| Methods |
A multicentre, randomised clinical trial in USA. Study began in June 1992 and was published in 1997 |
| Participants |
129 eyes of 120 participants with stage III and IV macular holes; relevant inclusion criteria were visual acuity less than 20/50, decreasing subjective vision, hole tissue loss at least 400 micron in diameter, 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 months |
| Notes |
No conflict of interest declaration reported in the manuscript. Funding sources: potential conflict of interest related to funding by Alcon Inc, Fort Worth, Texas, as surgical device producer. Other sources: grant from Research to Prevent Blindness Inc, New York, NY; and EY‐03040 Core Grant from National Eye Institute |
| 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 |
Randomisation code delivered in an envelope only after the participant had been judged to be eligible and agreed to enter the study |
| 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 |
Independent photograph‐reading centre |
| Blinding of outcome assessment (detection bias)
Visual acuity |
High risk |
Unmasked visual acuity examiners |
| Incomplete outcome data (attrition bias)
All outcomes |
Low risk |
At 6 months, 4/64 eyes versus 7/65 eyes were lost in vitrectomy group and observation group, respectively |
| Selective reporting (reporting bias) |
Low risk |
A protocol was not available, nor were predefined outcomes declared. 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 |
