title: Assessment of corneal hydration sensing in the terahertz band: in vivo results at 100 GHz.
abstract: Terahertz corneal hydration sensing has shown promise in ophthalmology applications and was recently shown to be capable of detecting water concentration changes of about two parts in a thousand in ex vivo corneal tissues. This technology may be effective in patient monitoring during refractive surgery and for early diagnosis and treatment monitoring in diseases of the cornea. In this work, Fuchs dystrophy, cornea transplant rejection, and keratoconus are discussed, and a hydration sensitivity of about one part in a hundred is predicted to be needed to successfully distinguish between diseased and healthy tissues in these applications. Stratified models of corneal tissue reflectivity are developed and validated using ex vivo spectroscopy of harvested porcine corneas that are hydrated using polyethylene glycol solutions. Simulation of the cornea's depth-dependent hydration profile, from 0.01 to 100 THz, identifies a peak in intrinsic reflectivity contrast for sensing at 100 GHz. A 100 GHz hydration sensing system is evaluated alongside the current standard ultrasound pachymetry technique to measure corneal hydration in vivo in four rabbits. A hydration sensitivity, of three parts per thousand or better, was measured in all four rabbits under study. This work presents the first in vivo demonstration of remote corneal hydration sensing.
authors.affiliation: Center for Advanced Surgical and Interventional Technology, Los Angeles, California 90095, USA. dbennett.mednet@gmail.com
authors.forename: David
authors.initials: D
authors.lastname: Bennett
authors.forename: Zachary
authors.initials: Z
authors.lastname: Taylor
authors.forename: Pria
authors.initials: P
authors.lastname: Tewari
authors.forename: Sijun
authors.initials: S
authors.lastname: Sung
authors.forename: Ashkan
authors.initials: A
authors.lastname: Maccabi
authors.forename: Rahul
authors.initials: R
authors.lastname: Singh
authors.forename: Martin
authors.initials: M
authors.lastname: Culjat
authors.forename: Warren
authors.initials: W
authors.lastname: Grundfest
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Hubschman
authors.forename: Elliott
authors.initials: E
authors.lastname: Brown
mesh_terms: D000465:Algorithms; D000818:Animals; D001834:Body Water / Q000378:metabolism*; D003315:Cornea / Q000737:chemistry*; D011817:Rabbits; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055068:Terahertz Spectroscopy / Q000379:methods*; D014867:Water / Q000032:analysis*
chemical_list: D014867:Water