The Effect of Tamsulosin on Iris Morphology, Ciliary Muscle Thickness, and Pupil Diameter.

Purpose: To investigate the effect of tamsulosin on iris morphology, ciliary muscle thickness (CMT), pupil diameter (PD), and pupil responses to light using anterior segment optical coherence tomography and corneal topography.

Design: Prospective clinical before-and-after study METHODS: The right eyes of 43 patients with newly diagnosed benign prostatic hyperplasia were included in this study. Iris dilator muscle region (DMR) thickness, sphincter muscle region (SMR) thickness, DMR/SMR ratio, PD (scotopic, mesopic and photopic light conditions), CMT1 (1 mm posterior to the scleral spur), CMT2 (2 mm posterior to the scleral spur), CMT3 (3 mm posterior to the scleral spur) and anterior chamber depth (ACD) were measured before and after dilation. Measurements were performed twice firstly before starting tamsulosin treatment and secondly at the 3rd month of tamsulosin treatment.

Results: Pre-dilation DMR thickness (P < .001), post-dilation DMR thickness (P < .001) pre-dilation DMR/SMR ratio (P = .001), and post-dilation DMR/SMR ratio (P = .001) were reduced significantly after tamsulosin treatment. Pre-dilation PD decreased after treatment in scotopic, mesopic and photopic conditions, but only photopic conditions showed a significant difference (P = .733, P = .142, and P = .04, respectively). Post-dilation PD was significantly reduced after tamsulosin treatment (P < .001). No significant differences were found in pre- and post-dilation iris SMR thickness (P = .08 and P = .784, respectively), pre-dilation CMT1, CMT2, and CMT3 (P = .841, 0.794, 0.880, respectively), post-dilation CMT1, CMT2, and CMT3 (P = .367, 0.114, 0.256, respectively), pupil dilation speed (P = .463), pre-dilation ACD (P = .583), and post-dilation ACD(P = .305) after treatment.

Conclusion: Tamsulosin treatment does not change the iris SMR thickness, CMT1, CMT2, CMT3, and ACD but statistically significantly reduces the iris DMR thickness, DMR/SMR ratio, pre-dilation photopic PD, and post-dilation PD.