Parameters for sample size estimates
| Total number eligible services | Anticipated percentage optimal | Spectacles from each service | Total number required | ||
| Spectacles | Services | ||||
| Cambodia | 265 | 50 | 5 | 900* | 180 |
| Malaysia | 319 | 70 | 3 | 198 | 66 |
| Pakistan | 90 | 50 | 4 | 256 | 64 |
| Intraclass correlation=0.1, design effect=1.2. | |||||
*The number of spectacles in Cambodia has been increased to provide an update on the precision of the intraclass coefficient.