Study of transmittance and reflectance spectra of the cornea and the sclera in the THz frequency range

Abstract

An adequate water balance (hydration extent) is one of the basic factors of normal eye function, including its external shells: the cornea and the sclera. Adequate control of corneal and scleral hydration is very important for early diagnosis of a variety of eye diseases, stating indications for and contraindications against keratorefractive surgeries and the choice of contact lens correction solutions. THz systems of creating images in reflected beams are likely to become ideal instruments of noninvasive control of corneal and scleral hydration degrees. This paper reports on the results of a study involving transmittance and reflectance spectra for the cornea and the sclera of rabbit and human eyes, as well as those of the rabbit eye, in the frequency range of 0.13 to 0.32 THz. The dependence of the reflectance coefficient of these tissues on water mass percentage content was determined. The experiments were performed on three corneas, three rabbit scleras, two rabbit eyes, and three human scleras. The preliminary results demonstrate that the proposed technique, based on the use of a continuous THz radiation, may be utilized to create a device for noninvasive control of corneal and scleral hydration, which has clear potential of broad practical application.

Terahertz scanning of the rabbit cornea with experimental UVB-induced damage: in vivo assessment of hydration and its verification

“…The experimental setup was preliminary tested in our previous work in the experiment of studying the dependence of the reflection coefficient of the extracted rabbit corneas on the water content in them. 26 To obtain optimal detector sensitivity, the incident radiation was modulated at a frequency of 10 Hz with a mechanical obturator. The rabbits were immobilized to exclude the impact of eye movements on the reflected signal.…”

“…In our previous work, for the first time in ophthalmology, we have created a test bed for studying corneal hydration using THz scanning, in particular, we have developed a laboratory prototype of the device for monitoring the state of the corneal water balance in vivo . 26 , 27 It is necessary to emphasize that THz radiation will interact with both the tear film and the cornea structure. The preliminary data showed that the proposed technology is effective and has the potential for widespread use in clinical ophthalmology.…”

An ANCOVA analysis of the results of planned and actually obtained hypocorrection after excimer laser surgery in middle-aged patients with myopia

“…Для более точного планирования гипокоррекции у пациентов с близорукостью средней и высокой степени от 35 до 50 лет, по-видимому, важно знать степень гидратации роговицы. В настоящее время ведется разработка технологии прижизненного бесконтактного контроля содержания воды в ткани роговицы на основе ее терагерцевого сканирования, внедрение которой в клиническую практику позволит эффективно решить данную проблему [12,13].…”

Investigating the Impact of Synchrotron THz Radiation on the Corneal Hydration Using Synchrotron THz-Far Infrared Beamline

“…The previous studies involved THz sensing of corneal tissue-induced damages and have used various THz radiation sources and hydration measurement systems. For instance, Iomdina et al, reported on the study of transmittance and reflectance of the cornea and sclera in the range of 0.13 to 0.32 THz followed by exposure to a backward-wave oscillator (BWO) with an effective bandwidth frequency of 10 MHz [ 13 ]. In another study, they explored the THz scanning of hydration of corneal tissue followed by damage caused by B-band ultraviolet (UVB) exposure at 50 Hz [ 14 ], while some studies have investigated THz sensing of ocular tissues, no studies have previously reported on the use of synchrotron continuous THz radiation source for both exposing and evaluating biological changes in corneal tissues or other ocular tissues.…”