Chromatic changes in vision with diffractive ophthalmic optics.

Diffractive optics is a valuable technique for designing presbyopia-correcting lenses, but its effectiveness is wavelength-dependent. This study investigates the spatio-chromatic alterations in visual resolution associated with diffractive multifocal lenses by using non-invasive, removable diffractive bifocal contact lenses. The study combines theoretical analysis, numerical simulation, and clinical intra-observer experiments to assess visual acuity under various lighting conditions. Results demonstrate the introduction of spatio-chromatic asymmetry and a change in visual acuity under red and blue lights, depending on the operating diffraction order employed in the lens design. The energy distribution of the diffractive contact lens studied favors resolution under red illumination at far distances and under blue illumination at near distances. These findings are consistent with computational simulations and provide insights into the visual changes induced by diffractive ophthalmic lenses.

Linear fitting of biconic surfaces for corneal modeling.

This paper presents a method for reconstructing the corneal surface. The proposed method was tested in 56 healthy and 15 post-orthokeratology corneas. The Medmont E300 Corneal Topographer was used to measure the anterior corneal elevation, and custom MATLAB scripts were employed for data analysis, fitting, and other computational processes. The results obtained were compared with the fitting to an ellipsoid and to a biconic, using an alternative method, showing similarities among the different approaches. Additionally, the advantages of this method and the biconic's generality over the ellipsoid were also demonstrated. In conclusion, the method proposed offers an approach with potential applications in the field of visual and ophthalmic optics related with modeling of the cornea and other optical surfaces.

Optical characterization and through-focus performance of two advanced monofocal intraocular lenses.

PURPOSE: To compare the refractive power profile, subjective depth-of-field and objective optical quality of two advanced monofocal intraocular lenses (IOLs) designed to improve intermediate vision. METHODS: This prospective study evaluated forty-six eyes of twenty-three patients, aged 54-68 years, binocularly implanted with two monofocal enhanced intraocular lenses (IOLs), the Tecnis Eyhance and the Physiol Isopure. Subjective through-focus visual acuity curves were obtained by placing trial lenses in front of the eye while wearing its best spherical-cylindrical correction for distance. Objective optical quality was defined as the area under the modulation transfer function, calculated from the wavefront maps measured with a high-resolution aberrometer. The optical design of both lenses was compared based on their refractive power profiles measured with the lenses immersed in saline solution. RESULTS: Both lenses have progressive aspherical geometries, in which the sagittal power decreases rapidly from the center to the edge of the optical zone. Mean monocular through-focus curves show a best corrected distance visual acuity of - 0.02 logMAR with both lenses. Through-focus visual acuity was marginally higher for the Eyhance, with a difference of 1 letter at the defocus position of - 0.5D and 3 letters between - 1.0D and - 2.0D. Objective assessment of optical quality revealed only a difference of about 2 points in MTF area at distance. CONCLUSION: Both IOLs use a similar approach to improve intermediate vision. The Eyhance showed marginally better subjective performance than the Isopure at the target vergences between - 1.00D and - 2.00D, although these results did not reach statistical significance and were not replicated by the objective findings.

Short-term delay in neural response with multifocal contact lens might start at the retinal level.

INTRODUCTION: Multifocal simultaneous imaging challenges the visual system to process the multiple overlaps of focused and defocused images. Retinal image processing may be an important step in neuroadaptation to multifocal optical images. Our aims are, firstly to evaluate the short-term effect of different multifocal contact lenses (MF) on retinal activity in young healthy subjects (Experiment#1) and secondly, to evaluate any changes in retinal activity in presbyopic patients fitted with MF over a 15-day period (Experiment#2). METHODS: In Experiment-#1, 10 emmetropic healthy young subjects were included to evaluate the short-term effect of different MFs designs. In Experiment #2, 4 presbyopic subjects were included to wear MF for 15 days. Following the ISCEV Standards, multifocal electroretinograms (mfERGs) were recorded to evaluate different retinal regions under different conditions: with single vision contact lens (SVCL) and with center-distance and center-near MF. RESULTS: In Exp#1 the peak time of N1, P1 and N2 were found to be delayed with the MF (p ≤ 0.040). There was a significant reduction for N1 amplitude in all retinal regions (p < 0.001), while for P1 and N2 amplitudes this reduction was more significant in the peripheral regions (p < 0.005, ring 5 to 6). With center-near MF the mean response density (nV/deg2) showed a significant decrease in all wave components of the mfERGs response, particularly from Ring 3 to Ring 6 (p < 0.001, all Rings). In Exp#2, the mean mfERG response is similar between SVCL and center-distance MF, while center-near MF showed an increase in implicit time N1 and P1 on day 1 that tends to recover to baseline values after 15 days of MF wear. CONCLUSIONS: significant changes in the mfERGs responses were found with the MF lens, being most noticeable with the center-near MF lens design. The present results suggest that the observed delay in cortical response described during the adaptation to multifocality may partially begin at the retina level.

Short-term tear film stability, optical quality and visual performance in two dual-focus contact lenses for myopia control with different optical designs.

PURPOSE: To assess and compare short-term visual and optical quality and tear film stability between two dual-focus (DF) prototype myopia control contact lenses (CLs) having different inner zone diameters. METHODS: Twenty-eight myopic subjects were included in this randomised, double-masked crossover study. Refraction, best-corrected visual acuity (VA) and tear film stability were measured at baseline (i.e., when uncorrected). Subjects were then binocularly fitted with the DF CLs, with only the sensorial dominant eye being assessed. Lenses were of the same material and had inner zone diameters of either 2.1 mm (S design) or 4.0 mm (M design). Visual and physical short-term lens comfort, over-refraction, best-corrected VA, stereopsis at 40 cm, best-corrected photopic and mesopic contrast sensitivity (CS), size and shape of light disturbance (LD), wavefront aberrations, subjective quality of vision (QoV Questionnaire) and tear film stability were measured for each lens. RESULTS: Both CL designs decreased tear film stability compared with baseline (p < 0.05). VA and photopic CS were within normal values for the subjects' age with each CL. When comparing lenses, the M design promoted better photopic CS for the 18 cycles per degree spatial frequency (p < 0.001) and better LD (p < 0.02). However, higher-order aberrations were improved with the S design (p = 0.02). No significant difference between the two CLs was found for QoV scores and tear film stability. CONCLUSIONS: Both DF CLs provided acceptable visual performance under photopic conditions. The 4.0 mm inner zone gave better contrast sensitivity at high frequencies and lower light disturbance, while the 2.1 mm central diameter induced fewer higher-order aberrations for a 5 mm pupil diameter. Both CLs produced the same subjective visual short-term lens comfort.

Optical Quality and Visual Performance for One Year in a Sample of Scleral Lens Wearers.

SIGNIFICANCE: This study shows the optical and visual quality behavior of modern scleral lenses (SLs) in the medium and long term in patients with irregular cornea (IC) and regular cornea (RC). PURPOSE: The purpose of this study was to evaluate the 12-month optical quality outcomes with SL in patients with IC and RC. METHODS: Sixty-nine patients completed the 12 months of follow-up (99 eyes with IC and 27 with RC). LogMAR high- and low-contrast visual acuity, whole eye aberrometry, and the size (Light Disturbance Index, %) and shape (BFCIrregSD, mm) of night vision disturbances were measured at baseline with habitual correction (HC), best spectacle correction (BSC), and SL at all the follow-up visits (1, 3, 6, and 12 months). Subjective visual quality was measured with the Quality of Vision (QoV) questionnaire. RESULTS: After SL fitting, high-contrast visual acuity improved significantly compared with HC and BSC in the IC group (average improvement of +0.35 ± 0.32 and +0.29 ± 0.26 to +0.08 ± 0.14, P < .001) and RC group (+0.17 ± 0.23 and +0.12 ± 0.23 to +0.10 ± 0.23, P < .05). Light Disturbance Index decreased significantly with SL compared with HC and BSC from 13.85 ± 13.99% and 15.89 ± 13.38% to 5.75 ± 4.51% in the IC group (P < .001) and 6.16 ± 5.38 and 5.98 ± 5.39 to 3.99 ± 3.05 in the RC group (P < .05). BFCIrregSD also decreased significantly, namely, in the IC group (-51%). All subscales of the QoV questionnaire had a statistically significant decrease (improvement) with SL (P < .05). CONCLUSIONS: Scleral lenses promote a better subjective and objective visual quality, mainly in patients with IC. Additional measurements such as night vision disturbances, aberrometry, and subjective perceptions should be considered to characterize the visual enhancement promoted by SL in RC and IC patients.

Multifocal contact lenses: towards customisation?

PURPOSE: Firstly, to determine if eyes with spherical aberration (SA) that deviates significantly from the average level underperform when fitted with a simultaneous-imaging contact lens (CL) with a power profile calculated for an 'average eye'. Secondly, to determine if CL customisation can improve image quality in these eyes after fitting with a bifocal CL. METHODS: A statistical model of the wavefront aberration function of normal eyes was used to generate a vector of Zernike fourth-order SA coefficients from 100 synthetic eyes. Four bifocal power profiles were modelled: centre-near (CN) or centre-distance (CD), and two-zone or four-zone. All designs had 0.1-mm-wide transition zones. Different levels of distance and add powers were modelled, using well-established computational wave-optics methods. Zone widths were optimised to obtain maximal multifocal efficiency (MFE), a metric based on the visual Strehl that synthesises the through-focus curve in one number. The MFE was calculated for each synthetic eye coupled with each bifocal power profile. RESULTS: For an 'average eye', the mean MFE values were 0.33 vs 0.25 and 0.32 vs 0.29, for CN vs CD and two vs four zone designs, respectively. When the four power profiles were assessed in eyes with non-average levels of ocular SA, the MFE decreased with higher levels of SA (eye and CL combined) for all designs. Some of this reduction in MFE could be prevented by adjusting the nominal distance and add power of the bifocal profiles to compensate for the increased or decreased level of combined SA. The four-zone CN profile showed better tolerance for different levels of ocular SA than the two-zone designs, but this was not true for the four-zone CD design. CONCLUSION: Eyes with SA levels differing significantly from the average level underperform when fitted with simultaneous-imaging CLs with power profiles calculated for average eyes. Our findings suggest that visual performance at distance and near when wearing bifocal CLs can be improved by using a semi-customised approach.

Foveal vision power errors induced by spectacle lenses designed to correct peripheral refractive errors.

PURPOSE: Radial Refractive Gradient (RRG) spectacles are lenses specifically designed to minimize peripheral hyperopic defocus typically found in conventional spectacles. Our goals were: (1) to demonstrate a method to design such lenses; and (2) to quantify the exact foveal vision power errors induced by them. METHODS: The design procedure was based on a point-by-point sequential surface construction algorithm that designs a front aspheric surface (back surface is spherical) to achieve a given overall tangential focal length of the lens. A peripheral refraction model was built based on average peripheral refractive errors from a set of eyes. We designed four negative lenses with optical powers: -2.5, -5.0, -7.5 and -10.0 D, so that the tangential focal length of the lens matches the retinal conjugate surface. RESULTS: The lenses induce very small sagittal power errors in a wide range of off-axis field angles (30°), solving the problem of peripheral hyperopic defocus. However, such designs introduce non-negligible mean power errors (above 0.25 D from 7°, 6.8°, 7.1° and 7.8° for the -2.5, -5.0, -7.5 and -10.0 D lenses, respectively) for foveal vision in a rotating eye. CONCLUSION: Our results show the unavoidable errors introduced by RRG spectacles when used for dynamic foveal vision. The described method offers valuable information towards determining the best trade-off between controlling power errors for peripheral and foveal vision.

Predicted accommodative response from image quality in young eyes fitted with different dual-focus designs.

PURPOSE: To investigate the separated and combined influences of inner zone (IZ) diameter and effective add power of dual-focus contact lenses (CL) in the image quality at distance and near viewing, in a functional accommodating model eye. METHODS: Computational wave-optics methods were used to define zonal bifocal pupil functions, representing the optic zones of nine dual-focus centre-distance CLs. The dual-focus pupil functions were defined having IZ diameters of 2.10 mm, 3.36 mm and 4.00 mm, with add powers of 1.5 D, 2.0 D and 2.5 D (dioptres), for each design, that resulted in a ratio of 64%/36% between the distance and treatment zone areas, bounded by a 6 mm entrance pupil. A through-focus routine was implemented in MATLAB to simulate the changes in image quality, calculated from the Visual Strehl ratio, as the eye with the dual-focus accommodates, from 0 to -3.00 D target vergences. Accommodative responses were defined as the changes in the defocus coefficient, combined with a change in fourth and sixth order spherical aberration, which produced a peak in image quality at each target vergence. RESULTS: Distance viewing image quality was marginally affected by IZ diameter but not by add power. Near image quality obtained when focussing the image formed by the near optics was only higher by a small amount compared to the other two IZ diameters. The mean ± standard deviation values obtained with the three adds were 0.28 ± 0.02, 0.23 ± 0.02 and 0.22 ± 0.02, for the small, medium and larger IZ diameters, respectively. On the other hand, near image quality predicted by focussing the image formed by the distance optics was considerably lower relatively to the other two IZ diameters. The mean ± standard deviation values obtained with the three adds were 0.15 ± 0.01, 0.38 ± 0.00 and 0.54 ± 0.01, for the small, medium and larger IZ diameters, respectively. CONCLUSIONS: During near viewing through dual-focus CLs, image quality depends on the diameter of the most inner zone of the CL, while add power only affects the range of clear focus when focussing the image formed by the CL near optics. When only image quality gain is taken into consideration, medium and large IZ diameters designs are most likely to promote normal accommodative responses driven by the CL distance optics, while a smaller IZ diameter design is most likely to promote a reduced accommodative response driven by the dual-focus CL near optics.

Effect of Pupil Size on Wavefront Refraction during Orthokeratology.

PURPOSE: It has been hypothesized that central and peripheral refraction, in eyes treated with myopic overnight orthokeratology, might vary with changes in pupil diameter. The aim of this work was to evaluate the axial and peripheral refraction and optical quality after orthokeratology, using ray tracing software for different pupil sizes. METHODS: Zemax-EE was used to generate a series of 29 semi-customized model eyes based on the corneal topography changes from 29 patients who had undergone myopic orthokeratology. Wavefront refraction in the central 80 degrees of the visual field was calculated using three different quality metrics criteria: Paraxial curvature matching, minimum root mean square error (minRMS), and the Through Focus Visual Strehl of the Modulation Transfer Function (VSMTF), for 3- and 6-mm pupil diameters. RESULTS: The three metrics predicted significantly different values for foveal and peripheral refractions. Compared with the Paraxial criteria, the other two metrics predicted more myopic refractions on- and off-axis. Interestingly, the VSMTF predicts only a marginal myopic shift in the axial refraction as the pupil changes from 3 to 6 mm. For peripheral refraction, minRMS and VSMTF metric criteria predicted a higher exposure to peripheral defocus as the pupil increases from 3 to 6 mm. CONCLUSIONS: The results suggest that the supposed effect of myopic control produced by ortho-k treatments might be dependent on pupil size. Although the foveal refractive error does not seem to change appreciably with the increase in pupil diameter (VSMTF criteria), the high levels of positive spherical aberration will lead to a degradation of lower spatial frequencies, that is more significant under low illumination levels.

Changes in Peripheral Refraction, Higher-Order Aberrations, and Accommodative Lag With a Radial Refractive Gradient Contact Lens in Young Myopes.

PURPOSE: To evaluate changes in the peripheral refraction (PR), visual quality, and accommodative lag with a novel soft radial refractive gradient (SRRG) experimental contact lens that produces peripheral myopic defocus. METHODS: 59 myopic right eyes were fitted with the lens. The PR was measured up to 30° in the nasal and temporal horizontal visual fields and compared with values obtained without the lens. The accommodative lag was measured monocularly using the distance-induced condition method at 40 cm, and the higher-order aberrations (HOAs) of the entire eye were obtained for 3- and 5-mm pupils by aberrometry. Visual performance was assessed through contrast sensitivity function (CSF). RESULTS: With the lens, the relative PR became significantly less hyperopic from 30° to 15° temporally and 30° nasally in the M and J0 refractive components (P<0.05). Cylinder foci showed significant myopization from 30° to 15° temporally and 30° to 25° nasally (P<0.05). The HOAs increased significantly, the CSF decreased slightly but reached statistical significance for 6 and 12 cycles per degree (P<0.05), and the accommodative lag decreased significantly with the SRRG lens (P=0.0001). There was a moderate correlation between HOAs and CSF at medium and high spatial frequencies. CONCLUSION: The SRRG lens induced a significant change in PR, particularly in the temporal retina. Tangential and sagittal foci changed significantly in the peripheral nasal and temporal retina. The decreased accommodative lag and increased HOAs particularly in coma-like aberration may positively affect myopia control. A longitudinal study is needed to confirm this potential.

Strategies to Regulate Myopia Progression With Contact Lenses: A Review.

PURPOSE: Higher myopic refractive errors are associated with serious ocular complications that can put visual function at risk. There is respective interest in slowing and if possible stopping myopia progression before it reaches a level associated with increased risk of secondary pathology. The purpose of this report was to review our understanding of the rationale(s) and success of contact lenses (CLs) used to reduce myopia progression. METHODS: A review commenced by searching the PubMed database. The inclusion criteria stipulated publications of clinical trials evaluating the efficacy of CLs in regulating myopia progression based on the primary endpoint of changes in axial length measurements and published in peer-reviewed journals. Other publications from conference proceedings or patents were exceptionally considered when no peer-review articles were available. RESULTS: The mechanisms that presently support myopia regulation with CLs are based on the change of relative peripheral defocus and changing the foveal image quality signal to potentially interfere with the accommodative system. Ten clinical trials addressing myopia regulation with CLs were reviewed, including corneal refractive therapy (orthokeratology), peripheral gradient lenses, and bifocal (dual-focus) and multifocal lenses. CONCLUSIONS: CLs were reported to be well accepted, consistent, and safe methods to address myopia regulation in children. Corneal refractive therapy (orthokeratology) is so far the method with the largest demonstrated efficacy in myopia regulation across different ethnic groups. However, factors such as patient convenience, the degree of initial myopia, and non-CL treatments may also be considered. The combination of different strategies (i.e., central defocus, peripheral defocus, spectral filters, pharmaceutical delivery, and active lens-borne illumination) in a single device will present further testable hypotheses exploring how different mechanisms can reinforce or compete with each other to improve or reduce myopia regulation with CLs.

Efficacy of a gas permeable contact lens to induce peripheral myopic defocus.

PURPOSE: The purpose of this work was to evaluate the potential of a novel custom-designed rigid gas permeable (RGP) contact lens to modify the relative peripheral refractive error in a sample of myopic patients. METHODS: Fifty-two right eyes of 52 myopic patients (mean [±SD] age, 21 [±2] years) with spherical refractive errors ranging from -0.75 to -8.00 diopters (D) and refractive astigmatism of 1.00 D or less were fitted with a novel experimental RGP (ExpRGP) lens designed to create myopic defocus in the peripheral retina. A standard RGP (StdRGP) lens was used as a control in the same eye. The relative peripheral refractive error was measured without the lens and with each of two lenses (StdRGP and ExpRGP) using an open-field autorefractometer from 30 degrees nasal to 30 degrees temporal, in 5-degree steps. The effectiveness of the lens design was evaluated as the amount of relative peripheral refractive error difference induced by the ExpRGP compared with no lens and with StdRGP conditions at 30 degrees in the nasal and temporal (averaged) peripheral visual fields. RESULTS: Experimental RGP lens induced a significant change in relative peripheral refractive error compared with the no-lens condition (baseline), beyond the 10 degrees of eccentricity to the nasal and temporal side of the visual field (p < 0.05). The maximum effect was achieved at 30 degrees. Wearing the ExpRGP lens, 60% of the eyes had peripheral myopia exceeding -1.00 D, whereas none of the eyes presented with this feature at baseline. There was no significant correlation (r = 0.04; p = 0.756) between the degree of myopia induced at 30 degrees of eccentricity of the visual field with the ExpRGP lens and the baseline refractive error. CONCLUSIONS: Custom-designed RGP contact lenses can generate a significant degree of relative peripheral myopia in myopic patients regardless of their baseline spherical equivalent refractive error.

Computing retinal contour from optical biometry.

PURPOSE: To describe a new methodology that derives horizontal posterior retinal contours from partial coherence interferometry (PCI) and ray tracing using the corneal topography. METHODS: Corneal topography and PCI for seven horizontal visual field eccentricities correspondent to the central 60 degrees of the posterior pole were obtained in 55 myopic eyes. A semicustomized eye model based on the subject's corneal topography and the Navarro eye model was generated using Zemax-EE software. The model was used to compute the optical path length in the seven directions where PCI measurements were obtained. Vitreous chamber depth was computed using the PCI values obtained at each of those directions. Matlab software was developed to fit the best conic curve to the set of points previously obtained. We tested the limit in the accuracy of the methodology when the actual cornea of the subject is not used and for two different lens geometries. RESULTS: A standard eye model can induce an error in the retina sagitta estimation of the order of hundreds of micrometers in comparison with the semicustomized eye model. However, the use of a different lens model leads to an error of the order of tens of micrometers. The apical radius and conic constant of the average fit were -11.91 mm and -0.15, respectively. In general, a nasal-temporal asymmetry in the retina contour was found, showing mean larger values of vitreous chamber depth in the nasal side of the eye. CONCLUSIONS: The use of a semicustomized eye model, together with optical path length measured by PCI for different angles, can be used to predict the retinal contour within tenths of micrometers. This methodology can be useful in studies trying to understand the effect of peripheral retinal location on myopia progression as well as modeling the optics of the human eye for a wide field.

Peripheral refraction and retinal contour in stable and progressive myopia.

PURPOSE: To compare the patterns of relative peripheral astigmatic refraction (tangential and sagittal power errors) and eccentric eye length between progressing and stable young-adult myopes. METHODS: Sixty-two right eyes of 62 white patients participated in the study, of which 30 were nonprogressing myopes (NP group) for the last 2 years and 32 were progressing myopes (P group). Groups were matched for mean spherical refraction, axial length, and age. Peripheral refraction and eye length were measured along the horizontal meridian up to 35 and 30 degrees of eccentricity, respectively. RESULTS: There were statistically significant differences between groups (p < 0.001) in the nasal retina for the astigmatic components of peripheral refraction. The P group presented a hyperopic relative sagittal focus at 35 degrees in the nasal retina of +1.00 ± 0.83 diopters, as per comparison with a myopic relative sagittal focus of -0.10 ± 0.98 diopters observed in the NP group (p < 0.001). Retinal contour in the P group had a steeper shape in the nasal region than that in the NP group (t test, p = 0.001). An inverse correlation was found (r = -0.775; p < 0.001) between retinal contour and peripheral refraction. Thus, steeper retinas presented a more hyperopic trend in the periphery. CONCLUSIONS: Stable and progressing myopes of matched age, axial length, and central refraction showed significantly different characteristics in their peripheral retinal shape and astigmatic components of tangential and sagittal power errors. The present findings may help explain the mechanisms that regulate ocular growth in humans.

Pitfalls of Using NIR-Based Clinical Instruments to Test Eyes Implanted with Diffractive Intraocular Lenses.

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.

Analysis of Wavefront Data Obtained With a Pyramidal Sensor in Pseudophakic Eyes Implanted With Diffractive Intraocular Lenses.

PURPOSE: To investigate the clinical validity of using wavefront measurements obtained with a recently available pyramidal aberrometer to assess the optical quality of eyes implanted with diffractive intraocular lenses (IOLs). METHODS: Individual biometric data were used to create models of pseudophakic eyes implanted with two diffractive IOLs. Their synthetic wavefronts were calculated by ray-tracing with near infrared wavelength (0.85 µm). Comparisons of the through-focus visual acuity of 12 pseudophakic eyes were obtained with three different methods: clinical defocus curves; simulated defocus curves calculated from ray-tracing in the customized model eyes; and through-focus simulated defocus curves calculated from the wavefront data measured with a pyramidal aberrometer. RESULTS: Image quality calculated from wavefront data obtained by ray-tracing with 0.85 µm wavelength, without scaling the phase to 0.55 µm, resulted in a significantly different through-focus curve compared to the reference values. Even so, after scaling of the wavefront data to 0.55 µm, the defocus curves calculated from the wavefronts measured with the pyramidal aberrometer did not match the shape and the depth of field of the clinical defocus curves or the theoretical expected values. CONCLUSIONS: Correcting for the longitudinal chromatic aberration of the eye when measuring the wavefront of eyes implanted with diffractive IOLs under near infrared light only accounts for the best focus shift due to the longitudinal chromatic aberration, but not for the wavelength dependence of the diffractive element. The pyramidal sensor does not seem to properly sample the slopes of a wavefront measured from a pseudophakic eye implanted with a presbyopia-correcting diffractive IOL to a clinically acceptable level. [J Refract Surg. 2023;39(7):438-444.].

Visual Performance and High-Order Aberrations with Different Contact Lens Prototypes with Potential for Myopia Control.

Purpose: Contact lenses (CLs) used for myopia control incorporate variable power distribution across the optic zone potentially creating degradation of the high-order aberrations. The present study aims to evaluate the retinal image quality and visual performance in three prototypes of CLs intended to control axial elongation of the eye before they are considered for clinical trials.Methods: This is a non-dispensing cross-over, double-blind study where 30 right eyes of myopic subjects worn 3 multifocal test lenses and 1 monofocal control lens in random order. Lens 1 was a radial refractive gradient design (center distance) and Lens 2 and 3 center-near with an additional annular ring for near. Nominal add power was 2.00D, 1.50D, and 2.00D, respectively. Subjects had an age 21.96 ± 2.23 years [18-30] and mean spherical equivalent refraction M = -2.23 ± 1.50D [-0.75 to -5.50] with refractive astigmatism below -0.75D. Higher-order aberrations (HOA), glare formation (halo), high- and low-contrast LogMAR visual acuity (VA), and contrast sensitivity function (CSF) was measured under monocular conditions.Results: All individual terms of HOA and total root mean square from 3rd to 8th order increased significantly with the 3 test lenses compared to control. Between test lenses, Lens 1 increased significantly the higher HOA compared with Lens 2 and Lens 3. Halo size was significantly larger with test lenses compared with control, with Lens 1 showing the largest. VA under high-contrast conditions was similar for all lenses. Under low-contrast conditions, Lens 1 and Lens 2 performed significantly worse than control (Bonferroni post hoc correction, p < 0.001). CSF was below normal limits with Lens 1 for 3 and 6 cpd spatial frequency but was not significantly different between test lenses and control.Conclusions: Lenses with larger stabilized areas for distance vision interfere less with VA and induce lower values of HOA and image degradation.

Morphology, topography, and optics of the orthokeratology cornea.

The goal of this work was to objectively characterize the external morphology, topography, and optics of the cornea after orthokeratology (ortho-k). A number of 24 patients between the ages of 17 and 30 years (median=24 years) were fitted with Corneal Refractive Therapy® contact lenses to correct myopia between −2.00 and −5.00 diopters (D) (median=−3.41 D). A classification algorithm was applied to conduct an automatic segmentation based on the mean local curvature. As a result, three zones (optical zone, transition zone, and peripheral zone) were delimited. Topographical analysis was provided through global and zonal fit to a general ellipsoid. Ray trace on partially customized eye models provided wave aberrations and retinal image quality. Monozone topographic description of the ortho-k cornea loses accuracy when compared with zonal description. Primary (C40) and secondary (C60) spherical aberration (SA) coefficients for a 5-mm pupil increased 3.68 and 19 times, respectively, after the treatments. The OZ area showed a strong correlation with C40 (r=−0.49, p<0.05) and a very strong correlation with C60 (r=0.78, p<0.01). The OZ, as well as the TZ, areas did not correlate with baseline refraction. The increase in the eye's positive SA after ortho-k is the major factor responsible for the decreased retinal optical quality of the unaccommodated eye.

Changes in Peripheral Refractive Profile after Orthokeratology for Different Degrees of Myopia.

PURPOSE: The purpose of this study was to evaluate the effect of orthokeratology for different degrees of myopia correction in the relative location of tangential (F(T)) and sagittal (F(S)) power errors across the central 70° of the visual field in the horizontal meridian. METHODS: Thirty-four right eyes of 34 patients with a mean age of 25.2 ± 6.4 years were fitted with Paragon CRT (Mesa, AZ) rigid gas permeable contact lenses to treat myopia (-2.15 ± 1.26D, range: -0.88 to -5.25D). Axial and peripheral refraction were measured along the central 70° of the horizontal visual field with the Grand Seiko WAM5500 open-field auto-refractor. Spherical equivalent (M), as well as tangential (FT) and sagittal power errors (FS) were obtained. Analysis was stratified in three groups according to baseline spherical equivalent: Group 1 [M(Baseline) = -0.88 to -1.50D; n = 11], Group 2 [M(Baseline) = -1.51 to -2.49D; n = 11], and Group 3 [M(Baseline) = -2.50 to -5.25D; n = 12]. RESULTS: Spherical equivalent was significantly more myopic after treatment beyond the central 40° of the visual field (p < 0.001). FT became significantly more myopic for all groups in the nasal and temporal retina with 25° (p ≤ 0.017), 30° (p ≤ 0.007) and 35° (p ≤ 0.004) of eye rotation. Myopic change in FS was less consistent, achieving only statistical significance for all groups at 35° in the nasal and temporal retina (p ≤ 0.045). CONCLUSIONS: Orthokeratology changes significantly FT in the myopic direction beyond the central 40° of the visual field for all degrees of myopia. Changes induced by orthokeratology in relative peripheral M, FT and FS with 35° of eye rotation were significantly correlated with axial myopia at baseline.