Appendix 1. CENTRAL search strategy

#1 MeSH descriptor Cataract
#2 cataract*
#3 eye*
#4 (#1 OR #2 OR #3)
#5 MeSH descriptor Carnosine
#6 carnosine*
#7 NAC
#8 (#5 OR #6 OR #7)
#9 (#4 AND #8)

Appendix 2. MEDLINE (OVID) search strategy

1. randomized controlled trial.pt.
2. (randomized or randomised).ab,ti.
3. placebo.ab,ti.
4. dt.fs.
5. randomly.ab,ti.
6. trial.ab,ti.
7. groups.ab,ti.
8. or/1‐7
9. exp animals/
10. exp humans/
11. 9 not (9 and 10)
12. 8 not 11
13. cataract/
14. cataract$.tw.
15. eye$.tw.
16. or/13‐15
17. carnosine/
18. carnosine$.tw.
19. NAC.tw.
20. or/17‐19
21. 16 and 20
22. 12 and 21

The search filter for trials at the beginning of the MEDLINE strategy is from the published paper by Glanville et al (Glanville 2006).

Appendix 3. EMBASE (OVID) search strategy

1. exp randomized controlled trial/
2. exp randomization/
3. exp double blind procedure/
4. exp single blind procedure/
5. random$.tw.
6. or/1‐5
7. (animal or animal experiment).sh.
8. human.sh.
9. 7 and 8
10. 7 not 9
11. 6 not 10
12. exp clinical trial/
13. (clin$ adj3 trial$).tw.
14. ((singl$ or doubl$ or trebl$ or tripl$) adj3 (blind$ or mask$)).tw.
15. exp placebo/
16. placebo$.tw.
17. random$.tw.
18. exp experimental design/
19. exp crossover procedure/
20. exp control group/
21. exp latin square design/
22. or/12‐21
23. 22 not 10
24. 23 not 11
25. exp comparative study/
26. exp evaluation/
27. exp prospective study/
28. (control$ or prospectiv$ or volunteer$).tw.
29. or/25‐28
30. 29 not 10
31. 30 not (11 or 23)
32. 11 or 24 or 31
33. exp cataract/
34. cataract$.tw.
35. eye$.tw.
36. or/33‐35
37. carnosine/
38. carnosine$.tw.
39. NAC.tw.
40. or/37‐39
41. 36 and 40
42. 32 and 41

Appendix 4. CINAHL search strategy

S7 S3 AND S6
S6 S4 OR S5
S5 NAC
S4 carnosine*
S3 S1 OR S2
S2 cataract*
S1 (MH "Cataract")

Appendix 5. AMED search strategy

1. cataract/
2. cataract$.tw.
3. eye$.tw.
4. or/1‐3
5. carnosine$.tw.
6. NAC.tw.
7. or/5‐6
8. 4 and 7

Appendix 6. metaRegister of Controlled Trials search strategy

cataract and carnosine

Appendix 7. ClinicalTrials.gov search strategy

Cataract AND Carnosine