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Author | Neroev, V. V.; Iomdina, E. N.; Khandzhyan, A. T.; Khodzhabekyan, N. V.; Sengaeva, M. D.; Ivanova, A. V.; Seliverstov, S. V.; Teplyakova, K. O.; Goltsman, G. N. | ||||
Title | Experimental study of the effect of corneal hydration and its biomechanical properties on the results of photorefractive keratectomy | Type | Journal Article | ||
Year | 2021 | Publication | Vestn. Oftalmol. | Abbreviated Journal | Vestn. Oftalmol. |
Volume | 137 | Issue | 3 | Pages | 68-75 |
Keywords | THz scanning, cornea, photorefractive keratectomy, medicine | ||||
Abstract | Water content in the cornea may affect the outcome of its excimer laser ablation, especially in presbyopic patients with myopic refraction. This hypothesis can be tested by scanning the cornea in the terahertz (THz) range to determine its hydration level. Purpose: To study the effect of hydration of the cornea determined by non-contact THz scanning and its biomechanical parameters on the results of photorefractive keratectomy (PRK) in an experiment. Material and methods: PRK was performed using the Nidek EC-5000 QUEST excimer laser on 8 rabbit eyes. Corneal hydration was evaluated by determining the reflection coefficient (RC) in the THz electromagnetic radiation range before PRK, after 3-5 days, and after 1, 2, 3, and 4 months. Clinical examination included autorefractometry, assessment of corneal thickness and other anatomical and optical parameters of the anterior eye segment (Galilei G6, Ziemer Ophthalmic Systems AG 6.0.2, Switzerland), measurement of corneal hysteresis (CH) and corneal resistance factor (CRF) using the Ocular Response Analyzer (ORA; Reichert, USA), as well as tear production (Schirmer test). Results: The initial water content in the cornea has a significant effect on the thickness of the removed layer, i.e. on the PRK effect, with correlation coefficient of Rs= -0.976 (p<0.01). The correlation between CH and the ablation depth is less pronounced (Rs=0.643), and CRF had no correlation with it (Rs= -0.089). Biomechanical indicators of the cornea depend on its hydration: changes in CH and CRF after excimer laser ablation qualitatively coincide with changes in RC, the correlation coefficient between RC and the initial value of CH is R= -0.619 (moderate negative correlation). Conclusion: THz scanning is an effective non-contact technology for monitoring corneal hydration level. The mismatch of the hypoeffect of keratorefractive excimer laser intervention planned for patients with presbyopia with the actual outcome can be caused by individual decrease in the initial water content in the cornea. |
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Russian | Summary Language | Original Title | ||
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Area | Expedition | Conference | |||
Notes | Approved | no | |||
Call Number | Serial | 1794 | |||
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Author | Iomdina, E. N.; Seliverstov, S. V.; Teplyakova, K. O.; Jani, E. V.; Pozdniakova, V. V.; Polyakova, O. N.; Goltsman, G. N. | ||||
Title | Terahertz scanning of the rabbit cornea with experimental UVB-induced damage: in vivo assessment of hydration and its verification | Type | Journal Article | ||
Year | 2021 | Publication | J. Biomed. Opt. | Abbreviated Journal | J. Biomed. Opt. |
Volume | 26 | Issue | 4 | Pages | |
Keywords | medicine; scheimpflug imaging; UVB; confocal microscopy; cornea; optical coherent tomography; rabbit eyes; terahertz radiation | ||||
Abstract | SIGNIFICANCE: Water content plays a vital role in the normally functioning visual system; even a minor disruption in the water balance may be harmful. Today, no direct method exists for corneal hydration assessment, while it could be instrumental in early diagnosis and control of a variety of eye diseases. The use of terahertz (THz) radiation, which is highly sensitive to water content, appears to be very promising. AIM: To find out how THz scanning parameters of corneal tissue measured by an experimental setup, specially developed for in vivo contactless estimations of corneal reflectivity coefficient (RC), are related to pathological changes in the cornea caused by B-band ultraviolet (UVB) exposure. APPROACH: The setup was tested on rabbit eyes in vivo. Prior to the course of UVB irradiation and 1, 5, and 30 days after it, a series of examinations of the corneal state was made. At the same time points, corneal hydration was assessed by measuring RC. RESULTS: The obtained data confirmed the negative impact of UVB irradiation course on the intensity of tear production and on the corneal thickness and optical parameters. A significant (1.8 times) increase in RC on the 5th day after the irradiation course, followed by a slight decrease on the 30th day after it was revealed. The RC increase measured 5 days after the UVB irradiation course generally corresponded to the increase (by a factor of 1.3) of tear production. RC increase occurred with the corneal edema, which was manifested by corneal thickening (by 18.2% in the middle area and 17.6% in corneal periphery) and an increased volume of corneal tissue (by 17.6%). CONCLUSIONS: Our results demonstrate that the proposed approach can be used for in vivo contactless estimation of the reflectivity of rabbit cornea in the THz range and, thereby, of cornea hydration. | ||||
Address | National Research University Higher School of Economics, Moscow Institute of Electronics and Mathema, Russia | ||||
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English | Summary Language | Original Title | ||
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Series Volume | Series Issue | Edition | |||
ISSN | 1083-3668 | ISBN | Medium | ||
Area | Expedition | Conference | |||
Notes | PMID:33834684; PMCID:PMC8027227 | Approved | no | ||
Call Number | Serial | 1258 | |||
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Author | Iomdina, E. N.; Goltsman, G. N.; Seliverstov, S. V.; Sianosyan, A. A.; Teplyakova, K. O.; Rusova, A. A. | ||||
Title | Study of transmittance and reflectance spectra of the cornea and the sclera in the THz frequency range | Type | Journal Article | ||
Year | 2016 | Publication | J. Biomed. Opt. | Abbreviated Journal | J. Biomed. Opt. |
Volume | 21 | Issue | 9 | Pages | 97002 (1 to 5) |
Keywords | BWO, IMPATT diode, Schottky diode, medicine, animals, cornea, physiology, humans, rabbits, sclera diagnostic imaging, physiology | ||||
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. | ||||
Address | Moscow State Pedagogical University, Department of Physics, 29 Malaya Pirogovskaya Street, Moscow 119435, Russia | ||||
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English | Summary Language | Original Title | ||
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Series Volume | Series Issue | Edition | |||
ISSN | 1083-3668 | ISBN | Medium | ||
Area | Expedition | Conference | |||
Notes | PMID:27626901 | Approved | no | ||
Call Number | Serial | 1335 | |||
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Author | Baksheeva, K.; Ozhegov, R.; Goltsman, G.; Kinev, N.; Koshelets, V.; Kochnev, A.; Betzalel, N.; Puzenko, A.; Ben Ishai, P.; Feldman, Y. | ||||
Title | The sub THz emission of the human body under physiological stress | Type | Journal Article | ||
Year | 2021 | Publication | IEEE Trans. Terahertz Sci. Technol. | Abbreviated Journal | IEEE Trans. Terahertz Sci. Technol. |
Volume | Issue | Pages | |||
Keywords | skin sub-THz emission, medicine | ||||
Abstract | We present evidence that in the sub-THz frequency band, human skin can be considered as an electromagnetic bio-metamaterial, in that its natural emission is a product of skin tissue geometry and embedded structures. Radiometry was performed on 32 human subjects from 480 to 700 GHz. Concurrently, the subjects were exposed to stress, while heart pulse rate (PS) and galvanic skin response (GSR) were also measured. The results are substantially different from the expected black body radiation signal of the skin surface. PS and GSR correlate to the emissivity. Using a simulation model for the skin, we find that the sweat duct is a critical element. The simulated frequency spectra qualitatively match the measured emission spectra and show that our sub-THz emission is modulated by our level of mental stress. This opens avenues for the remote monitoring of the human state. | ||||
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Notes | Approved | no | |||
Call Number | 9380570 | Serial | 1259 | ||
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Author | Baksheeva, K.; Vdovydchenko, A.; Gorshkov, K.; Ozhegov, R.; Kinev, N.; Koshelets, V.; Goltsman, G. | ||||
Title | Study of human skin radiation in the terahertz frequency range | Type | Conference Article | ||
Year | 2019 | Publication | J. Phys.: Conf. Ser. | Abbreviated Journal | J. Phys.: Conf. Ser. |
Volume | 1410 | Issue | Pages | 012076 (1 to 5) | |
Keywords | SIS mixer, SIR, applications, medicine, sympathetic nervous system, SNS | ||||
Abstract | The radiation of human skin in the terahertz frequency range under the influence of mental stresses has been studied in the current work. An experimental setup for observation of changes in human skin radiation, which occur under the influence of psychological stresses, by means of a superconducting integrated receiver has been developed. More than 30 volunteers participate in these studies, which allows us to verify presence of correlation between the signals from the superconducting integrated terahertz receiver and other sensors that monitor human mental stress. | ||||
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Series Volume | Series Issue | Edition | |||
ISSN | 1742-6588 | ISBN | Medium | ||
Area | Expedition | Conference | |||
Notes | Approved | no | |||
Call Number | Serial | 1272 | |||
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