Search Results (26)

Objectives: To compare the objective refraction of young hyperopes obtained by two wavefront autorefractors with identical measurement principles but different optical designs: a monocular closed-field (VX 120) and a binocular open-field (Eye Refract), both developed by the same manufacturer (Visionix; Pont-de-l’Arche, France). Methods: A randomized, cross-sectional study was carried out with 37 hyperopic participants (18.2 ± 7.8 years; range 8 to 31 years). Each participant underwent two measurement sessions (one with and one without cycloplegia), during which three measurements were taken per autorefractor (monocular and binocular). Refractive variables (M, J0, and J45) were analyzed in one randomly selected eye. Results: The spherical equivalent (M) showed significant differences between autorefractors under noncycloplegic and cycloplegic conditions (p < 0.001). Without cycloplegia, the binocular autorefractor measured +0.45 (+1.49, −0.58) D more hyperopia than the monocular device. Under cycloplegia, this difference decreased to +0.26 D (+0.99, −0.48) D. Both autorefractors provided higher hyperopia with cycloplegia, with differences inversely correlated with age (r = −0.4; p < 0.05). Conclusions: Whenever possible, refraction in young hyperopes should be measured under cycloplegic conditions using a binocular open-field autorefractor to promote greater accommodative relaxation and ensure more reliable hyperopia measurements in both clinical practice and research. Full article

Based on the widely used Gullstrand–Le Grand eye model, a scattering individual eye model was constructed with Zemax, which has individual ocular wavefront aberration and the scattering particles distributed in the eye. There are three main steps to build the model. Firstly, the Gullstand-Le Grand eye model was constructed, and converted into a non-sequential model. The axial lengths of all ocular components, and the corneal curvatures were input into the optical model. Secondly, a high-order aspheric surface-Zernike Fringe Sag surface was chosen to fit the wavefront aberrations measured with the ocular wavefront aberrometer. Thirdly, an embedded scattering lens within the crystalline lens was developed, of which parameters of scattering particles can be selected flexibly. The scattering individual eye model can be used to quantitatively investigate interaction between ocular aberrations and scattering light on retina image quality. The results demonstrated that when scattering particles were uniformly distributed across the optical pupil, MTFs at all spatial frequencies decreased proportionally with increasing particle density, independent of aberrations. When scattering particles were located in regions with smaller wavefront aberrations, the combined effect of scattering and aberrations synergistically degraded retinal image quality. In contrast, when particles were concentrated in zones of larger aberrations, the scattered light could partially compensate for the aberrational effects, leading to improved optical performance Full article

A multi-order combined diffraction spatial filter, integrated with a set of Zernike phase functions (representing wavefront aberrations) and Zernike polynomials, enables the simultaneous formation of multiple aberration-transformed point spread function (PSF) patterns in a single plane. This is achieved using an optical Fourier correlator and provides significantly more information than a single PSF captured in focal or defocused planes—all without requiring mechanical movement. To analyze the resulting complex intensity patterns, which include 49 diffraction orders, a convolutional neural network based on the Xception architecture is employed. This model effectively identifies wavefront aberrations up to the fourth Zernike order. After 80 training epochs, the model achieved a mean absolute error (MAE) of no more than 0.0028. Additionally, a five-fold cross-validation confirmed the robustness and reliability of the approach. For the experimental validation of the proposed multi-order filter, a liquid crystal spatial light modulator was used. Optical experiments were conducted using a Fourier correlator setup, where aberration fields were generated via a digital micromirror device. The experimental results closely matched the simulation data, confirming the effectiveness of the method. New advanced aberrometers and multichannel diffractive optics technologies can be used in industry for the quality control of optical elements, assessing optical system alignment errors, and the early-stage detection of eye diseases. Full article

Objectives: This study compared the visual outcomes and optical quality of two monofocal, aspheric intraocular lenses (IOLs; CT LUCIA 621P, Carl Zeiss Meditec; Eyhance ICB00, Johnson & Johnson Vision) by evaluating visual acuity, contrast sensitivity, and higher-order aberrations 1 month post-cataract surgery. Methods: In this retrospective, comparative study, 120 eyes (72 patients) that underwent cataract surgery with either CT LUCIA 621P (Lucia group) or Eyhance ICB00 (Eyhance group) implantation (60 eyes/group) were retrospectively investigated. Visual acuity at various distances and defocus curves were measured 1 month postoperatively. Optical quality was assessed by comparing contrast sensitivity and internal coma, spherical, and total aberrations by using iTrace (Tracey Technology), a ray-tracing-type aberrometer. Results: The visual acuity and defocus curves were similar between the two IOLs 1 month postoperatively. The Lucia group showed better contrast sensitivity at higher spatial frequencies: 12 cpd (p < 0.001, 1.32 LogCS vs. 1.02 LogCS) and 18 cpd (p = 0.009, 0.74 LogCS vs. 0.47 LogCS) unilaterally and 18 cpd (p = 0.044, 0.94 LogCS vs. 0.60 LogCS) bilaterally. Postoperative internal spherical aberration was significantly lower in the Lucia group (p < 0.001, −0.04 µm vs. −0.003 µm). Internal coma and total aberrations were similar. Conclusions: The visual acuity and defocus curves of the Lucia and Eyhance groups were comparable 1 month post-cataract surgery. The Lucia group’s superior contrast sensitivity and lower postoperative internal spherical aberration were due to differences in IOL designs, particularly the power variation patterns. Full article

Background: Given the lack of standardization in stimulus types for assessing accommodation, we aimed to evaluate accommodative response (AR) and Zernike coefficients using four different stimuli. Methods: Sixteen healthy subjects aged 22–32 years participated. Four black transilluminated stimuli (Snellen 6/12 “E”, 6/6 “e”, Maltese Cross 6/12 “X”, 6/6 “x”) were used to stimulate accommodation from 0 D to 5 D, in 1 D increments, using the irx3 aberrometer. From the results, AR was calculated with Seidel defocus and the change in Zernike coefficient value between the non-accommodative state and the fully accommodative state (5 D) was determined. Results: Larger pupils were observed with stimulus “E” (p-value < 0.05). The mean AR at the maximum accommodative level (5 D) for the different stimuli was −1.88 ± 1.00 for “E”, −2.60 ± 1.44 for “X”, −2.00 ± 1.32 for “e”, and −2.40 ± 1.27 for “x”. No statistically significant differences were found between AR and Zernike coefficients with the four different accommodative stimuli (p-value > 0.05, one-way ANOVA). Conclusions: The study evaluated accommodative stimulus design and size on AR and Zernike coefficients and found no significant differences. However, stimuli with higher spatial frequencies (“e” and “E”) provided larger ARs compared to the other stimuli. Full article

This study investigated the relationship between high-order aberrations (HOAs) and accommodative dysfunctions by analyzing their changes with accommodation. Understanding this relationship is important for understanding the mechanisms underlying these conditions. Sixty-three subjects were divided into five groups: control, infacility of accommodation (INFA), excess of accommodation (EA), insufficiency of accommodation (INSA), and symptomatic without dysfunction (SWD). Variations in root-mean-square (RMS) of the 3rd, 4th, 5th, and 6th orders and HOAs, and fluctuations of RMS HOAs, were measured using a Shack–Hartmann aberrometer at different accommodative stimuli and during residual accommodation after their removal, in the following order: 0.00 D, 1.00 D, 0.00 D, 2.45 D, 0.00 D, 4.73 D and 0.00 D. The SWD group showed a significant increase in RMS HOAs during accommodation and residual accommodation. In contrast, the EA group showed an improvement in the ocular optical quality at higher stimuli. Different patterns of changes in the 3rd, 4th, 5th, and 6th orders were observed across all groups, and fluctuations of RMS HOAs increased significantly in the SWD group during accommodation and residual accommodation. These distinct patterns of aberration changes in different accommodative dysfunctions suggest a potential link between their underlying mechanisms, providing insights that may aid their earlier diagnosis and improved management. Full article

Purpose: To assess the possible impact of minor changes in fixation on wavefront measurements as a potential constraint in detecting subtle temporal variations in ocular wavefront error. Methods: Twelve healthy subjects with an average age of 36.3 ± 8.8 were instructed to put their heads in the aberrometer’s chin-rest and look at a fixation target that was embedded in the device. The fixation targets were readily observable to the participants without accommodation, thanks to the aberrometer’s Badal system. When each eye was staring at the target, its wavefront aberration was recorded three times and then averaged for further analysis. The averaged Zernike coefficients were rescaled to the smallest value of the maximum round pupil found among all eyes (4.41 mm), and this procedure was repeated for each target. Results: Alteration of the fixation targets caused changes to the Zernike coefficients of defocus (C(2,0)), vertical trefoil (C(3,–3)), vertical coma (C(3,–1)), horizontal coma (C(3,1)), oblique trefoil (C(3,3)), primary spherical aberration (C(4,0)), and secondary spherical aberration (C(6,0)), but the changes were not statistically significant. Nevertheless, an alteration in the target’s size and shape exhibited a significant correlation across all of the aforementioned coefficients in both eyes (p < 0.05). The total RMS of aberrations and the RMS of the spherical-like aberrations were both lowest while choosing the larger Maltese cross, and the bigger E-letter minimized the RMS of HOA and comatic aberrations. Conclusion: The aberrometric changes occur as a consequence of altering the fixational gaze and are within the range of the changes found after performing a near-vision task, so they might potentially act as a confounding factor when attempting to identify such small variations in the ocular wavefront. Using a smaller E-letter (5 arcmin) as an internal fixation target resulted in the least standard deviation of measurements, fixational stability, and higher accuracy in ocular wavefront measurements. Full article

The objective of this study was to assess the effect of sustained reading on the temporal changes in the wavefront error in the presbyopic eye. The wavefront aberration of the eyes was measured using an IRX3 Shack–Hartmann aberrometer before and after (immediately, 5 min, and 10 min after) a reading task. Temporal changes in ${\mathrm{C}}_2^0$, ${\mathrm{C}}_4^0$, and ${\mathrm{C}}_3^{-1}$ coefficient values of the eyes were plotted, showing a predominant number of V-shaped patterns (for ${\mathrm{C}}_4^0$ and ${\mathrm{C}}_3^{-1}$) and inverse V-shaped patterns (for ${\mathrm{C}}_2^0$) among the study group, and the percentages (between 27 and 73%) were reported. The median of the total RMS of aberrations and the RMS of HOA (higher-order aberrations), which included comatic (3rd order) and spherical-like aberrations (4th and 6th order), increased immediately after finishing the near-vision reading task and then decreased. The median of RMS of comatic aberrations had a similar pattern of variations, while the median of RMS of spherical-like aberrations displayed an opposite pattern. Simulating the aberration changes due to lens decentration caused by relaxed zonules during 4 D accommodation in an eye model demonstrated that the expected range of changes for the vertical coma and spherical aberrations are in the order of 0.001 and 0.01 μm, respectively, which could justify why the observed changes were not statistically significant. The observed dynamic changes in HOA might be linked to the biomechanical characteristics and alterations in the displacement of the crystalline lens following prolonged near-vision tasks in presbyopic people. Although some predominant patterns under some conditions were shown, they exhibit considerable inter-subject and inter-ocular variability. This might be due to slight misalignments while fixating on the internal extended object in the aberrometer. Full article

This study proposes a custom-built aberrometer that measures peripheral defocus to evaluate myopia progression in the human eye. This advanced device can measure visual fields in both horizontal (up to 40°) and vertical (up to 30°) orientations. It incorporates a novel fixation target that is meticulously designed using an optical simulation software. Notably, each angular point of this novel fixation target differs considerably from the conventional fixation target. To mitigate the effects of the optical variations introduced by spectacles and the subject’s vision, we incorporated a position-variable lens positioned in front of the eye. This lens compensates for these variations, enhancing the precision of the measurements. To evaluate the performance of the proposed aberrometer, we conducted experiments under three distinct conditions: first, with the naked eye; second, while wearing spectacles; and third, while wearing a multifocal lens. Full article

To demonstrate the results of ray tracing higher- and lower-order aberrations in pseudophakic eyes with rotationally asymmetrical segment multifocal lenses, total high- and low-order aberrations, measured by root mean square value (RMS), refraction, uncorrected distance and uncorrected near visual acuity (UCDVA and UCNVA), and tear break-up time, were measured at scotopic size in 42 eyes of patients implanted with bifocal refractive Mplus15/Mplus30 IOL with +1.5 dpt near addition (42 eyes of patients implanted with Mplus15)/+3.0 dpt near addition (91 eyes of patients implanted with Mplus30), and 107 eyes of control group. No significant differences were noticed between the examined groups concerning UCDVA, UCNVA, and tear break-up time (p < 0.001). Coma and total high-order aberrations were significantly higher for the Mplus30 lens in comparison to the Mplus15 lens and the control group (Coma, Trefoil p < 0.001, Secondary Astigmatism p = 0.002). The spherical aberrations were significantly higher in the lower-addition lens (p = 0.016) in comparison to the control group and to the higher-addition lens group (p < 0.001). Both intraocular lens models were successful at reaching refractive aim, good distance, and near function with the lower higher-order aberrations for the low-addition lens. Full article

Background: The purpose of this study was to objectively evaluate visual discomfort using an eye tracker and aberrometer after a 21-min reading session on an iPad and an Ebook. Additionally, retinal changes were analyzed using optical coherence tomography (OCT). Methods: A total of 31 young subjects (24 ± 4 years) participated in this study. They read for 21 min on an Ebook and for another 21 min on an iPad under controlled lighting conditions while their eye movements were monitored using an eye tracker. Aberrometry and retinal OCT measurements were taken before and after each reading session. Parameters such as pupil diameter, fixations, saccades, blinks, total aberration, high-order aberration, low-order aberration, and central and peripheral retinal thickness in the nine early treatment diabetic retinopathy study (ETDRS) areas were measured for each reading situation. Statistical analysis was performed on the collected data. Results: No statistically significant differences (p > 0.05) between the two devices were observed in terms of the different types of eye movements or the changes in retinal thickness. However, the aberrometric analysis showed variations in post-reading situations depending on the device used. Conclusion: Reading speed and visual discomfort resulting from electronic device usage can be objectively assessed using an eye tracker and aberrometer. Additionally, changes found in central and peripheral retinal thickness between the two devices and the baseline measurements were not significant and remained relatively stable. Full article

Given the relationship between spherical aberrations and accommodation, the study of these aberrations can be helpful to understand accommodative response in subjects with accommodative dysfunctions. The purpose of this study was to evaluate on-axis and off-axis changes of primary and secondary spherical aberrations, Z(4,0) and Z(6,0), with accommodation in subjects with accommodative insufficiency (AI). Ten subjects with AI and eleven without any accommodative dysfunction (control) participated in this study. On-axis defocus Z(2,0), Z(4,0), and Z(6,0) were obtained in both groups with a Hartmann–Shack aberrometer for the unaccommodated state and with 1.00 D, 2.44 D, 3.83 D, and 4.73 D of accommodative stimuli. Z(4,0) and Z(6,0) were also measured on 11.5° and 23° temporal, nasal, superior, and inferior retinal areas for unaccommodated state and for 2.44 D of accommodative stimulus. In the control group, Z(4,0) became more negative with accommodation and Z(6,0) became more positive, as was expected according to previous studies. This tendency was not observed in the group of subjects with AI group for Z(4,0) or for Z(6,0). No differences on off-axis Z(4,0) and Z(6,0) were observed between the groups. The changes of spherical aberrations with accommodation seem different in subjects with AI compared to those without any accommodative dysfunction. Those with AI do not present a decrease in Z(4,0) and an increase in Z(6,0) with accommodation as occurs in eyes without this type of dysfunction. Understanding how the optics of the eye changes with accommodation can be helpful to understand the origin of accommodative dysfunctions. Full article

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

Cataract or refractive lens surgery, along with the implantation of multifocal intraocular lenses (MF-IOL), enables a complete range of functional far, near and intermediate vision. Refractive, diffractive and extended depth of focus (EDoF) or combination of these principles represent the technology used to obtain this multifocality. Aberrometry makes it possible to study the aberrations induced by MF-IOLs. Among the different optical principles available to measure ocular aberrations, pyramidal wavefront-based sensor (PWS) aberrometry shows the highest resolution with MF-IOLs. Retinal image quality measured by a PWS aberrometer differed significantly according to the technology of the implanted lens. Monofocal and diffractive lenses showed the highest values of far-distance retinal image quality, followed by refractive and EDoF lenses; however, retinal image quality analysed in diffractive lenses appears to be more dependent on residual refractive error. Considering this limitation, PWS-aberrometry could be used to compare diffractive lenses. Nevertheless, further studies are needed to provide additional information about the clinical retinal image quality of MF-IOLs and to help surgeons in the important preoperative selection of IOLs. Full article

The strong wavelength dependency of diffractive elements casts reasonable doubts on the reliability of near-infrared- (NIR)-based clinical instruments, such as aberrometers and double-pass systems, for assessing, post-surgery, the visual quality of eyes implanted with diffractive multifocal intraocular lenses (DMIOLs). The results obtained for such patients when using NIR light can be misleading. Ordinary compensation for the refractive error bound to chromatic aberration is not enough because it only considers the best focus shift but does not take into account the distribution of light energy among the foci which strongly depends on the wavelength-dependent energy efficiency of the diffractive orders used in the DMIOL design. In this paper, we consider three commercial DMIOL designs with the far focus falling within the range of (−1, 0, +1)-diffractive orders. We prove theoretically the differences existing in the physical performance of the studied lenses when using either the design wavelength in the visible spectrum or a NIR wavelength (780 to 850 nm). Based on numerical simulation and on-bench experimental results, we show that such differences cannot be neglected and may affect all the foci of a DMIOL, including the far focus. Full article