Comparison of intracameral mydriatic-anesthetic combination injection v/s topical mydriatics in pupillary dilation in MSICS and to assess the receptor downregulation mechanism in same eyes dilated on consecutive days

Aims: To assess the efficacy of intracameral mydriatic-anesthetic combination injection in eyes with successive pupillary dilation. To compare the pupillary dilation in intracameral combination injections (in the operating eye) compared to topical mydriatics (in the non-operating eye). To assess the receptor downregulation effect when the same eyes are dilated on two consecutive days. Methods: This comparative cross-sectional study included 50 subjects posted for small incision cataract surgery. Both eyes were dilated with topical mydriatics on the pre-operative day, and pupillary diameter (PD) was noted. On the next day, the operating eye was dilated with an intracameral combination injection, and the non-operating eye was dilated with topical mydriatics, and the PD of both was compared. Results: The average PD in the operating eye dilated with topical mydriatics was 7.940 ± 0.7117 mm on pre-operative evaluation and 7.310 ± 1.0197 mm following 30 s of intracameral combination injection on a successive day. There was no statistically significant difference in PD between the operating eye dilated with intracameral combination injection and the non-operating eye dilated with topical mydriatics on the operative day. However, there was a significant difference in PD in the operating eye dilated with topical mydriatics on pre-operative day and with intracameral combination injection on the operative day. Conclusions: Intracameral combination injection of tropicamide 0.02%, phenylephrine 0.32%, and lidocaine 1% are equally efficacious as topical mydriatics in pupillary dilation. The reduction in PD on the operative day when compared to that of the pre-operative day may be due to the receptor downregulation mechanism.