Ismail 2009

Methods	Randomized, double‐blind, placebo‐controlled study Location: Saudi Arabia Study design: parallel, 2‐armed
Participants	A total of 40 patients randomized 40 patients completed: 20 in melatonin group, 20 in placebo group Age: melatonin 72.8 ± 8.1, placebo 68.5 ± 7.9 Gender (M/F) in %: melatonin (55/45), placebo (50/50) ASA class: I‐III Type of surgery: cataract surgery Type of anaesthesia: topical Baseline (anxiety, pain) described: yes, no
Interventions	Melatonin: 10 mg Placebo Administration route: oral Time of administration: 90 min preoperatively
Outcomes	1. Anxiety assessed by Verbal Anxiety Score (0 to 10) (preoperative) 2. Pain assessed by Verbal Pain Score (0 to 10) 3. Analgesic consumption by fentanyl requirements 4. Intraocular pressure (IOP) measured by Shioetz tonometer 5. Haemodynamcis (heart rate and mean arterial pressure)
Notes	Sample size calculation: described
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients were randomly allocated using an online research randomizer..." (page 1147) (Ismail 2009)
Allocation concealment (selection bias)	Low risk	Quote: "...randomly allocated using an online research randomizer..." (page 1147)
Incomplete outcome data (attrition bias) All outcomes	Low risk	No reported dropouts or missing data
Selective reporting (reporting bias)	Unclear risk	Study protocol not available
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "an ophthalmologist who was blinded..." and "...the operating surgeon, who was blinded to patient allocation..." and "The attending anaesthesiologist who was unaware of patient group assignment..." (page 1147)
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "The attending anaesthesiologist who was unaware of patient group assignment managed the patients and recorded all data" (page 1147)