Commentary: Comparison of corneal endothelial cell loss during manual small-incision cataract surgery using viscoelastic-assisted nucleus removal versus continuous basal salt solution plus technique - Randomized controlled trial

There have been a few randomized control trials comparing phacoemulsification and manual small-incision cataract surgery (SICS);[1,2] however, there have been none comparing the different techniques of manual SICS using a rigorous scientific method. Morya et al.[3] need to be congratulated for bridging this lacuna. Randomized control trials are one of the highest hierarchies of evidence in scientific studies. The reporting of RCTs should be as per the CONSORT statement.[4] This study by Morya et al. fulfils many CONSORT criteria.

For the enrolment, the study should detail the eligibility criteria and also report those who declined to participate, or those who were excluded for other reasons. This study was done at a tertiary care center where enrolment went on for 3 years (due to the COVID pandemic?) to recruit 206 participants. The authors do not elucidate how many were excluded and the 206 were part of what larger sample was considered for enrolment. There were 63.2% males, a preponderance of one gender; however, they were equally divided among the two groups. Authors have included hard cataracts but there were a few cataracts with 4+ nuclear sclerosis. Preoperatively, group 1 had more myopic eyes, whereas group 2 had lesser preoperative vision.

CONSORT statement states details of randomization should be mentioned and how the masking is done. The randomization in this study was done using computer-generated binary numbers, and the single surgeon was masked until the start of the surgery, as were the team members to perform the pre- and post-operative evaluation. The details of allocation to intervention and who received what form of treatment have been reported.

The new CONSORT statement also looks at to delay between randomization and allocation and eligibility criteria for the eye care center and care providers.[5] It also asks whether important changes were made to interventions versus what was planned. Both these have not been mentioned in this study. There should also be details of follow-up, including those lost to follow-up, and those who discontinued the treatment. The follow-up was on day 1, and day 30 after surgery, by which times most postoperative parameters would be stable. The short follow-up was a major limitation but this period was enough to differentiate changes in the corneal thickness and visual acuity. The analysis should ideally have been on intention to treat basis; however, the authors do not report if any patient needed a larger incision, or if there was any deviation from the protocol. We may assume that nobody was excluded for a reason.

All participants underwent manual SICS under the peribulbar block, with a 7 mm scleral tunnel that was not sutured. The authors were concerned about patient safety and comfort.

There was no difference in the two groups with respect to vision, intraocular pressure, and horizontal and vertical keratometry readings after surgery. Randomization ensured that the groups were similar at baseline. There was a statistically significant difference in the central corneal thickness; however, it was not clinically significant as postoperative visual acuity on day 30 and intraocular pressure were similar in both groups. There was obviously a significant difference in vision before and after surgery!

The difference in the endothelial cell count was statistically significant, group 1 and group 2 had a 9% and 4.6% reduction on day 1, and 9.7% and 4.8% on day 30, respectively. Thus visco-assisted nucleus delivery had a more deleterious effect on endothelial cells as compared to a balanced solution.

The takeaway was that endothelial cell loss was slightly less in the BSS group. Although this was statistically significant, it did not translate into any difference in visual acuity or other parameters. This small difference would be important in cataract eyes with Fuchs dystrophy, corneal guttata, or similar condition with poor endothelial cell counts. One wonders what would have been the result if the more commonly used Ringer’s lactate was used instead of BSS plus as the irrigating solution?

Similar results were seen in a randomized control trial published in the Indian Journal of Ophthalmology in 2009, in which BSS was compared with Ringer’s lactate to observe the endothelial cell loss, central corneal thickness, and postoperative inflammation after phacoemulsification.[6] The BSS group had lesser endothelial cell loss and corneal edema; however, there was no mention of visual acuity in both arms, which was similar.[6,7]

The authors state that BSS may be used in settings where viscoelastic cannot be procured, as it was in some places during the COVID pandemic. However, supply chains in such situations would have interfered with most surgical consumables. Procuring intraocular lenses and ophthalmic surgical consumables is a challenge on islands and in some African countries but this is an exception rather than a rule.

This special issue highlights numerous techniques of manual SICS, all of which are reported to give excellent visual outcomes. It would be in the interest of our patients and the ophthalmic fraternity if the rigorous method of randomized control trials were to be applied to each new technique so that we may understand their benefits and limitations better. The authors Morya et al. have started this journey of holding a candle to various techniques of manual SICS. May their tribe increase.