Impact Of Corneal Hydration, Aging, And Ocular Diseases On In Vivo Brillouin Spectroscopy

Published 2026 - 44th Congress of the ESCRS

Reference: FP08.05 | Type: Free paper | DOI: 10.82333/dx28-vk85

Authors: Dr Robert Herber ¹ , Daniel Jelin De Weber ¹ , Sara Eskeif ¹ , Raghdan Hakim ¹ , Prof. Dr Riccardo Vinciguerra* ² , Prof. Dr Frederik Raiskup ¹ , Prof. Dr Karin R. Pillunat ¹ , Prof. Dr Ramin Khoramnia ¹

¹Department of Ophthalmology,Faculty of Medicine and University Hospital Carl Gustav Carus,Dresden,Germany, ²Department of Ophthalmology,Humanitas University,Rozzano,Italy

Purpose

In vivo Brillouin spectroscopy (IVBS) has recently gained clinical relevance because it enables localized, depth-resolved measurements of the corneal longitudinal modulus, providing deeper insight into corneal biomechanics. This study investigated how daily corneal hydration fluctuations, age, and ocular diseases including keratoconus (KC) and primary open angle glaucoma (HPG) affect the Brillouin modulus (BM).

Setting

Prospective study at a single university clinic.

Methods

This study enrolled four groups: young healthy subjects (n=42), elderly subjects without ocular disease except moderate cataract (n=14), clinical keratoconus (KC, n=44), and medicated high-pressure glaucoma (HPG, n=21). Exclusion criteria included diabetes mellitus and prior corneal surgery. All subjects underwent ophthalmic examination, including corneal tomography and IVBS using an FDA-approved device (BOSS, Intelon, USA). Measured outcomes comprised mean, minimum, maximum, and localized Brillouin modulus (BM). Depth-resolved anterior and posterior stromal BM was analyzed when data permitted. Linear mixed models were used accounting for inter-eye correlation (p < 0.05).

Results

The mean (95% CI) BM increased significantly from 2.88 (2.88–2.89) GPa in the morning to 2.90 (2.89–2.90) GPa in the afternoon (p < 0.001), while corneal thickness decreased slightly during the same period (p = 0.017). Anterior BM exceeded posterior BM (2.90 vs. 2.86 GPa, p < 0.001). Elderly corneas demonstrated higher mean and posterior BM compared to younger corneas (all p < 0.05). In KC, mean and minimum BM decreased significantly relative to healthy controls (p = 0.045 and p = 0.031), without expected disease-specific regional changes such as inferior BM reduction. In contrast, eyes with HPG showed higher mean and maximum BM than elderly controls (p = 0.006 and p = 0.002).

Conclusions

Daily corneal hydration changes and aging affect IVBS measurements, resulting in higher longitudinal modulus (BM) in the afternoon and in older corneas. In addition, eyes with HPG exhibited higher BM. Conversely, KC showed globally reduced BM without characteristic regional weakening. While IVBS is a promising clinical tool, time of day and age must be considered when interpreting measurements.