With technological advances in phacoemulsification instruments, emulsification and aspiration of the crystalline lens through even smaller incisions are now possible [
The High-Definition Surgical Media Center (HD-SMC) used with a phacoemulsification system.
An example of display by the High-Definition Surgical Media Center (HD-SMC).
Surgical recording devices with the above-mentioned features should be widely used as an educational tool for learners of cataract surgery. However, there are few reports on detailed analysis of these devices and their educational usefulness in training cataract surgeons. In this study, we examined the practical advantages of the new cataract surgery recording devices, SMC and HD-SMC, and verified that these devices are useful educational tools for cataract surgery.
Three hundred and sixty-eight patients (500 eyes) who underwent cataract surgery using Sovereign, Sovereign Compact, or Signature at the Jikei Medical University School of Medicine between April 2008 and July 2014 were analyzed. Surgeries were conducted by three experienced cataract surgeons and three surgeons who were learning the surgical techniques (trainee operators).
Phacoemulsification was conducted using a phacoemulsification system (Sovereign, Sovereign Compact, or Signature) connected to a surgical microscope and a surgical data recording device (SMC or HD-SMC). After surgery, the changes in phaco power, vacuum level, and aspiration rate over time recorded by the SMC or HD-SMC were displayed in graphs synchronized with the surgical video.
An experienced operator was defined as a surgeon who had conducted cataract surgeries in over 300 eyes per year and in a total of over 2000 eyes. A trainee operator was defined as a surgeon who had conducted cataract surgeries in a total of less than 200 eyes. Six surgeons conducted cataract surgeries during the study period: three were experienced and three were trainees.
This study aimed to examine whether SMC or HD-SMC is able to demonstrate the difference in techniques between experienced and trainee operators, to identify inappropriate phacoemulsification techniques from analyzing the graphs, and to elucidate the cause of intraoperative complications such as posterior capsule rupture.
To compare the performance of experienced and trainee operators, 20 cases of cataract with grade 2 nucleus hardness (Emery-Little classification) performed by each of the 6 surgeons were selected. During irrigation and aspiration (IA), the time taken for vacuum to increase from 0 to a plateau and the peak vacuum level were measured three times. The speed of increase in vacuum was calculated by dividing maximum vacuum level by the time to each maximum vacuum (Figure
Changes in vacuum level over time during irrigation and aspiration (IA).
In addition, the three experienced operators analyzed the relationship between the surgical video and surgical parameter data displayed in the overlays in cases, where phacoemulsification of nucleus or aspiration of cortex was difficult, and in cases with intraoperative complications.
The speed of increase in vacuum level is shown in Table
Time to maximum vacuum (time), maximum vacuum level (vacuum), and speed of increase in vacuum level (speed).
Time (sec) | Vacuum (mmHg) | Speed (mmHg/sec) | |
---|---|---|---|
Experienced | 1.49 ± 0.45 |
314 ± 70 | 225 ± 76 |
Operator 1 | 1.54 ± 0.38 | 367 ± 41 |
257 ± 90 |
Operator 2 | 1.32 ± 0.47 | 242 ± 50 |
199 ± 62 |
Operator 3 | 1.62 ± 0.45 | 334 ± 47 |
222 ± 63 |
Trainee | 2.80 ± 0.98 |
300 ± 65 | 115 ± 35 |
Operator 1 | 2.64 ± 0.68 | 321 ± 52 | 126 ± 28 |
Operator 2 | 3.42 ± 1.18 | 311 ± 57 | 99 ± 30 |
Operator 3 | 2.15 ± 1.00 | 268 ± 74 | 120 ± 40 |
Time (sec) | Vacuum (mmHg) | Speed (mmHg/sec) | |
---|---|---|---|
Trainee Operator 1 | |||
1–20 (operations) | 2.64 ± 0.68 |
321 ± 52 | 126 ± 28 |
21–40 (operations) | 1.54 ± 0.39 |
306 ± 29 | 208 ± 44 |
41–60 (operations) | 1.50 ± 0.26 |
297 ± 32 | 202 ± 36 |
Intragroup comparison was also conducted for the group of experienced operators and the group of trainee operators. In the group of experienced operators, time to reach maximum vacuum and speed of vacuum increase were not significantly different between operators, but maximum vacuum was significantly lower in Operator 2 compared to Operators 1 and 3 (both
For Trainee Operator 1, the time to reach maximum vacuum and speed of increase were
Analysis of the graphs recorded by SMC revealed inappropriate phacoemulsification techniques. The relationship between SMC parameter data and surgical video is demonstrated in representative examples below.
The correct method to fracture the nucleus is first to embed the phaco tip into the nucleus with a short blast of phaco, then stop phaco power, and engage the nucleus under vacuum mode (Figure
Nucleus fragmentation technique. (a) Correct nucleus fragmentation technique. (b) Case 1, inappropriate nucleus fragmentation technique.
When cortex aspiration is executed smoothly, vacuum increases steeply reaching a high level within a short time (Figure
Aspiration of cortex. (a) Appropriate cortex aspiration technique. (b) Case 2, inappropriate cortex aspiration technique.
In trenching, nonoccluded aspiration is usually conducted so that the phaco tip does not penetrate the nucleus; hence the vacuum level does not increase. In Case 3 (Figure
Case 3, trenching performed by trainee operator.
The causes of intraoperative complications including posterior capsule rupture were examined by analyzing SMC data.
Accidental aspiration of the posterior capsule during aspiration of cortex.
In SMC and HD-SMC, users can choose any method to display the system data such as phaco power, vacuum level, and aspiration rate. In other words, it is possible to display only those data that are necessary. The format of presentation can be selected either as line graphs (Figure
Conventional video overlay systems can only display phaco power, vacuum, and aspiration rate of an instant. Therefore the greatest merit of SMC and HD-SMC is the visualization of changes in various parameters over time. When the latest SMC is connected to Signature, the state of foot pedal control can also be visualized, which allows better understanding of the condition of the phacoemulsification device and the operator’s manipulations.
Previous reports on cataract surgery education described surgical training using simulations or the necessity of feedback in cataract surgical education [
First, we examined whether the surgical recording devices are capable of showing the differences of technical competence between experienced and trainee operators, focusing on the changes in vacuum level during IA. Experienced operators and trainee operators differed significantly in the time taken to reach maximum vacuum and the speed of increase in vacuum level. This difference is also illustrated in Case 2. Because of the lack of experience in cataract surgery, trainee operators are not skillful in operating the foot pedal and hence are unable to control the increase in vacuum by depressing the foot pedal. The SMC recordings showed that trainee operators did not depress the foot pedal sufficiently at the beginning and increased the depressing slowly thereafter. Moreover, surgical videos showed that experienced operators ensured that the IA tip was occluded. Therefore, use of SMC revealed that, in addition to foot pedal control, whether the IA tip is properly occluded also contributes to the difference in speed of vacuum increase.
For Trainee Operator 1, after the first 20 operations, she underwent technical retraining using the SMC aiming to perform IA more effectively. Thereafter, the mean time to reach maximum vacuum, maximum vacuum, and speed of vacuum increase were determined for every 20 consecutive operations. The results showed that as the number of operations increased, the time to reach maximum vacuum was shortened and the speed of increase was improved. These findings imply that, through instructions using the SMC, the operator achieved appropriate pedal control and proper occlusion of the IA tip.
Therefore, the time to reach maximum vacuum and the speed of increase in vacuum may be regarded as indicators for evaluation of the skillfulness of handling the operation device. Educating trainees on the status of pedal control and occlusion of the IA tip based on the values of the above parameters is useful in training surgical techniques.
Using SMC or HD-SMC, inappropriate phacoemulsification techniques were detected; most of the cases were performed by trainee operators.
In Case 1, during nucleus fragmentation, the operator generated ultrasound while trying to engage the nucleus. With the phaco power turned on, the nucleus continued to be fragmented, and it was difficult to stabilize the nucleus with the phaco tip. After the surgery, we reviewed the SMC records with the operator. We found that the operator did not have a good understanding of the principle of nucleus fragmentation, and, during routine surgeries, he was not able to stabilize the nucleus properly and had trouble with nucleus fragmentation. After reviewing the surgical technique using the SMC overlays, he generated ultrasound while embedding the phaco tip into the nucleus; once inside the nucleus, he engaged the nucleus on vacuum mode only. Using this method, he succeeded to conduct nucleus fragmentation reliably.
Case 2 was a case in which cortex aspiration was not smooth. The vacuum curve (arrow 1) increased slowly and reached a low maximum level. The reason was that the operator had not acquired the skills to control the foot pedal and to predict the vacuum response to pedal depression. Worried about accidentally aspirating the capsule, he depressed the foot pedal hesitantly.
Moreover, to increase the vacuum effectively, the IA tip opening has to be occluded properly. The video revealed that the IA tip opening was not occluded sufficiently, which resulted in inadequate increase in vacuum. After viewing the SMC recording, the operator was able to depress the foot pedal stronger than before and ensure that the tip opening was well occluded, achieving more efficient vacuum increase.
In Case 3, a trainee operator performed trenching. Even during trenching, vacuum continued to increase (arrow). Under this condition, nonoccluded aspiration cannot be obtained. In order to perform surgery safety, the operator must ensure complete open aspiration. In addition, decreasing the vacuum setting reduces the risk when occluded aspiration occurs. This case illustrates the usefulness of SMC in reviewing surgical technique and set values for the machine.
By viewing surgical videos, it is possible to have general idea about basic techniques such as manipulation of the hand piece or the hook. However, detailed operations such as the pressure applied to the foot pedal, the intensity of ultrasound generated, and their timing cannot be learnt from conventional surgical videos.
When an operator has problem with performing cataract surgery but does not know the reason, use of the SMC allows the operator to visualize his/her own surgical technique and to compare his/her techniques with the correct techniques. It is easy to comprehend which surgical techniques require improvement. The SMC is thus useful in training surgical techniques and further upgrading of surgical skills.
Moreover, various complications including posterior capsule rupture tend to occur during training. Case 4 illustrates the occurrence of posterior capsule rupture during surgery performed by a trainee operator. The SMC recording clearly showed that posterior capsule rupture was caused by a surge. Using conventional recording devices, one can visualize the occurrence of posterior capsule rupture but cannot understand why it happened. Therefore, there is a possibility that the same complication may occur again in future surgeries. However, reviewing the SMC recording with the operator revealed that the operator lacked knowledge on surge. Taking this opportunity, the operator understood the importance of foot pedal control for surge prevention and was able to put it in practice thereafter. Thus, this case demonstrates that SMC is useful for analyzing the cause of intraoperative complication of posterior capsule rupture and for improving surgical technique.
The present study had a limitation. We used the time taken to reach maximum vacuum and the speed of increase in vacuum as parameters to indicate the technical competence of operators. We hypothesized that skillful control of the foot pedal and timely occlusion of the phaco tip are reflected by a shorter time to reach maximum vacuum and higher speed of vacuum increase. However, further studies are required to investigate the validity of these parameters.
In the present study, use of SMC or HD-SMC that shows the time courses of phaco power, vacuum, and aspiration rate as well as the state of foot pedal depression superimposed on surgical video allowed more detailed and objective assessments of surgical techniques compared to conventional video overlays. The SMC was able to demonstrate the differences in techniques between experienced and trainee operators, detect inappropriate phacoemulsification techniques by analyzing the graphs, and elucidate the cause of intraoperative complication. Since this recording device allows the review of cataract surgery techniques and identification of the causes of intraoperative complications, it is a valuable tool for educating trainee surgeons on cataract surgery.
The authors declare that there is no conflict of interests regarding the publication of this paper.