedures. Moreover, we found no differences in procedural complications for 2D and 3D retinal surgeries (Table 2). Similar safety results have been already showed by many small retrospective studies.4,6,7–13 Our work, reporting for the first time comparison data from large number of cases, confirms this vital aspect.
Heads-up 3D retina surgery scored the best results in the satisfaction questionnaire, gaining more than the 80% of preferences over 2D one in almost all the parameters (comfort, visibility, image quality, depth perception, maneuverability and teaching potential). Interestingly, only 60% of our surgeons found 3D simpler to use, while 30% of them found it as simple as 2D and 10% of them found it less simple to use. A similar result is reported by Palacios et al. 13 In their satisfaction questionnaire the sole parameter that did not score in favor of 3D was “technical feasibility”. This could be explained by the complexity of the technology itself, that requires multiples settings and provides wide range of customization possibilities to appreciate the most of its potential. In fact, it is relatively common for the first-time users to obtain unsatisfying image on the screen if the system is not properly tuned. This complexity in use may explain the different results of the questionnaire published by Romano et al., 10 where 3D was no superior to former 2D in all the considered features (even if 3D scored higher overall). In fact, their study was conducted at the beginning of “3D era” on a limited number of cases. Moreover, we experience that 3D imaging systems allow an unprecedented advantage for the procedures on the peripheral retina: it maintains the depth of field even at high magnification, together extending the surgeon visual field on the periphery to a width of field not possible for 2D microscope.
Regarding 3D use for cataract surgery, our numbers show its use has been routinely and extensive almost as much as for retina surgery. Safety results are equally satisfying, but the questionnaire reveals that the majority of our surgeon find the 3D procedure equally or even less simple than the traditional microscope. Noteworthy, the 25% of our sample found a worse visibility and less depth of perception when performing 3D phacoemulsification. Berquet et al. 14 recently reported a satisfaction survey also on cataract surgery. Differently they report 3D and 2D scoring the same visual comfort with a slight advantage in surgical fluency when using 3D. We could explain this difference considering that their sample was made of retinal surgeons whilst ours included also anterior segment surgeons. While retina surgeons are used to change continuously the focus plane to make the most of their depth of field (e.g. during peeling maneuvers), cataract surgeons are used to set the focus plane at the beginning of each case and leave it frequently unchanged until the end. Conversely, to make the most out of the 3D system, the focus must be optimized plane by plane also during cataract surgery. As per cornea, glaucoma, strabismus and oculoplastic surgeries, poor literature is to date available.5,8,15,16 Our results reveal a very limited 3D use and our questionnaire data scored similarly to cataract surgery. This probably reflects the same focalization issues abovementioned.
Technically, Ngenuity and Artevo 800 share many similarities, such as the reliance on latest technology image sensors, 3D passive technology, high definition wide screen, filter use and digital processing for imaging enhancement.
Ngenuity modular approach consent adaptability to many surgical microscopes, hence adapting to already equipped surgical rooms. Nonetheless, the optic resolution of 3D imaging relies on the optic of the microscope in use, eventually not the latest update. Conversely, Artevo 800 is itself a 3D microscope, where optic, panoramic viewing, software and applications are entirely built in for optimal 3D imaging. The consistency of mechanical and functional integration of Artevo 800 results in a significant reduction of head up angle during surgery, while the high stack height of Ngenuity module still force the surgeon viewing axis to the side. The complete integration of Artevo 800 also promotes shorter set up time, direct control of microscope functions and data fusion, processing and storage, with easy conversion from 3D to 2D format.
Artevo 800 comes along with a higher resolution (1000 vs 800 TV lines), lower latency time and natural color reproduction. In our experience this is truly appreciable for anterior segment procedures. The Ngenuity OLED screen however has superior quality of deep black levels, maintaining high satisfactory contrast ratio in low light condition.
Both 3D heads up systems offer the benefits of greater magnification viewing and confortable photopic vision, rather than the former mesopic vision of traditional binocular microscopes.
Our retrospective study has several limitations. While the 3D versus 2D groups are numerically similar and surgeons operated in both rooms, surgical subgroups are quite unbalanced, being the 3D room preferred for retinal and cataract surgery. Consequently, other surgeries with a 3D approach are limitedly represented. A comparison between cases treated by using the two heads-up system, Ngenuity and Artevo 800, was not possible in our series, since the experience with Artevo 800 was limited to a shorter period and smaller number of cases and surgeons. However, out of our empirical observation, Artevo 800 emerged for a more real imaging experience with regards of cataract surgery, while on the posterior pole the performance of the two systems appeared quite similar.
In conclusion, our long-term experience with 3D heads-up surgery highlights its safety in all subtype of eye surgeries. Both the two major commercially available systems are overall highly performing. Although for non-retinal surgeries its advantage could be limited, we feel confident to state that nowadays such a technology is a must-have for vitreoretinal-oriented centres, especially in teaching environments.
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
Synopsis
On a long term, the procedural complication rate of 2D and 3D surgery is comparable in all surgery subtypes. 3D surgery highest satisfaction scores are recorded when applied in retina surgery, for its outstanding teaching potential.
