Assessment of image quality and acceptability for grading. Photographs were deemed ungradable if any of the criteria below resulted in rejection, unless a specific reason for referral could be identified (for example, foveal changes seen even if only half the field could be visualised
| Criteria judged | Acceptance for grading |
|---|---|
| (a) Definition of image | |
| (i) Good; all features fully assessable | Accepted |
| (ii) Moderate; some haziness of some small vessels | Accepted |
| (iii) Poor; unable to define small vessels | Rejected |
| (b) Field of image seen | |
| (i) Full image seen | Accepted |
| (ii) >3/4 of image seen | Accepted |
| (iii) <3/4, but >1/2 of image seen | Rejected |
| (iv) <1/2 of image seen | Rejected |
| (c) Fovea visible | |
| (i) Yes | Accepted |
| (ii) No | Rejected |