Directional sensitivity of the retina: A layered scattering model of outer-segment photoreceptor pigments

Vohnsen, Brian

doi:10.1364/boe.5.001569

Cited by 51 publications

(61 citation statements)

References 47 publications

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“…An in silico modeling suggested that contrast inversion of cones may results from the specific optical properties of outer segments. 23 Images very similar to negative cones have been obtained in vitro by focusing between the COST and the RPE, 24 probably because of the shorter length of the outer segment of cones. However, in our patients, defocusing did not result in a transition from positive to negative mosaic or vice versa.…”

Section: Discussionmentioning

confidence: 93%

The Negative Cone Mosaic: A New Manifestation of the Optical Stiles-Crawford Effect in Normal Eyes

Miloudi

Rossant

Bloch

et al. 2015

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. The purpose of this study was to describe a previously unreported manifestation of the optical Stiles-Crawford effect (oSCE) in normal eyes. METHODS.In a cohort of 50 normal subjects, the directional reflectance of cones in the retinal periphery was explored by flood-illuminated adaptive optics (FIAO) and optical coherence tomography (OCT). RESULTS.In 32 eyes (64%), off-axis FIAO images of the retinal periphery (~15-208 from the fovea) showed variably sized patches of hyporeflective dots (called here negative mosaic) coexisting with hyperreflective (positive) cones. In nine cases, shifting the entry pupil toward the optical axis restored the positive cone mosaic, with a point-by-point correspondence between positive and negative mosaics. Rods remained hyperreflective around negative and positive cones. These changes were paralleled by changes of the OCT reflectance of the cone outer segment tips and, to a lesser extent, of the inner/outer segment limit.CONCLUSIONS. By en face FIAO imaging of the retina, the contrast of cones over rods may be strongly dependent on the entry pupil to such an extent that their reflectance is lower than that of rods. We hypothesized that the negative cone mosaic aspect results from the differential Stiles-Crawford effect of cones and rods. Cone reflectance by en face FIAO parallels the reflectance from the cone outer segment tip line and to a lesser extent of the inner/outer segment limit by OCT. Taking this into account, the oSCE is of importance for the interpretation of high-resolution images of photoreceptors. (ClinicalTrials.gov number, NCT01546181.)

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Section: Discussionmentioning

confidence: 93%

The Negative Cone Mosaic: A New Manifestation of the Optical Stiles-Crawford Effect in Normal Eyes

Miloudi

Rossant

Bloch

et al. 2015

Invest. Ophthalmol. Vis. Sci.

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“…Since oblique incidence of light increases the amount of light which traverses more than one outer segment before being absorbed, this could affect the overall image quality of the cones and hence their identification with automated algorithms. However, Vohnsen [30] has previously shown that this can only have an impact when the angle of incidence on the retina is greater than 7 degrees corresponding to a pupil entrance displacement of 2.7 mm. In previous work [24], the reflectance of the cones in AO flood-illuminated images of the retinal periphery has been shown to be greatly influenced by large displacements of the entry pupil.…”

Section: Discussionmentioning

confidence: 99%

“…In recent years, there have been several studies focused on observation of the reflectance of living cones [9,[11][12][13][14][15][16]18], and on its modelling, suggesting how the cone reflectance could be due to constructive interference of scattered light which increases with penetration depth in the cone outer segment [30], but the origin of its variability is still not fully understood. The reflectance studies have been performed with all AO imaging modalities, including AO-SLO [11][12][13]16], AO-OCT [14] and flood-illuminated AO cameras [9,17,24].…”

Section: Discussionmentioning

confidence: 99%

“…Investigation of the cone reflectance in different retinal areas and over long time periods using an AO flood illumination camera is therefore lacking in the literature. It has already been observed that the position of the light source in an AO flood illumination system has an influence on the reflectance of the cone mosaic [9,24,[27][28][29], and this property has been used to study the angular tuning of single cones [15,28,30]. As the performance of the most commonly used cone detection algorithms depends on the quality of the images to which they are applied [31], it is also possible that the position of the light source itself affects not only the reflectance of the cones but also their detection and the subsequent estimation of the mosaic metrics.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years

Mariotti¹,

Devaney²,

Lombardo³

et al. 2016

Biomed. Opt. Express

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Abstract:Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation.

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“…Although they have not been tested experimentally, two theories have emerged recently. One proposes that retinal cones, acting as waveguides, produce individually and in small groups of cones, different patterns of photopigment bleaching depending whether the image is formed in front of or behind the retina 28. The other novel theory proposes that the eye may obtain an odd‐error cue for accommodation from the shadows of the blood vessels on the photopigment layer of the retina 29…”

Section: Discussionmentioning

confidence: 99%

Human eyes do not need monochromatic aberrations for dynamic accommodation

Bernal-Molina

Marín-Franch

Águila-Carrasco

et al. 2017

Ophthalmic Physiologic Optic

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PurposeTo determine if human accommodation uses the eye's own monochromatic aberrations to track dynamic accommodative stimuli.MethodsWavefront aberrations were measured while subjects monocularly viewed a monochromatic Maltese cross moving sinusoidally around 2D of accommodative demand with 1D amplitude at 0.2 Hz. The amplitude and phase (delay) of the accommodation response were compared to the actual vergence of the stimulus to obtain gain and temporal phase, calculated from wavefront aberrations recorded over time during experimental trials. The tested conditions were as follows: Correction of all the subject's aberrations except defocus (C); Correction of all the subject's aberrations except defocus and habitual second‐order astigmatism (AS); Correction of all the subject's aberrations except defocus and odd higher‐order aberrations (HOAs); Correction of all the subject's aberrations except defocus and even HOAs (E); Natural aberrations of the subject's eye, i.e., the adaptive‐optics system only corrected the optical system's aberrations (N); Correction of all the subject's aberrations except defocus and fourth‐order spherical aberration (SA). The correction was performed at 20 Hz and each condition was repeated six times in randomised order.ResultsAverage gain (±2 standard errors of the mean) varied little across conditions; between 0.55 ± 0.06 (SA), and 0.62 ± 0.06 (AS). Average phase (±2 standard errors of the mean) also varied little; between 0.41 ± 0.02 s (E), and 0.47 ± 0.02 s (O). After Bonferroni correction, no statistically significant differences in gain or phase were found in the presence of specific monochromatic aberrations or in their absence.ConclusionsThese results show that the eye's monochromatic aberrations are not necessary for accommodation to track dynamic accommodative stimuli.

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Directional sensitivity of the retina: A layered scattering model of outer-segment photoreceptor pigments

Cited by 51 publications

References 47 publications

The Negative Cone Mosaic: A New Manifestation of the Optical Stiles-Crawford Effect in Normal Eyes

The Negative Cone Mosaic: A New Manifestation of the Optical Stiles-Crawford Effect in Normal Eyes

Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years

Human eyes do not need monochromatic aberrations for dynamic accommodation

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