Intra-operative awareness is a large medico-Legal issue to the anesthesiologists and can lead to a postoperative psychosomatic dysfunction so it must be prevented under all possible settings by monitoring the depth of anaesthesia. Among multiple modalities of monitors. Aim: our study compares between Bispectral index and perfusion index. the prediction probability of perfusion index compared to bispectral index, as a gold standard, in detecting different stages of anaesthesia using propofol for induction and sevoflurane for anaesthesia maintenance. Methods: The study involved 50 adult patients of both sexes undergoing elective ophthalmic procedures under general anesthesia, This intervention before and after, clinical study was conducted in the Theatre of Ophthalmic Surgery - Kasr-Alainy Hospitals - Cairo University Hospitals. Diagnostic intervention using different concentrations of sevoflurane to have different degrees of depth of anaesthesia that were monitored using PI readings was compared to BIS readings. Results: Our primary outcome showed significant changes in perfusion index values (PI) to changes in depth of anaesthesia while BIS values decreased from 70 to 60. The difference between baseline value (soon after intubation) and 10 minutes later (BIS reading of 60 compared to 70) with significant P value (0.006) and AUROC more than 0.62, sensitivity 78 % ,specificity 42 % and accuracy 60 %.Our secondary outcomes were The correlation between change in PI and BIS immediately after induction of general anesthesia When BIS reading is 70, 20 minutes after intubation when BIS reading is 40 and 30 minutes after intubation when BIS reading is 30. Conclusion: compared with the BIS, the PI can track changes in the depth of anesthesia in adult patients undergoing ophthalmic surgeries under sevoflurane anesthesia with the surges and drops in the PI compared with its respective baseline are highly informative regardless of whatever this baseline value was.