scholarly journals The Relationship Between Visual Sensitivity and Eccentricity, Cone Density and Outer Segment Length in the Human Foveola

2021 ◽  
Vol 62 (9) ◽  
pp. 31
Author(s):  
Niklas Domdei ◽  
Jenny L. Reiniger ◽  
Frank G. Holz ◽  
Wolf M. Harmening
Keyword(s):  
Outer Segment ◽  
Visual Sensitivity ◽  
Segment Length ◽  
The Relationship ◽  
Cone Density

scholarly journals Retinal factors of visual sensitivity in the human fovea

2021 ◽  
Author(s):  
Niklas Domdei ◽  
Jenny L. Reiniger ◽  
Frank G. Holz ◽  
Wolf Harmening
Keyword(s):  
Adaptive Optics ◽  
Outer Segment ◽  
Visual Sensitivity ◽  
Segment Length ◽  
Retinal Eccentricity ◽  
Small Spot ◽  
Steep Decline ◽  
Human Participants ◽  
Specialized Region ◽  
Cone Density

AbstractHumans direct their gaze towards visual objects of interest such that the retinal images of fixated objects fall onto the fovea, a small anatomically and physiologically specialized region of the retina displaying highest visual fidelity. One striking anatomical feature of the fovea is its non-uniform cellular topography, with a steep decline of cone photoreceptor density and outer segment length with increasing distance from its center. We here assessed in how far the specific cellular organization of the foveola is reflected in visual function. Increment sensitivity to small spot visual stimuli (1 x 1 arcmin, 543 nm light) was recorded psychophysically in 4 human participants at 17 locations placed concentric within a 0.2-degree diameter around the preferred retinal locus of fixation with adaptive optics scanning laser ophthalmoscopy based microstimulation. While cone density as well as maximum outer segment length differed significantly among the four tested participants, the range of observed threshold was similar, yielding an average increment threshold of 3.3 ± 0.2 log10 photons at the cornea. Thresholds were correlated with retinal eccentricity, as well as cone density and outer segment length. Biophysical simulation allowed to develop a model of foveal sensitivity based on these parameters, explaining at least 37% of the observed threshold variability. Based on high reproducibility in replicate testing, the residual variability is assumed to be caused by individual cone and bipolar cell weighting at the specific target locations.

scholarly journals The Relationship Between Perifoveal L-Cone Isolating Visual Acuity and Cone Photoreceptor Spacing—Understanding the Transition Between Healthy Aging and Early AMD

2021 ◽  
Vol 13 ◽  
Author(s):  
Rigmor C. Baraas ◽  
Åshild Horjen ◽  
Stuart J. Gilson ◽  
Hilde R. Pedersen
Keyword(s):  
Outer Segment ◽  
Healthy Aging ◽  
Segment Length ◽  
Retinal Eccentricity ◽  
Cone Photoreceptor ◽  
Cone Structure ◽  
Age Related ◽  
Risk Of Progression ◽  
The Relationship ◽  
Cone Density

Background: Age-related macular degeneration (AMD) is a multifactorial degenerative disorder that can lead to irreversible loss of visual function, with aging being the prime risk factor. However, knowledge about the transition between healthy aging and early AMD is limited. We aimed to examine the relationship between psychophysical measures of perifoveal L-cone acuity and cone photoreceptor structure in healthy aging and early AMD.Methods and Results: Thirty-nine healthy participants, 10 with early AMD and 29 healthy controls were included in the study. Multimodal high-resolution retinal images were obtained with adaptive-optics scanning-light ophthalmoscopy (AOSLO), optical-coherence tomography (OCT), and color fundus photographs. At 5 degrees retinal eccentricity, perifoveal L-cone isolating letter acuity was measured with psychophysics, cone inner segment and outer segment lengths were measured using OCT, while cone density, spacing, and mosaic regularity were measured using AOSLO. The Nyquist sampling limit of cone mosaic (Nc) was calculated for each participant. Both L-cone acuity and photoreceptor inner segment length declined with age, but there was no association between cone density nor outer segment length and age. A multiple regression showed that 56% of the variation in log L-cone acuity was accounted for by Nc when age was taken into account. Six AMD participants with low risk of progression were well within confidence limits, while two with medium-to-severe risk of progression were outliers. The observable difference in cone structure between healthy aging and early AMD was a significant shortening of cone outer segments.Conclusion: The results underscore the resilience of cone structure with age, with perifoveal functional changes preceding detectable changes in the cone photoreceptor mosaic. L-cone acuity is a sensitive measure for assessing age-related decline in this region. The transition between healthy aging of cone structures and changes in cone structures secondary to early AMD relates to outer segment shortening.

The relationship between ambient lighting conditions, absolute dark-adapted thresholds, and rhodopsin in black and hypopigmented mice

2004 ◽  
Vol 21 (6) ◽  
pp. 925-934 ◽  
Author(s):  
GERARD H. DALY ◽  
JESSICA M. DILEONARDO ◽  
NATALIE R. BALKEMA ◽  
GRANT W. BALKEMA
Keyword(s):  
Bright Light ◽  
Visual Sensitivity ◽  
Segment Length ◽  
Single Strain ◽  
Photoreceptor Layer ◽  
Lighting Conditions ◽  
Ambient Lighting ◽  
Dim Light ◽  
Albino Mice ◽  
The Relationship

Significant variation in absolute dark-adapted thresholds is observed both within and between strains of mice with differing ocular pigmentation levels. Differences in threshold within a single strain are related to the Williams' photostasis effect, that is, photoreceptor rhodopsin levels are dependent upon ambient lighting conditions. To examine threshold differences among strains, we equalized rhodopsin levels by maintaining albino mice (c2J/c2J) at 2 × 10−4 cd/m2 (dim light) and black mice at 2 × 102 cd/m2 (bright light). This resulted in ocular rhodopsin levels for albino mice (albino—dim) of 494 ± 11 pmoles/eye and rhodopsin levels for black mice (black—bright) of 506 ± 25 pmoles/eye. For comparison, rhodopsin levels in black mice maintained in dim light are 586 ± 46 pmoles/eye and 217 ± 46 pmoles/eye in albino mice maintained in bright light. We found similar dark-adapted thresholds (6.38 log cd/m2vs. 6.47 log cd/m2)) in albino and black mice with equivalent rhodopsin determined with a water maze test. This suggests that dark-adapted thresholds are directly related to rhodopsin levels regardless of the level of ocular melanin. The number of photoreceptors, photoreceptor layer thickness, and outer segment length did not differ significantly between albino (dark) and black mice (bright). These results demonstrate that the visual sensitivity defect found in hypopigmented animals is secondary to abnormal rhodopsin regulation and that hypopigmented animals have either an improper input to the photostasis mechanism or that the photostasis mechanism is defective.

scholarly journals Evaluating outer segment length as a surrogate measure of peak foveal cone density

2017 ◽  
Vol 130 ◽  
pp. 57-66 ◽  
Author(s):  
Melissa A. Wilk ◽  
Brandon M. Wilk ◽  
Christopher S. Langlo ◽  
Robert F. Cooper ◽  
Joseph Carroll
Keyword(s):  
Outer Segment ◽  
Segment Length ◽  
Surrogate Measure ◽  
Cone Density

scholarly journals Macular Pigment Optical Density and Photoreceptor Outer Segment Length as Predisease Biomarkers for Age-Related Macular Degeneration

2020 ◽  
Vol 9 (5) ◽  
pp. 1347 ◽  
Author(s):  
Norihiro Nagai ◽  
Sakiko Minami ◽  
Misa Suzuki ◽  
Hajime Shinoda ◽  
Toshihide Kurihara ◽  
...  
Keyword(s):  
Macular Degeneration ◽  
Optical Density ◽  
Outer Segment ◽  
Macular Pigment ◽  
Age Related Macular Degeneration ◽  
Segment Length ◽  
Macular Pigment Optical Density ◽  
Photoreceptor Outer Segment ◽  
Age Related ◽  
Fellow Eyes

To explore predisease biomarkers, which may help screen for the risk of age-related macular degeneration (AMD) at very early stages, macular pigment optical density (MPOD) and photoreceptor outer segment (PROS) length were analyzed. Thirty late AMD fellow eyes, which are at high risk and represent the predisease condition of AMD, were evaluated and compared with 30 age-matched control eyes without retinal diseases; there was no early AMD involvement in the AMD fellow eyes. MPOD was measured using MPS2® (M.E. Technica Co. Ltd., Tokyo, Japan), and PROS length was measured based on optical coherence tomography images. MPOD levels and PROS length in the AMD fellow eyes were significantly lower and shorter, respectively, than in control eyes. MPOD and PROS length were positively correlated in control eyes (R = 0.386; p = 0.035) but not in AMD fellow eyes. Twenty (67%) AMD fellow eyes met the criteria of MPOD < 0.65 and/or PROS length < 35 μm, while only five (17%) control eyes did. After adjusting for age and sex, AMD fellow eyes more frequently satisfied the definition (p < 0.001; 95% confidence interval, 3.50–60.4; odds ratio, 14.6). The combination of MPOD and PROS length may be a useful biomarker for screening predisease AMD patients, although further studies are required in this regard.

scholarly journals PEMANFAATAN APLIKASI SMARTPHONE UNTUK MENGUKUR KEMANTAPAN PERMUKAAN JALAN BERDASARKAN INTERNATIONAL ROUGHNESS INDEX

2020 ◽  
Vol 19 (3) ◽  
pp. 205-214
Author(s):  
Arief Setiawan ◽  
Novita Pradani ◽  
Ferra Claudia Masoso
Keyword(s):  
Segment Length ◽  
Android Application ◽  
Smartphone Applications ◽  
International Roughness Index ◽  
Surface Conditions ◽  
Software Applications ◽  
Measurement Results ◽  
Roughness Index ◽  
Technological Developments ◽  
The Relationship

Abstract An assessment of road surface conditions is needed to determine an appropriate road evaluation program. One of the parameters used is the International Roughness Index or IRI. Currently, technological developments encourage the use of smartphone applications as a tool to determine the value of IRI. Comparisons between IRIs obtained using tools, such as roughometers, and IRIs obtained from software applications have not been made. The purpose of this study was to analyze the relationship between the results of the measurement of the roughometer and the results of the Android application Roadbump Pro. This research was carried out on the Sam Ratulangi Road in Palu City, with a segment length of 600 meters and analyzed per 100 meters. The results of this study indicate that smartphone applications provide good IRI measurement results, so they can be used in road stability assessments. In addition, the type of survey vehicle did not have a significant effect on IRI measurements. Keywords: smartphone, International Roughness Index, roughometer, Roadbump, road stability  Abstrak Penilaian kondisi permukaan jalan diperlukan untuk menentukan program evaluasi jalan yang tepat. Salah satu parameter yang digunakan adalah International Roughness Index atau IRI. Saat ini, perkembangan teknologi mendorong penggunaan aplikasi smartphone sebagai alat bantu untuk menentukan nilai IRI. Perbandingan antara IRI yang diperoleh dengan menggunakan alat bantu, seperti roughometer, dan IRI yang diperoleh dari aplikasi perangkat lunak belum dilakukan. Tujuan penelitian ini adalah menganalisis hubungan antara hasil pengukuran alat roughometer dan hasil aplikasi android Roadbump Pro. Penelitian ini dilakukan di ruas Jalan Sam Ratulangi di Kota Palu, dengan panjang segmen 600 meter dan dianalisis per 100 meter. Hasil penelitian ini menunjukkan bahwa aplikasi smartphone memberikan hasil pengukuran IRI yang baik, sehingga dapat digunakan dalam penilaian kemantapan jalan. Selain itu, jenis kendaraan survei tidak memberikan pengaruh yang signifikan terhadap pengukuran IRI. Kata-kata kunci: smartphone, International Roughness Index, roughometer, Roadbump, kemantapan jalan

Changes of outer retinal thickness with increasing age in normal eyes

2020 ◽  
Vol 1 (2) ◽  
pp. 108-112
Author(s):  
Zi-Jing Li ◽  
◽  
Jian-Hui Xiao ◽  
Peng Zeng ◽  
Xiang Gao ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Outer Segment ◽  
Retinal Thickness ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Retinal Layer ◽  
External Limiting Membrane ◽  
The Cost ◽  
The Relationship ◽  
Sd Oct

AIM: To comprehensively investigate the relationship between outer retinal layer thickness and age in normal eyes. METHODS: One hundred normal eyes of 100 subjects who underwent spectral-domain optical coherence tomography (SD-OCT) were included in this retrospective study. The distances between the external limiting membrane (ELM) line and the photoreceptor inner segment/outer segment (IS/OS) line (ELM-IS/OS), the IS/OS line and the cone outer segment tips (COST) line (IS/OS-COST), the COST line and the retinal pigment epithelium (RPE) complex (COST-RPE) and the full retinal thickness (RT) were measured at the fovea and on four quarters. The relationship between thickness and age or sex was then analysed. CONCLUSION: In normal eyes, the RT thickness on the nasal quarter and the ELM-IS/OS thickness were significantly and negatively correlated with age. The IS/OS-COST and COST-RPE thicknesses were not significantly correlated with age or sex.

Modeling the Elasticity of Oriented Electrospun Nano-Fibrous Scaffold

2011 ◽  
Vol 467-469 ◽  
pp. 1241-1244
Author(s):  
Bo Yuan ◽  
Qun Feng Liu ◽  
Cai Lin ◽  
Xiao Feng Chen
Keyword(s):  
Elastic Modulus ◽  
Micromechanical Model ◽  
Polymeric Materials ◽  
Segment Length ◽  
Fibrous Scaffold ◽  
Fiber Concentration ◽  
Linear Elastic ◽  
Electrospinning Method ◽  
Percolation Effect ◽  
The Relationship

A micromechanical model is constructed for the elastic modulus of nano-fibrous scaffold. The nano-fibrous scaffold was obtained using electrospinning method with polymeric materials, and was supposed to be created with linear elastic strain rods that are straight in the range of rod length. Statistical theory was introduced to model the random distribution of fiber segment length and the percolation effect was also studied. Model predictions were verified using experimental data. This model can be used to study the relationship between the elastic modulus of the scaffold with respect to the fiber concentration, fiber diameter and fiber orientation.

scholarly journals Comparison of photoreceptor outer segment length in diabetic and idiopathic epiretinal membranes

Eye ◽  
2015 ◽  
Vol 29 (11) ◽  
pp. 1446-1452 ◽  
Author(s):  
K Yüksel ◽  
Y Karaküçük ◽  
A Özkaya ◽  
G Pekel ◽  
Ö Baz ◽  
...  
Keyword(s):  
Outer Segment ◽  
Segment Length ◽  
Photoreceptor Outer Segment ◽  
Epiretinal Membranes

The ageing photoreceptor

2007 ◽  
Vol 24 (2) ◽  
pp. 151-155 ◽  
Author(s):  
ALEXANDER CUNEA ◽  
GLEN JEFFERY
Keyword(s):  
Aging Process ◽  
Outer Segment ◽  
Retinal Disease ◽  
Segment Length ◽  
Rod Photoreceptor ◽  
Retinal Neurons ◽  
Rod Photoreceptors ◽  
Outer Segments ◽  
Age Related ◽  
Similar Density

With age many retinal neurons are lost. In humans the rod photoreceptor population in the perimacular region is subject to approximately 30% loss over life. Those that remain have been reported to suffer from extensive convolutions and localized swellings of their outer segments abnormally increasing their disc content and outer segment length. Here we examine quantitatively age-related changes in rat rod photoreceptors. The rat retina is ∼97% rod dominated. Here, aged rods showed significant reductions in outer segment length. The discs in their outer segments had a similar density, irrespective of whether they were young or old, however, in aged animals a higher proportion were misregistered. Surprisingly, in all of the tissue examined, we found no evidence for any convolution of outer segments or localized swelling as reported in humans, rather all remained straight. There are methodological differences between the research reported here and that undertaken on human retinae. There are also major differences in overall retinal architecture between humans and rodents that could contribute to differences in the aging process of individual cells. If it is the case that individual photoreceptors age differently in rodents compared to humans, it may pose significant problems for the use of this animal model in studies of ageing and age related outer retinal disease.

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