Retinal pigment epithelium defects in humans and mice with mutations in MYO7A: imaging melanosome-specific autofluorescence

Monitoring basal autophagy in the retina utilizing CAG-mRFP-EGFP-MAP1LC3B reporter mouse: technical and biological considerations

We describe the utility of a tandem-tagged autophagy reporter mouse model (CAG-RFP-EGFP-MAP1LC3B) in investigating basal macroautophagic/autophagic flux in the neural retina. Western blot, in situ hybridization, immunohistochemistry, and confocal microscopy showed that CAG promoter-driven expression of RFP-EGFP-MAP1LC3B increased “cytosolic” RFP-EGFP-LC3B-I levels, whereas RFP-EGFP-LC3B-II decorates true phagosomes. We verified that the electroretinographic (ERG) responses of tandem-tagged LC3B mice were comparable to those of age-matched controls. Optimized microscope settings detected lipofuscin autofluorescence in retinas of abca4^−/- mice. The majority of retinal phagosomes in the reporter mice exhibited only RFP (not EGFP) fluorescence, suggesting rapid maturation of phagosomes. Only ~1.5% of the total phagosome population was EGFP-labeled; RFP-labeled (mature) phagosomes colocalized with lysosomal markers LAMP2 and CTSD. In the outer retina, phagosome sizes were as follows (in µm², ave ± SEM): RPE, 0.309 ± 0.015; photoreceptor inner segment-myoid, 0.544 ± 0.031; and outer nuclear layer, 0.429 ± 0.011. Detection of RPE phagosomes by fluorescence microscopy is challenging, due to the presence of melanin. Increased lipofuscin autofluorescence, such as observed in the abca4^−/- mouse model of Stargardt disease, is a strong confounding factor when attempting to study autophagy in the RPE. In addition to RPE and photoreceptor cells, phagosomes were detected in inner retinal cell types, microglia, astrocytes, and endothelial cells. We conclude that the tandem-tagged LC3B mouse model serves as a useful system for studying autophagy in the retina. This utility, however, is dependent upon several technical and biological factors, including microscope settings, transgene expression, choice of fluorophores, and lipofuscin autofluorescence.

Abbreviations: ACTB: actin, beta; AIF1: allograft inflammatory factor 1; ATG: autophagy related; CTSD: cathepsin D; DAPI: (4’,6-diamido-2-phenylindole); DIC: differential interference contrast; EGFP: enhanced green fluorescent protein; ELM: external limiting membrane; ERG: electroretinography; GCL: ganglion cell layer; GLUL: glutamine-ammonia ligase (glutamine synthetase); INL: inner nuclear layer; IS-E/M: inner segment – ellipsoid/myoid; ISH: in situ hybridization; LAMP2: lysosomal-associated membrane protein 2; L.I.: laser Intensity; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; O.C.T.: optimal cutting temperature; OS: outer segment; ONL: outer nuclear layer; PE: phosphatidylethanolamine; RFP: red fluorescent protein; R.O.I.: region of interest; RPE: retinal pigment epithelium

Measures of Function and Structure to Determine Phenotypic Features, Natural History, and Treatment Outcomes in Inherited Retinal Diseases

Inherited retinal diseases (IRDs) are at the forefront of innovative gene-specific treatments because of the causation by single genes, the availability of microsurgical access for treatment delivery, and the relative ease of quantitative imaging and vision measurement. However, it is not always easy to choose a priori, from scores of potential measures, an appropriate subset to evaluate efficacy outcomes considering the wide range of disease stages with different phenotypic features. This article reviews measurements of visual function and retinal structure that our group has used over the past three decades to understand the natural history of IRDs. We include measures of light sensitivity, retinal structure, mapping of natural fluorophores, evaluation of pupillary light reflex, and oculomotor control. We provide historical context and examples of applicability. We also review treatment trial outcomes using these measures of function and structure. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

In Situ Morphologic and Spectral Characterization of Retinal Pigment Epithelium Organelles in Mice Using Multicolor Confocal Fluorescence Imaging

Purpose

To investigate the major organelles of the retinal pigment epithelium (RPE) in wild-type (WT, control) mice and their changes in pigmented Abca4 knockout (Abca4^−/−) mice with in situ morphologic, spatial, and spectral characterization of live ex vivo flat-mounted RPE using multicolor confocal fluorescence microscopy (MCFM).

Methods

In situ imaging of RPE flat-mounts of agouti Abca4^−/− (129S4), agouti WT (129S1/SvlmJ) controls, and B6 albino mice (C57BL/6J-Tyr^c-Brd) was performed with a Nikon A1 confocal microscope. High-resolution confocal image z-stacks of the RPE cell mosaic were acquired with four different excitation wavelengths (405 nm, 488 nm, 561 nm, and 640 nm). The autofluorescence images of RPE, including voxel-by-voxel emission spectra, were acquired and processed with Nikon NIS-AR Elements software.

Results

The 3-dimensional multicolor confocal images provided a detailed visualization of the RPE cell mosaic, including its melanosomes and lipofuscin granules, and their varying characteristics in the different mice strains. The autofluorescence spectra, spatial distribution, and morphologic features of melanosomes and lipofuscin granules were measured. Increased numbers of lipofuscin and reduced numbers of melanosomes were observed in the RPE of Abca4^−/− mice relative to controls.

Conclusions

A detailed assessment of the RPE autofluorescent granules and their changes ex vivo was possible with MCFM. For all excitation wavelengths, autofluorescence from the RPE cells was predominantly contributed by lipofuscin granules, while melanosomes were found to be essentially nonfluorescent. The red shift of the emission peak confirmed the presence of multiple chromophores within lipofuscin granules. The elevated autofluorescence levels in Abca4^−/− mice correlated well with the increased number of lipofuscin granules.

Durable vision improvement after a single treatment with antisense oligonucleotide sepofarsen: a case report

Leber congenital amaurosis due to CEP290 ciliopathy is being explored by treatment with the antisense oligonucleotide (AON) sepofarsen. One patient who was part of a larger cohort (ClinicalTrials.gov NCT03140969 ) was studied for 15 months after a single intravitreal sepofarsen injection. Concordant measures of visual function and retinal structure reached a substantial efficacy peak near 3 months after injection. At 15 months, there was sustained efficacy, even though there was evidence of reduction from peak response. Efficacy kinetics can be explained by the balance of AON-driven new CEP290 protein synthesis and a slow natural rate of CEP290 protein degradation in human foveal cone photoreceptors.

Fundus autofluorescence imaging

Fundus autofluorescence (FAF) imaging is an in vivo imaging method that allows for topographic mapping of naturally or pathologically occurring intrinsic fluorophores of the ocular fundus. The dominant sources are fluorophores accumulating as lipofuscin in lysosomal storage bodies in postmitotic retinal pigment epithelium cells as well as other fluorophores that may occur with disease in the outer retina and subretinal space. Photopigments of the photoreceptor outer segments as well as macular pigment and melanin at the fovea and parafovea may act as filters of the excitation light. FAF imaging has been shown to be useful with regard to understanding of pathophysiological mechanisms, diagnostics, phenotype-genotype correlation, identification of prognostic markers for disease progression, and novel outcome parameters to assess efficacy of interventional strategies in chorio-retinal diseases. More recently, the spectrum of FAF imaging has been expanded with increasing use of green in addition to blue FAF, introduction of spectrally-resolved FAF, near-infrared FAF, quantitative FAF imaging and fluorescence life time imaging (FLIO). This article gives an overview of basic principles, FAF findings in various retinal diseases and an update on recent developments.

Autofluorescent Granules of the Human Retinal Pigment Epithelium: Phenotypes, Intracellular Distribution, and Age-Related Topography

Purpose

The human retinal pigment epithelium (RPE) accumulates granules significant for autofluorescence imaging. Knowledge of intracellular accumulation and distribution is limited. Using high-resolution microscopy techniques, we determined the total number of granules per cell, intracellular distribution, and changes related to retinal topography and age.

Methods

RPE cells from the fovea, perifovea, and near-periphery of 15 human RPE flat mounts were imaged using structured illumination microscopy (SIM) and confocal fluorescence microscopy in young (≤51 years, n = 8) and older (>80 years, n = 7) donors. Using custom FIJI plugins, granules were marked with computer assistance, classified based on morphological and autofluorescence properties, and analyzed with regard to intracellular distribution, total number per cell, and granule density.

Results

A total of 193,096 granules in 450 RPE cell bodies were analyzed. Based on autofluorescence properties, size, and composition, the RPE granules exhibited nine different phenotypes (lipofuscin, two; melanolipofuscin, five; melanosomes, two), distinguishable by SIM. Overall, lipofuscin (low at the fovea but increases with eccentricity and age) and melanolipofuscin (equally distributed at all three locations with no age-related changes) were the major granule types. Melanosomes were under-represented due to suboptimal visualization of apical processes in flat mounts.

Conclusions

Low lipofuscin and high melanolipofuscin content within foveal RPE cell bodies and abundant lipofuscin at the perifovea suggest a different genesis, plausibly related to the population of overlying photoreceptors (fovea, cones only; perifovea, highest rod density). This systematic analysis provides further insight into RPE cell and granule physiology and links granule load to cell autofluorescence, providing a subcellular basis for the interpretation of clinical fundus autofluorescence.

The cell biology of the retinal pigment epithelium

The retinal pigment epithelium (RPE), a monolayer of post-mitotic polarized epithelial cells, strategically situated between the photoreceptors and the choroid, is the primary caretaker of photoreceptor health and function. Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness. Decades of research have yielded valuable insight into the cell biology of the RPE. In recent years, new technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors. In this review, we aim to integrate these studies with an emphasis on appropriate models and techniques to investigate RPE cell biology and metabolism, and discuss how RPE cell biology informs our understanding of retinal disease.

Evaluation of Retinal Pigment Epithelium and Choroidal Neovascularization in Rats Using Laser-Scanning Optical-Resolution Photoacoustic Microscopy

PURPOSE

To demonstrate the value of the laser-scanning optical-resolution (LSOR)-photoacoustic (PA) microscopy (PAM) system and the conventional multimodal imaging techniques in the evaluation of laser-induced retinal injury and choroidal neovascularization (CNV) in rats.

METHODS

Different degrees of retinal injury were induced using laser photocoagulation. We compared the LSOR-PAM system with conventional imaging techniques in evaluating retinal injury with or without CNV. Six additional rats, treated with an anti-VEGF antibody or immunoglobulin G immediately after photocoagulation, were imaged 7 and 14 days after injection, and CNV lesion areas were compared.

RESULTS

In the retinal injury model, fundus autofluorescence showed well-defined hyperreflection, while the lesion displayed abundant PA signals demonstrating nonuniform melanin distribution in retinal pigment epithelium (RPE). RPE was detected with higher contrast in the PAM B-scan image than optical coherence tomography (OCT). Additionally, the CNV lesion was present with multiple PA signal intensities which distinctly characterized the location and area of CNV as found in fundus fluorescein angiography. Furthermore, the decreased PA signals extending from the CNV lesion were similar to those of the vascular bud in ex vivo imaging, which was invisible in other in vivo images. When treated with anti-VEGF agents, statistically significant differences can be demonstrated by PAM similar to other modalities.

CONCLUSIONS

LSOR-PAM can detect the melanin distribution of RPE in laser-induced retinal injury and CNV in rats. PAM imaging provides a potential new tool to evaluate the vitality and functionality of RPE in vivo as well as to monitor the development and treatment of CNV.

Age, lipofuscin and melanin oxidation affect fundus near-infrared autofluorescence

Background

Fundus autofluorescence is a non-invasive imaging technique in ophthalmology. Conventionally, short-wavelength autofluorescence (SW-AF) is used for detection of lipofuscin, a byproduct of the visual cycle which accumulates with age or disease in the retinal pigment epithelium (RPE). Furthermore, near-infrared autofluorescence (NIR-AF) is used as a marker for RPE and choroidal melanin, but contribution of lipofuscin to the NIR-AF signal is unclear.

Methods

We employed fluorescence microscopy to investigate NIR-AF properties of melanosomes, lipofuscin and melanolipofuscin granules in histologic sections of wildtype and Abca4^−/− mouse eyes, the latter having increased lipofuscin, as well as aged human donor eyes. Differentiation between these pigments was verified by analytical electron microscopy. To investigate the influence of oxidative and photic stress we used an in vitro model with isolated ocular melanosomes and an in vivo phototoxicity mouse model.

Findings

We show that NIR-AF is not an intrinsic property of melanin, but rather increases with age and after photic or oxidative stress in mice and isolated melanosomes. Furthermore, when lipofuscin levels are high, lipofuscin granules also show NIR-AF, as confirmed by correlative fluorescence and electron microscopy in human tissue. However, lipofuscin in albino Abca4^−/− mice lacks NIR-AF signals.

Interpretation

We suggest that NIR-AF is derived from melanin degradation products that accumulate with time in lipofuscin granules. These findings can help to improve the interpretation of patient fundus autofluorescence data.

Funding

This work was supported by Bundesministerium für Bildung und Forschung, Deutsche Forschungsgemeinschaft and Chinese Scholarship Council. Major instrumentation used in this work was supported by Deutsche Forschungsgemeinschaft, the European Fund for Regional Development and the state of Baden-Württemberg.

Near-infrared autofluorescence in young choroideremia patients

Purpose: To study near-infrared autofluorescence (NIR-AF) and short- wave autofluorescence (SW-AF) imaging modalities in young patients affected with choroideremia (CHM).Methods: NIR-AF and SW-AF images, Optical coherence tomography (OCT) and color fundus images were acquired from 3 young CHM patients (6 eyes) enrolled at the Regional Reference Center for Hereditary Retinal Degenerations of the Eye Clinic in Florence.Results: We studied 3 young CHM patients (6 eyes). The mean age of the patients was 17,3 years. Using NIR-AF, patient P1 was characterized by speckled hypo-autofluorescent areas at the posterior pole with a preserved central hyper-autofluorescence while patient P2 and P3 were characterized by a preserved NIR-AF signal only at the fovea. Using SW-AF, patient P1 was characterized by a normal macular autofluorescence and by a speckled FAF pattern involved the vascular arcades while patient P2 and P3 showed well-demarcated hypo-autofluorescence areas involving the posterior pole with a preserved macular autofluorescence. The differences between NIR-AF and SW-AF were more pronounced in advanced stages. In correspondence of preserved NIR-AF, the OCT examination showed regular and continuous outer retinal hyperreflective bands. We observed abnormal RPE/Bruch's membrane complex and EZ band externally to the NIR-AF signal area.Conclusions: NIR-AF imaging confirms an early RPE involvement allowing us to identify and to quantify the RPE pigment loss in choroideremia. For this reason, NIR-AF imaging can be useful for monitoring the progression of the disease and to study the effect of future treatments.

Lessons learned from quantitative fundus autofluorescence

Quantitative fundus autofluorescence (qAF) is an approach that is built on a confocal scanning laser platform and used to measure the intensity of the inherent autofluorescence of retina elicited by short-wavelength (488 nm) excitation. Being non-invasive, qAF does not interrupt tissue architecture, thus allowing for structural correlations. The spectral features, cellular origin and topographic distribution of the natural autofluorescence of the fundus indicate that it is emitted from retinaldehyde-adducts that form in photoreceptor cells and accumulate, under most conditions, in retinal pigment epithelial cells. The distributions and intensities of fundus autofluorescence deviate from normal in many retinal disorders and it is widely recognized that these changing patterns can aid in the diagnosis and monitoring of retinal disease. The standardized protocol employed by qAF involves the normalization of fundus grey levels to a fluorescent reference installed in the imaging instrument. Together with corrections for magnification and anterior media absorption, this approach facilitates comparisons with serial images and images acquired within groups of patients. Here we provide a comprehensive summary of the principles and practice of qAF and we highlight recent efforts to elucidate retinal disease processes by combining qAF with multi-modal imaging.

Human Retinal Pigment Epithelium: In Vivo Cell Morphometry, Multispectral Autofluorescence, and Relationship to Cone Mosaic

Purpose

To characterize in vivo morphometry and multispectral autofluorescence of the retinal pigment epithelial (RPE) cell mosaic and its relationship to cone cell topography across the macula.

Methods

RPE cell morphometrics were computed in regularly spaced regions of interest (ROIs) from contiguous short-wavelength autofluorescence (SWAF) and photoreceptor reflectance images collected across the macula in one eye of 10 normal participants (23–65 years) by using adaptive optics scanning light ophthalmoscopy (AOSLO). Infrared autofluorescence (IRAF) images of the RPE were collected with AOSLO in seven normal participants (22–65 years), with participant overlap, and compared to SWAF quantitatively and qualitatively.

Results

RPE cell statistics could be analyzed in 84% of SWAF ROIs. RPE cell density consistently decreased with eccentricity from the fovea (participant mean ± SD: 6026 ± 1590 cells/mm² at fovea; 4552 ± 1370 cells/mm² and 3757 ± 1290 cells/mm² at 3.5 mm temporally and nasally, respectively). Mean cone-to-RPE cell ratio decreased rapidly from 16.6 at the foveal center to <5 by 1 mm. IRAF revealed cells in six of seven participants, in agreement with SWAF RPE cell size and location. Differences in cell fluorescent structure, contrast, and visibility beneath vasculature were observed between modalities.

Conclusions

Improvements in AOSLO autofluorescence imaging permit efficient visualization of RPE cells with safe light exposures, allowing individual characterization of RPE cell morphometry that is variable between participants. The normative dataset and analysis of RPE cell IRAF and SWAF herein are essential for understanding microscopic characteristics of cell fluorescence and may assist in interpreting disease progression in RPE cells.

Multi-platform imaging in ABCA4-Associated Disease

Fundus autofluorescence (FAF) imaging is crucial to the diagnosis and monitoring of recessive Stargardt disease (STGD1). In a retrospective cohort study of 34 patients, we compared FAF imaging platforms varying in field size (30° and 55°: blue/SW-AF and NIR-AF; 200°: ultrawide-field, UWF-AF), excitation wavelength (488 nm, blue/SW-AF; 532 nm, UWF-AF and 787 nm, NIR-AF) and image processing. Due to reduced absorption of 532 nm and 787 nm light by macular pigment, foveal sparing was more readily demonstrable by green/UWF-AF and NIR-AF imaging. Prominent in green/UWF-AF images is a central zone of relatively elevated AF that is continuous inferonasal with a demarcation line bordering lower AF nasally and higher AF temporally. This zone and border are more visible in STGD1 than in healthy eyes and more visible with green/UWF-AF. With the development of AF flecks, inferonasal retina is initially spared. Central atrophic areas were larger in NIR-AF images than in blue/SW-AF and green/UWF-AF images and the presence of a contiguous hyperAF ring varied with imaging modality. Flecks visible as hyperAF foci in blue/SW-AF images were also visible in green/UWF-AF but were often hypoAF in NIR-AF. Since disease in STGD1 often extends beyond the 30° and 55° fields, green/UWF-AF has advantages including for pediatric patients. The imaging platforms examined provided complementary information.

Mutations in GPR143/OA1 and ABCA4 Inform Interpretations of Short-Wavelength and Near-Infrared Fundus Autofluorescence

Purpose

We sought to advance interpretations and quantification of short-wavelength fundus autofluorescence (SW-AF) emitted from bisretinoid lipofuscin and near-infrared autofluoresence (NIR-AF) originating from melanin.

Methods

Carriers of mutations in X-linked GPR143/OA1, a common form of ocular albinism; patients with confirmed mutations in ABCA4 conferring increased SW-AF; and subjects with healthy eyes were studied. SW-AF (488 nm excitation, 500–680 nm emission) and NIR-AF (excitation 787 nm, emission >830 nm) images were acquired with a confocal scanning laser ophthalmoscope. SW-AF images were analyzed for quantitative autofluoresence (qAF). Analogous methods of image acquisition and analysis were performed in albino and pigmented Abca4^−/− mice and wild-type mice.

Results

Quantitation of SW-AF (qAF), construction of qAF color-coded maps, and examination of NIR-AF images from GPR143/OA1 carriers revealed mosaics in which patches of fundus exhibiting NIR-AF signal had qAF levels within normal limits whereas the hypopigmented areas in the NIR-AF image corresponded to foci of elevated qAF. qAF also was increased in albino versus pigmented mice. Although melanin contributes to fundus infrared reflectance, the latter appeared to be uniform in en face reflectance images of GPR143/OA1-carriers. In patients diagnosed with ABCA4-associated disease, NIR-AF increased in tandem with increased qAF originating in bisretinoid lipofuscin. Similarly in Abca4^−/− mice having increased SW-AF, NIR-AF was more pronounced than in wild-type mice.

Conclusions

These studies corroborate RPE melanin as the major source of NIR-AF but also indicate that bisretinoid lipofuscin, when present at sufficient concentrations, contributes to the NIR-AF signal. Ocular melanin attenuates the SW-AF signal.

Live Imaging of Organelle Motility in RPE Flatmounts

The retinal pigment epithelium (RPE) performs several functions that are crucial for normal retinal function and vision, including the daily phagocytosis of photoreceptor outer segment (POS) membranes. Defects in the motility and degradation of POS phagosomes may be associated with some inherited and age-related retinal degenerations. Given the apical to basal translocation of phagosomes during maturation and degradation, studies of the underlying mechanisms require analyses of the dynamics in 3-D. In this chapter, we report a method for investigating the 3-D motility of POS phagosomes and lysosomes, utilizing high-speed, spinning disk confocal microscopy of live RPE flatmounts.

Imaging retinal melanin: a review of current technologies

The retinal pigment epithelium (RPE) is essential to the health of the retina and the proper functioning of the photoreceptors. The RPE is rich in melanosomes, which contain the pigment melanin. Changes in RPE pigmentation are seen with normal aging and in diseases such as albinism and age-related macular degeneration. However, most techniques used to this day to detect and quantify ocular melanin are performed ex vivo and are destructive to the tissue. There is a need for in vivo imaging of melanin both at the clinical and pre-clinical level to study how pigmentation changes can inform disease progression. In this manuscript, we review in vivo imaging techniques such as fundus photography, fundus reflectometry, near-infrared autofluorescence imaging, photoacoustic imaging, and functional optical coherence tomography that specifically detect melanin in the retina. These methods use different contrast mechanisms to detect melanin and provide images with different resolutions and field-of-views, making them complementary to each other.

A non-retinoid antagonist of retinol-binding protein 4 rescues phenotype in a model of Stargardt disease without inhibiting the visual cycle

A primary pathological defect in the heritable eye disorder Stargardt disease is excessive accumulation of cytotoxic lipofuscin bisretinoids in the retina. Age-dependent accumulation of lipofuscin in the retinal pigment epithelium (RPE) matches the age-dependent increase in the incidence of the atrophic (dry) form of age-related macular degeneration (AMD) and therefore may be one of several pathogenic factors contributing to AMD progression. Lipofuscin bisretinoid synthesis in the retina depends on the influx of serum retinol from the circulation into the RPE. Formation of the tertiary retinol-binding protein 4 (RBP4)-transthyretin-retinol complex in the serum is required for this influx. Herein, we report the pharmacological effects of the non-retinoid RBP4 antagonist, BPN-14136. BPN-14136 dosing in the Abca4^-/- mouse model of increased lipofuscinogenesis significantly reduced serum RBP4 levels and inhibited bisretinoid synthesis, and this inhibition correlated with a partial reduction in visual cycle retinoids such as retinaldehydes serving as bisretinoid precursors. BPN-14136 administration at doses inducing maximal serum RBP4 reduction did not produce changes in the rate of the visual cycle, consistent with minimal changes in dark adaptation. Abca4^-/- mice exhibited dysregulation of the complement system in the retina, and BPN-14136 administration normalized the retinal levels of proinflammatory complement cascade components such as complement factors D and H, C-reactive protein, and C3. We conclude that BPN-14136 has several beneficial characteristics, combining inhibition of bisretinoid synthesis and reduction in retinaldehydes with normalization of the retinal complement system. BPN-14136, or a similar compound, may be a promising drug candidate to manage Stargardt disease and dry AMD.

Classification and characterization of acute macular neuroretinopathy with spectral domain optical coherence tomography

PURPOSE

To classify and characterize AMN lesions with SD-OCT during a follow-up as long as 5 years.

METHODS

Retrospective study of 14 patients (18 eyes) with special focus on SD-OCT. We measured thickness of inner nuclear layer (INL), outer retinal layer (ONL), and hyperreflective band at baseline and during follow-up. AMN lesions were classified as type 1 and type 2.

RESULTS

Of 14 patients (six males, eight females, mean age 29.7 years), three patients (four eyes) had type 1 and nine (12 eyes) had type 2. Two patients did not meet the criteria for AMN type 1 or 2 and were therefore classified as new subtype of AMN. In all patients, statistically significant thinning of ONL and INL was observable. Mean ONL of all patients was 90.2 ± 7.81 and 72.3 ± 15.64 μm (p < 0.05) during follow-up; mean INL was 54.4 ± 10.71 and 37.5 ± 6.18 μm (p < 0.05) in the course. In the subgroup analysis in AMN type 2, the thinning of both ONL and INL was also statistically significant (mean ONL: 87.4 ± 6.02 and 71.6 ± 12.7 μm (p < 0.05); mean INL: 48.5 ± 5.04 and 38.5 ± 5.6 μm (p < 0.05)) in the course.

CONCLUSION

SD-OCT allows for classification, characterization, and further understanding of AMN lesions. Up to now, this is one of the largest AMN case series differentiating into different subtypes and following up for up to 5 years. Furthermore, we describe a new AMN subtype characterized by initially clinically visible yellowish parafoveal lesions, subtle pigmentary changes at late stage, lack of classic dark appearance on IR reflectance, involvement of RPE/Bruch's complex, and disruption of ellipsoid zone and interdigitation zone. The patients suffered from a prolonged visual impairment and paracentral scotomata. We propose the term AMN type 3 or "paracentral acute outer maculopathy."

Intraretinal Correlates of Reticular Pseudodrusen Revealed by Autofluorescence and En Face OCT

Purpose

We sought to determine whether information revealed from the reflectance, autofluorescence, and absorption properties of RPE cells situated posterior to reticular pseudodrusen (RPD) could provide insight into the origins and structure of RPD.

Methods

RPD were studied qualitatively by near-infrared fundus autofluorescence (NIR-AF), short-wavelength fundus autofluorescence (SW-AF), and infrared reflectance (IR-R) images, and the presentation was compared to horizontal and en face spectral domain optical coherence tomographic (SD-OCT) images. Images were acquired from 23 patients (39 eyes) diagnosed with RPD (mean age 80.7 ± 7.1 [SD]; 16 female; 4 Hispanics, 19 non-Hispanic whites).

Results

In SW-AF, NIR-AF, and IR-R images, fundus RPD were recognized as interlacing networks of small scale variations in IR-R and fluorescence (SW-AF, NIR-AF) intensities. Darkened foci of RPD colocalized in SW-AF and NIR-AF images, and in SD-OCT images corresponded to disturbances of the interdigitation (IZ) and ellipsoid (EZ) zones and to more pronounced hyperreflective lesions traversing photoreceptor-attributable bands in SD-OCT images. Qualitative assessment of the outer nuclear layer (ONL) revealed thinning as RPD extended radially from the outer to inner retina. In en face OCT, hyperreflective areas in the EZ band correlated topographically with hyporeflective foci at the level of the RPE.

Conclusions

The hyperreflective lesions corresponding to RPD in SD-OCT scans are likely indicative of degenerating photoreceptor cells. The darkened foci at positions of RPD in NIR-AF and en face OCT images indicate changes in the RPE monolayer with the reduced NIR-AF and en face OCT signal suggesting a reduction in melanin that could be accounted for by RPE thinning.

Fluorescence lifetime imaging ophthalmoscopy

Imaging techniques based on retinal autofluorescence have found broad applications in ophthalmology because they are extremely sensitive and noninvasive. Conventional fundus autofluorescence imaging measures fluorescence intensity of endogenous retinal fluorophores. It mainly derives its signal from lipofuscin at the level of the retinal pigment epithelium. Fundus autofluorescence, however, can not only be characterized by the spatial distribution of the fluorescence intensity or emission spectrum, but also by a characteristic fluorescence lifetime function. The fluorescence lifetime is the average amount of time a fluorophore remains in the excited state following excitation. Fluorescence lifetime imaging ophthalmoscopy (FLIO) is an emerging imaging modality for in vivo measurement of lifetimes of endogenous retinal fluorophores. Recent reports in this field have contributed to our understanding of the pathophysiology of various macular and retinal diseases. Within this review, the basic concept of fluorescence lifetime imaging is provided. It includes technical background information and correlation with in vitro measurements of individual retinal metabolites. In a second part, clinical applications of fluorescence lifetime imaging and fluorescence lifetime features of selected retinal diseases such as Stargardt disease, age-related macular degeneration, choroideremia, central serous chorioretinopathy, macular holes, diabetic retinopathy, and retinal artery occlusion are discussed. Potential areas of use for fluorescence lifetime imaging ophthalmoscopy will be outlined at the end of this review.

A homozygous MYO7A mutation associated to Usher syndrome and unilateral auditory neuropathy spectrum disorder

Usher syndrome (USH) is an autosomal recessive disorder characterized by sensorineural hearing loss, progressive visual loss and night blindness due to retinitis pigmentosa (RP), with or without vestibular dysfunction. The purpose of this study was to detect the causative gene in a consanguineous Chinese family with USH. A c.3696_3706del (p.R1232Sfs*72) variant in the myosin VIIa gene (MYO7A) was identified in the homozygous state by exome sequencing. The co‑segregation of the MYO7A c.3696_3706del variant with the phenotype of deafness and progressive visual loss in the USH family was confirmed by Sanger sequencing. The variant was absent in 200 healthy controls. Therefore, the c.3696_3706del variant may disrupt the interaction between myosin VIIa and other USH1 proteins, and impair melanosome transport in retinal pigment epithelial cells. Notably, bilateral auditory brainstem responses were absent in two patients of the USH family, while distortion product otoacoustic emissions were elicited in the right ears of the two patients, consistent with clinical diagnosis of unilateral auditory neuropathy spectrum disorder. These data suggested that the homozygous c.3696_3706del variant in the MYO7A gene may be the disease‑causing mutation for the disorder in this family. These findings broaden the phenotype spectrum of the MYO7A gene, and may facilitate understanding of the molecular pathogenesis of the disease, and genetic counseling for the family.

Variegated yet non-random rod and cone photoreceptor disease patterns in RPGR-ORF15-associated retinal degeneration

Mutations in the ORF15 exon of the RPGR gene cause a common form of X-linked retinitis pigmentosa, which often results in severe loss of vision. In dogs and mice, gene augmentation therapy has been shown to arrest the progressive degeneration of rod and cone photoreceptors. However, the distribution of potentially treatable photoreceptors across the human retinas and the rate of degeneration are not known. Here, we have defined structural and functional features of the disease in 70 individuals with ORF15 mutations. We also correlated the features observed in patients with those of three Rpgr-mutant (Rpgr-ko, Rd9, and Rpgr-cko) mice. In patients, there was pronounced macular disease. Across the retina, rod and cone dysfunction showed a range of patterns and a spectrum of severity between individuals, but a high symmetry was observed between eyes of each individual. Genotype was not related to disease expression. In the Rpgr-ko mice, there were intra-retinal differences in rhodopsin and cone opsin trafficking. In Rd9 and Rpgr-cko mice, retinal degeneration showed inter-ocular symmetry. Longitudinal results in patients revealed localized rod and cone dysfunction with progression rates of 0.8 to 1.3 log per decade in sensitivity loss. Relatively retained rod and cone photoreceptors in mid- and far-peripheral temporal-inferior and nasal-inferior visual field regions should be good targets for future localized gene therapies in patients.

NEAR-INFRARED AUTOFLUORESCENCE IN BILATERAL DIFFUSE UVEAL MELANOCYTIC PROLIFERATION ASSOCIATED WITH ESOPHAGEAL CARCINOMA AND CHOROIDAL METASTASIS

PURPOSE

To investigate the advantage of near-infrared autofluorescence (787 nm) for the detection of melanocytic lesions in a patient with bilateral diffuse uveal melanocytic proliferation in association with esophageal carcinoma complicated by most likely unilateral choroidal metastasis.

METHODS

In this retrospective case report, a 55-year-old woman referred for the evaluation of sudden visual loss underwent normal ophthalmological evaluation and, in addition, was examined with near-infrared reflectance, near-infrared autofluorescence, fundus autofluorescence (Heidelberg Retina Angiograph II [HRA2; Heidelberg Engineering]), spectral domain optical coherence tomography (Spectralis OCT; Heidelberg Engineering), and multifocal electroretinography (RetiScan; Roland Consult).

RESULTS

The patient had been diagnosed with esophageal carcinoma 3 months before the onset of visual symptoms. The visual acuity was 20/40 in the right eye and 20/20 in the left eye. Bilateral patchy melanocytic proliferation was detected on ophthalmoscopy. The extent of lesions was best detected with near-infrared reflectance and near-infrared autofluorescence, whereas fundus autofluorescence and spectral domain optical coherence tomography did not reveal alterations of the outer retina or retinal pigment epithelium in this early stage of bilateral diffuse uveal melanocytic proliferation. The right eye showed in addition to the findings on the left eye choroidal folds in the fovea and an elevated lesion inferotemporal of the fovea suspicious of a choroidal metastasis. In the B-scan ultrasonography, a homogenous lesion was seen. Spectral domain optical coherence tomography demonstrated a mild accumulation of subretinal fluid adjacent to and over the choroidal metastasis. Transretinal biopsy of this elevated lesion revealed a low differentiated carcinoma of squamous epithelium, compatible with choroidal metastasis of the esophageal carcinoma. The choroidal metastasis increased within 3 months after the first visit. The visual acuity dropped in both eyes. The patient died 6 months after her first visit.

CONCLUSIONS

Bilateral diffuse uveal melanocytic proliferation can be associated with esophageal carcinoma as a systemic malignancy. Near-infrared imaging can be helpful to detect early stages of BDUMP and can help offer recently reported treatment options at an early stage of disease.

Predicting Progression of ABCA4-Associated Retinal Degenerations Based on Longitudinal Measurements of the Leading Disease Front

PURPOSE

To evaluate the progression of the earliest stage of disease in ABCA4-associated retinal degenerations (RDs).

METHODS

Near-infrared excited reduced-illuminance autofluorescence imaging was acquired across the retina up to 80 degrees eccentricity in 44 patients with two ABCA4 alleles. The eccentricity of the leading disease front (LDF) corresponding to the earliest stage of disease was measured along the four meridians. A mathematical model describing the expansion of the LDF was developed based on 6 years of longitudinal follow-up.

RESULTS

The extent of LDF along the superior, inferior, and temporal meridians showed a wide spectrum from 3.5 to 70 degrees. In patients with longitudinal data, the average centrifugal expansion rate was 2 degrees per year. The nasal extent of LDF between the fovea and ONH ranged from 4.3 to 16.5 degrees and expanded at 0.35 degrees per year. The extent of LDF beyond ONH ranged from 19 to 75 degrees and expanded on average at 2 degrees per year. A mathematical model fit well to the longitudinal data describing the expansion of the LDF.

CONCLUSIONS

The eccentricity of the LDF in ABCA4-RD shows a continuum from parafovea to far periphery along all four meridians consistent with a wide spectrum of severity observed clinically. The model of progression may provide a quantitative prediction of the LDF expansion based on the age and eccentricity of the LDF at a baseline visit, and thus contribute significantly to the enrollment of candidates appropriate for clinical trials planning specific interventions, efficacy outcomes, and durations.

Long time remodeling during retinal degeneration evaluated by optical coherence tomography, immunocytochemistry and fundus autofluorescence

PURPOSE

To characterize the relationship between fundus autofluorescence (FAF), Optical Coherence Tomography (OCT) and immunohistochemistry (IHC) over the course of chronic retinal degeneration in the P23H rat.

METHODS

Homozygous albino P23H rats, Sprague-Dawley (SD) rats as controls and pigmented Long Evans (LE) rats were used. A Spectralis HRA OCT system was used for scanning laser ophthalmoscopy (SLO) imaging OCT and angiography. To determine FAF, fluorescence was excited using diode laser at 488 nm. A fast retina map OCT was performed using the optic nerve as a landmark. IHC was performed to correlate with the findings of OCT and FAF changes.

RESULTS

During the course of retinal degeneration, the FAF pattern evolved from some spotting at 2 months old to a mosaic of hyperfluorescent dots in rats 6 months and older. Retinal thicknesses progressively diminished over the course of the disease. At later stages of degeneration, OCT documented changes in the retinal layers, however, IHC better identified the cell loss and remodeling changes. Angiography revealed attenuation of the retinal vascular plexus with time.

CONCLUSION

We provide for the first time a detailed long-term analysis of the course of retinal degeneration in P23H rats using a combination of SLO and OCT imaging, angiography, FAF and IHC. Although, the application of noninvasive methods enables longitudinal studies and will decrease the number of animals needed for a study, IHC is still an essential tool to identify retinal changes at the cellular level.

Flecks in Recessive Stargardt Disease: Short-Wavelength Autofluorescence, Near-Infrared Autofluorescence, and Optical Coherence Tomography

PURPOSE

We evaluated the incongruous observation whereby flecks in recessive Stargardt disease (STGD1) can exhibit increased short-wavelength autofluorescence (SW-AF) that originates from retinal pigment epithelium (RPE) lipofuscin, while near-infrared AF (NIR-AF), emitted primarily from RPE melanin, is usually reduced or absent at fleck positions.

METHODS

Flecks in SW- and NIR-AF images and spectral-domain optical coherence tomography (SD-OCT) scans were studied in 19 STGD1 patients carrying disease-causing ABCA4 mutations. Fleck spatial distribution and progression were recorded in serial AF images.

RESULTS

Flecks observed in SW-AF images typically colocalized with darkened foci in NIR-AF images; the NIR-AF profiles were larger. The decreased NIR-AF signal from flecks preceded apparent changes in SW-AF. Spatiotemporal changes in fleck distribution usually progressed centrifugally, but in one case centripetal expansion was observed. Flecks in SW-AF images corresponded to hyperreflective deposits that progressively traversed photoreceptor-attributable bands in SD-OCT images. Outer nuclear layer (ONL) thickness negatively correlated with expansion of flecks from outer to inner retina.

CONCLUSIONS

In the healthy retina, RPE lipofuscin fluorophores form in photoreceptor cells but are transferred to RPE; thus the SW-AF signal from photoreceptor cells is negligible. In STGD1, NIR-AF imaging reveals that flecks are predominantly hypofluorescent and larger and that NIR-AF darkening occurs prior to heightened SW-AF signal. These observations indicate that RPE cells associated with flecks in STGD1 are considerably changed or lost. Spectral-domain OCT findings are indicative of ongoing photoreceptor cell degeneration. The bright SW-AF signal of flecks likely originates from augmented lipofuscin formation in degenerating photoreceptor cells impaired by the failure of RPE.

Autofluorescence imaging with near-infrared excitation:normalization by reflectance to reduce signal from choroidal fluorophores

PURPOSE

We previously developed reduced-illuminance autofluorescence imaging (RAFI) methods involving near-infrared (NIR) excitation to image melanin-based fluorophores and short-wavelength (SW) excitation to image lipofuscin-based flurophores. Here, we propose to normalize NIR-RAFI in order to increase the relative contribution of retinal pigment epithelium (RPE) fluorophores.

METHODS

Retinal imaging was performed with a standard protocol holding system parameters invariant in healthy subjects and in patients. Normalized NIR-RAFI was derived by dividing NIR-RAFI signal by NIR reflectance point-by-point after image registration.

RESULTS

Regions of RPE atrophy in Stargardt disease, AMD, retinitis pigmentosa, choroideremia, and Leber congenital amaurosis as defined by low signal on SW-RAFI could correspond to a wide range of signal on NIR-RAFI depending on the contribution from the choroidal component. Retinal pigment epithelium atrophy tended to always correspond to high signal on NIR reflectance. Normalizing NIR-RAFI reduced the choroidal component of the signal in regions of atrophy. Quantitative evaluation of RPE atrophy area showed no significant differences between SW-RAFI and normalized NIR-RAFI.

CONCLUSIONS

Imaging of RPE atrophy using lipofuscin-based AF imaging has become the gold standard. However, this technique involves bright SW lights that are uncomfortable and may accelerate the rate of disease progression in vulnerable retinas. The NIR-RAFI method developed here is a melanin-based alternative that is not absorbed by opsins and bisretinoid moieties, and is comfortable to view. Further development of this method may result in a nonmydriatic and comfortable imaging method to quantify RPE atrophy extent and its expansion rate.

Near-infrared autofluorescence: its relationship to short-wavelength autofluorescence and optical coherence tomography in recessive stargardt disease

PURPOSE

We compared hypoautofluorescent (hypoAF) areas detected with near-infrared (NIR-AF) and short-wavelength autofluorescence (SW-AF) in patients with recessive Stargardt disease (STGD1) to retinal structure using spectral domain optical coherence tomography (SD-OCT).

METHODS

The SD-OCT volume scans, and SW-AF and NIR-AF images were obtained from 15 eyes of 15 patients with STGD1 and registered to each other. Thickness maps of the total retina, receptor-plus layer (R+, from distal border of the RPE to outer plexiform/inner nuclear layer boundary), and outer segment-plus layer (OS+, from distal border of the RPE to ellipsoid zone [EZ] band) were created from SD-OCT scans. These were compared qualitatively and quantitatively to the hypoAF areas in SW-AF and NIR-AF images.

RESULTS

All eyes showed a hypoAF area in the central macula and loss of the EZ band in SD-OCT scans. The hypoAF area was larger in NIR than SW-AF images and it exceeded the area of EZ band loss for 12 eyes. The thickness maps showed progressive thinning towards the central macula, with the OS+ layer showing the most extensive and severe thinning. The central hypoAF areas on NIR corresponded to the OS+ thinned areas, while the hypoAF areas on SW-AF corresponded to the R+ thinned areas.

CONCLUSIONS

Since the larger hypoAF area on NIR-AF exceeded the region of EZ band loss, and corresponded to the OS+ thinned area, RPE cell loss occurred before photoreceptor cell loss. The NIR-AF imaging may be an effective tool for following progression and predicting loss of photoreceptors in STGD1.

The Fundus Autofluorescence Spectrum of Punctate Inner Choroidopathy

Purpose. To investigate the fundus autofluorescence (FAF) spectrum of punctate inner choroidopathy (PIC). Methods. This is a retrospective observational case series of 27 consecutive patients with PIC admitted from October 2013 to March 2015, who underwent short-wavelength- (SW-) and near-infrared- (NIR-) FAF imaging, spectral domain optical coherence tomography (SD-OCT), fluorescein angiography (FA), and indocyanine green angiography (ICGA). Results. There were three primary findings on the FAF imaging of patients with PIC. First, active PIC lesions revealed hypoautofluorescent spots with hyperautofluorescent margin. After the lesions regressed, the hyperautoflurescent margin faded. Second, subclinical and most of the atrophic PIC lesions appeared to be hypoautofluorescent spots. But subclinical PIC lesions were more distinctive on NIR-FAF imaging than on SW-FAF imaging. Third, hypoautofluorescent spots of PIC lesions coexisted with hyperautofluorescent patches on SW-FAF imaging. These hyperautofluorescent patches were demonstrated to be multiple evanescent white dot syndrome (MEWDS) or acute zonal occult outer retinopathy (AZOOR) lesions by subsequent multimodal imaging and faded during follow-up examinations. Conclusion. FAF imaging helps in noninvasively tracking the evolution of PIC lesions and identifying the combined MEWDS or AZOOR lesions, complementary to SD-OCT and angiographic studies.

MultiColor imaging in the evaluation of geographic atrophy due to age-related macular degeneration

PURPOSE

To compare different imaging modalities and to investigate the ability of MultiColor to evaluate geographic atrophy (GA) due to age-related macular degeneration (AMD).

METHODS

Twenty-two consecutive patients with GA underwent MultiColor, colour fundus photography, blue fundus autofluorescence (FAF) (excitation=488 nm; emission >500 nm), near-infrared FAF (NIR-FAF) (excitation=787 nm; emission >800 nm) and spectral-domain optical coherence tomography (SD-OCT) (Spectralis HRA+OCT; Heidelberg Engineering) imaging. Two readers independently measured the size (area) and the width of GA (on horizontal SD-OCT scan cutting the fovea), and evaluated the foveal sparing in each examination.

RESULTS

A total of 32 eyes (22 patients, mean age 79.2±8 years) with GA were included. Intragrader and intergrader agreement considering the evaluation of the size and width of GA was high for all the examinations. MultiColor and FAF showed the greatest intergrader agreement for GA area measurement (intraclass correlation (ICC)=0.990, 95% CI 0.980 to 0.995; ICC=0.998, 95% CI 0.996 to 0.999, respectively). SD-OCT showed the highest intergrader agreement of foveal involvement (k=1), followed by MultiColor and NIR-FAF (k=0.68).

CONCLUSIONS

We demonstrated that several different imaging modalities currently available in clinical practice are reliable for evaluating GA due to AMD. MultiColor is an excellent tool for the measurement of GA area and width, and for the detection of foveal sparing.

Correlations among near-infrared and short-wavelength autofluorescence and spectral-domain optical coherence tomography in recessive Stargardt disease

PURPOSE

Short-wavelength (SW) fundus autofluorescence (AF) is considered to originate from lipofuscin in retinal pigment epithelium (RPE) and near-infrared (NIR) AF from melanin. In patients with recessive Stargardt disease (STGD1), we correlated SW-AF and NIR-AF with structural information obtained by spectral-domain optical coherence tomography (SD-OCT).

METHODS

Twenty-four STGD1 patients (45 eyes; age 8 to 61 years) carrying confirmed disease-associated ABCA4 mutations were studied prospectively. Short-wavelength AF, NIR-AF, and SD-OCT images were acquired.

RESULTS

Five phenotypes were identified according to features of the central lesion and extent of fundus change. Central zones of reduced NIR-AF were typically larger than areas of diminished SW-AF and reduced NIR-AF usually approximated areas of ellipsoid zone (EZ) loss identified by SD-OCT (group 1; r, 0.93, P < 0.0001). In patients having a central lesion with overlapping parafoveal rings of increased NIR-AF and SW-AF (group 3), the extent of EZ loss was strongly correlated with the inner diameter of the NIR-AF ring (r, 0.89, P < 0.0001) and the eccentricity of the outer border of the NIR-AF ring was greater than that of the SW-AF ring.

CONCLUSIONS

Lesion areas were more completely delineated in NIR-AF images than with SW-AF. In most cases, EZ loss was observed only at locations where NIR-AF was reduced or absent, indicating that RPE cell atrophy occurs in advance of photoreceptor cell degeneration. Because SW-AF was often increased within the central area of EZ disruption, degenerating photoreceptor cells may produce lipofuscin at accelerated levels. Consideration is given to mechanisms underlying hyper-NIR-AF in conjunction with increased SW-AF.

EIAV-based retinal gene therapy in the shaker1 mouse model for usher syndrome type 1B: development of UshStat

Usher syndrome type 1B is a combined deaf-blindness condition caused by mutations in the MYO7A gene. Loss of functional myosin VIIa in the retinal pigment epithelia (RPE) and/or photoreceptors leads to blindness. We evaluated the impact of subretinally delivered UshStat, a recombinant EIAV-based lentiviral vector expressing human MYO7A, on photoreceptor function in the shaker1 mouse model for Usher type 1B that lacks a functional Myo7A gene. Subretinal injections of EIAV-CMV-GFP, EIAV-RK-GFP (photoreceptor specific), EIAV-CMV-MYO7A (UshStat) or EIAV-CMV-Null (control) vectors were performed in shaker1 mice. GFP and myosin VIIa expression was evaluated histologically. Photoreceptor function in EIAV-CMV-MYO7A treated eyes was determined by evaluating α-transducin translocation in photoreceptors in response to low light intensity levels, and protection from light induced photoreceptor degeneration was measured. The safety and tolerability of subretinally delivered UshStat was evaluated in macaques. Expression of GFP and myosin VIIa was confirmed in the RPE and photoreceptors in shaker1 mice following subretinal delivery of the EIAV-CMV-GFP/MYO7A vectors. The EIAV-CMV-MYO7A vector protected the shaker1 mouse photoreceptors from acute and chronic intensity light damage, indicated by a significant reduction in photoreceptor cell loss, and restoration of the α-transducin translocation threshold in the photoreceptors. Safety studies in the macaques demonstrated that subretinal delivery of UshStat is safe and well-tolerated. Subretinal delivery of EIAV-CMV-MYO7A (UshStat) rescues photoreceptor phenotypes in the shaker1 mouse. In addition, subretinally delivered UshStat is safe and well-tolerated in macaque safety studies These data support the clinical development of UshStat to treat Usher type 1B syndrome.

Functional principal component analysis reveals discriminating categories of retinal pigment epithelial morphology in mice

PURPOSE

To determine whether multivariate, functional principal component analysis of the size and shape of retinal pigment epithelial (RPE) cell morphology allows discrimination of mouse RPE genotypes and age.

METHODS

Flatmounts of RPE sheets obtained from C57BL/6J (n = 50) and rd10 (n = 61) mice at postnatal days 30 to 720 were stained for zonula occludens-1 (ZO-1) and imaged with confocal microscopy. A total of 111 flatmounts were prepared. Twenty-one morphometric measurements were made on tiled, composite images of complete flatmounts, including cell location, area, and eccentricity, using automated image analysis software for quantitatively measuring cell phenotypes.

RESULTS

In young (≤61-day-old) C57BL/6J mice, the RPE morphology resembled a regular hexagonal array of cells of uniform size throughout the retina, except near the ciliary body, where the shapes of RPE resembled a soft network. Old (≥180-day-old) C57BL/6J eyes had a subpopulation of large cells. A clear disruption of the regular cell size and shape appeared in rd10 mutants. Aspect ratio and cell area gave rise to principal components that predictively classified mouse age and genotype.

CONCLUSIONS

Quantitative differences in the RPE sheet morphology allowed discrimination of rd10 from C57BL/6J strains despite the confounding effect of aging. This has implications for RPE sheet morphology as a potential early biomarker for diagnosis of eye disease and prognosis of the eye at early stages when disease is subtle. We conclude that an RPE cell's area and aspect ratio are very early quantitative indicators that predict progression to advanced RPE disease as manifested in rd10.

Human cone visual pigment deletions spare sufficient photoreceptors to warrant gene therapy

Human X-linked blue-cone monochromacy (BCM), a disabling congenital visual disorder of cone photoreceptors, is a candidate disease for gene augmentation therapy. BCM is caused by either mutations in the red (OPN1LW) and green (OPN1MW) cone photoreceptor opsin gene array or large deletions encompassing portions of the gene array and upstream regulatory sequences that would predict a lack of red or green opsin expression. The fate of opsin-deficient cone cells is unknown. We know that rod opsin null mutant mice show rapid postnatal death of rod photoreceptors. Using in vivo histology with high-resolution retinal imaging, we studied a cohort of 20 BCM patients (age range 5-58) with large deletions in the red/green opsin gene array. Already in the first years of life, retinal structure was not normal: there was partial loss of photoreceptors across the central retina. Remaining cone cells had detectable outer segments that were abnormally shortened. Adaptive optics imaging confirmed the existence of inner segments at a spatial density greater than that expected for the residual blue cones. The evidence indicates that human cones in patients with deletions in the red/green opsin gene array can survive in reduced numbers with limited outer segment material, suggesting potential value of gene therapy for BCM.

Recent Innovations in Medical and Surgical Retina

PURPOSE

To highlight recent innovations in the medical and surgical treatment of retinal disease.

DESIGN

Retrospective literature review.

METHODS

The peer-reviewed, published (during 2012) English literature was searched using the Medline database. Articles deemed relevant were selected and highlighted.

RESULTS

A number of important innovations in the treatment of retinal disease have occurred during the past year. We review developments in regenerative medicine (e.g., retinal prosthesis, optogenetics, cell-based therapy), diagnostics (e.g., swept source optical coherence tomography [OCT], intraoperative OCT, multimodal imaging), surgical innovations (e.g., chemical vitreolysis with ocriplasmin, 27-gauge vitrectomy), and pharmacological therapy of retinal vascular disease (e.g., use of ranibizumab and aflibercept in the treatment of macular edema associated with diabetic retinopathy and retinal vein occlusion).

CONCLUSIONS

Many important innovations in regenerative medicine, diagnostic and surgical instrumentation, and pharmacological therapy for retinal vascular disease have occurred during the past year. In view of the number of agents in early phase clinical trials (e.g., treatments for dry age-related macular degeneration) as well as technologies under development (e.g., microrobots for vitreous surgery), this trend will continue.

Near-infrared and short-wavelength autofluorescence in resolved central serous chorioretinopathy: association with outer retinal layer abnormalities

PURPOSE

To evaluate the correlation between changes in fundus autofluorescence (AF) measured using 2 different sources (near-infrared fundus autofluorescence from melanin and short-wavelength fundus autofluorescence from lipofuscin) with changes in spectral-domain optical coherence tomography (SD OCT) and fluorescein angiography in resolved central serous chorioretinopathy (CSC).

DESIGN

Retrospective, observational case study.

METHODS

A total of 91 eyes from 86 patients with a history of resolved CSC and abnormal AF imaging findings were included. In addition to AF, patients were assessed by means of SD OCT and fluorescein angiography. Outer retinal layer alterations in OCT images and abnormalities in fluorescein angiography were analyzed and correlated with the corresponding AF data.

RESULTS

All eyes with abnormal near-infrared AF showed a hyperfluorescent angiography window defect in the corresponding area. There was a significant association between the OCT and short-wavelength AF findings. An abnormal short-wavelength AF signal was significantly associated with loss of the ellipsoid portion of the inner segments (EPIS, previously known as the junction between the inner and outer segments of the photoreceptors) on SD OCT (χ(2) test; P < .0001). Near-infrared AF could not predict the status of EPIS without the short-wavelength AF image.

CONCLUSIONS

Outer retinal layer changes in OCT images can be predicted by analyzing both short-wavelength AF and near-infrared AF images. Abnormal changes in the short-wavelength AF image were predictive of EPIS damage.

Molecular imaging of retinal disease

Imaging of the eye plays an important role in ocular therapeutic discovery and evaluation in preclinical models and patients. Advances in ophthalmic imaging instrumentation have enabled visualization of the retina at an unprecedented resolution. These developments have contributed toward early detection of the disease, monitoring of disease progression, and assessment of the therapeutic response. These powerful technologies are being further harnessed for clinical applications by configuring instrumentation to detect disease biomarkers in the retina. These biomarkers can be detected either by measuring the intrinsic imaging contrast in tissue, or by the engineering of targeted injectable contrast agents for imaging of the retina at the cellular and molecular level. Such approaches have promise in providing a window on dynamic disease processes in the retina such as inflammation and apoptosis, enabling translation of biomarkers identified in preclinical and clinical studies into useful diagnostic targets. We discuss recently reported and emerging imaging strategies for visualizing diverse cell types and molecular mediators of the retina in vivo during health and disease, and the potential for clinical translation of these approaches.

Comparison of near-infrared and short-wavelength autofluorescence in retinitis pigmentosa

PURPOSE

To compare near-infrared autofluorescence (NIR-AF) and short-wavelength (SW) AF in retinitis pigmentosa (RP) and assess their relationships to underlying retinal structure and visual function.

METHODS

SW-AF, NIR-AF, and spectral domain optical coherence tomography (SD-OCT) images were acquired from 31 patients (31 eyes) with RP and registered to each other. Microperimetry was performed on a subset of 12 patients. For both SW-AF and NIR-AF images, three independent observers measured the area enclosed by the outer border of the hyperautofluorescent ring and the distance from the fovea to the outer and inner border of the ring. For SD-OCT images, the distance from the fovea to the location where the inner segment ellipsoid (ISe) band became undetectable was measured.

RESULTS

All eyes had a hyperautofluorescent ring on both SW-AF and NIR-AF. The position of the outer border of the ring was similar for both modalities. On NIR-AF the signal outside the ring was lower than inside the ring, resulting in a high contrast between the two areas. Also, the inner border of the ring was closer to the fovea on NIR-AF than SW-AF, corresponding to a location on SD-OCT where the ISe band was at least partially intact. Visual sensitivity was relatively preserved within the ring, reduced across the ring, and markedly decreased or nonrecordable outside the ring.

CONCLUSIONS

SW-AF and NIR-AF are both useful for monitoring disease progression in RP; however, NIR-AF may have advantages clinically and could unveil a process that precedes the formation of fluorophores that emit the SW-AF signal.

Near-infrared fundus autofluorescence-visualized melanin in the choroidal abnormalities of neurofibromatosis type 1

Purpose:

To report a series of three cases of neurofibromatosis type 1 examined by near-infrared fundus autofluorescence (NIR-AF) with a scanning laser ophthalmoscope and spectral-domain optical coherence tomography (OCT) to show the characteristics of choroidal abnormalities.

Methods:

Retrospective case series. Six eyes of three patients were examined by conventional fundus examinations, near-infrared monochromatic light reflectance (NIR-R) and NIR-AF, OCT, fluorescein angiography, and indocyanine green angiography.

Results:

All eyes showed multiple bright patchy regions in the choroid of the posterior pole with NIR-R. NIR-AF revealed high fluorescent regions of similar sizes at fundus locations identical to those shown by NIR-R. In one case, hypofluorescent regions were shown by indocyanine green angiography in the bright fluorescent region shown by NIR-AF. The other two cases showed no abnormality under conventional fundus examination or fluorescein angiography. OCT images crossing the bright patchy region showed irregular hyper-reflectivity in the choroid in two cases and hyporeflectivity in one case.

Conclusions:

NIR-AF demonstrated that dense melanin was included in the choroidal nodules of neurofibromatosis type 1. The choroidal nodules showed hyper- or hyporeflectivity in the choroid on OCT, which did not affect the retinal structure.

Microperimetric correlations of autofluorescence and optical coherence tomography imaging in dry age-related macular degeneration

PURPOSE

To investigate the microperimetric correlations of autofluorescence imaging and optical coherence tomography (OCT) in dry age-related macular degeneration (AMD).

DESIGN

Retrospective, observational, cross-sectional study.

METHODS

Consecutive patients with dry AMD underwent a complete ophthalmologic examination, including best-corrected visual acuity (BCVA), blue fundus autofluorescence (FAF), near-infrared autofluorescence, and spectral-domain (SD)-OCT with integrated microperimetry.

RESULTS

A total of 58 eyes of 29 patients (21 women; mean age 73 ± 9 years) were included. Mean BCVA was 0.28 ± 0.3 logarithm of the minimal angle of resolution (logMAR). Overall, 2842 points were analyzed as regards FAF and near-infrared autofluorescence patterns, the status of inner segment/outer segment (IS/OS) interface, and retinal sensitivity. We observed a good correlation between the FAF and near-infrared autofluorescence patterns for all the points graded (increased FAF/near-infrared autofluorescence, Pearson rho = 0.6, P = .02; decreased FAF/near-infrared autofluorescence, Pearson rho = 0.7, P = .01; normal FAF/near-infrared autofluorescence, Pearson rho = 0.7, P = .01). Mean retinal sensitivity was significantly reduced in cases of decreased FAF (4.73 ± 2.23 dB) or increased FAF (4.75 ± 2.39 dB) compared with normal FAF (7.44 ± 2.34 dB) (P = .001). Mean retinal sensitivity was significantly reduced in case of decreased near-infrared autofluorescence (3.87 ± 2.28 dB), compared with increased near-infrared autofluorescence (5.76 ± 2.44 dB) (P = .02); mean retinal sensitivity in case of increased near-infrared autofluorescence was significantly reduced compared with normal near-infrared autofluorescence (7.15 ± 2.38 dB) (P = .002). On SD-OCT, there was a high inverse correlation between retinal sensitivity and rate of disruptions in IS/OS interface (Pearson rho = -0.72, P = .001).

CONCLUSION

A reduced retinal sensitivity consistently correlates with decreased FAF/near-infrared autofluorescence and a disrupted IS/OS interface. Increased near-infrared autofluorescence may represent a useful method for detection of retinal abnormalities early in dry AMD development.

Multimodal imaging of dry age-related macular degeneration

PURPOSE

The purpose of this study was to understand clinical significance of near-infrared reflectance (NIR), blue fundus autofluorescence (FAF) and near-infrared autofluorescence (NIA) in dry age-related macular degeneration (AMD), by correlation with fluorescein angiography (FA) and cross-sectional spectral domain optical coherence tomography (SD OCT).

METHODS

We evaluated 110 eyes (62 patients, mean age: 64 ± 8 years) diagnosed with dry AMD between January 2010 and December 2010, which underwent NIR (λ = 830 nm), FAF and FA (excitation λ = 488 nm; emission λ > 500 nm), NIA (excitation λ = 787 nm; emission λ > 800 nm), and simultaneous SD OCT scanning using a combined confocal scanning laser ophthalmoscope/SD OCT device (Spectralis HRA + OCT; Heidelberg Engineering, Heidelberg, Germany).

RESULTS

Drusen showed variable increased/decreased NIR, FAF, NIA and FA, which corresponded to variable increased/decreased thickness of the retinal pigment epithelium (RPE) and possible presence of subretinal deposits on SD OCT. Geographic atrophy (GA) was present in 43/110 eyes (39.0%) and showed increased NIR and fluorescence (FA), absent FAF and NIA, and loss of RPE on SD OCT. The hyperautofluorescence of the GA margin was never larger in FAF than that in NIA, while in 16.2% of cases, it was larger in NIA than that in FAF and corresponded to mild choroidal hyperreflectivity on SD OCT.

CONCLUSIONS

Simultaneous recording of SD OCT scans provided ultrastructural data for the evaluation of NIR, FAF, NIA and FA in dry AMD. Near-infrared autofluorescence might detect earlier than FAF areas of RPE cell loss at the GA margin.

Optimization of in vivo confocal autofluorescence imaging of the ocular fundus in mice and its application to models of human retinal degeneration

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-Pde6b(rd1/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/cm(2)), 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 Pde6b(rd1/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.

Macular function in macular degenerations: repeatability of microperimetry as a potential outcome measure for ABCA4-associated retinopathy trials

PURPOSE

To measure macular visual function in patients with unstable fixation, to define the photoreceptor source of this function, and to estimate its test-retest repeatability as a prerequisite to clinical trials.

METHODS

Patients (n = 38) with ABCA4-associated retinal degeneration (RD) or with retinitis pigmentosa (RP) were studied with retina-tracking microperimetry along the foveo-papillary profile between the fovea and the optic nerve head, and point-by-point test-retest repeatability was estimated. A subset with foveal fixation was also studied with dark-adapted projection perimetry using monochromatic blue and red stimuli along the horizontal meridian.

RESULTS

Macular function in ABCA4-RD patients transitioned from lower sensitivity at the parafovea to higher sensitivity in the perifovea. RP patients had the inverse pattern. Red-on-red microperimetric sensitivities successfully avoided ceiling effects and were highly correlated with absolute sensitivities. Point-by-point test-retest limits (95% confidence intervals) were ±4.2 dB; repeatability was not related to mean sensitivity, eccentricity from the fovea, age, fixation location, or instability. Repeatability was also not related to the local slope of sensitivity and was unchanged in the parapapillary retina.

CONCLUSIONS

Microperimetry allows reliable testing of macular function in RD patients without foveal fixation in longitudinal studies evaluating natural disease progression or efficacy of therapeutic trials. A single estimate of test-retest repeatability can be used to determine significant changes in visual function at individual retinal loci within diseased regions that are homogeneous and those that are heterogeneous and also in transition zones at high risk for disease progression.

Centrifugal expansion of fundus autofluorescence patterns in Stargardt disease over time

OBJECTIVE

To study the longitudinal changes in autofluorescence in Stargardt disease to reveal aspects of disease progression not previously evident. Changes in autofluorescence reflect changing fluorophore compositions of lipofuscin and melanin in retinal pigment epithelial cells, which has been hypothesized to contribute to Stargardt disease pathogenesis.

METHODS

We examined the temporospatial patterns of fundus autofluorescence with excitation at both 488 nm (standard fundus autofluorescence) and 795 nm (near-infrared autofluorescence) in a longitudinal case series involving 8 eyes of 4 patients (range of follow-up, 11-57 months; mean, 39 months). Image processing was performed to analyze spatial and temporal cross-modality associations.

RESULTS

Longitudinal fundus autofluorescence imaging of fleck lesions revealed hyperautofluorescent lesions that extended in a centrifugal direction from the fovea with time. Patterns of spread were nonrandom and followed a radial path that left behind a trail of diminishing autofluorescence. Longitudinal near-infrared autofluorescence imaging also demonstrated centrifugal lesion spread but with fewer hyperautofluorescent lesions, suggestive of more transient hyperautofluorescence and more rapid decay at longer wavelengths. Fundus autofluorescence and near-infrared autofluorescence abnormalities were spatially correlated with each other, and together they reflect systematic progressions in fleck distribution and fluorophore composition occurring during the natural history of the disease.

CONCLUSIONS

Stargardt disease fleck lesions do not evolve randomly in location but instead follow consistent patterns of radial expansion and a systematic decay of autofluorescence that reflect changing lipofuscin and melanin compositions in retinal pigment epithelial cells. These progressive foveal-to-peripheral changes are helpful in elucidating molecular and cellular mechanisms underlying Stargardt disease and may constitute potential outcome measures in clinical trials.

Variations in NPHP5 in patients with nonsyndromic leber congenital amaurosis and Senior-Loken syndrome

OBJECTIVE

To investigate whether mutations in NPHP5 can cause Leber congenital amaurosis (LCA) without early-onset renal disease.

METHODS

DNA samples from 276 individuals with nonsyndromic LCA were screened for variations in the NPHP5 gene. Each had been previously screened for mutations in 8 known LCA genes without identifying a disease-causing genotype.

RESULTS

Nine of the 276 LCA probands (3.2%) harbored 2 plausible disease-causing mutations (7 different alleles) in NPHP5. Four of these have been previously reported in patients with Senior-Loken syndrome (F141del, R461X, H506del, and R489X) and 3 are novel (A111del, E346X, and R455X). All 9 patients had severe visual loss from early childhood but none had overt renal disease in the first decade of life. Two patients were diagnosed with nephronophthisis in the second decade. Retinal imaging studies showed retained photoreceptor nuclei and retinal pigment epithelium integrity mainly in the cone-rich central retina, a phenotype with strong similarities to that of NPHP6 disease.

CONCLUSIONS

Mutations in NPHP5 can cause LCA without early-onset renal disease. Abnormalities observed in the photoreceptor outer segments (a cilial structure) may explain the severe visual loss in NPHP5 -associated LCA. Clinical Relevance  The persistence of central photoreceptor nuclei despite severe visual loss in NPHP5 disease is encouraging for future therapeutic interventions.

The genomic, biochemical, and cellular responses of the retina in inherited photoreceptor degenerations and prospects for the treatment of these disorders

The association of more than 140 genes with human photoreceptor degenerations, together with studies of animal models of these monogenic diseases, has provided great insight into their pathogenesis. Here we review the responses of the retina to photoreceptor mutations, including mechanisms of photoreceptor death. We discuss the roles of oxidative metabolism, mitochondrial reactive oxygen species, metabolic stress, protein misfolding, and defects in ciliary proteins, as well as the responses of Müller glia, microglia, and the retinal vasculature. Finally, we report on potential pharmacologic and biologic therapies, the critical role of histopathology as a prerequisite to treatment, and the exciting promise of gene therapy in animal models and in phase 1 trials in humans.

Cone photoreceptors are the main targets for gene therapy of NPHP5 (IQCB1) or NPHP6 (CEP290) blindness: generation of an all-cone Nphp6 hypomorph mouse that mimics the human retinal ciliopathy

Leber congenital amaurosis (LCA), a severe autosomal recessive childhood blindness, is caused by mutations in at least 15 genes. The most common molecular form is a ciliopathy due to NPHP6 (CEP290) mutations and subjects have profound loss of vision. A similarly severe phenotype occurs in the related ciliopathy NPHP5 (IQCB1)-LCA. Recent success of retinal gene therapy in one form of LCA prompted the question whether we know enough about human NPHP5 and NPHP6 disease to plan such treatment. We determined that there was early-onset rapid degeneration of rod photoreceptors in young subjects with these ciliopathies. Rod outer segment (OS) lamination, when detectable, was disorganized. Retinal pigment epithelium lipofuscin accumulation indicated that rods had existed in the past in most subjects. In contrast to early rod losses, the all-cone human fovea in NPHP5- and NPHP6-LCA of all ages retained cone nuclei, albeit with abnormal inner segments and OS. The rd16 mouse, carrying a hypomorphic Nphp6 allele, was a good model of the rod-dominant human extra-foveal retina. Rd16 mice showed normal genesis of photoreceptors, including the formation of cilia, followed by abnormal elaboration of OS and rapid degeneration. To produce a model of the all-cone human fovea in NPHP6-LCA, we generated rd16;Nrl-/- double-mutant mice. They showed substantially retained cone photoreceptors with disproportionate cone function loss, such as in the human disease. NPHP5- and NPHP6-LCA across a wide age spectrum are thus excellent candidates for cone-directed gene augmentation therapy, and the rd16;Nrl-/- mouse is an appropriate model for pre-clinical proof-of-concept studies.