Purpose: to investigate outcomes for small versus large pupils in cataract surgery using different pupil expansion techniques.Methods: retrospective case-series reviewing 20,175 patients' cataract surgery electronic medical records at Moorfields Eye Clinic in Bedford Hospital NHS Trust from January 2010 to April 2020. Outcomes such as visual acuity (VA), intraocular pressure, intraoperative, postoperative complications were recorded and small pupil expansion device outcome.Results: 1,426 patients were identified as having small pupil (SP). Of these, 1,110 patients (77.8%) had interventions to expand the pupil including 447 (31.3%) with intracameral phenylephrine (IC PE) alone, 194 (13.6%) with iris hooks and 469 (32.9%) with a Malyugin ring. The large pupil (LP) group had a statistically significant greater gain in VA than the SP group (p<0.05). SPs had a significantly higher rate of intraocular complications including posterior capsular rupture (PCR) with vitreous loss (OR 2.75, p<.001). There was also a significantly higher rate of post-operative complications such as corneal oedema (OR 2.64, p<.001) and anterior uveitis (OR 2.11, p<.001) in the SP group. However, VA improvement and complications between the different pupil expansion groups showed no significant differences (p>0.05) except for a greater rate of iris tears in the Malyugin group (p<0.05). Conclusion:To date, this is the largest reported case series comparing Malyugin rings and iris hooks with other pupil expansion techniques. The various techniques to expand pupil size appear to be safe and equally effective in improving VA with a similar rate of complications except for a greater rate of iris tears with Malyugin ring.