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

Detailed phenotype and long-term follow-up of RAB28-associated cone-rod dystrophy

PURPOSE

To gain an insight into the pathophysiology of RAB28-associated inherited retinal degeneration through detailed phenotyping and long-term longitudinal follow-up.

METHODS

The patient underwent complete ophthalmic examinations. Visual function was assessed with microperimetry, full-field electroretinography (ffERG), imaging with optical coherence tomography (OCT), short-wave (SW), and near-infrared (NIR) fundus autofluorescence (FAF).

RESULTS

A healthy Haitian woman with homozygous pathogenic variants (c.68C > T; p.Ser23Phe) in RAB28 presented at 16 years of age with a four-year history of blurred vision. Visual acuities were 20/125 in each eye, which remained relatively stable since. At age 27, cone ffERGs were non-detectable and borderline for rod-mediated responses. Kinetic fields were full to a V-4e target, undetectable to a small I-4e stimulus. Microperimetry showed an absolute central scotoma surrounded by a pericentral relative scotoma. SD-OCT showed an undetectable or barely detectable foveal and parafoveal photoreceptor outer nuclear layer (ONL), photoreceptor outer segment (POS), and retinal pigment epithelium (RPE) signals and loss of the SW- and NIR-FAF signals. This atrophic region was separated from a normally laminated retina by a narrow transition zone (TZ) of hyper SW- and NIR-FAF that co-localized with preserved ONL but abnormally thinned POS and RPE. There was minimal centrifugal (<100 μ m) expansion over a six-year period.

CONCLUSION

The cone-rod dystrophy phenotype documented herein supports a critical role of RAB28 for cone function and POS maintenance. Severe central photoreceptor and RPE loss with a predilection for POS loss in TZs suggests possible disruptions of complex mechanisms that maintain central cone photoreceptor and RPE homeostasis.

Near Infrared Autofluorescence Lifetime Imaging of Human Retinal Pigment Epithelium Using Adaptive Optics Scanning Light Ophthalmoscopy

Purpose

To demonstrate the first near-infrared adaptive optics fluorescence lifetime imaging ophthalmoscopy (NIR-AOFLIO) measurements in vivo of the human retinal pigment epithelial (RPE) cellular mosaic and to visualize lifetime changes at different retinal eccentricities.

Methods

NIR reflectance and autofluorescence were captured using a custom adaptive optics scanning light ophthalmoscope in 10 healthy subjects (23-64 years old) at seven eccentricities and in two eyes with retinal abnormalities. Repeatability was assessed across two visits up to 8 weeks apart. Endogenous retinal fluorophores and hydrophobic whole retinal extracts of Abca4-/- pigmented and albino mice were imaged to probe the fluorescence origin of NIR-AOFLIO.

Results

The RPE mosaic was resolved at all locations in five of seven younger subjects (<35 years old). The mean lifetime across near-peripheral regions (8° and 12°) was longer compared to near-foveal regions (0° and 2°). Repeatability across two visits showed moderate to excellent correlation (intraclass correlation: 0.88 [τm], 0.75 [τ1], 0.65 [τ2], 0.98 [a1]). The mean lifetime across drusen-containing eyes was longer than in age-matched healthy eyes. Fluorescence was observed in only the extracts from pigmented Abca4-/- mouse.

Conclusions

NIR-AOFLIO was repeatable and allowed visualization of the RPE cellular mosaic. An observed signal in only the pigmented mouse extract infers the fluorescence signal originates predominantly from melanin. Variations observed across the retina with intermediate age-related macular degeneration suggest NIR-AOFLIO may act as a functional measure of a biomarker for in vivo monitoring of early alterations in retinal health.

MULTIMODAL RETINAL IMAGING REVEALS NEW PATHOGENIC INSIGHTS IN CENTRAL AREOLAR CHOROIDAL DYSTROPHY: A CASE SERIES

PURPOSE

To describe novel imaging findings in a family affected by central areolar choroidal dystrophy.

METHODS

Case series with multimodal retinal imaging assessment.

RESULTS

A 19-year-old asymptomatic woman was referred for bilateral macular defects of the retinal pigment epithelium. Blue-light autofluorescence of her right eye revealed a speckled pattern in the macular area with a ring of decreased autofluorescence using near-infrared autofluorescence. Multimodal assessment of her left eye disclosed a single parafoveal spot of decreased pigmentation that was clearly visible as hyperautofluorescent using blue-light autofluorescence and as hypoautofluorescent using near-infrared autofluorescence. Optical coherence tomography angiography revealed several tiny areas of flow voids in correspondence of the retinal pigment epithelium alterations of both eyes. Three family members were recently diagnosed with presumed age-related macular degeneration and demonstrated well-demarcated areas of retinal pigment epithelium atrophy surrounded by yellowish deposits and a hypopigmented halo. Next-generation genetic analysis for inherited macular dystrophies was performed on the index case and the affected family members and revealed a p.Arg172Gln missense mutation in PRPH2 gene, leading to the diagnosis of central areolar choroidal dystrophy.

CONCLUSION

Multimodal imaging can reveal new pathogenic insights in central areolar choroidal dystrophy. Of notice, near-infrared autofluorescence and optical coherence tomography angiography are able to detect retinal pigment epithelium hypopigmentation and choriocapillaris rarefaction, respectively, since the earliest stages of the disease.

Monitoring Lesion Area Progression in Stargardt Disease: A Comparison of En Face Optical Coherence Tomography and Fundus Autofluorescence

Purpose

To compare longitudinal changes in en face spectral domain-optical coherence tomography (SD-OCT) measurements of ellipsoid zone (EZ) and retinal pigment epithelium (RPE) loss to changes in the hypoautofluorescent and hyperautofluorescent (AF) areas detected with short-wavelength (SW)-AF in ABCA4-associated retinopathy.

Methods

SD-OCT volume scans were obtained from 20 patients (20 eyes) over 2.6 ± 1.2 years (range 1-5 years). The EZ, and RPE/Bruch's membrane boundaries were segmented, and en face slab images generated. SubRPE and EZ slab images were used to measure areas of atrophic RPE and EZ loss. These were compared to longitudinal measurements of the hypo- and abnormal AF (hypoAF and surrounding hyperAF) areas.

Results

At baseline, the en face area of EZ loss was significantly larger than the subRPE atrophic area, and the abnormal AF area was significantly larger than the hypoAF area. The median rate of EZ loss was significantly greater than the rate of increase in the subRPE atrophic area (1.2 mm2/yr compared to 0.5 mm2/yr). The median rate of increase in the abnormal AF area was significantly greater than the increase in the hypoAF area (1.6 mm2/yr compared to 0.6 mm2/yr).

Conclusions

En face SD-OCT can be used to quantify changes in RPE atrophy and photoreceptor integrity. It can be a complementary or alternative technique to SW-AF with the advantage of monitoring EZ loss. The SW-AF results emphasize the importance of measuring changes in the hypo- and abnormal AF areas.

Translational Relevance

The findings are relevant to the selection of outcome measures for monitoring ABCA4-associated retinopathy.

Abnormal Appearance of the Area Centralis in Labrador Retrievers With an ABCA4 Loss-of-function Mutation

PURPOSE

To study retinal appearance and morphology in Labrador retrievers (LRs) heterozygous and homozygous for an ABCA4 loss-of-function mutation.

METHODS

Ophthalmic examination, including ophthalmoscopy and simple testing of vision, was performed in five ABCA4wt/wt, four ABCA4wt/InsC, and six ABCA4InsC/InsC LRs. Retinas were also examined with confocal scanning laser ophthalmoscopy (cSLO) and optical coherence tomography (OCT). Infrared and fundus autofluorescence (FAF) images were studied, and outer nuclear layer (ONL) and neuroretinal thickness were measured in the central and peripheral area centralis.

RESULTS

Clinical signs in young ABCA4InsC/InsC LRs were subtle, whereas ophthalmoscopic findings and signs of visual impairment were obvious in old ABCA4InsC/InsC LRs. Retinal appearance and vision testing was unremarkable in heterozygous LRs regardless of age. The cSLO/OCT showed abnormal morphology including ONL thinning, abnormal outer retinal layer segmentation, and focal loss of retinal pigment epithelium in the fovea equivalent in juvenile ABCA4InsC/InsC LRs. The abnormal appearance extended into the area centralis and visual streak in middle-aged ABCA4InsC/InsC and then spread more peripherally. A mild phenotype was seen on cSLO/OCT and FAF in middle-aged to old ABCA4wt/InsC LRs.

CONCLUSIONS

Abnormal appearance and morphology in the fovea equivalent are present in juvenile ABCA4InsC/InsC. In the older affected LRs, the visual streak and then the peripheral retina also develop an abnormal appearance. Vision deteriorates slowly, but some vision is retained throughout life. Older heterozygotes may show a mild retinal phenotype but no obvious visual impairment. The ABCA4InsC/InsC LR is a potential model for ABCA4-mediated retinopathies/juvenile-onset Stargardt disease in a species with human-sized eyes.

TRANSLATIONAL RELEVANCE

The ABCA4InsC mutation causes juvenile-onset abnormal appearance of the fovea equivalent in affected dogs that slowly spreads in the retina, while only a mild phenotype is seen in older carriers. This is the first non-primate, large-animal model for ABCA4-related/STGD1 retinopathies in a species with a fovea equivalent.

Comparisons Among Optical Coherence Tomography and Fundus Autofluorescence Modalities as Measurements of Atrophy in ABCA4-Associated Disease

Purpose

In ABCA4-associated retinopathy, central atrophy was assessed by spectral domain optical coherence tomography (SD-OCT) and by short-wavelength (SW-AF) and near-infrared (NIR-AF) autofluorescence.

Methods

Patients exhibited a central atrophic lesion characterized by hypoautofluorescence (hypoAF) surrounded either by hyperautofluorescent (hyperAF) rings in both AF images (group 1, 4 patients); or a hyperAF ring in SW-AF but not in NIR-AF images (group 2, 11 patients); or hyperAF rings in neither AF images (group 3, 11 patients). Choroidal hypertransmission and widths of ellipsoid zone (EZ) loss were measured in foveal SD-OCT scans, and in AF images hypoAF and total hypo+hyperAF widths were measured along the same axis. Bland-Altman and repeated measures analysis of variance with Tukey post hoc were applied.

Results

For all groups, hypertransmission widths were significantly smaller than EZ loss widths. In Groups 1 and 2, hypertransmission width was not significantly different than SW-hypoAF width, but hypertransmission was narrower than the width of SW-hypo+hyperAF (groups 1, 2) and NIR-hypo+hyperAF (group 1). In group 3, the hypertransmission width was also significantly less than the width of SW-hypoAF and NIR-hypoAF. The EZ loss widths were not significantly different than measurements of total lesion size, the latter being the widths of SW-hypo+hyperAF and NIR-hypo+hyperAF (group 1); widths of NIR-hypoAF and SW-hypo+hyperAF (group 2); and widths of NIR-hypoAF and SW-hypoAF (group 3).

Conclusions

Hypertransmission and SW-hypoAF (except when reflecting total lesion width) underestimate lesion size detected by EZ loss, SW-hypoAF+hyperAF, and NIR-hypo+hyperAF.

Translational Relevance

The findings are significant to the selection of outcome measures in clinical studies.

Stargardt disease: Multimodal imaging: A review

Stargardt disease (STGD1) is an autosomal recessive retinal dystrophy, characterised by bilateral progressive central vision loss and subretinal deposition of lipofuscin-like substances. Recent advances in molecular diagnosis and therapeutic options are complemented by the increasing recognition of new multimodal imaging biomarkers that may predict genotype and disease progression. Unique non-invasive imaging features of STDG1 are useful for gene variant interpretation and may even provide insight into the underlying molecular pathophysiology. In addition, pathognomonic imaging features of STGD1 have been used to train neural networks to improve time efficiency in lesion segmentation and disease progression measurements. This review will discuss the role of key imaging modalities, correlate imaging signs across varied STGD1 presentations and illustrate the use of multimodal imaging as an outcome measure in determining the efficacy of emerging STGD1 specific therapies.

Association of Near-Infrared and Short-Wavelength Autofluorescence With the Retinal Sensitivity in Eyes With Resolved Central Serous Chorioretinopathy

Purpose

The purpose of this study was to compare the results of near-infrared autofluorescence (NIRAF) and short-wavelength autofluorescence (SWAF) imaging of eyes with resolved central serous chorioretinopathy (CSC) and to assess the retinal sensitivity (RS) in areas with abnormal autofluorescence (AF) using white-on-white (WW) and blue-on-yellow (BY) perimetries.

Methods

We examined 20 consecutive eyes with resolved CSC. We calculated the areas of abnormal AF detected by SWAF and NIRAF imaging as SWAF_area and NIRAF_area, respectively, and the number of measurement points within and outside abnormal SWAF and NIRAF regions were counted. The results of WW and BY perimetries were superimposed on the AF images, and the mean overall RS within and outside abnormal SWAF and NIRAF regions were calculated using both WW and BY perimetries (W-RSin_SWAF, W-RSout_SWAF, W-RSin_NIRAF, W-RSout_NIRAF, B-RSin_SWAF, B-RSout_SWAF, B-RSin_NIRAF, and B-RSout_NIRAF, respectively).

Results

The mean age of the participants was 54.1 years. The SWAF_area was significantly smaller than the NIRAF_area (P < 0.0001, Wilcoxon signed rank test). A χ2 test suggested a significant relationship between the number of measurement points within/outside abnormal SWAF and NIRAF regions (P < 0.0001). In the results of measurement by WW perimetry, there was a significant difference between W-RSin_NIRAF and W-RSout_NIRAF (P < 0.0001), but not between W-RSin_SWAF and W-RSout_SWAF (P = 0.060, Wilcoxon rank sum test). In contrast, on BY perimetry, there were significant differences between both B-RSin_SWAF and B-RSout_SWAF and between B-RSin_NIRAF and B-RSout_NIRAF (P < 0.0001).

Conclusions

NIRAF was useful for predicting impaired RS in eyes with resolved CSC.

Retinal Pigment Epithelium Atrophy in Recessive Stargardt Disease as Measured by Short-Wavelength and Near-Infrared Autofluorescence

Purpose

To compare the detection of retinal pigment epithelium (RPE) atrophy in short-wavelength (SW-AF) and near-infrared autofluorescence (NIR-AF) images in Stargardt disease (STGD1) patients.

Methods

SW-AF and NIR-AF images (115 eyes from 115 patients) were analyzed by two independent graders. Hypoautofluorescent (hypoAF) areas, indicative of RPE atrophy, were measured, and the two modalities were compared.

Results

Patients were segregated into four groups: nascent (6 [5%]), widespread (21 [18%]), discrete (55 [48%]), and chorioretinal atrophy (33 [29%]). The areas of hypoAF were larger in NIR-AF compared to SW-AF images in discrete (3.9 vs. 2.2 mm², P < 0.001) and chorioretinal atrophy (12.7 vs. 11.4 mm², P = 0.015). Similar findings were observed qualitatively in nascent and widespread atrophy patients. Using the area linear model (ALM), lesion area increased at similar rates in SW-AF and NIR-AF images of discrete atrophy (0.20 vs. 0.32 mm²/y, P = 0.275) and chorioretinal atrophy (1.30 vs. 1.74 mm²/y, P = 0.671). Using the radius linear model (RLM), the lesion effective radius also increased similarly in SW-AF and NIR-AF images in discrete (0.03 vs. 0.05 mm²/y, P = 0.221) and chorioretinal atrophy (0.08 vs. 0.10 mm²/y, P = 0.754) patients.

Conclusions

NIR-AF reveals a larger area of RPE atrophy in STGD1 patients compared to SW-AF images, but rates of lesion enlargement in the two modalities are similar.

Translational Relevance

Measurements of RPE atrophy by AF imaging are crucial for monitoring STGD1 disease progression and given our findings we advocate greater use of NIR-AF for patients.

Artificial Intelligence for Automated Overlay of Fundus Camera and Scanning Laser Ophthalmoscope Images

Purpose

The purpose of this study was to evaluate the ability to align two types of retinal images taken on different platforms; color fundus (CF) photographs and infrared scanning laser ophthalmoscope (IR SLO) images using mathematical warping and artificial intelligence (AI).

Methods

We collected 109 matched pairs of CF and IR SLO images. An AI algorithm utilizing two separate networks was developed. A style transfer network (STN) was used to segment vessel structures. A registration network was used to align the segmented images to each. Neither network used a ground truth dataset. A conventional image warping algorithm was used as a control. Software displayed image pairs as a 5 × 5 checkerboard grid composed of alternating subimages. This technique permitted vessel alignment determination by human observers and 5 masked graders evaluated alignment by the AI and conventional warping in 25 fields for each image.

Results

Our new AI method was superior to conventional warping at generating vessel alignment as judged by masked human graders (P < 0.0001). The average number of good/excellent matches increased from 90.5% to 94.4% with AI method.

Conclusions

AI permitted a more accurate overlay of CF and IR SLO images than conventional mathematical warping. This is a first step toward developing an AI that could allow overlay of all types of fundus images by utilizing vascular landmarks.

Translational Relevance

The ability to align and overlay imaging data from multiple instruments and manufacturers will permit better analysis of this complex data helping understand disease and predict treatment.

Laser Pointer: A Possible Risk for the Retina

In recent years, an increasing incidence of laser pointer-associated retinal injuries has been observed, likely due to easy access to incorrectly classified laser pointers, their labelling as toys, and lack of awareness concerning the associated risk. Laser pointer exposure can lead to irreversible retinal damage and associated vision loss, depending on the wavelength, radiation power, duration of exposure, localization, and spot size. Pronounced retinal laser damage is especially seen in children and teenagers. The structural appearance of retinal laser pointer damage varies and, in some cases, may be a diagnostic challenge. Besides often subtle findings on optical coherence tomography examination, characteristic alterations on near-infrared autofluorescence imaging may be valuable for the diagnosis of retinal laser pointer injuries and for differentiating other retinal lesions with similar appearance. The increase in laser pointer injuries indicates that regulatory actions and increased public awareness are required regarding the dangers of laser pointers.

Analysis of retinal sublayer thicknesses and rates of change in ABCA4-associated Stargardt disease

Stargardt disease, the most common inherited macular dystrophy, is characterized by vision loss due to central retinal atrophy. Although clinical trials for Stargardt are currently underway, the disease is typically slowly progressive, and objective, imaging-based biomarkers are critically needed. In this retrospective, observational study, we characterize the thicknesses of individual retinal sublayers by macular optical coherence tomography (OCT) in a large cohort of patients with molecularly-confirmed, ABCA4-associated Stargardt disease (STGD1) relative to normal controls. Automated segmentation of retinal sublayers was performed with manual correction as needed, and thicknesses in various macular regions were compared using mixed effects models. Relative to controls (42 eyes, 40 patients), STGD1 patients (107 eyes, 63 patients) had slight thickening of the nerve fiber layer and retinal pigment epithelium-Bruch’s membrane, with thinning in other sublayers, especially the outer nuclear layer (ONL) (p < 0.0015). When comparing the rate of retinal sublayer thickness change over time (mean follow-up 3.9 years for STGD1, 2.5 years for controls), STGD1 retinas thinned faster than controls in the outer retina (ONL to photoreceptor outer segments). OCT-based retinal sublayer thickness measurements are feasible in STGD1 patients and may provide objective measures of disease progression or treatment response.

Progressive Choriocapillaris Impairment in ABCA4 Maculopathy Is Secondary to Retinal Pigment Epithelium Atrophy

Purpose

To analyze the progression of choriocapillaris (CC) impairment in recessive Stargardt disease (STGD) and compare it to the progression of retinal pigment epithelium (RPE) atrophy.

Methods

Fifty-five patients with a clinical diagnosis of STGD and genetic confirmation of pathogenic biallelic variants in ABCA4 were imaged with short-wavelength fundus autofluorescence (SW-AF) and optical coherence tomography angiography (OCTA) at a single clinic visit, whereas a subset of 12 patients were imaged with the same modalities at two different clinic visits.

Results

We observed three stages of CC impairment: an area of bright yet intact macular CC (11 patients), regions of vascular rarefaction and incomplete CC atrophy within an area of bright CC (10 patients), and areas of extensive CC atrophy (26 patients). These changes correlated to the degree of RPE atrophy observed in SW-AF imaging. Furthermore, 8 patients presented with early changes on SW-AF, but healthy CC. Quantitative analyses of the atrophic changes revealed that the area of RPE atrophy is larger (9.6 ± 1.7 mm2 vs. 6.9 ± 1.3 mm2, P < 0.001) and that it progresses at a faster rate (1.1 ± 0.1 mm2/year vs. 0.8 ± 0.2 mm2/year, P = 0.004) than the corresponding area of CC atrophy.

Conclusions

CC impairment is progressive and OCTA imaging can be used to demonstrate the stages, which culminate in extensive CC atrophy. Furthermore, CC impairment is secondary to RPE atrophy in STGD. We further advocate the use of SW-AF and OCTA imaging in monitoring the progression of STGD.

Factors Influencing Retinal Pigment Epithelium-Atrophy Progression Rate in Stargardt Disease

Purpose

To evaluate demographic, clinical, imaging, and genetic factors associated with retinal pigment epithelium enlargement in Stargardt disease (STGD1) and to measure the agreement between short-wavelength fundus autofluorescence (SW-FAF) and near-infrared fundus autofluorescence (NIR-FAF).

Methods

Retrospective cohort study of patients with STGD1 with ≥2 gradable SW-FAF images. RPE-atrophy areas were measured on SW-FAF and NIR-FAF at each visit and regressed against time to obtain the rate of RPE-atrophy enlargement. Agreement between SW-FAF and NIR-FAF with regards to baseline atrophic areas and rates of enlargement was evaluated. Baseline factors predictive of faster SW-FAF RPE-atrophy enlargement were investigated with linear mixed models.

Results

Fifty-four eyes of 28 patients (median age: 45 years; 13 males) were included. SW-FAF and NIR-FAF agreed well for slow rates of RPE-atrophy progression, but agreement decreased as the rate increased. Median (interquartile range [IQR]) rate of RPE-atrophy expansion was 0.18 (0.10–0.85) mm²/year on SW-FAF and 0.24 (0.08–0.33) mm²/year on NIR-FAF. Larger baseline RPE-atrophy area (estimate: 0.057 mm²/year, P < 0.001), worse visual acuity (0.305 mm²/year, P = 0.005), multifocal disease (0.401 mm²/year, P = 0.02), and SW-FAF pattern (0.534 mm²/year, P =0 .03) were associated with a faster rate of progression (predictive R²: 0.65).

Conclusions

SW-FAF and NIR-FAF are not interchangeable in the evaluation of RPE-atrophy enlargement, and both imaging modalities may be required for optimal detection of disease progression. A multivariable model based on baseline clinical and imaging information may identify patients at higher risk of fast disease progression.

Translational Relevance

The knowledge of the agreement of different FAF modalities, the estimated rates of RPE-atrophy enlargement, and factors predictive of faster anatomic decay in STGD1 may allow tailored clinical management and better clinical trials design.

Short-Wavelength and Near-Infrared Autofluorescence in Patients with Deficiencies of the Visual Cycle and Phototransduction

Fundus autofluorescence is a valuable imaging tool in the diagnosis of inherited retinal dystrophies. With the advent of gene therapy and the numerous ongoing clinical trials for inherited retinal degenerations, quantifiable and reliable outcome measurements continually need to be identified. In this retrospective analysis, normalized and non-normalized short-wavelength (SW-AF) and near-infrared (NIR-AF) autofluorescence images of ten patients with mutations in visual cycle (VC) genes and nineteen patients with mutations in phototransduction (PT) genes were analyzed. Normalized SW-AF and NIR-AF images appeared darker in all patients with mutations in the VC as compared to patients with mutations in PT despite the use of significantly higher detector settings for image acquisition in the former group. These findings were corroborated by quantitative analysis of non-normalized SW-AF and NIR-AF images; signal intensities were significantly lower in all patients with mutations in VC genes as compared to those with mutations in PT genes. We conclude that qualitative and quantitative SW-AF and NIR-AF images can serve as biomarkers of deficiencies specific to the VC. Additionally, quantitative autofluorescence may have potential for use as an outcome measurement to detect VC activity in conjunction with future therapies for patients with mutations in the VC.

A distinct retinal pigment epithelial cell autofluorescence pattern in choroideremia predicts early involvement of overlying photoreceptors

PURPOSE

Choroideremia is an X-linked retinal disease characterized by early retinal pigment epithelium (RPE) loss and subsequent retinal degeneration. The RPE adopts either a smooth or mottled appearance on fundus autofluorescence (FAF). It is not known how RPE changes predict the health of the overlying ellipsoid zone (EZ).

METHODS

A retrospective review of FAF and optical coherence tomography (OCT) images from 20 patients with choroideremia was performed. The percentage of intact EZ in each smooth and mottled FAF region was determined using one horizontal trans-foveal OCT section.

RESULTS

Fourteen out of 20 patients had distinct smooth and mottled areas in both eyes and were included in the sub-analysis. On average, 62.5 ± 10.1% of the EZ in each smooth region of the right eyes was intact compared to 10.0 ± 4.3% in the mottled areas. The same trend was observed in left eyes: 76.5 ± 7.2% of the EZ was intact in the smooth regions versus 9.8 ± 3.9% in the mottled areas (two-way anova, p < 0.0001). Thus, the mottled FAF regions were associated with EZ disruption more so than the smooth areas.

CONCLUSION

Retinal pigment epithelium (RPE) changes correlate with the health of the overlying EZ in choroideremia. The smooth FAF region likely represents early stages of the disease, with most of the area containing preserved EZ, whereas the mottled zone indicates more advanced stages and has mostly disrupted EZ. Because of the clear relationship between FAF findings and EZ integrity, FAF imaging can be used to monitor disease progression and identify areas of preserved EZ that could be rescued by gene therapy.

Abnormal Visual Function Outside the Area of Atrophy Defined by Short-Wavelength Fundus Autofluorescence in Stargardt Disease

Purpose

To examine the extent of visual function abnormality outside the dark lesion on short-wavelength fundus autofluorescence (SW-AF), and its correlation with background SW-AF features and optical coherence tomography (OCT) in recessive Stargardt disease (STGD1).

Methods

Forty-nine eyes of 25 participants in the ProgStar (the Natural History of the Progression of Atrophy Secondary to Stargardt Disease) study at our center were included. Patients underwent microperimetry (both threshold and dense scotoma mapping), OCT, SW-AF, and visual acuity testing. The Fisher's exact test, the χ2 test, and unpaired t-tests were used to analyze the data.

Results

Of 40 eyes without central fixation, 33 (82%) placed fixation remote (most ≥5°) from the dense scotoma edge, despite good intervening retinal sensitivity. OCT findings accounted for the remote fixation in 75%. Eighteen (37%) of all 49 eyes had dense scotoma extending past the dark lesion border. OCT was not adequate to define the edge of the scotoma. Of the 49 eyes, 28 (57%) had the mottled background pattern, 10 (20%) had the uniform pattern, and 11 (22%) had the other pattern, with >75% of eyes in each pattern having remote fixation. The dense scotoma exceeded the dark lesion primarily in the mottled pattern. The two eyes of each patient were concordant in all features.

Conclusions

Functional abnormalities in STGD1 extend past the SW-AF dark lesion. The disruption of the ellipsoid zone shows that photoreceptor abnormality extends peripheral to the dark lesion, and it explains in part the remote fixation pattern and the dense scotoma exceeding the dark lesion. This has implications for clinical trials for STGD1.

Peripapillary Sparing With Near Infrared Autofluorescence Correlates With Electroretinographic Findings in Patients With Stargardt Disease

Purpose

To evaluate the correlation between the quantification of peripapillary sparing and electroretinogram (ERG) outcomes in autosomal recessive Stargardt disease (STGD1).

Methods

Near infrared fundus autofluorescence (NIR-FAF) images of 101 eyes of 101 patients were retrospectively reviewed. Peripapillary sparing was assessed both qualitatively and quantitatively. The area of spared tissue (AST) was calculated in a 1-mm-wide ring around the optic disc after binarization of the 55° NIR-FAF. These measurements were correlated with the presence of normal ERG (group I), abnormal photopic responses (group II), or abnormal photopic and scotopic responses (group III).

Results

AST showed significant correlations with ERG groups (R = -0.802, P < 0.001). While qualitative assessment of peripapillary sparing (i.e., present or not) also showed a significant correlation with ERG groups (R = -0.435, P < 0.001), it was weaker than by AST quantification. The ordinal regression analysis showed that the increase in AST was associated with a decrease in the odds of belonging to ERG groups II and III, with an odds ratio of 0.82 (95% confidence interval [CI] 0.78-0.87), P < 0.001.

Conclusions

The AST around the optic disc in eyes with STGD1 correlates with the impairment of photoreceptors as shown in the ERG. If replicated in future longitudinal studies, the quantification of peripapillary sparing may prove to be a useful parameter for evaluating the visual prognosis of these eyes.

Functional Relevance and Structural Correlates of Near Infrared and Short Wavelength Fundus Autofluorescence Imaging in ABCA4-Related Retinopathy

Purpose

To evaluate the functional relevance and structural correlates of autofluorescence (AF) alterations under short-wavelength (SW) and near-infrared (NIR) excitation light in ABCA4-related retinopathy.

Methods

In this prospective, cross-sectional case series, 88 eyes of 44 patients with ABCA4-related retinopathy (mean age, 37.6 years; range, 9-77 years) underwent SW-AF and NIR-AF imaging. The AF images were graded for disease characteristic patterns by two independent readers and correlated with alterations in optical coherence tomography (OCT) and impairment of retinal sensitivity along a foveo-papillary line assessed by fundus-controlled microperimetry.

Results

A centrifugal sequence of AF patterns from atrophic lesions to homogeneous background was found for both AF modalities. The eccentricity of each AF pattern in NIR-AF was larger compared to those in SW-AF (P < 0.001). Increasing eccentricity of each pattern correlated with increasing retinal sensitivity. The distant border of the zone of hyperfluorescent flecks in SW-AF and hypoautofluorescent flecks in NIR-AF correlated with the margins of the ellipsoid zone loss in OCT (r = 0.979 and r = 0.971, P < 0.001). The expansion of hypofluorescent flecks in SW-AF was associated with the boundaries of external limiting membrane loss (r = 0.933, P < 0.001).

Conclusions

SW-AF and NIR-AF revealed a characteristic sequence of AF patterns that correlated with functional and structural alterations, suggesting different stages in disease progression.

Translational Relevance

Alterations in NIR-AF exceeded those in SW-AF images, substantiating the hypothesis of different AF origins and suggesting NIR-AF as surrogate marker for early disease-related changes.

Improved Diagnosis of Retinal Laser Injuries Using Near-Infrared Autofluorescence

PURPOSE

To assess whether near infrared autofluorescence (NIR-AF) imaging is a useful imaging modality in the diagnosis of handheld laser retinal injuries.

DESIGN

Retrospective observational case series.

METHODS

Twelve patients identified to have handheld laser retinal injuries were included at 2 academic centers. Patients underwent ophthalmic assessment and retinal imaging including fundus photography, optical coherence tomography (OCT), conventional blue autofluorescence (B-AF), and NIR-AF imaging.

RESULTS

In all cases, lesions consistent with retinal laser injury were detected by NIR-AF imaging. The lesions showed a characteristic appearance with central hyperfluorescence and surrounding hypofluorescence, although the number and extent of lesions varied between patients. Findings using other imaging modalities were variable: on color fundus photography these included localized pigmentary changes and on OCT imaging an ellipsoid zone interruption or outer nuclear layer changes. Only subtle changes were evident on B-AF imaging. Other macular conditions, such as poppers retinopathy or solar maculopathy, which may have similar findings on OCT imaging as laser damage, can be differentiated using NIR-AF imaging.

CONCLUSION

An increased incidence of retinal injuries secondary to handheld lasers has been reported in recent years. We show that the diagnosis and full extent of retinal laser injuries is best demonstrated by NIR-AF, as other modalities give variable results. We propose that NIR-AF should be included when investigating patients suspected of macular injury secondary to exposure to handheld lasers.

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.

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.

Monitoring and Management of the Patient with Stargardt Disease

Stargardt disease (STGD1) represents one of the major common causes of inherited irreversible visual loss. Due to its high phenotypic and genotypic heterogeneity, STGD1 is a complex disease to understand. Non-invasive imaging, biochemical, and genetic advances have led to substantial improvements in unveiling the disease processes and novel promising therapeutic landscapes have been proposed. This review recapitulates the modalities for monitoring patients with STGD1 and the therapeutic options currently under investigation for the different stages of the disease.

Quantitative Comparison of Near-infrared Versus Short-wave Autofluorescence Imaging in Monitoring Progression of Retinitis Pigmentosa

PURPOSE

To quantitatively compare near-infrared autofluorescence (NIR-AF) and short-wave autofluorescence (SW-AF) as imaging modalities used to monitor retinitis pigmentosa (RP) disease progression, measured as a function of hyperautofluorescent ring constriction over time.

DESIGN

Retrospective cohort study.

METHODS

NIR-AF and SW-AF images were acquired from 22 participants (44 eyes) at 2 clinic visits separated by an average of 2 years. On the images from each modality, the horizontal and vertical diameters and area of the hyperautofluorescent rings were measured twice, 2 weeks apart. A progression rate for each parameter was obtained. Descriptive and comparative statistics were calculated to analyze these parameters and their respective progression rates.

RESULTS

At both visits, the hyperautofluorescent ring exhibited a larger horizontal diameter (both visits: P < .001), vertical diameter (visit 1: P < .001, visit 2: P = .040), and ring area (visit 1: P = .001, visit 2: P = .011) in SW-AF vs NIR-AF images. In SW-AF, the horizontal diameter, vertical diameter, and ring area decreased yearly by 168 ± 204 μm, 131 ± 159 μm, and 0.7 ± 1.1 mm², respectively, while in NIR-AF, they decreased by 151 ± 156 μm, 135 ± 190 μm, and 0.7 ± 1.0 mm². No difference was observed in these rates between SW-AF and NIR-AF. Similar results were observed in the left eye.

CONCLUSIONS

In SW-AF and NIR-AF images, similar rates of RP disease progression are observed. As such, NIR-AF may confer more advantages as the primary tool for tracking disease progression over the commonly used SW-AF, given the increased patient comfort and cooperation during imaging.

ELLIPSOID ZONE MAPPING AND OUTER RETINAL ASSESSMENT IN STARGARDT DISEASE

PURPOSE

To quantify and correlate ellipsoid zone and photoreceptor outer segment changes with visual acuity in Stargardt disease.

METHODS

An institutional review board-approved study of 32 eyes with Stargardt disease was performed. After spectral domain optical coherence tomography, the macular cube was exported into a novel analysis tool and volumetric assessment from the ellipsoid zone to the retinal pigment epithelium was performed. Using this information, mapping was completed with en face representation of the height between the ellipsoid zone and retinal pigment epithelium. This analysis provided quantification of ellipsoid zone and photoreceptor outer segments, including atrophy (ellipsoid zone to retinal pigment epithelium thickness = 0 μm) and attenuation (ellipsoid zone to retinal pigment epithelium thickness <20 μm). These parameters were compared with visual acuity and controls (n = 12 eyes).

RESULTS

Visual acuity ranged from 20/30 to 20/250. The central foveal B-scan area of ellipsoid and photoreceptor outer segments was significantly less than controls (0.13 ± 0.05 mm vs. 0.17 ± 0.03 mm, respectively, P = 0.0074). The central foveal B-scan mean thickness measured 22.52 ± 9.0 μm in Stargardt versus 30.0 ± 5.08 μm (P = 0.0096). Atrophy and attenuation were significantly higher in Stargardt patients (22% vs. 1%, P = 0.005 and 43% vs. 1%, P = 0.0002). Visual acuity directly correlated with ellipsoid zone/outer segment volume (R = 0.57, P < 0.005) and inversely correlated with attenuation and atrophy (R = -0.53 and -0.57; P < 0.005 for all).

CONCLUSION

Eyes with Stargardt disease frequently have significant disruption of the ellipsoid zone and outer segments. This degenerative change was successfully quantified with a novel assessment platform and identified correlates with visual function. This software provides the opportunity for quantitative assessment and possible longitudinal surveillance.

ULTRAWIDEFIELD AUTOFLUORESENCE IN ABCA4 STARGARDT DISEASE

PURPOSE

To report the ultrawidefield fundus autofluorescence (UWF-FAF) patterns in ABC4A Stargardt disease.

METHODS

A retrospective cohort study of patients with a clinical diagnosis of Stargardt disease, confirmed ABCA4 genotype, and ultrawidefield fundus autofluorescence imaging using an Optos P200Tx. Four independent graders evaluated the images. Ultrawidefield fundus autofluorescence images were evaluated for the presence of posterior pole and peripheral findings, and were classified into one of three types (Type I: lesions confined to the macula with no peripheral findings; Type II: macular atrophy with flecks only in the periphery; Type III: macular atrophy and varying degrees of peripheral atrophy).

RESULTS

Ultrawidefield fundus autofluorescence was performed on 58 eyes of 29 patients. Reviews of images revealed the presence of peripheral (outside the 55° view of standard nonwidefield FAF imaging) alterations on UWF-FAF in 76% of eyes. Overall, the UWF-FAF pattern was classified as Type I in 24% eyes (14/58), Type II in 24% (14/58), and Type III in 52% (30/58). The most common genetic mutations were c.2588G>C (6/29 patients, 20.7%), and c.5882G>A (5/29 patients, 17.2%).

CONCLUSION

Ultrawidefield fundus autofluorescence reveals peripheral changes in the majority of patients with Stargardt disease. Peripheral FAF changes may have implications for diagnosis, prognosis, and management of individual patients with Stargardt disease.

Multimodal imaging including semiquantitative short-wavelength and near-infrared autofluorescence in achromatopsia

Multimodal imaging provides insights into phenotype and disease progression in inherited retinal disorders. Congenital achromatopsia (ACHM), a cone dysfunction syndrome, has been long considered a stable condition, but recent evidence suggests structural progression. With gene replacement strategies under development for ACHM, there is a critical need for imaging biomarkers to define progression patterns and follow therapy. Using semiquantitative plots, near-infrared (NIR-AF) and short-wavelength autofluorescence (SW-AF) were explored and correlated with clinical characteristics and retinal structure on optical coherence tomography (OCT). In sixteen ACHM patients with genetic confirmation (CNGA3, n = 8; CNGB3, n = 7; PDE6C, n = 1), semiquantitative plots allowed the detailed analysis of autofluorescence patterns, even in poorly fixating eyes. Twelve eyes showed perifoveal hyperautofluorescent rings on SW-AF, and 7 eyes had central hypoautofluorescent areas on NIR-AF, without association between these alterations (P = 0.57). Patients with central NIR-AF hypoautofluorescence were older (P = 0.004) and showed more advanced retinal alterations on OCT than those with normal NIR-AF (P = 0.051). NIR-AF hypoautofluorescence diameter was correlated to patient age (r = 0.63, P = 0.009), size of ellipsoid zone defect on OCT (r = 0.67, P = 0.005), but not to the size of SW-AF hyperautofluorescence (P = 0.27). These results demonstrate the interest of NIR-AF as imaging biomarker in ACHM, suggesting a relationship with age and disease progression.

Quantifying the Rate of Ellipsoid Zone Loss in Stargardt Disease

PURPOSE

To determine a reliable method of using the ellipsoid zone (EZ) on optical coherence tomography (OCT) to track disease progression in Stardgardt disease (STGD).

DESIGN

Retrospective reliability study.

METHODS

STGD patients with genetically confirmed ABCA4 gene mutations seen at the Wilmer Eye Institute with follow-up visits separated by at least 12 months were identified. Spectral-domain optical coherence tomography (SD-OCT) macula volume scans centered at the fovea and fundus autofluorescence (FAF) images were obtained. The area of EZ loss was calculated from the SD-OCT and the area of retinal pigment epithelium (RPE) loss from the FAF. Scans were reanalyzed by the primary grader to assess intragrader reliability, and reanalyzed by a second grader to assess intergrader reliability.

RESULTS

Sixteen STGD patients (total of 31 eyes) were followed for a mean of 2 years (range 1-4.7 years). The mean rate of EZ loss, 0.31 ± 0.31 mm²/year, was similar to the average rate of RPE loss, 0.33 ± 0.38 mm²/year. The average area of EZ loss at the initial examination, 4.18 ± 1.91 mm², was larger than the initial area of RPE loss, 2.25 ± 1.66 mm² (P < .01). The absolute difference of the area of EZ loss on test-retest for the first grader was 0.12 ± 0.10 mm², and between graders 0.21 ± 0.21 mm². The intraclass correlation (ICC) of both intragrader and intergrader reliability for EZ loss was excellent at 0.99.

CONCLUSIONS

Tracking the area of EZ loss on SD-OCT macular volume scans longitudinally is a reliable way of monitoring disease progression in STGD. This could be used as a sensitive anatomic outcome measure in clinical trials related to STGD.

Progression of Stargardt Disease as Determined by Fundus Autofluorescence in the Retrospective Progression of Stargardt Disease Study (ProgStar Report No. 9)

Importance

Sensitive outcome measures for disease progression are needed for treatment trials of Stargardt disease.

Objective

To describe the yearly progression rate of atrophic lesions in the retrospective Progression of Stargardt Disease study.

Design, Setting, and Participants

A multicenter retrospective cohort study was conducted at tertiary referral centers in the United States and Europe. A total of 251 patients aged 6 years or older at baseline, harboring disease-causing variants in ABCA4 (OMIM 601691), enrolled in the study from 9 centers between August 2, 2013, and December 12, 2014; of these patients, 215 had at least 2 gradable fundus autofluorescence images with atrophic lesion(s) present in at least 1 eye.

Exposures

Areas of definitely decreased autofluorescence (DDAF) and questionably decreased autofluorescence were quantified by a reading center. Progression rates were estimated from linear mixed models with time as the independent variable.

Main Outcomes and Measures

Yearly rate of progression using the growth of atrophic lesions measured by fundus autofluorescence.

Results

A total of 251 participants (458 study eyes) were enrolled. Images from 386 eyes of 215 participants (126 females and 89 males; mean [SD] age, 29.9 [14.7] years; mean [SD] age of onset of symptoms, 21.9 [13.3] years) showed atrophic lesions present on at least 2 visits and were graded for 2 (156 eyes), 3 (174 eyes), or 4 (57 eyes) visits. A subset of 224 eyes (123 female participants and 101 male participants; mean [SD] age, 33.0 [15.1] years) had areas of DDAF present on at least 2 visits; these eyes were included in the estimation of the progression of the area of DDAF. At the first visit, DDAF was present in 224 eyes (58.0%), with a mean (SD) lesion size of 2.2 (2.7) mm2. The total mean (SD) area of decreased autofluorescence (DDAF and questionably decreased autofluorescence) at first visit was 2.6 (2.8) mm2. Mean progression of DDAF was 0.51 mm2/y (95% CI, 0.42-0.61 mm2/y), and of total decreased fundus autofluorescence was 0.35 mm2/y (95% CI, 0.28-0.43 mm2/y). Rates of progression depended on the initial size of the lesion.

Conclusions and Relevance

In Stargardt disease with DDAF lesions, fundus autofluorescence may serve as a monitoring tool for interventional clinical trials that aim to slow disease progression. Rates of progression depended mainly on initial lesion size.

A Comparison of En Face Optical Coherence Tomography and Fundus Autofluorescence in Stargardt Disease

Purpose

To compare morphologic changes on en face images derived from wide-field swept-source optical coherence tomography (ssOCT) to hypo- and hyperautofluorescent (hypoAF, hyperAF) areas on short-wavelength autofluorescence (SW-AF), and near-infrared (NIR)-AF in recessive Stargardt disease (STGD1).

Methods

Wide-field ssOCT cube scans were obtained from 16 patients (16 eyes). Averaged B-scans and SW-AF images were obtained using Spectralis HRA+OCT. NIR-AF images were obtained from 6 eyes. The inner/outer segment (IS/OS), OS/RPE, and RPE/Bruch's membrane boundaries were segmented, and en face slab images generated. A subRPE slab image was used to measure the abnormal RPE area, and an IS/OS slab image, the IS/OS junction loss area. These were compared to hypo- and abnormal SW-AF areas, and hypoNIR-AF areas. A preRPE(OS) slab image was used to evaluate the spatial and intraretinal locations of flecks.

Results

For all eyes, RPE atrophy was visualized as a central hyperreflective area on the subRPE slab, and IS/OS junction loss as an abnormal reflective area on the IS/OS slab; the latter was significantly larger (P = 0.04). There was good agreement between the hyperreflective area on the subRPE slab image and hypoSW-AF area, and between the abnormal reflective area on the IS/OS slab and hypo-hyperSW-AF area; the hypoNIR-AF area indicated that the hyperreflective area on the subRPE slab underestimated RPE atrophy. The spatial locations of hyperreflective flecks on the en face preRPE(OS) slab image corresponded to those on the SW-AF images.

Conclusions

Wide-field en face OCT imaging has the potential to be a clinically useful tool for the management of STGD1.

En Face Spectral-Domain Optical Coherence Tomography for the Monitoring of Lesion Area Progression in Stargardt Disease

Purpose

We investigated the progression of Stargardt disease (STGD1) over a multiyear follow-up by evaluating the macular lesion area as computed by an automatic algorithm from spectral-domain optical coherence tomography (SD-OCT).

Methods

We reviewed medical records of STGD1 patients, with a clinical and molecular diagnosis of STGD1 at a single institution, who underwent best-corrected visual acuity (BCVA), fundus photography, SD-OCT, full-field electroretinography, and, when available, fundus autofluorescence (FAF). Regression models were fitted on the selected clinical parameters; in particular, on the macular lesion area computed by SD-OCT, to evaluate the disease progression over a multiyear follow-up.

Results

The comparison between SD-OCT and FAF, available for 22 patients, showed that macular lesion area, assessed by SD-OCT, significantly correlated with the area of absent FAF (P < 0.001). Moreover, the longitudinal analysis, performed in 98 patients, showed a significant enlargement of macular lesion area at an estimated exponential rate of 4.6% per year (P = 0.046), together with a significant worsening of BCVA (0.06 logMAR per year; P < 0.001) and a significant decrease of macular thickness (1.6% per year; P = 0.005) over the follow-up.

Conclusions

The current study describes, for the first time in literature, a longitudinal analysis of the macular lesion area assessed by SD-OCT in STGD1 disease, showing a significant progression over the follow-up. Our findings suggest that the evaluation of macular lesion area by en face SD-OCT, together with FAF, could drive the choice of the most amenable candidates and the most suitable area to be treated in gene therapy clinical trials.

Multimodal analysis of the Preferred Retinal Location and the Transition Zone in patients with Stargardt Disease

PURPOSE

The purpose of our study was to investigate morpho-functional features of the preferred retinal location (PRL) and the transition zone (TZ) in a series of patients with recessive Stargardt disease (STGD1).

METHODS

Fifty-two STGD1 patients with at least one ABCA4 mutation, atrophy of the central macula (MA) and an eccentric PRL were recruited for the study. Microperimetry, fundus autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT) were performed. The location and stability of the PRL along with the associated FAF pattern and visual sensitivities were determined and compared to the underlying retinal structure.

RESULTS

The mean visual sensitivity of the PRLs for the 52 eyes was 10.76 +/- 3.70 dB. For the majority of eyes, PRLs were associated with intact ellipsoid zone (EZ) bands and qualitatively normal FAF patterns. In 17 eyes (32.7%) the eccentric PRL was located at the edge of the MA. In 35 eyes (67.3%) it was located at varying distances from the border of the MA with a TZ between the PRL and the MA. The TZ was associated with decreased sensitivity values (5.92 +/- 4.69 dB) compared to PRLs (p<0.05), with absence/disruption of the EZ band and abnormal FAF patterns (hyper or hypo-autofluorescence).

CONCLUSIONS

In STGD1 eccentric PRLs are located away from the border of MA and associated with intact EZ bands and normal FAF. The TZ is characterized by structural and functional abnormalities. The results of multimodal imaging of the PRL and TZ suggest a possible sequence of retinal and functional changes with disease progression that may help in the planning of future therapies; RPE dysfunction appears to be the primary event leading to photoreceptor degeneration and then to RPE loss.

Correlating Photoreceptor Mosaic Structure to Clinical Findings in Stargardt Disease

Purpose

To demonstrate a method for correlating photoreceptor mosaic structure with optical coherence tomography (OCT) and microperimetry findings in patients with Stargardt disease.

Methods

A total of 14 patients with clinically diagnosed Stargardt disease were imaged using confocal and split-detection adaptive optics scanning light ophthalmoscopy. Cone photoreceptors were identified manually in a band along the temporal meridian. Resulting values were compared to a normative database (n = 9) to generate cone density deviation (CDD) maps. Manual measurement of outer nuclear layer plus Henle fiber layer (ONL+HFL) thickness was performed, in addition to determination of the presence of ellipsoid zone (EZ) and interdigitation zone (IZ) bands on OCT. These results, along with microperimetry data, were overlaid with the CDD maps.

Results

Wide variation in foveal structure and CDD maps was seen within this small group. Disruption of ONL+HFL and/or IZ band was seen in all patients, with EZ band preservation in regions with low cone density in 38% of locations analyzed. Normality of retinal lamellar structure on OCT corresponded with cone density and visual function at 50/78 locations analyzed. Outer retinal tubulations containing photoreceptor-like structures were observed in 3 patients.

Conclusions

The use of CDD color-coded maps enables direct comparison of cone mosaic local density with other measures of retinal structure and function. Larger normative datasets and improved tools for automation of image alignment are needed.

Translational Relevance

The approach described facilitates comparison of complex multimodal data sets from patients with inherited retinal degeneration, and can be expanded to incorporate other structural imaging or functional testing.

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.

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.