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Table 4 Methodological quality of the included studies

From: Effectiveness of screening preschool children for amblyopia: a systematic review

Reference Prospective sample size planning Blinding of outcome assessor Comparability of groups Consideration of confounding factors Transparency of patient flow
Bray
1996 33
No* Not specified Not specified Not specified Yes||
Eibschitz-Tsimhoni
2000 27
No Not specified Not specified# Not specified No
82% of the originally recruited children were included in the analysis**
Rasmussen
2000 34
No No Not specified No Yes||
Williams
2002 31,32
No Yes Yes Yes§ No
about 55% of the originally recruited children (equally distributed in both groups) were included in the analysis††
Williams
2003 28,29,30
No* Yes No Yes§ No
only children who took part at the final assessment were presented and analysed (62% of the originally recruited children)
  1. * Retrospective power-analysis.
  2. Retrospective power-analysis for the outcome measure: visual acuity; prospective power-analysis for a not relevant endpoint.
  3. Parents of screened children were older, higher educated and smoked less during pregnancy; however, results were almost identical after adjustment for confounding factors.
  4. § For example: duration of breastfeeding, mother's educational level, 1st degree relative with squint, sex.
  5. || No children were excluded from the analysis.
  6. # It was only noted that the two communities were similar in terms of race, social status, health care facilities, education, nutrition and climate.
  7. ** Unclear, if only children who attended the final assessment were analysed.
  8. †† Only children who attended the final assessment were analysed.