Real-time measurement of ocular wavefront aberrations in symptomatic subjects

Te purpose of this work was to study the real-time changes of the optical properties of the eye with accommodation in subjects with symptoms of accommodative disorders. From ocular aberrations, it is possible to compute several parameters like the response and lag of accommodation. Te ocular aberrations were measured in 4 subjects, with diferent accommodative disorders, during several cycles of accommodation/disaccommodation and for diferent accommodative stimuli. Te measurement was done continuously and in real time during diferent accommodative stimuli. It was possible to see the changes in accommodative response during the several stimuli of accommodation. Subjects with accommodative disorders showed diferent accommodative responses. Te use of wavefront ocular aberrations can be a tool to diagnose accommodative disorders. In some subjects with complaints, this method showed irregularities even when the results of the usual clinical exams were normal.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013.info:eu-repo/semantics/publishedVersio

Crystalline lens imaging during accommodation with a slit-scanning tomography system: preliminary results

A slit-scanning tomography system previously developed in the Centre of Physics of University of Minho allows to capture images of the eye and posteriorly calculus of the biometric (thickness and curvature) and optical (wavefront aberrations) properties of the corneal and crystalline lens surfaces. It is intended to optimise the system for an accurate computing of these properties of the crystalline lens in the relaxed state and during ocular accommodation. In this study, preliminary experimental results of the crystalline lens imaging of a subject during accommodation are presented.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FIS-OTI/31486/2017 and POCI-01-0145-FEDER 031486

Central and peripheral ocular high-order aberrations and their relationship with accommodation and refractive error: a review

High-order aberrations (HOAs) are optical defects that degrade the image quality. They change with factors such as pupil diameter, age, and accommodation. The changes in optical aberrations during accommodation are mainly due to lens shape and position changes. Primary spherical aberration (Z(4.0)) is closely related to accommodation and some studies suggested that it plays an important role in the control of accommodation. Furthermore, central and peripheral HOAs vary with refractive error and seem to influence eye growth and the onset and progression of myopia. The variations of central and peripheral HOAs during accommodation also appear to be different depending on the refractive error. Central and peripheral high-order aberrations are closely related to accommodation and influence the accuracy of the accommodative response and the progression of refractive errors, especially myopia.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/ FISOTI/31486/2017 and POCI-01-0145-FEDER-031486. The author Jessica Gomes is also supported by PhD grant 2020.08737.BD from the FCT

Effect of accommodation on coma at central and peripheral retina

Coma is one of the most common ocular higher order aberrations and highly affects the quality of image. It is assumed that corneal aberrations are balanced by internal (lenticular) aberrations so that retinal image quality may not have great impact. However, during accommodation, the shape, position, and curvature of the crystalline lens changes which might disrupt this balance between internal and corneal aberration. This study aimed to investigate the effect of accommodation on primary coma (3 −1 and 3 1 ) and secondary coma (5 −1 and 5 1 ) in relaxed and accommodated eyes. Zernike coefficients were measured in 53 subjects with Hartmann-Shack aberrometer both at the central and peripheral retina up to 30º off-axis in horizontal and vertical meridians. The process was repeated with 2.50 D accommodation stimulus and comas were compared with and without accommodation. Root-mean-square of total coma was also assessed. With accommodation, vertical comas changed to more negative value and horizontal comas changed to more positive values in most of the off-axis positions. In contrast, the secondary vertical comas became less negative and secondary horizontal comas became more negative with accommodation in most of the off-axis fixations. Thus, the results showed that accommodation affects coma which depends up on position of the fixation.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FIS-OTI/31486/2017 and POCI-01-0145-FEDER-031486

Assessment of central and peripheral accommodative lag by aberrometry

Accommodation lag is important factor for normal vision. Higher lag of accommodation may cause various ocular symptoms particularly during near tasks. In this study, the lag of accommodation was assessed in the peripheral retina and it was compared with the central accommodative lag with aberrometer. In this cross-sectional study, fifty-three young subjects with normal visual acuity and without any active ocular disease or past ocular surgery were included. Aberrations in the central and peripheral field of view up to 30° off axis from the centre in horizontal and vertical meridian in 10° steps were measured with Hartmann-Shack aberrometer with stimulation of accommodation by -2.50D lens. Accommodative stimulus and accommodative response were calculated with defocus and hence accommodative lag was obtained. Accommodative lag in the centre and periphery was compared. Repeated measure of ANOVA showed that there were significant differences in lag of accommodation in various eccentricities (F(8.912, 454.514) = 2.372, p = 0.013). Pairwise test showed that lag in the centre was similar with lag on other peripheral field of view (p > 0.05). However, accommodative lag at 10° nasal field was significantly lower than the lag at 20° temporal, 20° nasal, 30° temporaland 30° nasal (p < 0.05). Similarly, lag at 10° superior fixation was lower than lag at 20° temporal, 20° nasal, 30° temporal and 30° nasal fixations (p < 0.05). We found higher lag of accommodation in horizontal off-axis fixations in comparison to that of vertical off-axis fixations (p < 0.05). Lag of accommodation was positive correlated with vertical coma and primary spherical aberrations but negative correlated with secondary spherical aberrations (p < 0.05). Thus, Hartmann-Shack aberrometer was successfully used to assess accommodative lag in the peripheral field of view up to 60° visual field. Peripheral lag of accommodation depends up on eccentricity. Lag was found higher in horizontal off-axis fixation than at vertical fixations. Coma and spherical aberration had association with lag.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FISOTI/31486/2017 and POCI-01-0145-FEDER-031486.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FIS-OTI/31486/2017 and POCI-01-0145-FEDER-031486

Real-time wavefront aberrometry in subjects with accommodative excess

The purpose of this study was to use real-time wavefront aberrometry to detect accommodative excess (AE) and to analyse the optical quality of the eye in subjects with this dysfunction. AE was detected from the accommodative response obtained by real-time wavefront aberrometry. These subjects had a significant accommodative lead to all stimuli and had difficulty relaxing accommodation. The root mean square (RMS) of high order aberrations (HOA) was higher in subjects with AE for lower stimulus and for disaccommodation than in the control group. However, the subjects with AE showed a decrease in the RMS of HOA with an increase in accommodative response. Primary spherical aberration tended to become more negative with accommodation in both subjects and there was no difference between the groups. Real-time wavefront aberrometry can be used as an objective method to detect accommodative excess.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FIS-OTI/31486/2017 and POCI-01-0145-FEDER-031486. The author Jessica Gomes is also supported by the PhD grant 2020.08737.BD from FCT

Improving Future Policy Responses to Foreseeable Bank Risk-Taking

This brief offers new perspectives on the behavior of banks during the financial crisis of 2007-08 and the limited success of unconventional monetary policies in stimulating bank credit to the private sector during the subsequent economic recovery. The common narrative about the financial crisis is that it was caused by a large credit expansion with overly risky loan-granting behavior by banks. We argue, however, that banks actually made optimal financial decisions in the lead-up to the crisis, based on their calculation of their franchise value. The brief explains the mechanics of franchise value—how it led banks to shift their portfolios toward riskier household loans before the crisis, as well as how it dampened the impact of quantitative easing and other novel monetary policies meant to stimulate the investment of capital into the private sector. Policymakers have failed to recognize the role that franchise value plays in all bank decisions. If they wish to devise appropriate fiscal or monetary policies to prevent or mitigate a future crisis, they need to properly account for how franchise value drives the decision-making of bank managers.https://repository.upenn.edu/pennwhartonppi/1068/thumbnail.jp

Near Vision Tasks and Optical Quality of the Eye

Purpose: To study the effect of near-vision reading task on optical quality of the eye when performed on a computer monitor and on printed paper, and to identify which of the two results in greater changes. Methods: Two groups of subjects performed a 30-min reading task in two different conditions: on a computer monitor and on printed paper. Ocular, corneal, and internal wavefront aberrations (Zernike coefficients up to 6th order), root-mean-square of low- and high-order aberrations, spherical equivalent, vectoral components of ocular astigmatism ( J45 and J0), and the compensation factor between internal and corneal aberrations were measured before and after the tasks. Their changes were analyzed in each group and between groups. Results: Statistically significant changes in wavefront aberrations and in root mean square of low- and high-order aberrations were observed in both groups which was significantly greater when the task was performed on printed paper. Partial loss of compensation mechanism and variation in spherical equivalent in a negative direction occurred after both reading tasks; however, it was statistically significant only with printed paper reading task. The vectoral components of ocular astigmatism did not show statistically significant changes in either groups. Conclusion: Near-vision reading tasks can change the optical quality of the eye, especially when the task is performed on printed paper

Perceção e memória de faces em epilepsias occipitais e temporais

A epilepsia é uma condição neurológica caracterizada por uma predisposição persistente para a ocorrência de crises epiléticas e pelo conjunto das consequências neurobiológicas, cognitivas, psicológicas e sociais associadas a esta condição (ILAE). Cerca de 25% dos casos são refratários à terapêutica farmacológica e candidatos a cirurgia (Elger, 2008). Nestes casos é crucial determinar a integridade funcional das áreas cerebrais adjacentes ao foco epilético, no sentido de as preservar. O diagnóstico das epilepsias occipitais e temporais constitui, no entanto, um grande desafio, como resultado da rápida propagação da atividade para os restantes lobos cerebrais, no primeiro caso (cf. Leal et al., 2007), e pela dificuldade de lateralização do foco, no segundo caso (Baxendale & Thompson, 2010). Considerando que uma das funções com representação cerebral alargada é a do processamento de faces (Haxby, Hoffman & Gobbini, 2000), o processamento deste estímulo poderá constituir um excelente teste de funcionamento de áreas occipitais e temporais. O presente trabalho testa a validade da utilização de uma prova de perceção de faces (Philadelphia Face Perception Battery; Thomas et al., 2008) e de uma prova de memória de faces (Cambridge Face Memory Test; Duchaine & Nakayama, 2006), para a identificação de focos epiléticos. A comparação de diferentes grupos clínicos, e destes com uma amostra de participantes saudáveis, permitiram demonstrar o importante contributo que estas provas podem oferecer para a localização de epilepsias occipitais e para a lateralização das epilepsias temporais.Epilepsy is a neurological condition characterized by an enduring predisposition for the occurrence of seizures and by a set of neurobiological, cognitive, psychological and social consequences associated with those seizures (ILAE). About 25% of cases are refractory to drug therapy and become surgery candidates (Elger, 2008). In those cases, it is crucial to establish the functional integrity of the brain areas adjacent to the epileptic focus, in order to preserve them. However, the diagnosis of occipital and temporal epilepsies is difficult to perform, as consequence of the rapid spread of anomalous electric activity to other cerebral lobes, in the first case (cf. Leal et al., 2007), and the difficulty of lateralizing the focus of that activity, in the second case (Baxendale & Thompson, 2010). Considering that one of the functions with more extensive cerebral representation is that of face processing (Haxby, Hoffman & Gobbini, 2000), the processing of this stimulus may constitute an excellent functional test of temporal and occipital areas. The current study tests the validity of a face perception test (Philadelphia Face Perception Battery; Thomas et al., 2008) and of a face memory test (Cambridge Face Memory Test; Duchaine & Nakayama, 2006) as tools to help identifying epileptic foci. The comparison of different clinical groups, and of those with a sample of healthy participants, demonstrated the contribution of those tests for the location of occipital epilepsies and for the lateralization of temporal epilepsy