# Development and Validation of a Standardized Palpebral Conjunctival Redness Scale

## TL;DR

This study created a new scale to measure redness in the eyelid conjunctiva, which is more reliable and better suited for its unique anatomy than existing methods.

## Contribution

A new 10-point palpebral conjunctival redness scale was developed and validated for clinical use.

## Key findings

- The PCR scale showed strong inter-rater reliability (ICC of 0.773) and internal consistency (Cronbach's alpha of 0.880).
- PCR scores were significantly higher than BCR scores by 15.90 units (p<0.0001).
- PCR and BCR combined achieved an ICC of 0.852, indicating improved diagnostic sensitivity.

## Abstract

Purpose: This study aims to develop and validate a standardized palpebral conjunctival redness (PCR) scale for clinical assessment of ocular inflammation, addressing the distinct vascular anatomy and immune characteristics of the palpebral conjunctiva compared to the bulbar conjunctiva.

Methods: A study was conducted using digital image manipulation to create a 10-point PCR grading scale (10-100 in increments of 10). The scale was developed through Adobe Photoshop modification of high-resolution ocular photographs and validated by trained ophthalmic professionals. A total of 24 eyes from 12 patients were assessed using both the newly developed PCR scale and the established Schulze bulbar conjunctival redness (BCR) scale. Statistical analysis included Cronbach's alpha for internal consistency, intraclass correlation coefficients (ICC) for inter-rater reliability, paired t-tests for comparison between PCR and BCR scores, and Pearson's correlation coefficient to assess the relationship between the two measures.

Results: The PCR scale demonstrated excellent inter-rater reliability with an ICC of 0.773 (95% CI: 0.537-0.896) and strong internal consistency with a Cronbach's alpha of 0.880. Individual components showed robust reliability ranging from 0.842 to 0.891. Mean PCR scores were significantly higher than BCR scores by 15.90 units (p<0.0001), with a moderate correlation coefficient of 0.45 between the two measures. The combined PCR and BCR assessment achieved an ICC of 0.852 (95% CI: 0.780-0.902).

Conclusion: This study successfully established a reliable and clinically applicable PCR grading scale that addresses the unique anatomical and immunological characteristics of the palpebral conjunctiva. The moderate correlation between PCR and BCR measurements supports the necessity of independent assessment tools for different conjunctival regions. The PCR scale complements existing BCR assessments and provides enhanced diagnostic sensitivity for conditions affecting the eyelid margins and inner conjunctival surfaces. Further validation in larger, more diverse patient populations is recommended before widespread clinical implementation.