**What it is**
Decentration measures how far the pupil center is offset from the geometrical center of the iris, expressed as a percentage of the iris radius.
| Decentration | Classification |
|————-|—————-|
| < 5% | **Normal** — pupil centered within physiological limits |
| ≥ 5% | **Notable** — decentration flagged with directional pattern |
**Directional patterns**
When decentration is notable, the direction is reported as a named pattern:
| Direction | Pattern name | Zone implication |
|———–|————-|—————–|
| Toward nose | Nasal | OD: pulmonary reflexes · OS: cardiac reflexes |
| Away from nose | Temporal | Renal, reproductive zones |
| Upward | Frontal | Cerebral, cognitive zones |
| Downward | Basal | OD: intracranial pressure reflexes · OS: cerebral patterns |
| Upper-inward | Upper-nasal | OD: hepatobiliary · OS: splenic, diaphragmatic |
| Upper-outward | Upper-temporal | Renal, reproductive zones |
The decentration angle is also reported in degrees (0–360°) from the horizontal, providing precise directional information for charting.
