| Methods |
A multicentre, randomised clinical trial in USA conducted between 1991 and 1994 |
| Participants |
42 of 213 eyes enrolled in the Vitrectomy for Macular Hole Study had stage II macular hole. Inclusion criteria: Eccentric macular hole diameter between 100 and 650 micron, centric macular hole diameter less than 300 micron and a dark yellow ring, positive Watzke‐Allen test result |
| Interventions |
Vitrectomy versus observation |
| Outcomes |
4 measures of best‐corrected visual function, standardised photographic evaluation of the extent of hole closure, evaluation of lens opacification, and adverse events at 6 and 12 months |
| Notes |
|
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Low risk |
Computer‐generated random sequence |
| Allocation concealment (selection bias) |
Low risk |
Quote: "Each center opened a sealed envelope containing the randomization card for a given patient after informed consent was signed". |
| Blinding of participants and personnel (performance bias)
Hole closure |
Low risk |
Unmasked, but hole closure is an anatomic outcome and no such bias is expected |
| Blinding of participants and personnel (performance bias)
Visual acuity |
High risk |
Unmasked, and visual acuity is a subjective outcome that can be influenced by participants' knowledge of allocation status |
| Blinding of outcome assessment (detection bias)
Hole closure |
Low risk |
Masked reading of the fundus photographs. Two photograph readers read fundus photographs. Where the 2 principal photograph readers were not in complete agreement, the images were reviewed by the principal investigator and by a fundus photographer reader from an outside institution. |
| Blinding of outcome assessment (detection bias)
Visual acuity |
High risk |
Unmasked visual acuity examiners |
| Incomplete outcome data (attrition bias)
All outcomes |
Low risk |
At 12 months 2/15 and 4/21 were lost in vitrectomy group and observation group, respectively |
| Selective reporting (reporting bias) |
Low risk |
A protocol was not available, nor were predefined outcomes. However, hole closure and mean logMAR visual acuity are key expected outcomes in this research field. |
| Other bias |
Low risk |
No other source of bias |
