Investigation of the Relationship Between Postmortem Interval and Pupil Response Following Pilocarpine Application in Rat Eyes: An Experimental Animal Study

Objective:The aim of this study was to investigate the relationship between pupil diameter and postmortem interval (PMI) following topical pilocarpine application in rat eyes.Methods: Thirty rats were grouped into 5 groups according to PMI (0-24 hours).One eye of each rat was used as the experimental eye and the other as the control eye.Topical pilocarpine (2%) was applied to the experimental eyes, while no application was made to the control eyes.Pupil diameter measurements were taken using a digital caliper with 0.01 mm precision.The difference between pre-and post-pilocarpine pupil diameters was recorded as the amount of pupil diameter change.Positive, negative, and paradoxical responses were classified.Results: In the experimental group, pupil diameter after pilocarpine application was significantly reduced compared to the baseline pupil diameter at 0, 6, 9, and 18 hours postmortem (hpm).No significant difference in pupil diameter change was observed between the experimental and control groups at any PMI (P > .05).Additionally, no significant correlation was found between PMI and the amount of pupil diameter change in the experimental eyes (P = .154,r = -0.201).In the experimental group, positive responses were observed in all subjects at 0, 9, and 18 hpm, while paradoxical responses predominated at 3, 12, and 21 hpm. Conclusion:This study found no correlation between PMI and the amount of pupil diameter change in rat eyes, and the distribution of positive, negative, and paradoxical responses after pilocarpine application was irregular.These results suggest that using topical pilocarpine for PMI estimation may be misleading.