Cataract is the leading cause of reversible blindness and visual impairment worldwide. Blindness due to cataracts is more prevalent in populations with low socioeconomic status and in developing countries compared to developed countries. The sole treatment for cataracts is surgery.^(1,2)

The primary method for treating cataracts involves surgical removal of the lens, which is then replaced with a permanent artificial intraocular lens (IOL). Successful cataract surgery universally enhances vision and quality of life.⁽¹⁾

It is widely recognized that phacoemulsification, a technique involving the ultrasonic emulsification of the lens contents, is considered the gold standard for surgery in developed countries. However, it is important to note that manual small incision cataract surgery (MSICS) with a self-sealing and sutureless incision is still performed in various developing countries with limited resources due to cost constraints. Both phacoemulsification and MSICS deliver excellent visual outcomes.^(1-4)

Nonetheless, even in developed countries, when surgeons encounter mature cataracts, a discussion ensues about the most suitable technique, as several studies recommend the manual technique as the preferred approach in such cases.( ) The literature reports good visual outcomes and comparatively lower complication rates when MSICS is employed for challenging cases, including brunescent cataracts, white cataracts, and cataracts causing phacolytic and phacomorphic glaucoma.^(8-12)

Thus, based on the literature, the authors conducted a systematic review and meta-analysis to compare MSICS with phaco for mature cataracts.

In 1987, Blumenthal et al. were the first to describe the use of an anterior chamber maintainer (ACM) in extracapsular cataract extraction (ECCE) while reducing the incision size. The classic ‘mininuc’ MSICS procedure, as outlined by Blumenthal, involves extensive use of the ACM to perform nearly all steps under positive irrigation pressure. The ACM cannula is self-retained, a side port is created, and a capsulotomy is executed. The scleral tunnel incision is made, and the hydro procedures are initiated. The nucleus is maneuvered out of the eye using a glide, aided by the positive pressure generated by the ACM. Cortex aspiration is carried out through a side port aspirating cannula, while the ACM ensures continuous irrigation. The ACM is only removed after the IOL has been inserted and the incision's integrity is confirmed to be watertight.^(2,18)

Another significant modification to the MSICS technique was introduced later by Ruit et al. They created a 6.5- to 7-mm temporal scleral tunnel with a straight incision, starting 2 mm posterior to the limbus. A side-port incision was made to facilitate further intraocular manipulation. A V-shaped capsulotomy and hydro dissection were performed. Viscoelastic material was injected above and behind the nucleus, subsequently prolapsing into the anterior chamber. An irrigating Simcoe cannula with a serrated surface was inserted below the nucleus, facilitating its extraction through the scleral tunnel. The remaining cortex was manually removed using the same Simcoe irrigation-aspiration cannula. After implanting a polymethyl methacrylate (PMMA) lens into the capsular bag, the unsutured scleral pocket incision was confirmed to be watertight.^(2,19)

As described in the literature, substantial modifications to the MSICS technique include various aspects, such as changes to the incision procedure and advancements in nucleus delivery methods.

Regarding incision variations, Kratz was the first surgeon to move the cataract incision posteriorly from the limbus to the sclera, aiming to enhance wound healing and reduce astigmatism.⁽²⁾ Subsequently, Girard et al. coined the term ‘scleral tunnel’ incision.⁽²⁰⁾ Singer described the ‘frown incision,’ which involved a modified scleral pocket incision curved in opposition to the natural limbal contour. This frown-shaped configuration was designed to minimize wound-induced astigmatism.⁽²¹⁾

Lam et al. developed the sutureless large-incision manual cataract extraction technique, a modification of the manual ECCE technique. This approach was specifically crafted to enable less experienced surgeons in developing countries to safely extract the nucleus through a self-sealing temporal scleral pocket incision. Notable features of this technique include a medium to large scleral pocket incision (8-mm linear length) for safe and efficient nucleus expression, a long sclerocorneal tunnel (4 mm) for a self-sealing, sutureless wound, a posterior incision location (2 mm posterior to the limbus), and a frown-shaped wound configuration designed for astigmatic neutrality. The use of an ACM facilitates the delivery of the nucleus.⁽²²⁾

MSICS employs diverse nucleus delivery methods, including hyperexpression and vis coexpression,⁽²³⁾ the sandwich technique,⁽²⁴⁾ the modified fish hook technique,⁽²⁵⁾ the use of an ACM,⁽¹⁸⁾ an irrigating cannula,⁽²⁶⁾ nucleus trisection,⁽²⁷⁾ nuclear management by snare technique,⁽²⁸⁾ and the Sinskey hook method.⁽²⁹⁾

On the other hand, phacoemulsification was first developed by Charles Kelman in the late 1960s. This technique utilizes ultrasonic energy to vibrate a titanium needle at high frequencies, fragmenting the rigid lens nucleus. The resulting emulsate is simultaneously aspirated from the eye.⁽³⁰⁾

One of the primary advantages of phacoemulsification over purely manual methods is its ability to extract a large nucleus through a small incision of ≤ 3.0 mm. Subsequently, foldable IOLs are implanted through this small incision, which generally can be left unsutured. Advances in technology now allow surgery through mini incisions of 2.2 mm or micro-incisions of ≤1.8 mm. The benefits of small incisions are numerous: topical anesthesia can be used, especially if the incision is made in the peripheral cornea; the surgeon gains better control of the intraocular environment, ensuring greater safety in case the patient moves; structural integrity of the incision is quickly reestablished, requiring fewer physical restrictions after surgery; and smaller incisions minimize alterations of the corneal shape, reducing the risk of astigmatism.⁽¹⁾

Phacoemulsification has been considered the best surgical technique for cataract surgery in developed countries for over two decades. This technique has several advantages such as reducing astigmatism, enabling faster recovery, and allowing for smaller incisions.

However, the effectiveness of MSICS versus phacoemulsification for mature cataracts remains unclear. When determining the optimal surgical technique for cataract surgery, several factors must be considered, including improvement in BCVA, surgical complications, CCT, and surgical duration. These factors are influenced by individual characteristics, including the size and chronicity of the cataract. This systematic review compares MSICS and phacoemulsification as surgical techniques for cataract surgery. By analyzing and evaluating this approach, a better understanding of the advantages and disadvantages of each technique can be achieved, leading to a more comprehensive discussion of the various options available for cataract surgery.

We conducted a systematic review and meta-analysis of 5 studies and 577 eyes to compare the effectiveness of MSICS and phacoemulsification for mature cataract surgery. We found that the mean age of patients in both groups was similar, with the majority being 55 years or older when the research studies began. The results showed that the MSICS group had lower rates of ECL during surgery and a shorter surgery time compared to the phacoemulsification group. However, there was no statistically significant difference in BCVA, CCT, and complications between the two groups.

The analysis showed no significant difference between groups in BCVA better than 20/60 in the postoperative period, consistent with results from three randomized, prospective studies conducted in developing countries comparing phacoemulsification with MSICS. These studies demonstrated that MSICS is comparably effective to phacoemulsification, achieving excellent visual outcomes. These findings indicate that both techniques yielded similar BCVA outcomes in the postoperative period.^(2-4,8)

The analysis indicates a significant difference between the groups with a better outcome for ECL in the MSICS group. This finding may be related to the absence of ultrasonic energy and reduced intraocular turbulence during MSICS. However, this outcome differs from previous studies that focused on non-restrictive types of cataracts and included only softer grades or other types of cataracts, resulting in negligible corneal endothelial alteration.^(31-33)

Nevertheless, the CCT remained stable in both groups. This suggests that corneal endothelial function was unaffected. This supports the notion that both MSICS and phacoemulsification, with proper technique and viscoelastic use, did not cause significant harm to the endothelium, which could have resulted in postoperative corneal edema due to a marked impairment of the corneal endothelial pump. Our study's findings align with previous research that noted a return to normal CCT values in the postoperative period.^(15,16,34)

Notably, the analysis revealed a more favorable outcome of surgery time for the group of MISCS, as indicated by the MD, when compared to the phacoemulsification group. According to the literature, MSICS has the potential of achieving outstanding results with lower costs and shorter surgical times when compared to phacoemulsification. In addition to being fast and affordable, MSICS is easier for less experienced surgeons to learn and is considered safer for managing advanced mature cataracts.^(1,2,35-37)

When considering complications, our findings demonstrated that the overall rates of complications were not significantly different between the two groups. This is reassuring, as it suggests that the use of MSICS or phacoemulsification does not inherently introduce a greater risk of complications, as previously observed in other studies. Notably, the incidence of a severe complication, such as dropped nuclei, which involves the dislocation of the nucleus onto the retina, is rare in MSICS. Thus, both MSICS and phacoemulsification are deemed safe procedures.^(1,2)

According to previous studies, the incidence of anterior chamber contamination is similar between eyes undergoing MSICS and phacoemulsification.⁽³⁸⁾ Furthermore, both phacoemulsification and MSICS resulted in significant and similar reductions in intraocular pressure (IOP) 6 months after surgery. Additionally, both surgeries produced similar changes in anterior chamber and angle parameters.⁽³⁹⁾

Only one study reported surgically induced astigmatism, suggesting better results in the phacoemulsification group.⁽⁸⁾ Similarly, many studies conclude that phacoemulsification reduces surgically induced astigmatism at a 6-week follow-up compared to MSICS for all types of cataract.^{(3,8,33,40,41)}

In a study by Gokhale and Sawhney, they compared surgically induced astigmatism with various scleral incision locations for MSICS. Their findings revealed that surgically induced astigmatism was lower with temporal and superotemporal incisions than with superior incisions.⁽⁴²⁾

It is important to note that our analysis shows a low level of variation, with an I² value of 0% in most of the analysis, except for the ECL that utilized random-effect models. This indicates a significant level of consistency among the studies included in the analysis.

Furthermore, patients with pseudoexfoliation syndrome have a high prevalence of mature cataracts. Naik et al. reported that, with careful pre-operative assessment, intraoperative modifications, and surgical expertise, both PHACO and MSICS appear to be safe procedures for those with pseudoexfoliation syndrome.⁽⁴³⁾ However, according to Subudhi et al., in moderately hard nuclear cataracts with pseudoexfoliation syndrome grades II and III (LOCS II grading system), phacoemulsification provides better unaided visual outcomes with less endothelial dysfunction than MSICS in the immediate and subsequent postoperative periods.⁽⁴⁴⁾

The stage of cataract in a population significantly affects surgical outcomes. Along with CCT and ECL, BCVA and complications are also important factors. Advanced and complicated cataracts are more common among impoverished populations. As a result, the MSICS technique emerges as a more fitting option for developing nations due to its minimal capital and consumable expenses, particularly regarding fluid and tubing. This makes MSICS an economically viable choice, addressing the resource constraints often faced by developing countries in comparison to phacoemulsification surgery, which requires expensive equipment. The cost-effectiveness of MSICS renders it a pragmatic and sustainable solution for cataract surgery in these regions, ensuring that essential eye care services can be efficiently provided without straining limited financial resources.^(45-51)

In conclusion, we found manual small incision cataract surgery to be a safe and effective alternative to phacoemulsification for mature cataracts, showing no noteworthy disparities in complications or outcomes related to best-corrected visual acuity and central corneal thickness, while also demonstrating a reduction in endothelial cell loss. Manual small incision cataract surgery has a notable advantage because it does not rely on advanced technology, making it a faster and more affordable surgical choice. These characteristics position manual small incision cataract surgery as a viable procedure, particularly for mature cataracts and challenging cases, including brunescent cataracts, white cataracts, and cataracts causing phacolytic and phacomorphic glaucoma, and in regions where access to high-cost phacoemulsification techniques remains limited.