Pharmacologic interventions for mydriasis in cataract surgery

Background: Cataract surgery is one of the most common surgical procedures performed worldwide. Achieving appropriate intraoperative mydriasis is one of the critical factors associated with the safety and performance of the surgery. Inadequate pupillary dilation or constriction of the pupil during cataract surgery can impair the surgeon’s field of view and make it difficult to maneuver instruments. Objectives: To evaluate the relative effectiveness of achieving pupillary dilation during phacoemulsification for cataract extraction using three methods of pupillary dilation: topical mydriatics, intracameral mydriatics, or depot delivery systems. We also planned to document and compare the risk of intraoperative and postoperative complications following phacoemulsification for cataract extraction, as well as the cost-effectiveness of these methods for pupillary dilation. Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register) (2021, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature Database (LILACS); ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not use any date or language restrictions in the electronic search for trials. We last searched the electronic databases on 22 January 2021. Selection criteria: We included only randomized controlled trial (RCTs) in which participants underwent phacoemulsification for cataract extraction. Data collection and analysis: We followed standard Cochrane methodology. Main results: We included a total of 14 RCTs (1670 eyes of 1652 participants) in this review. Of the 14 trials, 7 compared topical versus intracameral mydriatics, 6 compared topical mydriatics versus depot delivery systems, and 1 compared all three methods. We were unable to calculate overall estimates of comparative effectiveness for most outcomes due to statistical heterogeneity among the estimates from individual studies or because outcome data were available from only a single study. Furthermore, the certainty of evidence for most outcomes was low or very low, due primarily to imprecision and risk of bias. Comparison 1: topical mydriatics versus intracameral mydriatics. Four RCTs (739 participants, 757 eyes) of the 8 RCTs that had compared these two methods reported mean pupillary diameters at the time surgeons had performed capsulorhexis; all favored topical mydriatics, but heterogeneity was high (I² = 95%). After omitting 1 RCT that used a paired-eyes design, evidence from three RCTs (721 participants and eyes) suggests that mean pupil diameter at the time of capsulorhexis may be greater with topical mydriatics than with intracameral mydriatics, but the evidence is of low certainty (mean difference 1.06 mm, 95% confidence interval (CI) 0.81 mm to 1.31 mm; I² = 49%). Four RCTs (224 participants, 242 eyes) reported mean pupillary diameter at the beginning of cataract surgery; the effect estimates from all trials favored topical mydriatics, with very low-certainty evidence. Five RCTs (799 participants, 817 eyes) reported mean pupillary diameter at the end of cataract surgery. Data for this outcome from the largest RCT (549 participants and eyes) provided evidence of a small difference in favor of intracameral mydriasis. On the other hand, 2 small RCTs (78 participants, 96 eyes) favored topical mydriatics, and the remaining 2 RCTs (172 participants) found no meaningful difference between the two methods, with very low-certainty evidence. Five RCTs (799 participants, 817 eyes) reported total intraoperative surgical time. The largest RCT (549 participants and eyes) reported decreased total intraoperative time with intracameral mydriatics, whereas 1 RCT (18 participants, 36 eyes) favored topical mydriatics, and the remaining 3 RCTs (232 participants) found no difference between the two methods, with very low-certainty evidence. Comparison 2: topical mydriatics versus depot delivery systems. Of the 7 RCTs that compared these two methods, none reported mean pupillary diameter at the time surgeons performed capsulorhexis. Six RCTs (434 participants) reported mean pupillary diameter at the beginning of cataract surgery. After omitting 1 RCT suspected to be responsible for high heterogeneity (I² = 80%), meta-analysis of the other 5 RCTs (324 participants and eyes) found no evidence of a meaningful difference between the two methods, with very low-certainty evidence. Three RCTs (210 participants) reported mean pupillary diameter at the end of cataract surgery, with high heterogeneity among effect estimates for this outcome. Estimates of mean differences and confidence intervals from these three RCTs were consistent with no difference between the two methods. A fourth RCT reported only means for this outcome, with low-certainty evidence. Two small RCTs (118 participants) reported total intraoperative time. Surgical times were lower when depot delivery was used, but the confidence interval estimated from one trial was consistent with no difference, and only mean times were reported from the other trial, with very low-certainty evidence. Comparison 3: Intracameral mydriatics versus depot delivery systems. Only one RCT (60 participants) compared intracameral mydriatics versus depot delivery system. Mean pupillary diameter at the time the surgeon performed capsulorhexis, phacoemulsification time, and cost outcomes were not reported. Mean pupil diameter at the beginning and end of cataract surgery favored the depot delivery system, with very low-certainty evidence. Adverse events. Evidence from one RCT (555 participants and eyes) comparing topical mydriatics versus intracameral mydriatics suggests that ocular discomfort may be greater with topical mydriatics than with intracameral mydriatics at one week (risk ratio (RR) 10.57, 95% CI 1.37 to 81.34) and one month (RR 2.51, 95% CI 1.36 to 4.65) after cataract surgery, with moderate-certainty evidence at both time points. Another RCT (30 participants) reported iris-related complications in 11 participants in the intracameral mydriatics group versus no complications in the depot delivery system group, with very low-certainty evidence. Cardiovascular related adverse events were rarely mentioned. Authors' conclusions: Data from 14 completed RCTs were inadequate to establish the superiority of any of three methods to achieve mydriasis for cataract surgery, based on pupillary dilation at different times during the surgery or on time required for surgery. Only one trial had a 
sample size adequate to yield a robust effect estimate. Larger, well-designed trials are needed to provide robust estimates for the comparison of mydriasis approaches for beneficial and adverse effects.