Peng Shao1, Theo G Seiler1,2,3, Amira M Eltony1, Antoine Ramier1,4, Sheldon J J Kwok1,4, Giuliano Scarcelli1,5, Roberto Pineda Ii6, Seok-Hyun Yun1,4,7. 1. Wellman Center for Photomedicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States. 2. Institut für Refraktive und Ophthalmo-Chirurgie (IROC), Zürich, Switzerland. 3. Universitätsklinik für Augenheilkunde, Inselspital, Bern, Switzerland. 4. Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States. 5. Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, United States. 6. Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, United States. 7. Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States.
Abstract
Purpose: To investigate how corneal hydration affects the Brillouin frequency of corneal stroma. Methods: From a simple analytical model considering the volume fraction of water in corneal stroma, we derived the dependence of Brillouin frequency on hydration and hydration-induced corneal thickness variation. The Brillouin frequencies of fresh ex vivo porcine corneas were measured as their hydration was varied in dextran solution and water. Healthy volunteers (8 eyes) were scanned in vivo repeatedly over the course of 9 hours, and the diurnal variations of Brillouin frequency and central corneal thickness (CCT) were measured. Results: The measured dependence of Brillouin frequency on hydration, both ex vivo and in vivo, agreed well with the theoretical prediction. The Brillouin frequencies of human corneas scanned immediately after waking were on average ∼25 MHz lower than their daytime average values. For stabilized corneas, the typical variation of Brillouin frequency was ± 7.2 MHz. With respect to CCT increase or swelling, the Brillouin frequency decreased with a slope of -1.06 MHz/μm in vivo. Conclusions: The ex vivo and in vivo data agree with our theoretical model and support that the effect of corneal hydration on Brillouin frequency comes predominantly from the dependence of the tissue compressibility on the water. Corneal hydration correlates negatively with the Brillouin frequency. During daytime activities, the influence of physiological hydration changes in human corneas is < ± 10 MHz. The sensitivity to hydration may potentially be useful in detecting abnormal hydration change in patients with endothelial disorders.
Purpose: To investigate how corneal hydration affects the Brillouin frequency of corneal stroma. Methods: From a simple analytical model considering the volume fraction of water in corneal stroma, we derived the dependence of Brillouin frequency on hydration and hydration-induced corneal thickness variation. The Brillouin frequencies of fresh ex vivo porcine corneas were measured as their hydration was varied in dextran solution and water. Healthy volunteers (8 eyes) were scanned in vivo repeatedly over the course of 9 hours, and the diurnal variations of Brillouin frequency and central corneal thickness (CCT) were measured. Results: The measured dependence of Brillouin frequency on hydration, both ex vivo and in vivo, agreed well with the theoretical prediction. The Brillouin frequencies of human corneas scanned immediately after waking were on average ∼25 MHz lower than their daytime average values. For stabilized corneas, the typical variation of Brillouin frequency was ± 7.2 MHz. With respect to CCT increase or swelling, the Brillouin frequency decreased with a slope of -1.06 MHz/μm in vivo. Conclusions: The ex vivo and in vivo data agree with our theoretical model and support that the effect of corneal hydration on Brillouin frequency comes predominantly from the dependence of the tissue compressibility on the water. Corneal hydration correlates negatively with the Brillouin frequency. During daytime activities, the influence of physiological hydration changes in human corneas is < ± 10 MHz. The sensitivity to hydration may potentially be useful in detecting abnormal hydration change in patients with endothelial disorders.
Authors: Ronald H Silverman; Monica S Patel; Omer Gal; Aman Sarup; Avnish Deobhakta; Haitham Dababneh; Dan Z Reinstein; Ernest J Feleppa; D Jackson Coleman Journal: Ultrasound Med Biol Date: 2009-02-05 Impact factor: 2.998
Authors: Keyton Clayson; Thomas Sandwisch; Yanhui Ma; Elias Pavlatos; Xueliang Pan; Jun Liu Journal: Curr Eye Res Date: 2019-09-18 Impact factor: 2.424
Authors: Brecken J Blackburn; Shi Gu; Matthew R Ford; Vinícius de Stefano; Michael W Jenkins; William J Dupps; Andrew M Rollins Journal: Invest Ophthalmol Vis Sci Date: 2019-01-02 Impact factor: 4.799