PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-8 (8)
 

Clipboard (0)
None

Select a Filter Below

Journals
Year of Publication
Document Types
1.  Quantitative Fundus Autofluorescence in Healthy Eyes 
Purpose.
Fundus autofluorescence was quantified (qAF) in subjects with healthy retinae using a standardized approach. The objective was to establish normative data and identify factors that influence the accumulation of RPE lipofuscin and/or modulate the observed AF signal in fundus images.
Methods.
AF images were acquired from 277 healthy subjects (age range: 5–60 years) by employing a Spectralis confocal scanning laser ophthalmoscope (cSLO; 488-nm excitation; 30°) equipped with an internal fluorescent reference. For each image, mean gray level was calculated as the average of eight preset regions, and was calibrated to the reference, zero-laser light, magnification, and optical media density from normative data on lens transmission spectra. Relationships between qAF and age, sex, race/ethnicity, eye color, refraction/axial length, and smoking status were evaluated as was measurement repeatability and the qAF spatial distribution.
Results.
qAF levels exhibited a significant increase with age. qAF increased with increasing eccentricity up to 10° to 15° from the fovea and was highest superotemporally. qAF values were significantly greater in females, and, compared with Hispanics, qAF was significantly higher in whites and lower in blacks and Asians. No associations with axial length and smoking were observed. For two operators, between-session repeatability was ±9% and ±12%. Agreement between the operators was ±13%.
Conclusions.
Normative qAF data are a reference tool essential to the interpretation of qAF measurements in ocular disease.
Fundus autofluorescence was quantified (qAF) in 277 subjects, to assess the relationship of qAF to age, sex, race/ethnicity, refraction/axial length, and smoking, as well as spatial distribution and repeatability.
doi:10.1167/iovs.13-12445
PMCID: PMC3759220  PMID: 23860757
lipofuscin; melanin; quantitative fundus autofluorescence; retina; retinal pigment epithelium; scanning laser ophthalmoscope
2.  Quantitative Fundus Autofluorescence in Mice: Correlation With HPLC Quantitation of RPE Lipofuscin and Measurement of Retina Outer Nuclear Layer Thickness 
Purpose.
Our study was conducted to establish procedures and protocols for quantitative autofluorescence (qAF) measurements in mice, and to report changes in qAF, A2E bisretinoid concentration, and outer nuclear layer (ONL) thickness in mice of different genotypes and age.
Methods.
Fundus autofluorescence (AF) images (55° lens, 488 nm excitation) were acquired in albino Abca4−/−, Abca4+/−, and Abca4+/+ mice (ages 2–12 months) with a confocal scanning laser ophthalmoscope (cSLO). Gray levels (GLs) in each image were calibrated to an internal fluorescence reference. The bisretinoid A2E was measured by quantitative high performance liquid chromatography (HPLC). Histometric analysis of ONL thicknesses was performed.
Results.
The Bland-Altman coefficient of repeatability (95% confidence interval) was ±18% for between-session qAF measurements. Mean qAF values increased with age (2–12 months) in all groups of mice. qAF was approximately 2-fold higher in Abca4−/− mice than in Abca4+/+ mice and approximately 20% higher in heterozygous mice. HPLC measurements of the lipofuscin fluorophore A2E also revealed age-associated increases, and the fold difference between Abca4−/− and wild-type mice was more pronounced (approximately 3–4-fold) than measurable by qAF. Moreover, A2E levels declined after 8 months of age, a change not observed with qAF. The decline in A2E levels in the Abca4−/− mice corresponded to reduced photoreceptor cell viability as reflected in ONL thinning beginning at 8 months of age.
Conclusions.
The qAF method enables measurement of in vivo lipofuscin and the detection of genotype and age-associated differences. The use of this approach has the potential to aid in understanding retinal disease processes and will facilitate preclinical studies.
We established a standardized approach for quantitative autofluorescence (qAF) measurements in mice, and report changes in qAF, A2E bisretinoid concentration, and outer nuclear layer (ONL) thickness in mice of different genotypes and age.
doi:10.1167/iovs.12-11490
PMCID: PMC3632269  PMID: 23548623
Abca4; RPE lipofuscin; quantitative fundus autofluorescence; mouse; bisretinoid
3.  QUANTIFICATION OF FLUORESCEIN-STAINED DRUSEN ASSOCIATED WITH AGE-RELATED MACULAR DEGENERATION 
Retina (Philadelphia, Pa.)  2012;32(1):19-24.
Background
Previous studies of age-related macular degeneration have not quantified the number of drusen that accumulate fluorescein. Histopathologic studies have demonstrated druse subregions with different degrees of hydrophobicity, and these subregions might potentially exhibit different degrees of fluorescein uptake.
Methods
We evaluated macular drusen from 35 age-related macular degeneration patients by measuring druse area in color digital images and fluorescein angiograms, using 2 morphometric methods.
Results
Of 828 drusen evaluated, 405 had a corresponding fluorescein angiogram signal. About half of all drusen per eye (49.57%) stained in each participant. Among fluorescein-stained drusen, druse size measured in color images did not differ significantly from the sizes measured in corresponding fluorescein images (P = 0.8105), across the range of druse sizes.
Conclusion
These findings indicate that our understanding of drusen subregion staining may not directly correlate to in vivo observations of macular drusen in age-related macular degeneration.
doi:10.1097/IAE.0b013e318219e5e9
PMCID: PMC3619108  PMID: 21878853
age-related macular degeneration; drusen; fluorescein angiography; fundus photography
4.  Vitamin A activates rhodopsin and sensitizes it to ultraviolet light 
Visual neuroscience  2011;28(6):485-497.
The visual pigment, rhodopsin, consists of opsin protein with 11-cis retinal chromophore, covalently bound. Light activates rhodopsin by isomerizing the chromophore to the all-trans conformation. The activated rhodopsin sets in motion a biochemical cascade that evokes an electrical response by the photoreceptor. All-trans retinal is eventually released from the opsin and reduced to vitamin A. Rod and cone photoreceptors contain vast amounts of rhodopsin, so after exposure to bright light, the concentration of vitamin A can reach relatively high levels within their outer segments. Since a retinal analog, β-ionone, is capable of activating some types of visual pigments, we tested whether vitamin A might produce a similar effect. In single-cell recordings from isolated dark-adapted salamander green-sensitive rods, exogenously applied vitamin A decreased circulating current and flash sensitivity and accelerated flash response kinetics. These changes resembled those produced by exposure of rods to steady light. Microspectrophotometric measurements showed that vitamin A accumulated in the outer segments and binding of vitamin A to rhodopsin was confirmed in in vitro assays. In addition, vitamin A improved the sensitivity of photoreceptors to ultraviolet (UV) light. Apparently, the energy of a UV photon absorbed by vitamin A transferred by a radiationless process to the 11-cis retinal chromophore of rhodopsin, which subsequently isomerized. Therefore, our results suggest that vitamin A binds to rhodopsin at an allosteric binding site distinct from the chromophore binding pocket for 11-cis retinal to activate the rhodopsin, and that it serves as a sensitizing chromophore for UV light.
doi:10.1017/S0952523811000423
PMCID: PMC3601037  PMID: 22192505
Retinol; Retinal photoreceptors; GPCR; Allosteric regulation; Electrophysiology
5.  Visualization of the Optic Fissure in Short-Wavelength Autofluorescence Images of the Fundus 
Purpose.
To document and explain the presence, inferior to the optic disc, of a distinct vertical boundary between two retinal areas of different short-wavelength autofluorescence (SW-AF) intensities.
Methods.
SW-AF images of the inferonasal region were acquired from 32 healthy subjects. Additionally, color, 488-nm reflectance (488-R), near-infrared reflectance (NIR-R), NIR autofluorescence (NIR-AF) images, and a spectral domain optical coherence tomography (SD-OCT) image were obtained in selected subjects. Gray levels (GL) on both sides of the demarcation line were measured in SW-AF and 488-R at fixed distances from the disc center.
Results.
A curved demarcation line inferior to the optic disc was observed on SW-AF images in 31/32 subjects. AF levels on the nasal side were 13% (±6%) lower than on the temporal side at 20° inferior to the disc center. The contrast between the nasal and the temporal areas was not significantly affected by age, sex, refractive error, race, or iris color. The demarcation line visible in SW-AF was also seen, though with reduced contrast, in approximately 80% of the 488-R images (lower reflectance on the nasal side) and 50% of color images. The boundary was not detected by NIR-R, NIR-AF, or by SD-OCT imaging.
Conclusions.
The location and the distinctness of the demarcation line may indicate a relationship to the closed embryonic optic fissure. The reduced SW-AF intensity and 488-R reflectance observed on the nasal side of this line may be attributable to lower lipofuscin and melanin content per unit area, possibly resulting from a difference in RPE cell shape.
In short-wavelength autofluorescence images a curved demarcation line can be observed inferior to the optic disc.
doi:10.1167/iovs.12-10004
PMCID: PMC3462479  PMID: 22956617
6.  Optimization of In Vivo Confocal Autofluorescence Imaging of the Ocular Fundus in Mice and Its Application to Models of Human Retinal Degeneration 
Standardized imaging procedures allow quantitative and qualitative assessment of fundus autofluorescence in mice. The technique will be useful as an outcome measure in preclinical trials aimed at lowering RPE-lipofuscin and for correlating findings on fundus autofluorescence with postmortem analysis.
Purpose.
To investigate the feasibility and to identify sources of experimental variability of quantitative and qualitative fundus autofluorescence (AF) assessment in mice.
Methods.
Blue (488 nm) and near-infrared (790 nm) fundus AF imaging was performed in various mouse strains and disease models (129S2, C57Bl/6, Abca4−/−, C3H-Pde6brd1/rd1, Rho−/−, and BALB/c mice) using a commercially available scanning laser ophthalmoscope. Gray-level analysis was used to explore factors influencing fundus AF measurements.
Results.
A contact lens avoided cataract development and resulted in consistent fundus AF recordings. Fundus illumination and magnification were sensitive to changes of the camera position. Standardized adjustment of the recorded confocal plane and consideration of the pupil area allowed reproducible recording of fundus AF from the retinal pigment epithelium with an intersession coefficient of repeatability of ±22%. Photopigment bleaching occurred during the first 1.5 seconds of exposure to 488 nm blue light (∼10 mW/cm2), resulting in an increase of fundus AF. In addition, there was a slight decrease in fundus AF during prolonged blue light exposure. Fundus AF at 488 nm was low in animals with an absence of a normal visual cycle, and high in BALB/c and Abca4−/− mice. Degenerative alterations in Pde6brd1/rd1 and Rho−/− were reminiscent of findings in human retinal disease.
Conclusions.
Investigation of retinal phenotypes in mice is possible in vivo using standardized fundus AF imaging. Correlation with postmortem analysis is likely to lead to further understanding of human disease phenotypes and of retinal degenerations in general. Fundus AF imaging may be useful as an outcome measure in preclinical trials, such as for monitoring effects aimed at lowering lipofuscin accumulation in the retinal pigment epithelium.
doi:10.1167/iovs.11-8767
PMCID: PMC3317405  PMID: 22169101
7.  The Value of Measurement of Macular Carotenoid Pigment Optical Densities and Distributions in Age-Related Macular Degeneration and Other Retinal Disorders 
Vision research  2009;50(7):716-728.
There is increasing recognition that the optical and antioxidant properties of the xanthophyll carotenoids lutein and zeaxanthin play an important role in maintaining the health and function of the human macula. In this review article, we assess the value of non-invasive quantification of macular pigment levels and distributions to identify individuals potentially at risk for visual disability or catastrophic vision loss from age-related macular degeneration, and we consider the strengths and weaknesses of the diverse measurement methods currently available.
doi:10.1016/j.visres.2009.10.014
PMCID: PMC2840187  PMID: 19854211
8.  Light-Induced Retinal Changes Observed with High-Resolution Autofluorescence Imaging of the Retinal Pigment Epithelium 
Purpose
Autofluorescence fundus imaging using an adaptive optics scanning laser ophthalmoscope (AOSLO) allows for imaging of individual retinal pigment epithelial (RPE) cells in vivo. In this study, the potential of retinal damage was investigated by using radiant exposure levels that are 2 to 150 times those used for routine imaging.
Methods
Macaque retinas were imaged in vivo with a fluorescence AOSLO. The retina was exposed to 568- or 830-nm light for 15 minutes at various intensities over a square ½° per side. Pre-and immediate postexposure images of the photoreceptors and RPE cells were taken over a 2° field. Long-term AOSLO imaging was performed intermittently from 5 to 165 days after exposure. Exposures delivered over a uniform field were also investigated.
Results
Exposures to 568-nm light caused an immediate decrease in autofluorescence of RPE cells. Follow-up imaging revealed either full recovery of autofluorescence or long-term damage in the RPE cells at the exposure. The outcomes of AOSLO exposures and uniform field exposures of equal average power were not significantly different. No effects from 830-nm exposures were observed.
Conclusions
The study revealed a novel change in RPE autofluorescence induced by 568-nm light exposure. Retinal damage occurred as a direct result of total average power, independent of the light-delivery method. Because the exposures were near or below permissible levels in laser safety standards, these results suggest that caution should be used with exposure of the retina to visible light and that the safety standards should be re-evaluated for these exposure conditions.
doi:10.1167/iovs.07-1430
PMCID: PMC2790526  PMID: 18408191

Results 1-8 (8)