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A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Biophotonics and Biomedical Optics".

Deadline for manuscript submissions: 15 October 2024 | Viewed by 9123

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Special Issue Editors

Dr. Laura Remón

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Guest Editor

Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain
Interests: visual optics; optical design; optical quality; imaging systems; biomechanics
Special Issues, Collections and Topics in MDPI journals

Dr. Pablo Pérez-Merino

E-Mail Website
Guest Editor

Centre for Microsystems Technology, Ghent University and imec, Technologiepark 126, 9052 Ghent, Belgium
Interests: visual optics; biomedical optics; eye modelling; imaging systems; intraocular lenses; optical coherence tomography; smart ophthalmic devices

Special Issue Information

Dear Colleagues,

The exceptional collection of high-speed and high-resolution imaging techniques, visual simulators, and new customized lenses offers remarkable opportunities and challenges for personalized healthcare in ophthalmology. The present Special Issue aims to capture this rapid and exciting scientific progress in the field of vision research, focusing on new methods to correct refractive errors and high-order aberrations with applications in myopia control, presbyopia, and keratoconus; innovations in optical biometry and customized lens technologies; the development of innovative optical ophthalmic imaging techniques; methods to understand the link between eye movements and refractive errors; numerical simulations and optical methods for the evaluation of ocular biomechanics; and implantable sensors in ophthalmic solutions. We hope to improve our knowledge and understanding of emerging optical technologies in this research field.

For this, we call for the submission of multidisciplinary manuscripts in the field of visual optics to provide a broad scope covering experimental, theoretical, and clinical studies. Submissions may include original research papers, short communications, or targeted reviews. Topics of interest include, but are not limited to, the following aspects:

Recent advances in intraocular lens technology;
Development and application of ophthalmic imaging technology and biometry;
New insights on corneal refractive surgery;
Advances in the monitoring and correction of keratoconus;
Instruments to measure and/or manipulate optical aberrations and their application in myopia, presbyopia, and cataracts;
New methods to understand the influence of eye movements on refractive error development;
Novel optical designs for myopia control;
Opto-biomechanical eye models and technology to assess ocular biomechanics.

Dr. Laura Remón
Dr. Pablo Pérez-Merino
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

vision science
optics of the eye and vision correction
ophthalmic imaging techniques
ocular aberrations and adaptive optics
ocular biomechanics
ocular biometry
eye movements

Published Papers (7 papers)

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Research

11 pages, 2290 KiB

Open AccessArticle

Optimization of the Spot Spacings for Reducing Roughness in Laser-Induced Optical Breakdown Processes for Corneal Laser Vision Correction

by Helen Amann and Samuel Arba Mosquera

Photonics 2024, 11(2), 114; https://doi.org/10.3390/photonics11020114 - 26 Jan 2024

Viewed by 782

Abstract

The aim of this work is to implement an algorithm that simulates a simplified cutting surface based on laser-induced optical breakdown (LIOB). The algorithm includes the definition of a possible positioning of the laser pulses and calculation of the roughness for different parameter settings (including LIOB threshold, pulse energies, and spot spacings) as the difference between simulated and ideal target cut (local differences within the cut, i.e., the waviness of the simulated cut vs. the homogeneity of the ideal target cut). Furthermore, optimizations of specific variables, such as spot distance (along the pathway), track distance (between lines/tracks), and pulse energy, are performed. The simulations suggest that lower pulse energies (well above the LIOB threshold) combined with asymmetric spacings (spot-to-track distance ratio >> 1) may be effective to lower the roughness of laser cuts generated by LIOB processes. The importance of lowering pulse energies (well above the threshold) emphasizes the need for the LIOB threshold to remain low (as low as possible). Reducing roughness by decreasing spacings (thus, increasing dose for same pulse energies) may have negative implications in visual recovery (risk for overdose). In all cases, the roughness is multiple times larger (rougher) than equivalent simulations for ablative procedures. Full article

(This article belongs to the Special Issue Visual Optics)

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8 pages, 1117 KiB

Open AccessArticle

Numerical Analysis of the Effect of Decentered Refractive Segmented Extended Depth of Focus (EDoF) Intraocular Lenses on Predicted Visual Outcomes

by Scott García, Luis Salvá, Salvador García-Delpech, Anabel Martínez-Espert and Vicente Ferrando

Photonics 2023, 10(7), 850; https://doi.org/10.3390/photonics10070850 - 22 Jul 2023

Viewed by 746

Abstract

This study aimed to evaluate the optical performance of a rotationally asymmetric intraocular lens (IOL) when it is decentered relative to the visual axis. The FEMTIS Comfort IOL (Teleon Surgical B.V., Spankeren, The Netherlands) was assessed using ray tracing software in the Atchison model eye at apertures of 3.0 mm and 4.5 mm. The metric used for assessment was the through-the-focus area under the modulation transfer function (TF-MTFa). Decentrations of 0.2 mm and 0.4 mm were considered. Our results indicated that the MTFa defocus curves exhibited significant differences depending on the direction of vertical decentration. Downward decentrations shifted the MTFa curve towards virtual vergences, resulting in improved optical quality at far distances but decreased optical quality at intermediate and near vision. Conversely, upward decentrations produced the opposite effect. Since, on one hand, this lens is fixed within the capsulorhexis during surgery, demonstrating excellent stability, and on the other hand, the precise centration of the capsulorhexis can be made accurately off the visual axis, these results provide surgeons with the opportunity to plan various clinical scenarios to optimize surgical outcomes with this IOL by selecting the optimal location for capsulorhexis centration in each patient. Full article

(This article belongs to the Special Issue Visual Optics)

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6 pages, 226 KiB

Open AccessArticle

Accuracy of Haigis Formula Using Total Keratometry for IOL Power Calculation in Eyes with Previous Myopic and Hyperopic LASIK and PRK

by Alice Galzignato, Virgilio Galvis, Alejandro Tello, Juan F. Urrea, Kenneth J. Hoffer, Catarina P. Coutinho, Domenico Schiano-Lomoriello and Giacomo Savini

Photonics 2023, 10(6), 624; https://doi.org/10.3390/photonics10060624 - 28 May 2023

Cited by 1 | Viewed by 1244

Abstract

Background: this retrospective study aimed to analyze the results of the combination of the Haigis formula and total keratometry (TK) in calculating the IOL power in eyes with previous corneal refractive surgery. Methods: the TK value provided by the IOL Master 700 (Carl Zeiss Meditec) was introduced into the Haigis formula; the mean prediction error (PE), mean absolute error (MAE), median absolute error (MedAE) and percentage of eyes with a PE within ±0.25 D, ±0.5 D, ±0.75 D and ±1.00 D were calculated. Results: ninety-three eyes of 93 patients with previous laser refractive surgery were evaluated. Two groups were defined: the Myopic Group included 51 previously myopic eyes and the Hyperopic Group included 42 previously hyperopic eyes. The mean PE in the Myopic Group was +0.09 ± 0.44 D and 76.47% of eyes had a PE within ±0.50 D. In the Hyperopic Group, the mean PE was −0.15 ± 0.46 D and 66.67% of eyes had a PE within ±0.50 D. Discussion: when compared to the results previously published with other formulas or methods, the Haigis formula combined with TK provided very accurate refractive outcomes for IOL power calculation in eyes with prior myopic and hyperopic corneal refractive surgery. In such eyes the results are similar to or better than those reported in previous studies. Full article

(This article belongs to the Special Issue Visual Optics)

10 pages, 1657 KiB

Open AccessArticle

Corneal Densitometry with Galilei Dual Scheimpflug Analyzer

by Alejandra Consejo, Silvia Basabilbaso and Laura Remon

Photonics 2023, 10(4), 467; https://doi.org/10.3390/photonics10040467 - 19 Apr 2023

Cited by 1 | Viewed by 1098

Abstract

This study aims to apply the densitometry distribution analysis (DDA) method to study corneal densitometry depending on age and corneal region from Galilei Dual Scheimpflug Analyzer tomography. A total of 83 healthy participants aged 39.02 ± 18.34 years (range 9–81 years) were screened using a Ziemer Galilei G2. Images were analysed using the DDA, and two parameters, α (corneal transparency) and β (corneal homogeneity), were estimated. A two-way ANOVA analysis was performed to investigate whether α and β are influenced by age, corneal región (four concentric areas were considered), and their interaction. The parameters α and β statistically change with age and corneal region. A statistically significant interaction effect of 13% (α) and 11% (β) exists between age and corneal region. However, the corneal region plays a more significant role than aging in corneal densitometry; 31% (α) and 51% (β) of the variance can be attributed to the corneal region, while 28% (α) and 5% (β) can be attributed solely to aging. Corneal densitometry can be objectively assessed from Galilei G2 images using the DDA method. The corneal region plays a more significant role than aging in corneal densitometry. Consequently, general results on corneal densitometry and aging should be taken cautiously. Full article

(This article belongs to the Special Issue Visual Optics)

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11 pages, 2823 KiB

Open AccessArticle

Changes in Wavefront Error of the Eye for Different Accommodation Targets under the Application of Phenylephrine Hydrochloride

by María Mechó-García, Iñaki Blanco-Martínez, Paulo Fernandes, Rute J. Macedo-de-Araújo, Miguel Faria-Ribeiro and José Manuel González-Méijome

Photonics 2023, 10(4), 381; https://doi.org/10.3390/photonics10040381 - 30 Mar 2023

Cited by 1 | Viewed by 1002

Abstract

Pharmacological dilation of the eye to have a larger pupil diameter may allow a better understanding of the wavefront error changes with accommodation. This work aimed to investigate whether dilation of the pupil with Phenylephrine Hydrochloride (PHCl) application changes the accommodative response and the Zernike coefficient magnitude with accommodative demand when computed to a common pupil size. Sixteen right eyes of healthy young subjects were measured with the commercial Hartmann–Shack aberrometer IRX3 (Imagine Eyes, Orsay, France) 30 min after two drops of 1.0% PHCl were applied. The eye wavefronts for accommodative demands from 0 to 5 D were measured in natural conditions and after pupil dilatation. Statistically significant differences between both conditions were found for the Zernike coefficients

C_{3}^{- 1}

C_{3}^{1},

C_{4}^{0}

and

C_{6}^{0}

. Without the effect of PHCl, higher values were found for all higher-order Zernike coefficients (HOA). With increased accommodative response, an increase of

C_{3}^{- 1}

and a decrease of

C_{3}^{1}

was observed and the

C_{4}^{0}

becomes more negative; the change from positive to negative is shown in the accommodative demand of 1.5 D. Conversely,

C_{6}^{0}

increases with increasing accommodative demand. To conclude, the results demonstrated that the mydriatic effect of PHCl causes changes in the magnitude of HOA when accommodation is stimulated. The trends observed in the different Zernike coefficients were the same reported in previous studies. Full article

(This article belongs to the Special Issue Visual Optics)

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10 pages, 1480 KiB

Open AccessArticle

Luminous Flux in Ex-Vivo Porcine Eyes during Endoillumination and during Transscleral Illumination Depending on the Transmission Properties of the Eyewall

by Nicole Fehler and Martin Heßling

Photonics 2023, 10(4), 362; https://doi.org/10.3390/photonics10040362 - 23 Mar 2023

Viewed by 806

Abstract

(1) Background: During eye surgery, it is important that sufficient light enlightens the inside of the eye for small structures to become visible. The intraocular brightness is influenced by the luminous flux of the illumination system. However, the intraocular luminous flux during surgery has not been investigated so far. Insufficient luminous flux makes vision difficult for the surgeon, whereas excessive luminous flux can cause damage to the retina. Therefore, the luminous flux in lightly and strongly pigmented eyes is determined by endoillumination and diaphanoscopic illumination. (2) Methods: First, the luminous flux emitted from a diaphanoscopic illumination fiber is measured. For determining the intraocular luminous flux, this is multiplied with the transmission properties of the eyewall, which are determined for ex vivo porcine eyes. In order to compare the luminous flux of transscleral illumination with that of endoillumination, the luminous flux of various endoillumination fibers is examined. (3) Results: The results reveal that the total transmission of the eyewall is up to 2.5 times higher for blue/lightly pigmented eyes than for brown/strongly pigmented eyes. With this, the intraocular luminous flux in ex vivo porcine eyes is around 95% higher for less pigmented eyes than for strong pigmented eyes, considering intraocular reflections. (4) Conclusion: To obtain the same brightness in blue and brown eyes, the surgeon can reduce the intensity of the light source when illuminating blue eyes to reduce their retinal risk. Full article

(This article belongs to the Special Issue Visual Optics)

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11 pages, 1536 KiB

Open AccessArticle

Photostress Recovery Time after Flash-Lighting Is Increased in Myopic Eyes

by Francisco J. Ávila, Pilar Casado and Jorge Ares

Photonics 2023, 10(1), 86; https://doi.org/10.3390/photonics10010086 - 12 Jan 2023

Cited by 1 | Viewed by 2092

Abstract

Background: It is well-known that non-pathological axial myopic eyes present physiological and functional differences in comparison with emmetropic eyes due to altered retinal anatomy. Photostress tests have shown very significant capabilities to discriminate a normal retina from an abnormal retina. Accordingly, the aim of this work was to investigate the differences between myopic and emmetropic eyes in the measured photostress recovery time (PSRT) after retinal light-flashing in a population of young healthy subjects. Methods: A coaxial illumination total disability glare instrument was employed to measure the recovery time after photostress was induced by a 240 milliseconds flash-lighting (535 nm) exposure on 66 myopic and 66 emmetropic eyes. The measurements were carried out for different combinations of glare angles and contrasts of the visual stimuli. Results: In general terms, PSRT in myopic eyes was found at a statistically higher than in emmetropic eyes (Bonferroni correction). For both groups, the measured recovery strongly depends on the contrast of the test object used to measure baseline recovery function and markedly less on the source of glare angles explored. When the PSRTs obtained for different glare angles are averaged, the differences between PSRTs drastically increase with the reduction in the contrast of the stimuli between both groups of study. Conclusions: PSRT is higher for myopic than for young healthy emmetropic eyes (1.2 s and 0.2 s for 5% and 100% contrast test object, respectively). Though seemingly small, the magnitude of this finding can be relevant when flash-lighting happens while driving a car or while performing actions where the reaction time after a visual stimulus can be critical. Full article

(This article belongs to the Special Issue Visual Optics)

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