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Komar K. Two-photon vision - Seeing colors in infrared. Vision Res 2024; 220:108404. [PMID: 38608547 DOI: 10.1016/j.visres.2024.108404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/21/2024] [Accepted: 03/25/2024] [Indexed: 04/14/2024]
Abstract
This review discusses the current state of knowledge regarding the phenomenon called two-photon vision. It involves the visual perception of pulsed infrared beams in the range of 850-1200 nm as having colors corresponding to one-half of the IR wavelengths. It is caused by two-photon absorption (TPA), which occurs when the visual photopigment interacts simultaneously with two infrared photons. The physical mechanism of TPA is described, and implications about the efficiency of the process are considered. The spectral range of two-photon vision is defined, along with a detailed discussion of the known differences in color perception between normal and two-photon vision. The quadratic dependence of the luminance of two-photon stimuli on the power of the stimulating beam is also explained. Examples of recording two-photon vision in the retinas of mice and monkeys are provided from the literature. Finally, applications of two-photon vision are discussed, particularly two-photon microperimetry, which has been under development for several years; and the potential advantages of two-photon retinal displays are explained.
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Affiliation(s)
- Katarzyna Komar
- International Centre for Translational Eye Research, Skierniewicka 10a, 01-230 Warsaw, Poland; Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, M. Kasprzaka 44/52, 01-224 Warsaw, Poland; Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Torun, Grudziądzka 5, 87-100 Toruń, Poland.
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Doyle HK, Herbeck SR, Boehm AE, Vanston JE, Ng R, Tuten WS, Roorda A. Boosting 2-photon vision with adaptive optics. J Vis 2023; 23:4. [PMID: 37801322 PMCID: PMC10561787 DOI: 10.1167/jov.23.12.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 09/05/2023] [Indexed: 10/07/2023] Open
Abstract
The 2-photon effect in vision occurs when two photons of the same wavelength are absorbed by cone photopigment in the retina and create a visual sensation matching the appearance of light close to half their wavelength. This effect is especially salient for infrared light, where humans are mostly insensitive to 1-photon isomerizations and thus any perception is dominated by 2-photon isomerizations. This phenomenon can be made more readily visible using short-pulsed lasers, which increase the likelihood of 2-photon excitation by making photon arrivals at the retina more concentrated in time. Adaptive optics provides another avenue for enhancing the 2-photon effect by focusing light more tightly at the retina, thereby increasing the spatial concentration of incident photons. This article makes three contributions. First, we demonstrate through color-matching experiments that an adaptive optics correction can provide a 25-fold increase in the luminance of the 2-photon effect-a boost equivalent to reducing pulse width by 96%. Second, we provide image-based evidence that the 2-photon effect occurs at the photoreceptor level. Third, we use our results to compute the specifications for a system that could utilize 2-photon vision and adaptive optics to image and stimulate the retina using a single infrared wavelength and reach luminance levels comparable to conventional displays.
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Affiliation(s)
- Hannah K Doyle
- Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, CA, USA
| | - Sofie R Herbeck
- Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, CA, USA
| | - Alexandra E Boehm
- Herbert Wertheim School of Optometry and Vision Science, University of California Berkeley, Berkeley, CA, USA
| | - John E Vanston
- Herbert Wertheim School of Optometry and Vision Science, University of California Berkeley, Berkeley, CA, USA
| | - Ren Ng
- Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, CA, USA
| | - William S Tuten
- Herbert Wertheim School of Optometry and Vision Science, University of California Berkeley, Berkeley, CA, USA
| | - Austin Roorda
- Herbert Wertheim School of Optometry and Vision Science, University of California Berkeley, Berkeley, CA, USA
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Stachowiak D, Marzejon M, Bogusławski J, Łaszczych Z, Komar K, Wojtkowski M, Soboń G. Femtosecond Er-doped fiber laser source tunable from 872 to 1075 nm for two-photon vision studies in humans. BIOMEDICAL OPTICS EXPRESS 2022; 13:1899-1911. [PMID: 35519271 PMCID: PMC9045895 DOI: 10.1364/boe.452609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 02/16/2022] [Accepted: 02/24/2022] [Indexed: 06/14/2023]
Abstract
We report the development of a widely-tunable femtosecond fiber laser system and its application for two-photon vision studies. The source is based on an Er-doped fiber laser with spectral shift up to 2150 nm, followed by a second harmonic generation module to generate a frequency-doubled beam tunable from 872 to 1075 nm. The source delivers sub-230 fs pulses with nearly-constant duration over the entire tuning range, with output powers between 0.68-1.24 mW, which corresponds to a pulse energy of 13.2-24.1 pJ. Such pulse energy is sufficient for employing a system for measurements of two-photon scotopic spectral sensitivity of two-photon vision in humans. The laser parameters allow for very efficient and safe two-photon stimulation of the human visual system, as proved by a good separation between one- and two-photon thresholds for wavelengths below 950 nm, which we have confirmed for 3 healthy subjects.
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Affiliation(s)
- Dorota Stachowiak
- Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Marcin Marzejon
- Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
- Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, G. Narutowicza 11/12, 80-233 Gdańsk, Poland
| | - Jakub Bogusławski
- Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
- Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
- International Centre for Translational Eye Research, Skierniewicka 10a, 01-230 Warszawa, Poland
| | - Zbigniew Łaszczych
- Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
| | - Katarzyna Komar
- Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
- International Centre for Translational Eye Research, Skierniewicka 10a, 01-230 Warszawa, Poland
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Torun, Grudziądzka 5, 87-100 Toruń, Poland
| | - Maciej Wojtkowski
- Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
- International Centre for Translational Eye Research, Skierniewicka 10a, 01-230 Warszawa, Poland
| | - Grzegorz Soboń
- Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
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Two-Photon Vision in Age-Related Macular Degeneration: A Translational Study. Diagnostics (Basel) 2022; 12:diagnostics12030760. [PMID: 35328313 PMCID: PMC8947013 DOI: 10.3390/diagnostics12030760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 03/14/2022] [Accepted: 03/16/2022] [Indexed: 11/17/2022] Open
Abstract
The recently introduced term “two-photon vision” relates to the visual perception resulting from a simultaneous absorption of two photons by photoreceptors. In this study, we determined two-photon retinal sensitivity in age-related macular degeneration (AMD) and compared it that in normal aging. Microperimetry was performed with visible (white) light and infrared (IR) light, which was perceived as green in the two-photon stimulation. In total, 45 subjects were included with one (better) eye studied. Furthermore, best-corrected visual acuity (VA) and ocular straylight were assessed. AMD resulted in decreased median (interquartile range) logMAR VA, i.e., 0.15 (0.05; 0.24), which in normal eyes was −0.02 (−0.06; 0.02). The two groups showed comparable straylight levels. Sensitivity to IR light was significantly lower in the AMD group (p < 0.001): 8.3 (7.4, 9.3) dB than in controls 10.7 (9.7, 11.2) dB. AMD also significantly affected visible light sensitivity (p < 0.001): 14.0 (11.0; 15.5) dB vs. 18.0 (16.3; 18.9) dB. Notably, the two-photon approach yielded a lower data spread. In conclusion, AMD considerably impairs retinal sensitivity measured in the single- and two-photon realm. However, two-photon-vision microperimetry may improve the testing accuracy and offer an additional diagnostic parameter (beyond VA measurements) for retinal function assessment.
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