Longitudinal Chromatic Aberration Research Articles

The Role of Chromatic Aberration in Vision.

The study of biological optics would be complicated enough if light only came in a single wavelength. However, altering the wavelength (or distribution of wavelengths) of light has multiple effects on optics, including on diffraction, scattering (of various sorts), transmission through and reflection by various media, fluorescence, and waveguiding properties, among others. In this review, we consider just one wavelength-dependent optical effect: longitudinal chromatic aberration (LCA). All vertebrate eyes that have been tested have significant LCA, with shorter (bluer) wavelengths of light focusing closer to the front of the eye than longer (redder) wavelengths. We consider the role of LCA in the visual system in terms of both how it could degrade visual acuity and how biological systems make use of it.

Two different visual stimuli that cause axial eye shortening have no additive effect

Previous studies identified two visual stimuli that can shorten the human eye by thickening the choroid after short-term visual stimulation, potentially inhibiting myopia: (1) watching digitally filtered movies where the red plane has full spatial resolution while green and blue are low-pass filtered according to the human longitudinal chromatic aberration (LCA) function (the “red in focus” filter), and (2) reading text with inverted contrast. This study aimed to determine whether combining these two stimuli would have an additive effect on axial length. Twenty-two emmetropic subjects were recruited to read text (standard and inverted contrast) for 30 min from a large screen, 2 m away, either unfiltered or filtered with the “red in focus” filter. Axial length was measured before and after each reading episode using low-coherence interferometry (Lenstar LS 900, Haag Streit). Reading text with conventional contrast polarity (dark letters on a bright background) resulted in no significant axial length change. Adding the “red in focus” filter did not alter the outcome. Consistent with previous findings, reading inverted contrast text made emmetropic eyes shorter. Surprisingly, when the text was combined with the “red in focus” filter, eyes became longer rather than shorter. A possible explanation for this contradictory result is that, for the text stimulus, the “red in focus” filter removes spatial information in the blue channel needed by the retina to use LCA analysis to thicken the choroid.

Chromatic Light Therapy for Inhibiting Myopia Progression: Human Studies.

Myopia, a common refractive error, has been associated with various risk factors, but time outdoors has emerged as a significant protective factor against its onset. This association is believed to be mediated by the influence of sunlight on dopamine release, a neurotransmitter crucial for regulating eye growth. Recent research has explored the specific properties of light in order to identify potential interventions for myopia control in children. Low-level red light therapy has gained attention, and has shown promise in inhibiting myopia progression, although there are concerns about safety and rebound effects. Similarly, blue light stimulation aims to upregulate retinal dopamine activity, yet conclusive evidence supporting its efficacy is lacking. Moreover, researchers explored the use of the entire visible light spectrum by digitally imposing longitudinal chromatic aberration to adjust proper eye growth. Preliminary findings suggest that digitally simulated chromatic aberration could potentially serve as a myopia control strategy and highlights the need for further investigation into long-term effects. As research progresses, understanding the efficacy and safety of light-based interventions for myopia control remains crucial for informing clinical practice and optimizing patient outcomes.

Design of polythiourethane (PTU) polymer contact lens to correct the longitudinal chromatic aberration

Design of polythiourethane (PTU) polymer contact lens to correct the longitudinal chromatic aberration

The knowledge structure and research trends between light and myopia: A bibliometric analysis from 1981 to 2024.

This bibliometric analysis explored the knowledge structure of and research trends in the relationship between light and myopia. Relevant literature published from 1981 to 2024 was collected from the Web of Science Core Collection database. Visual maps were generated using CiteSpace and VOSviewer. We analyzed the included studies in terms of the annual publication count, countries, institutional affiliations, prolific authors, source journals, top 10 most cited articles, keyword co-occurrence, and cocitations. A total of 525 papers examining the relationship between light and myopia published between 1981 and 2024 were collected. The United States ranked first in terms of the number of publications and actively engaged in international cooperation with other countries. The New England College of Optometry, which is located in the United States, was the most active institution and ranked first in terms of the number of publications. Schaeffel Frank was the most prolific author. The most active journal in the field was Investigative Ophthalmology & Visual Science. The most frequently cited paper in the included studies was written by Saw, SM and was published in 2002. The most common keywords in basic research included "refractive error," "longitudinal chromatic aberration," and "compensation." The most common keywords in clinical research mainly included "light exposure," "school," and "outdoor activity." The current research hotspots in this field are "progression," "refractive development," and "light exposure." The cocitation analysis generated 17 clusters. This study is the first to use bibliometric methods to analyze existing research on the relationship between light and myopia. In recent years, the intensity and wavelength of light have become research hotspots in the field. Further research on light of different intensities and wavelengths may provide new perspectives in the future for designing more effective treatments and interventions to reduce the incidence of myopia.

Influence of Aberration-Free, Narrowband Light on the Choroidal Thickness and Eye Length.

To determine whether light chromaticity without defocus induced by longitudinal chromatic aberration (LCA) is sufficient to regulate eye growth. An interferometric setup based on a spatial light modulator was used to illuminate the dominant eyes of 23 participants for 30minutes with three aberration-free stimulation conditions: (1) short wavelength (450nm), (2) long wavelength (638nm), and (3) broadband light (450-700nm), covering a retinal area of 12°. The non-dominant eye was occluded and remained as the control eye. Axial length and choroidal thickness were measured before and after the illumination period. Axial length increased significantly from baseline for short-wavelength (P < 0.01, 7.4 ± 2.2 µm) and long-wavelength (P = 0.01, 4.8 ± 1.7 µm) light. The broadband condition also showed an increase in axial length with no significance (P = 0.08, 5.1 ± 3.5 µm). The choroidal thickness significantly decreased in the case of long-wavelength light (P < 0.01, -5.7 ± 2.2 µm), but there was no significant change after short-wavelength and broadband illumination. The axial length and choroidal thickness did not differ significantly between the test and control eyes or between the illumination conditions (all P > 0.05). Also, the illuminated versus non-illuminated choroidal zone did not show a significant difference (all P > 0.05). All stimulation conditions with short- and long-wavelength light and broadband light led to axial elongation and choroidal thinning. Therefore, light chromaticity without defocus induced by LCA is suggested to be insufficient to regulate eye growth. This study helps in understanding if light chromaticity alone is a sufficient regulator of eye growth.

Ocular accommodation and wavelength: The effect of longitudinal chromatic aberration on the stimulus-response curve.

The longitudinal chromatic aberration (LCA) of the eye creates a chromatic blur on the retina that is an important cue for accommodation. Although this mechanism can work optimally in broadband illuminants such as daylight, it is not clear how the system responds to the narrowband illuminants used by many modern displays. Here, we measured pupil and accommodative responses as well as visual acuity under narrowband light-emitting diode (LED) illuminants of different peak wavelengths. Observers were able to accommodate under narrowband light and compensate for the LCA of the eye, with no difference in the variability of the steady-state accommodation response between narrowband and broadband illuminants. Intriguingly, our subjects compensated more fully for LCA at nearer distances. That is, the difference in accommodation to different wavelengths became larger when the object was placed nearer the observer, causing the slope of the accommodation response curve to become shallower for shorter wavelengths and steeper for longer ones. Within the accommodative range of observers, accommodative errors were small and visual acuity normal. When comparing between illuminants, when accommodation was accurate, visual acuity was worst for blue narrowband light. This cannot be due to the sparser spacing for S-cones, as our stimuli had equal luminance and thus activated LM-cones roughly equally. It is likely because ocular LCA changes more rapidly at shorter wavelength and so the finite spectral bandwidth of LEDs corresponds to a greater dioptric range at shorter wavelengths. This effect disappears for larger accommodative errors, due to the increased depth of focus of the eye.

Theoretical analysis of a compensator of the secondary longitudinal chromatic aberration.

A theoretical analysis of an afocal compensator of the secondary longitudinal chromatic aberration is provided. Such a compensator is able to compensate for chromatic aberration of an achromatic optical system and make an apochromatic correction of the system. The parameters of the proposed chromatic aberration compensator are described and the principle is presented in examples.

Inhibiting myopia development by the digital chromatic filters

We had previously found that simulated chromatic defocus, imposed by spatially filtering the RGB channels of the computer screen, induces significant changes in choroidal thickness already after 45 min (Swiatczak and Schaeffel, 2022). In emmetropes, the “red in focus” filter, which blurs the image in the blue channel and simulates myopic chromatic defocus, induced thickening of the choroid and eye shortening, while the “blue in focus” filter, which blurs the image in the red channel and simulates hyperopic chromatic defocus, induced thinning of the choroid and eye elongation. Strikingly, eyes that were already myopic were not responsive to these filters, suggesting that (1) they may no longer detect longitudinal chromatic aberration (LCA), (2) the imposed signal was too weak to induce significant changes in choroidal thickness, or (3) the signal was detected by the retina, but it was not transmitted to the choroidal tissue. To gain a better understanding of the underlying mechanisms and their roles in emmetropization, we measured in emmetropic and myopic subjects (1) the long‐term effect of repetitive exposure to the “red in focus” filter over 12 days of treatment, followed by 2 days of recovery, (2) the accommodation responses to visual targets with simulated myopic and hyperopic LCA, and (3) visual acuity and contrast sensitivity in red and blue light.Our results showed that as previously found for choroidal changes, simulated hyperopic or myopic LCA also affected accommodation. The “blue in focus” filter induced more accommodation than the “red in focus” filter (difference in emmetropes: 0.13D, p &lt; 0.05). Strikingly, accommodation in myopic eyes was not responsive to simulated LCA. Moreover, visual acuity was severely reduced when subjects were looking through a short‐pass blue filter (cut‐off at 490 nm) compared to visual acuity in red light (long‐pass red filter, cut‐off at 610 nm) which was observed in both emmetropic and myopic subjects. Furthermore, emmetropes displayed higher contrast sensitivity in red than in blue light, but this difference was not found in myopes.Our findings confirm that there is a difference in retinal processing between emmetropes and myopes which includes lower sensitivity to LCA in myopes. Furthermore, we showed that these differences show up in both, changes in choroidal thickness as well as accommodation.

Functional changes in the myopic retina compromise emmetropization

During emmetropization, the retina analyses the focus of the image and generates appropriate biochemical signals to control choroidal thickness and scleral growth. Using commercially available optical low coherence interferometry (the Lenstar LS 900), changes in eye length in the micrometre range can be picked up already after 30 min when young human subjects watch movies that were digitally filtered. We found that the emmetropic retina can distinguish real optical positive defocus from simulated/calculated defocus. It triggered choroidal thickening in the first case, and thinning in the second. Strikingly, the myopic retina was not responsive, and the choroid became thinner in both cases. Longitudinal chromatic aberration (LCA) would be a perfect signal to tell the retina where the focal plane is. We simulated chromatic defocus in our movies. Either the red or the blue plane of the RGB format was spatially filtered to simulate chromatic defocus. When blue was ‘in focus’, eyes became longer, but when red was ‘in focus’ eyes became shorter. Again, myopic eyes did not respond, suggesting that the myopic retina no longer responded to LCA. Taken together, we found that the myopic retina had undergone functional changes such that no growth‐inhibiting signal was generated. As a consequence, eye growth would become open loop, explaining why myopia does not inhibit itself.

Two different visual stimuli that cause axial eye shortening and choroidal thickening have no additive effect

Aims/Purpose: Previous studies identified two visual stimuli that can make the human eye shorter and potentially inhibit myopia: [1] watching digitally filtered movies that kept the red channel in focus but were low pass filtered in the blue and [2] reading text with inverted contrast. We have tested whether the two mechanisms may be additive, perhaps causing even more inhibition of eye growth.Methods: Fifteen emmetropic (average refraction: −0.6 ± 0.7 D) and fifteen myopic (average refraction: −3.7 ± 1.8 D, range −6 to −1.5D) young subjects (average age: 26 ± 4 years) read text from a large screen (65″) in a dark room at 2 m distance. Text with inverted contrast (bright letters on dark background) was digitally filtered in real time by custom‐developed software written in Visual C++ to present the red channel of the RGB colour format unfiltered while green and blue were blurred (red in focus) accordingly to the human longitudinal chromatic aberration function. Changes in axial length before and after 30 min of reading were measured using low coherence interferometry with auto positioning system (Lenstar LS‐900).Results: Unexpectedly, in emmetropes, significant eye elongation was found after 30 min of reading text with inverted contrast, combined with the red in focus filter (+5.7 ± 15.3 μm). As previously found, unfiltered text with inverted contrast made eyes shorter (−7.9 ± 14.7 μm, p &lt; 0.05). Strikingly, no such changes were observed in myopic eyes, neither with the red in focus filter, nor when text with inverted contrast remained unfiltered.Conclusions: In emmetropes, the two stimuli had no additive effects but rather cancelled each other out. There may be a simple explanation: the red in focus filter made the text very blurry in the blue channel. Apparently, this removed the spatial information that is needed by the retina to detect defocus in the blue. Therefore, our finding supports the view that the emmetropic retina needs some spatial information in the blue to generate eye growth inhibiting signals—and they were lost in myopes.

Altering chromatic aberration: how this latest trend in intraocular-lens design affects visual quality in pseudophakic patients

BackgroundChromatic aberration of the eye results from the dispersion of polychromatic light at the interfaces of ocular media. An intraocular lens (IOL) based approach utilizing the diffractive-multifocal principle has been proposed for its correction, but the clinical evidence on the impact of reducing or increasing chromatic aberration on the visual quality of pseudophakic patients remains scarce.MethodsIn this cross-sectional study, longitudinal chromatic aberration (LCA) effects were studied monocularly in 37 patients implanted with a monofocal lens. LogMAR corrected distance visual acuity (VA) and defocus curve at the + 1.0 D to − 2.0 D range were assessed. Contrast sensitivity (CS) was evaluated at far and at four spatial frequencies. Measurements were performed with the eye's natural conditions, as well as with increased and corrected (by the same amount) LCA, which was altered by introducing zero-power trial triplets.ResultsThe mean (± standard deviation) logMAR VA was − 0.11 ± 0.07 for the natural condition, − 0.13 ± 0.07 for the LCA-corrected eye, and − 0.06 ± 0.08 for the eye with increased LCA. A sharp decline of the defocus tolerance was found after the LCA correction with the VA value of 0.38 ± 0.15 logMAR at − 1.5 D. However, for the natural and increased LCA, it was 0.32 ± 0.16 logMAR and 0.25 ± 0.13 logMAR, respectively. CS was improved at all spatial frequencies after the LCA correction, which was closely followed by the natural-eye performance. Increased LCA resulted in reduced CS, mainly at higher spatial frequencies.ConclusionsWe demonstrated that elevating chromatic aberration above the natural level of monofocal patients extends their depth of focus while causing a measurable albeit minimal reduction in visual function. Still, the observed changes indicate that neither correction nor increase of LCA yields a substantial clinical effect on distance VA and CS in monofocal pseudophakia.

Poster Session II: The impact of eye's longitudinal chromatic aberration on visual acuity and accommodation response.

Chromatic composition of displays might affect vision and accommodation,possibly influencing myopia development.We investigated differences in visual acuity(VA) and accommodative lag(AccL) for steady accommodative demands (up to 5D,1D steps) with visual stimuli illuminated by monochromatic wavelengths (mono-λ 480,555&630nm,3nm bandwidth) and white light (WL).Data was obtained on 3 young emmetrope using an Adaptive Optics system with a supercontinuum laser,a DMD for stimuli,and a optunable lens to change vergence.Best focus for far was set at 555nm.VA was measured using QUEST(tumbling E).AccL was obtained from the peak shift of through-focus Visual Strehl,calculated from HS aberrometry.All subjects showed myopic shifts in blue consistent with longitudinal chromatic aberration.However,the response to wavelength differed across subjects.S#1 showed a sustained VA across distances(average VA standard deviation 0.054,-0.005logMAR),low AccL(slope:0.3 D/D) and systematic SA negative shift (slope:-0.04um/D),similar across mono-λ and WL.S#2 showed a more sustained VA,lower AccL and higher SA change in blue (0.09logMAR std,0.3D/D,-0.02um/D) than in WL(0.14logMAR std,0.52D/D,-0.013um/D).S#3 showed a steeper decrease in VA at near and higher AccL for mono-λ(0.218logMAR std,0.78D/D,on average)than in WL(0.05logMAR std,0.38D/D).Different subjects use chromatic cues in different ways to accommodate,likely affected by the interplay of chromatic blur,depth-of-focus and defocus sign perception.

Measuring visual acuity and spherical refraction with smartphone screens emitting blue light

IntroductionA periodical self-monitoring of spherical refraction using smartphones may potentially allow a quicker intervention by eye care professionals to reduce myopia progression. Unfortunately, at low levels of myopia, the far point (FP) can be located far away from the eye which can make interactions with the device difficult. To partially remedy this issue, a novel method is proposed and tested wherein the longitudinal chromatic aberration (LCA) of blue light is leveraged to optically bring the FP closer to the eye. MethodsFirstly, LCA was obtained by measuring spherical refraction subjectively using blue pixels in stimuli shown on organic light-emitting diode (OLED) screens and also grey stimuli with matching luminance. Secondly, the visual acuity (VA) measured with a smartphone located at 1.0 m and 1.5 m and displaying blue optotypes was compared with that obtained clinically standard measurements. Finally, the spherical over refraction obtained in blue light with a smartphone was compared with clinical over-refraction with black and white (B&W) optotypes placed at 6 m. ResultsMean LCA of blue OLED smartphone screens was −0.67 ± 0.11 D. No significant differences (p > 0.05) were found between the VA measured with blue optotypes on a smartphone screen and an eye chart. Mean difference between spherical over-refraction measured subjectively by experienced subjects with smartphones and the one obtained clinically was 0.08 ± 0.34 D. ConclusionsSmartphones using blue light can be used as a tool to detect changes in visual acuity and spherical refraction and facilitate monitoring of myopia progression.

Poster Session: Peripheral blur may provide the eye with a cue for the sign of defocus.

The sign of defocus is used by the retina to guide emmetropization. However, the means by which the eye determines whether light is focused in front of, or behind the retina, remains elusive. In the current study, we propose a new cue for the sign of defocus: the orientation of the anisotropic peripheral blur. Previously published [1] population averages of wavefront aberrations across the horizontal visual field in hyperopes, emmetropes and myopes were used to assess peripheral optical quality and blur orientation. Due to the large magnitudes of off-axis astigmatism and coma, the peripheral retinal image quality was dominated by anisotropic blur, whose direction was also correlated with refractive error (vertically elongated peripheral blur in myopic eyes and horizontally elongated peripheral blur in emmetropic and hyperopic eyes). The differences in groups may be due to the interaction between peripheral wavefront aberrations and globe shape (i.e. peripheral axial length). We also found an interaction between longitudinal chromatic aberration and off-axis astigmatism, wherein peripheral blur orientation is wavelength dependent, raising additional questions pertaining to the nature of chromatic cues. The orientation of peripheral blur may provide the retina with an optical cue for the sign of defocus, potentially playing an important role in emmetropization. [1] Romashchenko et al., "Peripheral refraction and higher order aberrations." Clin Exp Optom 103.1 (2020): 86-94.

Effects of blue light exposure on ocular parameters and choroidal blood perfusion in Guinea pig

PurposeTo investigate the impact of different duration of blue light exposure on ocular parameters and choroidal blood perfusion in guinea pigs with lens-induced myopia. MethodThree-week-old Guinea pigs were randomly assigned to different light-environment groups. All groups were subjected to 12-h light/dark cycle. The control (NC) group was conditioned without intervention. While lens-induced myopia (LIM) groups had a −10D lens placed in the right eye and 0D in the left eye. The guinea pigs were exposed to increasing periods of blue-light (420 nm) environment for 3,6,9,12 h per day. Changes in refraction, axial length (AL), the radius of corneal curvature (CCR), choroidal thickness (ChT), and choroidal blood perfusion (ChBP)were measured in both LIM-eye and fellow-eye during the second and fourth week of LIM duration. ResultsDuring the first two weeks of the experiment, blue light exposure raised ChBP and ChT, and the effect of suppressing myopia was proportional to the duration of blue light exposure. However, in the fourth week of the experiment, prolonged blue light (12BL) exposure led to a reduction in retinal thickness and the increase in ChT and ChBP ceased. Shorter blue light exposure had a better effect on myopia suppression, with all blue light groups statistically different from the LIM group. ConclusionExposure to blue-light appears to have the potential to improve ChBP and ChT, thereby inhibiting the development of myopia. we speculate that blue-light inhibits the development of myopia for reasons other than longitudinal chromatic aberration (LCA). However,long-term exposure to blue-light may have adverse effects on ocular development. The next step is to investigate in depth the mechanisms by which the rational use of blue light regulates choroidal blood flow, offering new hope for the treatment of myopia.

Spatio-chromatic vision with multifocal diffractive intraocular lens

BackgroundThis study aims to detect alterations in the spatio-chromatic pseudophakic vision produced by multifocal diffractive intraocular lenses (IOLs) and provides a physical interpretation.MethodsIn vitro characterization of the imaging performance of two diffractive IOLs: AT LISA Tri (Zeiss) and FineVision (PhysIOL) in on-bench model eye illuminated with red (R, 625 nm), green (G, 530 nm) and blue (B, 455 nm) lights. We used the metrics: energy efficiency (EE), area under the modulation transfer function, longitudinal chromatic aberration (LCA), and halo intensity. Through-focus (TF) analysis and calculation of the expected defocus curve under white (W) daylight were included. In vivo visual acuity (VA) of 50 pseudophakics (60 eyes) was assessed under W, R, G, B lights at far and near. Two clinical experiments evaluated LCA and R, G, B TF-EE effects on pseudophakic vision and their relative importance.ResultsClinical mean VA values under W light agreed with the predicted values at far and near for both IOLs. LCA measurements and R, G, B TF-EE curves were consistent with their lens design based on the 0th and 1st diffraction orders operative for far and near vision, respectively. LCA effects were compensated at near but noticed at far (− 0.75 D under B light). We detected strong asymmetry in visual resolution depending on the object distance and the illuminating wavelength—red predominance at far, blue predominance at near—in consistency with the TF-EE measurements.ConclusionsDiffractive multifocal IOL designs produce asymmetries in the spatio-chromatic vision of pseudophakics beyond the alterations strictly due to LCA. VA asymmetry for far/near object distance under R and B illumination is clinically detectable in subjects implanted with IOLs with 0th and 1st diffraction orders for far and near vision, respectively. Such VA asymmetry cannot be explained solely from the influence of defocus, as would be derived from a chromatic difference of power, but mainly from the wavelength dependence of the EE.

Comparison of the Polychromatic Image Quality of Two Refractive-Segmented and Two Diffractive Multifocal Intraocular Lenses.

Evaluating chromatic aberration for a multifocal intraocular lens (MIOL) in vitro is essential for studying its performance because it helps determine the most appropriate lens for each patient, enhancing surgical outcomes. While refractive MIOLs with angular power variation have shown positive clinical outcomes, studies of these MIOLs on optical benches primarily employed monochromatic green light, neglecting the impact of longitudinal chromatic aberration (LCA) on MIOL performance. To address this gap, we evaluated the through-focus modulation transfer function (TF-MTF) and the point spread function (PSF) of two refractive segmented extended depth of focus intraocular lenses (IOLs) (Femtis Comfort and Precizon Presbyopic), comparing the results with those obtained with two widely known diffractive multifocal intraocular lenses (AcrySof IQ ReSTOR and FineVision Pod F). Measurements of the TF-MTF were conducted using both monochromatic and polychromatic light in a customized optical bench. The refractive designs exhibited distinct haloes in the PSFs. When comparing the refractive and diffractive designs, opposite signs of LCA were observed at near foci. These findings emphasize the influence of the optical design of IOLs on their performance under polychromatic light, providing valuable information for vision care professionals when selecting the most suitable lens for each patient.

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

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). 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. 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. 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.].

Parasympathetic and sympathetic control of emmetropization in chick

Emmetropization can be altered by temporal visual stimulation and the spectral properties of the visual environment. The goal of the current experiment is to test the hypothesis that there is an interaction between these properties and autonomic innervation. For that purpose, selective lesions of the autonomic nervous system were performed in chickens followed by temporal stimulation. Parasympathetic lesioning involved transection of both the ciliary ganglion and the pterygopalatine ganglion (PPG_CGX; n = 38), while sympathetic lesioning involved transection of the superior cervical ganglion (SCGX; n = 49). After one week of recovery, chicks were then exposed to temporally modulated light (3 days, 2 Hz, Mean: 680 lux) that was either achromatic (with blue [RGB], or without blue [RG]), or chromatic (with blue [B/Y] or without blue [R/G]). Control birds with lesions, or unlesioned, were exposed to white [RGB] or yellow [RG] light. Ocular biometry and refraction (Lenstar and a Hartinger refractometer) was measured before and after exposure to light stimulation. Measurements were statistically analyzed for the effects of a lack of autonomic input and the type of temporal stimulation.In PPG_CGX lesioned eyes, there was no effect of the lesions one-week post-surgery. However, after exposure to achromatic modulation, the lens thickened (with blue) and the choroid thickened (without blue) but there was no effect on axial growth. Chromatic modulation thinned the choroid with R/G.In the SGX lesioned eye, there was no effect of the lesion 1-week post-surgery. However, after exposure to achromatic modulation (without blue), the lens thickened and there was a reduction in vitreous chamber depth and axial length. Chromatic modulation caused a small increase in vitreous chamber depth with R/G.Both autonomic lesion and visual stimulation were necessary to affect the growth of ocular components. The bidirectional responses observed in axial growth and in choroidal changes suggest that autonomic innervation combined with spectral cues from longitudinal chromatic aberration may provide a mechanism for homeostatic control of emmetropization.