Introduction
Divide and conquer (D&C) and phaco-chop are two popular techniques used in phacoemulsification. The latter is estimated to reduce phaco energy by up to one-third, making it desirable for denser nuclei [1]. No phaco machine offers a direct measure of energy delivered during phacoemulsification; instead relying on the platform’s calculations. Herein, we report a mini-systematic review to examine the comparative ultrasonic requirements for phaco-chop and D&Q techniques in standard-incision phacoemulsification.
Methodology
This review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [2] (Fig. 1). Inclusion and exclusion criteria are outlined in Table 1. Pubmed and EMBASE were searched from their incision through May 10, 2022. The search strategy included combinations of the keywords “phaco [Title/Abstract]” and “chop [Title/Abstract]” and “divide and conquer [Title/Abstract]”. Additional studies were screened by reviewing reference lists of relevant studies. The Scottish Intercollegiate Guidelines Network (SIGN) tool was used for assessing methodological quality of included studies [3]. Risk of bias was assessed using the methodological index for non-randomised studies (MINORS) criteria [4]. The following parameters were analysed: phacoemulsification machine, cataract grade, effective phaco-time (EFT), phaco-time (PT) and phaco energy.
Fig. 1.
PRISMA flow-diagram showing the selection of included studies.
Table 1.
Studies selection criteria and PICOS question.
| Inclusion | Exclusion | |
|---|---|---|
| Participants | Adult humans with cataracts | Deceased/cadaveric studies |
| Intervention | Standard-incision phacoemulsification surgery | Micro-incision surgery |
| Femto-second laser | ||
| Manual small incision surgery | ||
| Extracapsular cataract extraction | ||
| Comparison/control | Phaco-chop versus divide-and conquer phaco technique | |
| Outcome | Mean phaco time, effective phaco time, absolute phaco time, phaco energy | |
| Studies | Prospective studies; retrospective studies; cohort studies | Studies without comparative nuclear density. Other designs e.g. Commentary, opinions, data based on meetings, non-comparative studies |
| Other | English language; full-texts | Other language; abstracts only |
Results
Description of included studies
Of the seven studies included three were published from Egypt [5–7], and the remaining studies were from the UK [8], Denmark [9], Turkey [10] and India [11]. In total, our review comprised a pool of 692 eyes. Sample sizes ranged between 30 and 120. The mean cataract grade ranged from N1.7 to N3.9 (LOCS) and 2.8–2.9 (emery scale). Where stated, five different phacoemulsification units were used.
Risk of bias
Six studies were prospective, comparative studies (Supplementary Table 1). One study reported the results of two separate arms: (1) a pilot, retrospective study and (2) a prospective comparative study [8].
Two studies were rated as having a high risk of bias and four studies were deemed to have a low risk of bias (Supplementary Table 2). For the aforementioned dual study [8], the retrospective arm was deemed to have a high risk of bias, and the prospective arm to have low risk of bias [8]. The above should be taken into consideration when interpreting our findings.
Summary of findings
Seven studies reported mean EPT [5–11]. A statistically significant reduction in EPT with phaco-chop technique was universally reported. This was across cataract grades 1–3. Mean PT was reported in three studies [5, 8, 10]. In all the studies a reduction in mean PT was statistically significant in favour of phaco-chop technique (Table 2).
Table 2.
Summary details of studies comparing the energy requirements of phaco-chop and divide-and-conquer phacoemulsification.
| Study | Year | Machine | Technique | Mean cataract grade | Mean effective phaco time (s) | Mean phaco time (s) | Mean phaco energy/power | Findings |
|---|---|---|---|---|---|---|---|---|
| El-Sobky et al. [5] | 2016 | Geuder Megatron G | PC (n = 25) | 2.5 (LOCS III) | 12.6 | 18 | – | Reduced phaco-time (p < 0.001) and EFT (p < 0.001) for phaco-chop technique |
| DQ (n = 25) | 2.6 (LOCS III) | 19.9 | 27.7 | – | ||||
| El-Din Farahat et al. [6] | 2016 | Geuder Megatron s3 | PC (n = 15) | 3 (LOCS III) | 22.57 | – | – | Reduced EFT (p < 0.001) for phaco-chop technique |
| DQ (n = 15) | 3 (LOCS III) | 48.47 | – | – | ||||
| Elnaby et al. [7] | 2008 | Geuder Megatron G | PC (n = 7) | N1 (LOCS III) | 14.57 | – | 1559.14 J | Reduced EFT (p < 0.033) for phaco-chop technique |
| DQ (n = 8) | N1 (LOCS III) | 21.62 | – | 2313.87 J | N1: 33% reduction in phaco energy using phaco-chop | |||
| PC (n = 14) | N2 (LOCS III) | 17.5 | – | 1872.5 J | N2: 22% reduction in phaco energy using phaco-chop | |||
| DQ (n = 13) | N2 (LOCS III) | 22.38 | – | 2395.15 J | N3: 7% reduction in phaco energy using phaco-chop | |||
| PC (n = 4) | N3 (LOCS III) | 34.25 | – | 3664.75 J | No statistical analysis of phaco energy | |||
| DQ (n = 4) | N3 (LOCS III) | 36.75 | – | 3932.25 J | ||||
| Wong et al. [8] | 2000 | Series 20,000 Legacy phacoemulsification unit (Alcon Laboratories) | ||||||
| (a) | PC (n = 75) | 1.52 (LOCS) | 23.4 | 84 | 26.90% | Reduced mean phaco time (p < 0.0001) and EFT (p < 0.0001) for phaco-chop | ||
| DQ (n = 50) | 1.66 (LOCS) | 58.8 | 204 | 28.60% | No difference in mean phaco power (p = 0.0701) | |||
| (b) | PC (n = 62) | 1.7 (LOCS) | 17.4 | 72 | 25.30% | Reduced mean phaco time (p < 0.001) and EFT (p = 0.01) for phaco-chop technique | ||
| DQ (n = 55) | 1.7 (LOCS) | 50.4 | 144 | 35.10% | Reduced phaco energy for phaco-chop technique (p < 0.001) | |||
| Storr-Paulsen et al. [9] | 2008 | Storz Millennium phacoemulsification machine (Bausch & Lomb, Inc.) | PC (n = 60) | 2.9 (Emery scale) | 3.98 | – | – | Reduced EFT (p < 0.0001) for phaco-chop technique |
| DQ (n = 60) | 2.8 (Emery scale) | 12.79 | – | – | ||||
| Yigit et al. [10] | 2019 | Bausch & Lomb Stellaris, Inc | PC (n = 50) | 3.7 (LOCS III) | 22.54 | 41.2 | 30.20% | Reduced mean phaco time (p = 0.013) and EFT (p = 0.024) for phaco-chop technique |
| DQ (n = 50) | 3.9 (LOCS III) | 30.62 | 63 | 32.90% | No difference in mean phaco energy (p = 0.0701) | |||
| Prasad et al. [11] | 2020 | – | PC (n = 50) | 2 (LOCS III) | 16.58 | – | – | |
| Reduced EFT (p < 0.0001) for phaco-chop technique | ||||||||
| DQ (n = 50) | 2 (LOCS III) | 27.12 | – | – |
a retrospective, pilot study, b prospective study, DQ divide-and conquer, EFT effective phaco-time, J joules, LOCS Lens Opacities Classification System, PC phaco-chop, PT phaco-time, s seconds.
Mean phaco power was reported in three studies [7, 8, 10]. The study findings were inconsistent. In the retrospective, pilot study by Wong et al., no significant difference in phaco power was observed for mean cataract grade N1.5–1.7 [8]. In their prospective study, a statistically significant reduction in phaco power was reported with phaco-chop technique for mean cataract grade N1.7 [8]. Yigit et al. reported no significant difference in mean phaco power for cataract densities N3.7–3.9 [10]. Elnaby et al. reported mean phaco energy in joules for nuclear densities N1–N3 [7]. No conversion factor for this calculation was stated. An increase in energy with increasing cataract density was observed for both techniques, however this was more pronounced with phaco-chop. No statistical analysis was performed.
Discussion
In this mini-systematic review, we showed a reduced EFT and PT with phaco-chop technique did not translate to a consistent reduction in phaco energy. Our results suggest the energy benefits of phaco-chop are less evident with denser nuclei. However, our review is limited by the low number of studies included. Furthermore, differences in surgeon experience, phacoemulsification units and parameters makes a direct comparison between the chosen articles difficult. Other factors, such as the tip design, and the surgeon’s technique can also affect the amount of energy delivered to the eye [12].
Conclusion
The phaco-chop technique reduces EFT and PT, but not total phaco power. Our motivation for this systemic review is an academic exercise, rather than a need for improvement. Ultimately, the same density of cataract needs to be extracted. Further prospective studies on dense nuclei, employing accurate algorithms for total phaco energy, are required to support the lack of current scientific evidence present in the literature.
Disclaimer
This article should not replace individual clinical judgement. The views expressed in this mini-systematic review are the views of the authors and not necessarily from the host institution.
Supplementary information
Author contributions
OY performed manuscript screening, data extraction and analyses, protocol design and manuscript preparation. DL contributed and reviewed the manuscript.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
The online version contains supplementary material available at 10.1038/s41433-023-02616-7.
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