In this study, we evaluated and compared the efficiency and safety of the 27G, 20,000-cpm and 27G, 10,000-cpm vitreous cutters through the retrospective analysis of the records of 40 eyes of 40 patients with ERM who underwent vitrectomy. The results suggested that the 27G, 20,000-cpm cutter has the same safety profile as that of the 27G, 10,000-cpm cutter but is slightly more efficient.
In a previous non-clinical study conducted using swine vitreous, the 27G, 20,000-cpm cutter was reported to aspirate more vitreous per unit time than that of the 27G, 10,000-cpm cutter [12]. However, the efficacy of the 27G, 20,000-cpm cutter has not been evaluated in actual clinical practice. Regarding complications, there have been reports of complications associated with 27G vitrectomy [14]. However, there are no reports on the comparison of the complications associated with use of the 27G 20,000-cpm cutter or the 27G 10,000-cpm cutter.
In the present study, the mean duration of surgery in the 20,000-cpm group was significantly shorter (p = 0.047, Table 2) than that in the 10,000-cpm group. The 10,000-cpm cutter has a single-blade structure, whereas the 20,000-cpm cutter has a dual-blade structure. The 20,000-cpm cutter achieves 20,000 cpm because its inner cylinder drives the dual-blade structure 10,000 times.
In non-clinical studies, the 27G dual-blade cutter has been reported to achieve a higher aspiration flow rate in swine vitreous than that of the 27G single-blade cutter [12]. The duty cycle of the single-blade cutter decreases as the cut rate increases, resulting in a decrease in vitreous aspiration flow. However, the duty cycle of the dual-blade cutter does not decrease as the cut rate increases, resulting in an increase in vitreous aspiration flow. In the present study, the significantly shorter duration of vitrectomy in the 20,000-cpm group than in the 10,000 cpm group may be attributable to the differences between the structures of these vitreous cutters.
In the present study, one patient in the 10,000-cpm group showed vitreous hemorrhage 1 day after surgery. However, no postoperative complications were observed in the 20,000-cpm group. None of the patients in both groups showed intraoperative retinal tear or postoperative retinal detachment. The beveled-tip cutters used to treat the patients in both groups have been reported to have a more proximal mean aspiration flow angle than flat-tip cutters [13], which may mitigate retinal movement during aspiration. This may have contributed to the absence of intraoperative retinal tears or postoperative retinal detachments in both groups. The duty cycle of the dual-blade cutter does not decrease even when the cut rate is increased; thus, its suction flow rate is more stable than that of the single-blade cutter [12]. Therefore, the 20,000-cpm cutter is expected to be associated with a lower rate of complications, such as iatrogenic retinal tear or rhegmatogenous retinal detachment, than those of the 10,000-cpm cutter. However, there were no significant differences in the occurrence of complications between the two groups in the present study. This may be because the postoperative follow-up period was short, and both intraoperative retinal tear and retinal detachment are rare complications.
As expected, there was no significant difference in wound suturing between the two groups. Wound size was the same for patients treated using the 20,000-cpm cutter and those treated using the 10,000-cpm cutter.
Limitations
This study had some limitations. First, this was a retrospective study; hence, the conditions of the patients in the two groups were not rigorously standardized. Second, evaluation of the duration of vitrectomy may not have been rigorous because it was done using video recordings of the surgeries. However, the average duration of each surgery, which was independently recorded by two ophthalmologists (YM and YD), was calculated. Third, although there were statistically significant differences between the efficiency of the 27G 10,000-cpm and 20,000-cpm cutters, the sample size of this study was relatively small.
This study had several strengths as well. As this was not a prospective study, bias attributable to the discretion of the surgeon was excluded. In addition, since the surgeries were performed by a single surgeon, there is a very low possibility of inconsistencies in results owing to variations in technique.