# Archetypal Analysis Reveals Consistent Visual Field Patterns for Stimulus Size III and Size Modulation Perimetry in Glaucoma

## TL;DR

This study shows that two types of eye tests for glaucoma detect similar patterns of vision loss, suggesting they could be used interchangeably in some cases.

## Contribution

The study introduces archetypal analysis to compare visual field patterns from two perimetry methods in glaucoma patients.

## Key findings

- Archetypal analysis revealed strong overlap in absolute visual field patterns between stimulus size III and size modulation perimetry.
- Patterns of change showed less similarity, with only 30% of archetypes having cosine similarity ≥0.50.
- The results suggest that standard automated perimetry and size modulation perimetry capture similar patterns of vision loss in glaucoma.

## Abstract

Optic nerve disorders produce identifiable visual field (VF) patterns. Size modulation perimetry (SMP) unlike standard automated perimetry (SAP) shows little degradation of retest variability with increasing VF damage. We hypothesize that VF testing with stimulus size III (size III) and SMP would reveal analogous patterns, supporting interchangeability in clinical practice.

We analyzed 274 same-day pairs of VFs from 83 eyes of patients with glaucoma. Participants underwent testing every 6 months using size III and SMP VFs. We converted raw sensitivity data to total deviation (TD) scores relative to normative datasets, censoring size III sensitivities below 20 decibels (dB). Archetypal analysis (AA) was applied separately to each modality to identify characteristic VF patterns, or archetypes (ATs). We evaluated both absolute VF patterns and longitudinal VF changes by subtracting baseline measurements. Cosine similarity measured the overlap between ATs in size III and SMP.

Absolute size III and SMP VFs exhibited overlapping patterns, with 95% of ATs demonstrating a cosine similarity of ≥0.50. Change ATs showed lower similarity scores (30% with cosine similarity ≥0.50). However, some ATs still revealed similar underlying defects.

AA consistently extracted comparable VF defect patterns from size III and SMP in glaucoma. Absolute size III patterns closely aligned with SMP, whereas patterns of change showed partial agreement.

These findings suggest that SAP and SMP capture similar patterns of VF loss.