**What it is**
Ellipseness measures how circular the pupil is, expressed as the ratio of the pupil’s minor axis to its major axis (100% = perfect circle, lower = more elliptical).
| Ellipseness | Classification |
|————-|—————|
| ≥ 95% | **Normal** — essentially circular |
| < 95% | **Anomaly** — pupil form deviation detected |
**Pupil form types**
When ellipseness falls below the normal threshold, the orientation of the ellipse is assessed to determine the form type:
| Form | Description | Historical association |
|——|————-|———————-|
| Circle | Normal round pupil | No pattern |
| Horizontal oval | Wider than tall | Respiratory/glandular autonomic zones |
| Vertical oval | Taller than wide | Cerebral circulation zones |
| Diagonal oval | Tilted ellipse | Urogenital zone reflexes |
| Chord-like | Flat edge on one side | Localized autonomic influence |
| Irregular | Non-uniform distortion | Multiple autonomic zone influences |
