---
title: 3.6 Ellipseness (Pupil Shape)
description: "****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%…"
url: "https://cnri.edu/docs/3-6-ellipseness-pupil-shape/"
updated: "2026-03-24"
category: Reading the Analysis Results
---

# 3.6 Ellipseness (Pupil Shape)

****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 |