cSLO Imaging Research Articles

617. Identification of Novel AAV Capsid Variants with Enhanced Tropism for the Canine Outer Retina Following Intravitreal Delivery

The delivery of AAV vectors across physical barriers to target the outer retina is key to the success of retinal gene therapies. Subretinal injection of AAV vectors is the most common approach to deliver genes to photoreceptors and RPE; however, this route of administration presents surgical challenges and potential complications, as well as mediates transfer to only a limited region of the retinal surface. Intravitreal administration may represent a safer way of targeting larger areas of the outer retina; physical barriers such as the internal limiting membrane significantly limit efficiency of natural AAVs through this route. In a prior murine proof of concept study, we showed that directed evolution is promising method for engineering new AAV capsid variants with enhanced permissivity for the outer retina. Here, we show results from a screen performed in the canine retina, a large animal model with eye structure and size similar to the human eye. A library of >107 distinct capsid variant AAV vectors was injected intravitreally into the eye of a wildtype dog. A subset of the AAV vectors injected was recovered from samples of outer retina by PCR amplification. Isolated variants were then pooled and re-injected in additional wildtype canine eyes, and following 5 total rounds of selection the pool had converged to a relatively small number of variants. High throughput sequencing was used to characterize the convergence of variants over all rounds of selection. The final candidate variants were then evaluated by packaging a GFP reporter controlled by a ubiquitous CAG promoter. Retinal distribution and cellular tropism of the variants was examined by cSLO (AF mode) imaging, histology and immunocytochemistry. Nineteen variants were identified as candidate vectors for targeting the canine outer retina. Intravitreal injection of a mixture of equal amounts of these variants carrying GFP fused to a barcode resulted in efficient targeting of all retinal layers including photoreceptors and RPE in 6 eyes of 3 wildtype dogs. Thus, directed evolution performed in a large animal model, with an eye structure similar to that of humans, resulted in new AAV capsid variants with improved abilities to bypass significant structural barriers and efficiently transduce the outer retina. High throughput sequencing allowed for identification of promising variants and monitoring of convergence. These vectors show promise for gene therapy delivery via the intravitreal route of administration, potentially providing a safer approach for targeting a larger area of outer retina than currently achieved by the more traumatic and focal subretinal injection method.

Spontaneously occurring fundus findings observed using confocal scanning laser ophthalmoscopy in wild type Sprague Dawley rats

PurposeNon-invasive in vivo imaging is an increasingly used component of pre-clinical research. However, to reliably interpret data, it may be necessary to identify and document pre-existent findings prior to initiating long-term or intensive protocols, particularly where toxicity or efficacy is under investigation. Here we report here spontaneously occurring findings from the Sprague Dawley (SD) rat eye using multi-modal confocal scanning laser ophthalmoscopy (cSLO). MethodsAs part of ongoing studies, with the goal of excluding animals with abnormalities from further investigation, a total of 165 wild type SD rats (312 eyes) were assessed using cSLO imaging at baseline prior to initiating experiments to detect, describe, and determine the prevalence of spontaneous fundus findings. ResultsUsing fundus autofluorescence (FAF) as the primary screening modality, over 30% of analyzed eyes possessed some fundus finding that differed from the normal composite reference image. Unexpectedly, 100% of eyes demonstrated a diffuse hyperfluorescent region in the posterior pole that was ultimately considered normal, and formed part of the reference. Evaluated by three independent reviewers, five groups of FAF abnormalities were defined, based primarily on shape and size of the lesion. Of these, the most extensive lesions were further analyzed using infrared reflectance (IR) and red free (RF) imaging. White light and autofluorescent microscopy of excised tissue confirmed that the extensive lesions were derived from abnormalities in both the isolated retina and posterior eyecups. ConclusionsGiven the newly described hyperfluorescent glow that appears in all eyes, and the high basal rate of spontaneous lesions in the outbred SD rat, we suggest that investigators be aware of the variants of normal, and that baseline in vivo screening be considered prior to initiating intensive or expensive investigation.

Foveal Sparing of Reticular Drusen in Eyes With Early and Intermediate Age-Related Macular Degeneration.

To analyze the central distribution of reticular drusen (RDR) in eyes with early and intermediate AMD without soft drusen or pigmentary changes within the central subfield using confocal scanning laser ophthalmoscopy (cSLO) and spectral-domain optical coherence tomography (SD-OCT). Fifty-two eyes of 46 subjects (median age: 76.3 years, interquartile range [IQR], 71-80) were examined by simultaneous combined near-infrared cSLO and raster SD-OCT imaging. The appearance and the topographic distribution of RDR were analyzed within the macula area using the Early Treatment Diabetic Retinopathy Study grid. In addition, longitudinal examinations during an observation period of at least 6 months were included (median observation time: 1.5 years, IQR, 0.9-2.8). The RDR involvement within the central subfield (46%) was less compared with the surrounding subfields (62%-100%), slices (67%-100%), and zones (94%-100%) (P < 0.001). RDR were typically distributed as one continuous zone around the fovea in an incomplete or complete ring-shaped pattern, whereas the fovea itself was either spared or only a few lesions were present. Over time, the RDR density increased and new RDR lesions occurred at the border of the RDR zone toward a closure of the ring-shaped pattern. Within the fovea, development of RDR was observed in 8 of 28 eyes. The fovea appears to be less vulnerable to RDR development as compared with peripheral macula areas. Factors for initial sparing of the foveal retina are yet unknown but may relate to topographic differences of choroidal blood flow and/or photoreceptor distribution.

Retinal regeneration following OCT-guided laser injury in zebrafish.

Establish a focal injury/regeneration model in zebrafish using laser photocoagulation guided by optical coherence tomography (OCT). Adult zebrafish were imaged by OCT and confocal scanning laser ophthalmoscopy (cSLO) in room air through a contact lens. Using a beam combiner, 532-nm laser photocoagulation was applied using the OCT C-scan image for targeting. Laser spots of 42 to 47 mW were delivered to the retina. At multiple intervals post injury, fish were imaged using both OCT and cSLO to follow the progression of each lesion. Histologic sections and TUNEL staining were performed to monitor the injury response. Round lesions (26057 ± 621 μm(2)) localized to the outer retina were successfully applied. Laser application was visualized by real-time OCT and lesions were detectable by both OCT and cSLO in vivo. Lesion size increased 1 day post lesion then decreased in size. Histologic sections showed focal areas of damage localized primarily to the outer retina. By 3 weeks, the damaged areas had regenerated and a fully laminated structure was re-established. However, subtle changes can still be detected by OCT, cSLO imaging, and histology. Infrared darkfield imaging was more sensitive than OCT at revealing subtle changes in regenerated areas. Optical coherence tomography-guided laser photocoagulation is a useful tool for inducing localized lesions and studying retinal regeneration in zebrafish. This novel method will allow us to characterize the cellular and molecular changes that take place at the interface between normal and damaged tissue. Regeneration can be observed using high-resolution OCT and cSLO imaging in vivo.

Vessel labeling in combined confocal scanning laser ophthalmoscopy and optical coherence tomography images: criteria for blood vessel discrimination.

IntroductionThe diagnostic potential of optical coherence tomography (OCT) in neurological diseases is intensively discussed. Besides the sectional view of the retina, modern OCT scanners produce a simultaneous top-view confocal scanning laser ophthalmoscopy (cSLO) image including the option to evaluate retinal vessels. A correct discrimination between arteries and veins (labeling) is vital for detecting vascular differences between healthy subjects and patients. Up to now, criteria for labeling (cSLO) images generated by OCT scanners do not exist.ObjectiveThis study reviewed labeling criteria originally developed for color fundus photography (CFP) images.MethodsThe criteria were modified to reflect the cSLO technique, followed by development of a protocol for labeling blood vessels. These criteria were based on main aspects such as central light reflex, brightness, and vessel thickness, as well as on some additional criteria such as vascular crossing patterns and the context of the vessel tree.Results and ConclusionThey demonstrated excellent inter-rater agreement and validity, which seems to indicate that labeling of images might no longer require more than one rater. This algorithm extends the diagnostic possibilities offered by OCT investigations.

Altered fundus appearance resulting from autofluorescence imaging with the confocal scanning laser ophthalmoscope (cSLO) in cats.

This paper is to report that imaging the tapetal fundus of cats with the 488 nm laser of the Spectralis(®) HRA+OCT (Heidelberg Engineering Inc., Heidelberg, Germany) can result in a pale appearance of the imaged area. Wild-type and Rdy kittens (CRX mutant heterozygotes-CRX(Rdy+/-) ) (8-20 weeks of age) and adult cats (1-4 years of age) were imaged by confocal scanning laser ophthalmoscope (cSLO) and spectral domain optical coherence tomography (SD-OCT) using the Spectralis(®) HRA+OCT. Color fundus photography (RetCam II(®) , Clarity Medical Systems, Inc., Pleasanton, CA) was performed after imaging using the Spectralis(®) HRA+OCT. Following retinal cSLO imaging using the 488 nm laser (autofluorescence imaging) in both wild-type kittens and adult cats, the imaged region appeared paler than the adjacent retina that had not been imaged. This change was probably due to retinal bleaching and was fully reversible. Imaging CRX(Rdy+/-) kittens or adults, which had very reduced levels of visual pigments, did not induce the altered fundus appearance. Those using autofluorescence imaging by cSLO should be aware that it can induce a characteristic pale appearance of the tapetal fundus in the imaged area of normal cats.

Characterisation of reticular pseudodrusen and their central target aspect in multi-spectral, confocal scanning laser ophthalmoscopy

To analyse reticular pseudodrusen (RPD) in patients with age-related macular degeneration (AMD) using multi-spectral (MS), confocal scanning laser ophthalmoscopy (cSLO). cSLO images (blue fundus autofluorescence [FAF; exc., λ = 488; em., λ = 500-700 nm], near-infrared reflectance [IR; λ = 820 nm], MS [blue reflectance (BR) λ = 488 nm, green reflectance (GR) λ = 515 nm, IR λ = 820 nm], as well as colour fundus photographs (CFP) were taken of 200 eyes from 100 AMD patients suspected to show RPD on the basis of funduscopy or previous fundus imaging. FAF and IR images were graded by two independent readers. If both readers concordantly confirmed the presence of RPD in both modalities, eyes were subsequently also graded for RPD in MS, BR, GR, green-blue enhanced mode (GBE), and CFP. Besides, FAF, IR, and MS images were evaluated for the presence of a target aspect, which represents a common feature of RPD lesions. The presence of RPD was confirmed using FAF and IR images by both readers in 130 eyes of 76 patients. In those eyes, both readers concordantly diagnosed RPD in MS images in 124 (95.4%) eyes (BR: 52 [40.0%], GR: 63 [48.5%], GBE: 101 [77.7%], CF: 27 [20.8%]). Cohen kappa statistics revealed excellent inter-observer agreement for MS (0.95) and GBE (0.85), substantial agreement for BR (0.75), GR (0.78), and moderate agreement for CFP (0.59). A target aspect within RPD lesions was detected in 45 of 130 (35.0%) included eyes using FAF and IR. The presence of a target aspect improved the recognition of RPD lesions in all modalities. If a target aspect was present, RPD were diagnosed in 45 eyes (100%) using MS (GBE: 42 eyes [93.3%], BR: 30 eyes [66.7%], GR: 37 eyes [82.2%], CFP: 17 eyes [37.8%]). Using MS cSLO, a target aspect could be identified in 75 of 130 (57.7%) included eyes. MS cSLO imaging is equivalent to FAF and IR in identifying RPD in AMD patients. Higher identification rates in BR and GR of those RPD lesions featuring a target aspect confirm the current hypothesis of RPD localisation and its progression further into the photoreceptor layers. MS seems to be more sensitive in identifying a central target aspect in RPD lesions compared to blue FAF and IR.

Retikuläre Drusen über die Zeit mittels SD-OCT

The aim of the study was the analysis of reticular drusen (RDR) in patients with age-related macular degeneration using simultaneous confocal scanning laser ophthalmoscopy (cSLO) and spectral domain optical coherence tomography (SD-OCT) at different time points. Included in this retrospective analysis were 47 eyes from 32 patients (median age 80.1 years, range 66-89 years) with RDR at baseline and at least one follow-up visit. Registration of the cSLO near-infrared reflectance image and the SD-OCT B-scan (Spectralis HRA + OCT, Heidelberg Engineering, Heidelberg) at different time points was carried out using the AutoRescan tool. While either no alterations or increase in the RDR area (n=19 eyes) or RDR density (n=15) were seen by cSLO imaging, the analysis of the SD-OCT B-scans at different time points revealed a more complex picture. An increase in two well visible lesions at the baseline visit was detected in 8 eyes at the first follow-up and in 3 eyes at the second follow-up examination. A regression was seen in 5 eyes at the first follow-up and in 3 eyes at the second follow-up visit. In most eyes (n=23), an increase of one with a parallel decrease of the second RDR lesion in the identical B-scan was identified at the first follow-up visit, whereas individual RDR showed an increase at the second follow-up examination that had initially shown a decrease in size at the first follow-up visit. The results indicate underlying dynamic processes in the development and changes of RDR over time. For a more accurate analysis, the exact registration of SD-OCT B-scans at different time points and the use of high-resolution very dense volume scans would be helpful in order to assess such discrete changes of miniscule intraretinal lesions over time.

Cone Photoreceptor Neuroprotection Conferred by CNTF in a Novel In Vivo Model of Battlefield Retinal Laser Injury

To develop a reproducible laboratory model to simulate a battlefield foveal laser injury and to test potential neuroprotective effects of a single injection treatment that might be administered in a military setting. Frequency-doubled 532-nm Nd:YAG laser was used to induce a threshold retinal injury bilaterally in transgenic reporter mice that have fluorescent cones. Intravitreal injection of ciliary neurotrophic factor (CNTF) was then administered to the lasered eye and compared with a contralateral sham injection of saline. The effect on fluorescent cone cell survival was quantified using a confocal scanning laser ophthalmoscope (cSLO), TUNEL assays, and quantitative real-time PCR (qPCR). At 3 weeks post-laser, cSLO imaging showed that the proportion of surviving cones expressing green fluorescent protein (GFP) was greater in CNTF-treated (54.1 ± 5.15% of baseline count) than in sham-injected eyes (28.7 ± 4.4%), which was accompanied by a reduction in TUNEL-positive cells. This difference in cone survival persisted at the 6-week point (treated, 39.6 ± 3.2% versus sham, 18.0 ± 3.8%). These changes were accompanied by a reduction in TUNEL-positive cells. The Bcl-2/Bax ratio was increased in CNTF-treated eyes at 1 week postlaser exposure relative to controls. A single intravitreal injection of CNTF protein was shown to improve cone survival when administered immediately after laser exposure. Similar treatments with CNTF might also have a role in attenuating retinal laser damage sustained by combat personnel in the military setting.

Confocal scanning laser ophthalmoscope in the retromode imaging modality in exudative age-related macular degeneration

To evaluate the ability of confocal scanning laser ophthalmoscope (cSLO) in the retromode imaging modality in detecting retinal changes secondary to exudative age-related macular degeneration (AMD). Seventeen eyes of 13 consecutive patients affected by CNV secondary to AMD were evaluated with optical coherence tomography (OCT) to detect neuroretinal detachment (NRD), pigment epithelial detachment (PED), cystoid macular edema (CME), and epiretinal membranes (ERM). All eyes were examined with a cSLO equipped with infrared retromode (RM) imaging modality. Infrared and fundus autofluorescence images were also obtained (IR and FAF). The intermethod agreement between OCT and cSLO was evaluated considering single cSLO imaging modality separately (IR, FAF, and RM), and all imaging modalities together. Eight eyes (47 %) had NRD at OCT; intermethod agreement was poor for any single cSLO imaging modality considered separately (k: 0.14, 0.01, and 0.29 for cSLO IR, FAF, and RM, respectively). Four eyes had PED at OCT (24 %); intermethod agreement was mild for cSLO RM, poor for IR and FAF (k: 0.51, 0.16, and 0.00, respectively). CME was present in eight eyes (47 %); intermethod agreement was excellent for cSLO RM, poor for IR and FAF (k: 0.88, 0.38, and 0.26, respectively). ERM was present in three eyes (18 %); intermethod agreement was mild for cSLO IR, poor for FAF, and excellent for RM (k: 0.59, 0.00, and 0.76, respectively). cSLO RM imaging is a useful and reproducible technique in detecting retinal features associated with CNV, particularly CME.

Abnormal Fundus Autofluorescence Results of Patients in Long-term Treatment with Deferoxamine

To describe and classify patterns of abnormal fundus autofluorescence (FAF) of patients with β-thalassemia receiving long-term treatment with deferoxamine (DFO). Prospective, cross-sectional, case-control study. A total of 197 consecutive patients with β-thalassemia major or intermedia with at least 10 years of treatment with DFO were recruited in a tertiary referral center in Milan, Italy, and were investigated. Seventy-nine thalassemic patients without a history of chelation therapy were included as a control group. All of the patients were investigated using best-corrected visual acuity (BCVA), fundus photography, and FAF imaging by confocal scanning laser ophthalmoscopy (cSLO) and were compared with the control group. Identification of abnormal FAF patterns in thalassemic patients treated with long-term DFO and their progression and relationship with visual function. Abnormal FAF not related to other diseases was observed in 18 of the 197 patients (9%) and was classified into 4 phenotypic patterns: minimal change, focal, patchy, and speckled. The abnormal increased or decreased FAF was bilateral in all the cases, and only in some cases did it correspond to funduscopically visible alterations. There were no FAF abnormalities in the control group. During the follow-up, progressive FAF changes related to retinal pigment epithelium (RPE) damage occurred in the patchy pattern, associated with decreasing BCVA. Patients with speckled and focal patterns showed limited or no changes in FAF during the follow-up. No changes in FAF were found in patients with a minimal change pattern. No treated patient with a normal baseline examination demonstrated FAF changes. Patients with patterns other than the minimal change showed significant BCVA deterioration (P<0.001). Various phenotypic patterns of abnormal FAF can be identified with cSLO imaging. Fundus autofluorescence is a helpful, fast, and noninvasive tool for monitoring the status of the macula in patients at risk of DFO toxicity. It may be useful in the decision to discontinue or switch the therapy in cases of particular high risk for disease progression. The progressive alteration of the RPE suggests an important role of pathologic RPE changes in the evolution of visual loss during long-term treatment with DFO.

Reticular Drusen Associated with Geographic Atrophy in Age-Related Macular Degeneration

To characterize reticular drusen (RDR) in patients with geographic atrophy (GA) secondary to age-related macular degeneration (AMD) in a prospective, multicenter, natural history study. Confocal scanning laser ophthalmoscopy (cSLO) three-field fundus autofluorescence (FAF; exc., 488; em., 500-700 nm), near-infrared reflectance (IR; 820 nm), and blue reflectance (BR; 488 nm) images as well as red-free (RF) and color fundus (CF) camera photographs were recorded in 458 GA patients. The digital images were evaluated by two independent readers with subsequent senior reader arbitration for prevalence and topographic distribution of RDR using a modified Early Treatment Diabetic Retinopathy Study grid. RDR were detected with at least one cSLO modality in 286 of 458 (62%) patients in either eye (bilateral 207 [45%]) and were visible in fundus camera photographs in 66 of 371 (18%) patients (bilateral 48 [13%]). Prevalence of RDR by cSLO imaging was associated with increasing age (P = 0.007) and female sex (P = 0.007), but not with GA total lesion area (P = 0.38). Cohen kappa statistics showed good interobserver agreement for FAF (0.81) and IR (0.82) imaging modes, and moderate agreement was found for BR (0.48), RF (0.48), and CF (0.40). On three-field FAF images RDR were present most frequently superior to the fovea (99%). RDR represent a common phenotypic hallmark in GA eyes. RDR are readily identified using cSLO imaging technology. These observations may explain the high prevalence determined herein, in contrast to previous reports based on fundus photographs. Incorporation of these novel imaging modalities in future natural history studies may facilitate efforts aimed at defining the role and predictive value of RDR in the progression of AMD. (ClinicalTrials.gov number, NCT00599846.)

Insights into pathology of cuticular drusen from integrated confocal scanning laser ophthalmoscopy imaging and corresponding spectral domain optical coherence tomography

To analyze the integrated confocal scanning laser ophthalmoscopy (cSLO) fundus and angiographic imaging and corresponding spectral domain optical coherence tomography (SD-OCT) features of cuticular drusen. Twenty-one consecutive patients with cuticular drusen were submitted to cSLO fundus and angiographic imaging [infrared reflectance (IR), fundus autofluorescence (FAF), near-infrared autofluorescence (NIA), fluorescein angiography (FA), and indocyanine green angiography (ICGA)) and "eye-tracked" SD-OCT. A total of 42 eyes were included for analysis. BCVA ranged from 20/20 to 20/400. In 5/42 eyes, cSLO imaging and corresponding SD-OCT showed coincident vitelliform macular detachment, and in 9/42 eyes showed coincident geographic atrophy (GA). The "typical" cuticular drusen, intensely staining on early FA phase ("stars-in-the-sky" appearance in the fundus), appeared as "sawtooth" retinal pigment epithelium (RPE) elevation on SD-OCT. Some "atypical" cuticular drusen appeared, on early FA and ICGA frames, as hyper-fluoresecent lesions surrounded by faint hypo-fluoresecent halos. These lesions, which became intensely hyper-fluorescent in the late FA and ICGA phases, appeared, on SD-OCT, as small, confluent "dome-shaped" RPE elevations. Interestingly, some less intensely staining cuticular drusen (FA and ICGA) appeared as irregular slight thickening of RPE/Bruch's membrane complex on SD-OCT scans. Integrated imaging makes it possible to highlight different features within cuticular drusen-containing regions, and gives insights into pathology. We suggest that "typical" cuticular drusen may represent a continuous layer of early basal laminar deposit (BLamD) associated with membranous debris accumulation. As early BLamD thicken, the lesions become richer in solid lipid particles, and "atypical" cuticular drusen may develop.

Clinical evaluation of simultaneous confocal scanning laser ophthalmoscopy imaging combined with high‐resolution, spectral‐domain optical coherence tomography

To evaluate the clinical relevance of a new diagnostic modality, simultaneous confocal scanning laser ophthalmoscopy (cSLO) and high-speed, high-resolution, spectral-domain optical coherence tomography (OCT), for the visualization of macular pathologies. OCT images and simultaneous recording of fluorescein angiography, indocyanine green (ICG) angiography, infrared, and blue reflectance ('red-free') or fundus autofluorecence (FAF) images were obtained with a novel imaging device (Spectralis HRA + OCT; Heidelberg Engineering, Heidelberg, Germany). An optically pumped solid-state laser generated the excitation wavelength (488 nm) required for blue reflectance, FAF and fluorescein angiography images. For ICG angiography and infrared imaging, diode laser sources at 790 and 815 nm were used. For OCT, 40 000 A-scans per second were acquired with 7 μm axial and 14 μm lateral optical resolution. The B-scans covering a transversal range of 30° had a scan width up to 1.536 A-scans with a digital lateral resolution of 5 μm/pixel, a scan depth of 1.8 mm with 3.5 μm/pixel digital axial resolution and a scan rate of up to 48 B-scans/second. In addition, volume scans could be obtained at 15, 20 and 30° fields of view. An integrated eye tracking allowed for live averaging of cSLO images as well as OCT B-scans. Early, neovascular and atrophic age-related macular degeneration, macular telangiectasia, retinal arterial, branch vein occlusion and other pathologies were imaged, and cSLO and OCT frames correlated. Fluorescein and ICG angiographic phenomena recorded in cSLO images could be analysed accurately in corresponding OCT cross-sections. Abnormal FAF signals were correlated to alterations at the outer retinal/retinal pigment epithelial cell layer in high-resolution OCT scans. Three-dimensional OCT enabled comprehensive retinal coverage. The imaging software tracked eye movements accurately. Averaging of live B-scans enhanced image quality considerably. The combined cSLO/OCT system allowed for simultaneous recordings of topographic and tomographic images with accurate correlation between the confocal angiograms, FAF images as well as other imaging modes with the OCT scans. The instrument thus provides simultaneous multi-modal imaging of retinal pathologies and disease.

In Vivo Assessment of Retinal Vascular Wall Dimensions

Retinal blood vessel diameter and arteriovenous ratio (AVR) are commonly used diagnostic parameters. Because vascular walls are typically not visible in funduscopy, clinical AVR estimation is based on the lumen rather than the entire vessel diameter. Here the authors used a transgenic mouse model to quantify AVR in vivo based on total vessel dimensions (wall and lumen). Confocal scanning laser ophthalmoscopy (cSLO) and indocyanine green angiography of the retinal vasculature were performed in wild-type and transgenic mice expressing green fluorescent protein (GFP) under the transcriptional control of the smooth muscle type α-actin (αSMA) promoter. Spectral-domain-OCT and ERG were performed to control for integrity of retinal structure and function in vivo and histology to demonstrate the location of GFP expression. Native cSLO imaging and angiography yielded only inner vessel diameters similar to those observed through clinical funduscopy. In αSMA-GFP mice, autofluorescence imaging of the GFP-marked vascular walls also allowed the determination of outer vessel diameters. The mean AVR based on either inner diameter (AVR(id) = 0.72 ± 0.08) or outer diameter (AVR(od) = 0.97 ± 0.09) measurements were significantly different (P < 0.01). Transgenic αSMA-GFP expression in murine vessel wall components allowed quantification of retinal vessel outer diameters in vivo. Although arterioles and venules differ in lumen and vessel wall width, they share a common outer diameter, leading to an AVR(od) close to unity. Because vessel walls are primary targets in common hypertensive and metabolic diseases, αSMA-GFP transgenic mice may prove valuable in the detailed assessment of such disorders in vivo.

Tracking Progression with Spectral-Domain Optical Coherence Tomography in Geographic Atrophy Caused by Age-Related Macular Degeneration

To investigate, with the use of spectral-domain optical coherence tomography (SD-OCT), microstructural alterations over time in eyes with progressive geographic atrophy (GA) due to age-related macular degeneration. Forty-six eyes of 26 patients (median age, 77.9 years [interquartile range (IQR), 71.8-81.0]) with GA without evidence of active or previous neovascular disease at baseline were examined by simultaneous confocal scanning laser ophthalmoscopy (cSLO) and SD-OCT. Serial examinations with alignment of follow-up to baseline scans were performed over a median period of 12.2 months (IQR, 10.2-15.3). Longitudinal SD-OCT variations were evaluated, including quantification of retinal thickness (RT) change and lateral spread of GA (LSGA) at a temporal, nasal, inferior, and superior GA border-section in each eye. GA-enlargement was characterized by progressive loss of the outer hyperreflective SD-OCT bands and by thinning of the outer nuclear layer with subsequent approach of the outer plexiform layer toward Bruch's membrane. In the perilesional zone, various dynamic changes were recorded, including migration of hyperreflective material and changes in drusen height. At the borders, there was a median RT change of -14.09 microm/y (IQR -26.21 to -7.48 microm/y). The median LSGA was 106.90 microm/y (IQR, 55.44-161.70 microm/y). Both parameters showed only moderate intraocular agreement (RT change: intraclass correlation coefficient [ICC], 0.54; 95% CI, 0.39-0.67; LSGA: ICC, 0.49; 95% CI, 0.34-0.64) and no statistical significant difference for one location (RT change, P = 0.125; LSGA, P = 0.516; likelihood ratio test). Combined cSLO and SD-OCT imaging provides unprecedented insight into dynamic microstructural changes of GA enlargement that may help to better understand the pathogenesis of the disease. Quantitative progression data indicate local factors may exist that drive progression in junctional areas (ClinicalTrials.gov number, NCT00393692).

Spectral Domain Optical Coherence Tomography in Mouse Models of Retinal Degeneration

Spectral domain optical coherence tomography (SD-OCT) allows cross-sectional visualization of retinal structures in vivo. Here, the authors report the efficacy of a commercially available SD-OCT device to study mouse models of retinal degeneration. C57BL/6 and BALB/c wild-type mice and three different mouse models of hereditary retinal degeneration (Rho(-/-), rd1, RPE65(-/-)) were investigated using confocal scanning laser ophthalmoscopy (cSLO) for en face visualization and SD-OCT for cross-sectional imaging of retinal structures. Histology was performed to correlate structural findings in SD-OCT with light microscopic data. In C57BL/6 and BALB/c mice, cSLO and SD-OCT imaging provided structural details of frequently used control animals (central retinal thickness, CRT(C57BL/6) = 237 +/- 2 microm and CRT(BALB/c) = 211 +/- 10 microm). RPE65(-/-) mice at 11 months of age showed a significant reduction of retinal thickness (CRT(RPE65) = 193 +/- 2 microm) with thinning of the outer nuclear layer. Rho(-/-) mice at P28 demonstrated degenerative changes mainly in the outer retinal layers (CRT(Rho) = 193 +/- 2 microm). Examining rd1 animals before and after the onset of retinal degeneration allowed monitoring of disease progression (CRT(rd1 P11) = 246 +/- 4 microm, CRT(rd1 P28) = 143 +/- 4 microm). Correlation of CRT assessed by histology and SD-OCT was high (r(2) = 0.897). The authors demonstrated cross-sectional visualization of retinal structures in wild-type mice and mouse models for retinal degeneration in vivo using a commercially available SD-OCT device. This method will help to reduce numbers of animals needed per study by allowing longitudinal study designs and will facilitate characterization of disease dynamics and evaluation of putative therapeutic effects after experimental interventions.

Multimodal Imaging Including Spectral Domain OCT and Confocal Near Infrared Reflectance for Characterization of Outer Retinal Pathology in Pseudoxanthoma Elasticum

To investigate the value of multimodal confocal scanning laser ophthalmoscopy (cSLO) for phenotyping fundus lesions in patients with pseudoxanthoma elasticum (PXE) and to correlate these findings with morphologic alterations detected by spectral domain optical coherence tomography (SD-OCT). Imaging was performed with a combined SD-OCT-cSLO system (Spectralis HRA-OCT; Heidelberg Engineering, Heidelberg, Germany). OCT scans were placed at locations of interest on near-infrared (NIR) reflectance, fundus autofluorescence (FAF), and fluorescein angiography (FA) images. The instrument allowed for exact topographic correlation of findings on OCT and cSLO images. NIR reflectance imaging showed the highest sensitivity to detect angioid streaks and peau d'orange compared to FAF or FA. On OCT scans, angioid streaks reliably showed breaks in Bruch's membrane. Peau d'orange was associated with alternating reflectivity within Bruch's membrane. Characteristic mid-peripheral chorioretinal atrophies showed hyporeflective spaces involving the outer neurosensory retina. In eyes with pattern dystrophy like alterations, subneurosensory accumulation of material was observed within areas of increased FAF. SD-OCT in combination with cSLO imaging using NIR light locates the primary pathologic formations of angioid streaks and peau d'orange in Bruch's membrane. NIR reflectance imaging may be superior for detecting PXE-related fundus lesions at the level of Bruch's membrane, because the blue laser light that is used in FAF and FA is markedly absorbed by the pigment epithelium and therefore may only detect alterations if this cell layer is also affected. The findings indicate that multimodal cSLO and SD-OCT imaging of the outer retina allows for screening of PXE related retinal alterations.

Evaluation of Autofluorescence Imaging with the Scanning Laser Ophthalmoscope and the Fundus Camera in Age-related Geographic Atrophy

To compare fundus autofluorescence images (FAF) between a modified fundus camera (mFC) and a confocal scanning laser ophthalmoscope (cSLO). Evaluation of diagnostic technology. Thirty-two eyes of 16 patients with age-related geographic atrophy (GA) treated in an institutional setting were included. FAF images were obtained with both the cSLO (excitation, 488 nm; emission, > 500 nm) and the mFC (excitation, approximately 500 to 610 nm; emission, approximately 675 to 715 nm). Using established algorithms, images were graded by two independent observers and agreements were evaluated. The main outcome measures were image quality, quantification of total atrophy, and classification of FAF patterns. In two eyes with advanced cataract (lens grade 7 according to the Age-Related Eye Disease Study classification), FAF image quality with both systems was not sufficient for any meaningful analysis. In the remaining 30 eyes, the mean differences of the interobserver agreements for atrophy quantification were 0.16 mm2 (95% confidence interval [CI], 0.07 to 0.38) for mFC and 0.15 mm2 (95% CI, -0.04 to 0.33) for cSLO images. Because of inferior signal-to-noise ratios, FAF pattern classification was possible in a lower number of mFC images (69%) compared with cSLO images (88%). This study suggests that the agreements for atrophy quantification are similar with both devices. The lesser visualization of FAF patterns with the mFC and thus inferior determination of disease markers may be the result of the nonconfocality and the use of single instead of mean images compared with the cSLO. These findings may be important for the design of interventional trials as well as the routine use of FAF imaging in age-related geographic atrophy.

060 SLO et OCT à haute résolution en imagerie simultanée dans la DMLA

Purpose To image alterations associated with various phenotypes of age-related macular degeneration (AMD) by simultaneous confocal scanning laser ophthalmoscopy (cSLO) and high-resolution, spectral-domain optical coherence tomography (OCT). Methods OCT-images and simultaneous recording of fluorescein angiography, indocyanine green (ICG) angiography, infrared, redfree, or fundus autofluorecence (FAF) images were obtained with a novel imaging device (Spectralis HRA+OCT, Heidelberg Engineering, Heidelberg, Germany). An optically pumped solid state laser generates the excitation wavelength (488 nm) required for redfree, FAF and fluorescein angiography images. For ICG angiography and infrared imaging diode laser sources at 790 and 815 nm are used. For OCT 40.000 A-scans are acquired per second with 7 μm depth and 14 μm lateral optical resolution. The B-scans with an angle of 30 degrees have a scan width up to 1.536 A-scans with a digital lateral resolution of 6 μm/pixel, a scan depth of 500 pixels with 4 μm/pixel resolution and a scan rate up to 50 B-scans/sec. An integrated eye tracking allows for live averaging of cSLO-images as well as OCT B- scans. Results Early, atrophic and neovascular manifestations of age-related macular degeneration were examined and cSLO and OCT frames correlated. Fluorescein and ICG-angiographic phenomena recorded in cSLO images could be analysed in corresponding OCT-cross sections. Abnormal FAF-signals were correlated to alterations at the outer retinal/retinal pigment epithelial cell layer in high resolution OCT-scans. Three-dimensional OCT enabled comprehensive retinal coverage. The imaging software accurately tracked eye movements and allowed for precise monitoring at identical retinal sites at different time points following anti-VEGF-therapy. This facilitated evaluation of the drug-repsonse and indication for retreatments. Conclusion The combined cSLO/OCT system allows for simultaneous recordings of topographic and tomographic images. Particularly the pixel-to-pixel correlation between the confocal angiograms, FAF images and other imaging modes with the OCT scans may contribute to our understanding of the pathogenesis, and improve diagnosis and management of patients with AMD.