Novel mutations in the 3-box motif of the BACK domain of KLHL7 associated with nonsyndromic autosomal dominant retinitis pigmentosa

Background

Mutations in the Kelch-like protein 7 (KLHL7) represent a recently described and, to date, poorly characterized etiology of inherited retinal dystrophy. Dominant mutations in KLHL7 are a cause of isolated, non-syndromic retinitis pigmentosa (RP). In contrast, recessive loss-of-function mutations are known to cause Crisponi or Bohring-Opitz like cold induced sweating syndrome-3 (BOS-3). In this study, the phenotype and progression of five unrelated patients with KLHL7 mediated autosomal dominant RP (adRP) are characterized. Clinical evaluation of these patients involved a complete ophthalmic exam, full-field electroretinography (ffERG), and imaging, including fundus photography, spectral domain optical coherence tomography (SD-OCT), short wavelength fundus autofluorescence (SW-AF), and near-infrared fundus autofluorescence (NIR-AF). Molecular diagnoses were performed using whole-exome sequencing or gene panel testing. Disease progression was monitored in three patients with available data for a mean follow up time of 4.5 ± 2.9 years. Protein modeling was performed for all variants found in this study in addition to those documented in the literature for recessive loss-of-function alleles causing Crisponi or Bohring-Opitz like cold-induced sweating syndrome.

Results

Genetic testing in three patients identified two novel variants within the 3-box motif of the BACK domain: c.472 T > C:p.(Cys158Arg) and c.433A > T:p.(Asn145Tyr). Clinical imaging demonstrated hyperautofluorescent ring formation on both SW-AF and NIR-AF in three patients, with diffuse peripheral and peripapillary atrophy seen in all but one case. SD-OCT demonstrated a phenotypic spectrum, from parafoveal atrophy of the outer retina with foveal sparing to widespread retinal thinning and loss of photoreceptors. Incidence of cystoid macular edema was high with four of five patients affected. Protein modeling of dominant alleles versus recessive loss-of-function alleles showed dominant alleles localized to the BTB and BACK domains while recessive alleles were found in the Kelch domain.

Conclusions

We report the phenotype in five patients with KLHL7 mediated adRP, two novel coding variants, and imaging biomarkers using SW-AF and NIR-AF. These findings may influence future gene-based therapies for adRP and pave the way for mechanistic studies that elucidate the pathogenesis of KLHL7-mediated RP.

Investigation and Restoration of BEST1 Activity in Patient-derived RPEs with Dominant Mutations

BEST1 is a Ca2+-activated Cl- channel predominantly expressed in retinal pigment epithelium (RPE), and over 250 genetic mutations in the BEST1 gene have been identified to cause retinal degenerative disorders generally known as bestrophinopathies. As most BEST1 mutations are autosomal dominant, it is of great biomedical interest to determine their disease-causing mechanisms and the therapeutic potential of gene therapy. Here, we characterized six Best vitelliform macular dystrophy (BVMD)-associated BEST1 dominant mutations by documenting the patients' phenotypes, examining the subcellular localization of endogenous BEST1 and surface Ca2+-dependent Cl- currents in patient-derived RPEs, and analyzing the functional influences of these mutations on BEST1 in HEK293 cells. We found that all six mutations are loss-of-function with different levels and types of deficiencies, and further demonstrated the restoration of Ca2+-dependent Cl- currents in patient-derived RPE cells by WT BEST1 gene supplementation. Importantly, BEST1 dominant and recessive mutations are both rescuable at a similar efficacy by gene augmentation via adeno-associated virus (AAV), providing a proof-of-concept for curing the vast majority of bestrophinopathies.

Compound heterozygous novel frameshift variants in the PROM1 gene result in Leber congenital amaurosis

The PROM1 (prominin 1) gene encodes an 865-amino acid glycoprotein that is expressed in retinoblastoma cell lines and in the adult retina. The protein is localized to photoreceptor outer segment disc membranes, where it plays a structural role, and in the retinal pigment epithelium (RPE), where it acts as a cytosolic protein that mediates autophagy. Mutations in PROM1 are typically associated with cone-rod dystrophy 12 (OMIM#3612657), autosomal dominant retinal macular dystrophy 2 (OMIM#608051), autosomal recessive retinitis pigmentosa 41 (OMIM#612095), and Stargardt disease 4 (OMIM#603786). Here we describe the first case of PROM1-associated Leber congenital amaurosis (LCA) in a 12-yr-old Asian male, caused by two not previously described deleterious frameshift variants in the compound heterozygous state. Clinical features include the presence of bull's eye maculopathy, pendular horizontal nystagmus, and photodysphoria consistent with the clinical diagnosis of LCA. The patient was evaluated using ophthalmic imaging, electroretinography, and whole-exome sequencing. Electroretinography revealed extinguished retinal activity.

Characterization of Retinal Structure in ATF6-Associated Achromatopsia

Purpose

Mutations in six genes have been associated with achromatopsia (ACHM): CNGA3, CNGB3, PDE6H, PDE6C, GNAT2, and ATF6. ATF6 is the most recent gene to be identified, though thorough phenotyping of this genetic subtype is lacking. Here, we sought to test the hypothesis that ATF6-associated ACHM is a structurally distinct form of congenital ACHM.

Methods

Seven genetically confirmed subjects from five nonconsanguineous families were recruited. Foveal hypoplasia and the integrity of the ellipsoid zone (EZ) band (a.k.a., IS/OS) were graded from optical coherence tomography (OCT) images. Images of the photoreceptor mosaic were acquired using confocal and nonconfocal split-detection adaptive optics scanning light ophthalmoscopy (AOSLO). Parafoveal cone and rod density values were calculated and compared to published normative data as well as data from two subjects harboring CNGA3 or CNGB3 mutations who were recruited for comparative purposes. Additionally, nonconfocal dark-field AOSLO images of the retinal pigment epithelium were obtained, with quantitative analysis performed in one subject with ATF6-ACHM.

Results

Foveal hypoplasia was observed in all subjects with ATF6 mutations. Absence of the EZ band within the foveal region (grade 3) or appearance of a hyporeflective zone (grade 4) was seen in all subjects with ATF6 using OCT. There was no evidence of remnant foveal cone structure using confocal AOSLO, although sporadic cone-like structures were seen in nonconfocal split-detection AOSLO. There was a lack of cone structure in the parafovea, in direct contrast to previous reports.

Conclusions

Our data demonstrate a near absence of cone structure in subjects harboring ATF6 mutations. This implicates ATF6 as having a major role in cone development and suggests that at least a subset of subjects with ATF6-ACHM have markedly fewer cellular targets for cone-directed gene therapies than do subjects with CNGA3- or CNGB3-ACHM.

Spectrum of Disease Severity and Phenotype in Choroideremia Carriers

PURPOSE

To characterize and bring awareness to the disease spectrum of female choroideremia patients, as severity can vary from mild to severe disease, comparable to that observed in male patients.

DESIGN

Retrospective cohort study.

METHODS

Twelve female carriers of disease-causing variants in the CHM gene confirmed by molecular genetic sequencing were characterized clinically and imaged with short-wave fundus autofluorescence (SW-FAF), spectral-domain optical coherence tomography (OCT), and color fundus imaging.

RESULTS

Twelve unrelated female patients with a clinical and genetic diagnosis of choroideremia carriers were included in this study. Disease severity among these phenotypes ranged from mild to severe, resembling the typical presentation of choroideremia in male patients. Mild disease presented with retinal pigment epithelium mottling, a patchy pattern of hypoautofluorescent speckles on SW-FAF, and intact retinal layers on spectral-domain OCT. Severe disease presented with widespread chorioretinal atrophy as shown by SW-FAF and spectral-domain OCT. Each of the identified genetic variants in CHM was predicted to be disease-causing according to in silico prediction software. Disease progression analysis of 4 patients with follow-up showed a decline in visual acuity for 2 patients, with progression observed on spectral-domain OCT in 1 of the patients. No significant disease progression on SW-FAF was observed for any of the patients.

CONCLUSIONS

Female carriers of choroideremia can present with a wide range of clinical phenotypes and disease severity, from mild to severe disease, similar to male subjects. Symptomatic female subjects should be considered for current and upcoming gene replacement therapy clinical trials.

Multimodal Imaging in Best Vitelliform Macular Dystrophy

Purpose

In patients diagnosed with Best vitelliform macular dystrophy (BVMD), quantitative fundus autofluorescence (qAF), near-infrared fundus autofluorescence (NIR-AF), and spectral-domain optical coherence tomography (SD-OCT) were used to elucidate pathogenic mechanisms.

Methods

Fourteen patients heterozygous for BEST1 mutations were recruited. qAF was analyzed using short-wavelength fundus autofluorescence (SW-AF) images. Mean gray levels (GL) were determined in nonlesion areas (7 to 9° eccentricity) and adjusted by GL measured in an internal fluorescent reference. NIR-AF images (787 nm; sensitivity of 96) were captured and saved in non-normalized mode. Horizontal SD-OCT images also were acquired and BVMD was staged according to the OCT findings.

Results

In the pre-vitelliform stage, NIR-AF imaging revealed an area of reduced fluorescence, whereas in the vitelliruptive stage, puncta of elevated NIR-AF signal were present. In both SW-AF and NIR-AF images, the vitelliform lesion in the atrophic stage was marked by reduced signal. At all stages of BVMD, nonlesion qAF was within the 95% confidence intervals for healthy eyes. Similarly, the NIR-AF intensity measurements outside the vitelliform lesion were comparable to the healthy control eye. SD-OCT scans revealed a fluid-filled detachment between the ellipsoid zone and the hyperreflectivity band attributable to RPE/Bruch's membrane.

Conclusions

NIR-AF imaging can identify the pre-vitelliform stage of BVMD. Mutations in BEST1 are not associated with increased levels of SW-AF outside the vitelliform lesion. Elevated SW-AF within the fluid-filled lesion likely reflects the inability of RPE to phagocytose outer segments due to separation of RPE from photoreceptor cells, together with progressive photoreceptor cell impairment.

Novel REEP6 gene mutation associated with autosomal recessive retinitis pigmentosa

PURPOSE

This study reports the ophthalmic and genetic findings of a Cameroonian patient with autosomal recessive retinitis pigmentosa (arRP) caused by a novel Receptor Expression Enhancing Protein 6 (REEP6) homozygous mutation.

PATIENT AND METHODS

A 33-year-old man underwent comprehensive ophthalmic examinations, including visual acuity measurements, dilated fundus imaging, electroretinography (ERG), and spectral-domain optical coherence tomography (SD-OCT). Short-wavelength fundus autofluorescence (SW-AF) and near-infrared fundus autofluorescence (NIR-AF) were also evaluated. Whole exome sequencing (WES) was used to identify potential pathogenic variants.

RESULTS

Fundus examination revealed typical RP findings with additional temporal ten micron yellow dots. SD-OCT imaging revealed cystoid macular edema and perifoveal outer retinal atrophy with centrally preserved inner segment ellipsoid zone (EZ) bands. Hyperreflective spots were seen in the inner retinal layers. On SW-AF images, a hypoautofluorescent area in the perifoveal area was observed. NIR-AF imaging revealed an irregularly shaped hyperautofluorescent ring. His visual acuity was mildly affected. ERG showed undetectable rod responses and intact cone responses. Genetic testing via WES revealed a novel homozygous mutation (c.295G>A, p.Glu99Lys) in the gene encoding REEP6, which is predicted to alter the charge in the transmembrane helix.

CONCLUSIONS

This report is not only the first description of a Cameroonian patient with arRP associated with a REEP6 mutation, but also this particular genetic alteration. Substitution of p.Glu99Lys in REEP6 likely disrupts the interactions between REEP6 and the ER membrane. NIR-AF imaging may be particularly useful for assessing functional photoreceptor cells and show an "avocado" pattern of hyperautofluorescence in patients with the REEP6 mutation.

Modification of the PROM1 disease phenotype by a mutation in ABCA4

Background: The extensive phenotypic heterogeneity of monogenic diseases can be largely traced to intragenic variation; however, recent advances in clinical detection and gene sequencing have uncovered the emerging role of non-allelic variation (i.e. genetic trans-modifiers) in shaping disease phenotypes. Identifying these associations are not only of significant diagnostic value, but also provides scientific insight into the expanded molecular etiology of rare diseases. This reports describes the discordant clinical manifestation of a family segregating mutations in ABCA4 and PROM1. Methods: Three patients across a two generation family underwent multimodal imaging and functional testing of the retina including color photography, fundus autofluorescence (AF), spectral domain-optical coherence tomography (SD-OCT) and full-field electroretinography (ffERG). Genetic characterization was carried out by direct Sanger and whole exome sequencing. Results: Clinical examination revealed similar retinal degenerative phenotypes in the proband and her mother. Despite being younger, the proband's phenotype was more advanced and exhibited additional features related to Stargardt disease not found in the mother. Whole exome sequencing identified a pathogenic missense variant in PROM1, c.400C > T, p.(Arg134Cys), as the underlying cause of retinal disease in both the proband and mother. Sequencing of the ABCA4 locus uncovered a single disease-causing variant, c.5714 + 5G > A in the daughter segregating from the father who, surprisingly, also exhibited very subtle disease changes associated with STGD1 despite being a heterozygous carrier. Conclusions: Harboring an additional heterozygous ABCA4 mutation increases severity and confers STGD1-like features in patients with PROM1 disease which provides supporting evidence for their shared pathophysiology and potential treatment prospects.

Mechanisms of neurodegeneration in a preclinical autosomal dominant retinitis pigmentosa knock-in model with a RhoD190N mutation

D190N, a missense mutation in rhodopsin, causes photoreceptor degeneration in patients with autosomal dominant retinitis pigmentosa (adRP). Two competing hypotheses have been developed to explain why D190N rod photoreceptors degenerate: (a) defective rhodopsin trafficking prevents proteins from correctly exiting the endoplasmic reticulum, leading to their accumulation, with deleterious effects or (b) elevated mutant rhodopsin expression and unabated signaling causes excitotoxicity. A knock-in D190N mouse model was engineered to delineate the mechanism of pathogenesis. Wild type (wt) and mutant rhodopsin appeared correctly localized in rod outer segments of D190N heterozygotes. Moreover, the rhodopsin glycosylation state in the mutants appeared similar to that in wt mice. Thus, it seems plausible that the injurious effect of the heterozygous mutation is not related to mistrafficking of the protein, but rather from constitutive rhodopsin activity and a greater propensity for chromophore isomerization even in the absence of light.

CAPN5 genetic inactivation phenotype supports therapeutic inhibition trials

Small molecule pharmacological inhibition of dominant human genetic disease is a feasible treatment that does not rely on the development of individual, patient-specific gene therapy vectors. However, the consequences of protein inhibition as a clinical therapeutic are not well-studied. In advance of human therapeutic trials for CAPN5 vitreoretinopathy, genetic inactivation can be used to infer the effect of protein inhibition in vivo. We created a photoreceptor-specific knockout (KO) mouse for Capn5 and compared the retinal phenotype to both wild-type and an existing Capn5 KO mouse model. In humans, CAPN5 loss-of-function (LOF) gene variants were ascertained in large exome databases from 60,706 unrelated subjects without severe disease phenotypes. Ocular examination of the retina of Capn5 KO mice by histology and electroretinography showed no significant abnormalities. In humans, there were 22 LOF CAPN5 variants located throughout the gene and in all major protein domains. Structural modeling of coding variants showed these LOF variants were nearby known disease-causing variants within the proteolytic core and in regions of high homology between human CAPN5 and 150 homologs, yet the LOF of CAPN5 was tolerated as opposed to gain-of-function disease-causing variants. These results indicate that localized inhibition of CAPN5 is a viable strategy for hyperactivating disease alleles.

CLIC4 regulates late endosomal trafficking and matrix degradation activity of MMP14 at focal adhesions in RPE cells

Dysregulation in the extracellular matrix (ECM) microenvironment surrounding the retinal pigment epithelium (RPE) has been implicated in the etiology of proliferative vitreoretinopathy and age-related macular degeneration. The regulation of ECM remodeling by RPE cells is not well understood. We show that membrane-type matrix metalloproteinase 14 (MMP14) is central to ECM degradation at the focal adhesions in human ARPE19 cells. The matrix degradative activity, but not the assembly, of the focal adhesion is regulated by chloride intracellular channel 4 (CLIC4). CLIC4 is co-localized with MMP14 in the late endosome. CLIC4 regulates the proper sorting of MMP14 into the lumen of the late endosome and its proteolytic activation in lipid rafts. CLIC4 has the newly-identified “late domain” motif that binds to MMP14 and to Tsg101, a component of the endosomal sorting complex required for transport (ESCRT) complex. Unlike the late domain mutant CLIC4, wild-type CLIC4 can rescue the late endosomal sorting defect of MMP14. Finally, CLIC4 knockdown inhibits the apical secretion of MMP2 in polarized human RPE monolayers. These results, taken together, demonstrate that CLIC4 is a novel matrix microenvironment modulator and a novel regulator for late endosomal cargo sorting. Moreover, the late endosomal sorting of MMP14 actively regulates its surface activation in RPE cells.

Choroidal neovascularization in an adolescent with RDH12-associated retinal degeneration

Background: Leber congenital amaurosis (LCA) due to RDH12 mutations typically manifests with severe vision loss and panretinal dystrophy. We sought to describe a case of LCA with choroidal neovascularization (CNV) in a 17-year-old patient. Materials and Methods: Case report of a 17-year old with LCA who presented with acute central vision loss of the right eye in the context of a chronic retinal dystrophy. Multimodal retinal imaging including spectral-domain optical coherence tomography and indocyanine green angiography revealed CNV. Results: A 17-year-old boy with previously diagnosed LCA/early-onset retinal dystrophy (EOSRD), with subsequently identified biallelic mutations in RDH12 was found to have type 2 CNV. Patient was treated with intravitreal ranibizumab and exhibited improvement on follow-up exam. Conclusions: Choroidal neovascularization may be a unique occurrence in RDH12-associated retinal dystrophy. Successful treatment of the neovascularization could be accomplished with intravitreal antivasogenic therapy.

Comparison of structural progression between ciliopathy and non-ciliopathy associated with autosomal recessive retinitis pigmentosa

BACKGROUND

To evaluate and compare the progression of ciliopathy and non-ciliopathy autosomal recessive Retinitis Pigmentosa patients (arRP) by measuring the constriction of hyperautofluorescent rings in fundus autofluorescence (FAF) images and the progressive shortening of the ellipsoid zone line width obtained by spectral-domain optical coherence tomography (SD-OCT).

RESULTS

For the ciliopathy group, the estimated mean shortening of the ellipsoid zone line was 259 μm per year and the ring area decreased at a rate of 2.46 mm² per year. For the non-ciliopathy group, the estimated mean shortening of the ellipsoid zone line was 84 μm per year and the ring area decreased at a rate of 0.7 mm² per year.

CONCLUSIONS

Our study was able to quantify and compare the loss of EZ line width and short-wavelength autofluorescence (SW-AF) ring constriction progression over time for ciliopathy and non-ciliopathy arRP genes. These results may serve as a basis for modeling RP disease progression, and furthermore, they could potentially be used as endpoints in clinical trials seeking to promote cone and rod survival in RP patients.

Non-paraneoplastic related retinopathy: clinical challenges and review

Autoimmune retinopathy (AIR) is a rare inflammatory condition characterized by progressive visual loss, abnormalities in visual fields and electroretinographic exams, along with presence of circulating anti-retinal antibodies. There are two main forms of AIR: paraneoplastic AIR (pAIR) and presumed non-paraneoplastic AIR (npAIR). NpAIR is considered a diagnosis of exclusion, since it is typically made after other causes of retinopathy have been investigated and the absence of malignancy is confirmed. Work-up of a npAIR case is challenging since there are no standartizaded protocols for diagnosis and treatment. The treatment regimen may vary from case to case, and it can be best guided by a set of parameters including electrophysiological responses, visual outcomes, and presence of anti-retinal antibodies. The purpose of this review is to summarize the principal clinical features, investigation, and management of npAIR.

Pattern Dystrophy

The pattern dystrophies of the retinal pigment epithelium (RPE) include a group of disorders: Butterfly-type pattern dystrophy (Figs. 17.1, 17.2, 17.3, 17.4 and 17.5) Adult-onset foveomacular vitelliform dystrophy Sjögren's reticular-type pattern dystrophy Fundus pulverulentus.

Rod Monochromatism (Achromatopsia)

Rod monochromatism (achromatopsia) is a congenital cone photoreceptor disorder, which is rare, affecting about 1 in 30,000 individuals. These patients have normal rod function but no detectable cone function; therefore, everything they see is in shades of gray (total color blindness). Patients usually present in infancy with nystagmus and photophobia. Vision is usually about 20/200 or worse; patients have a hyperopic refractive error. Some patients show paradoxical pupillary response; that is, the pupils dilate in bright light. Fundus examination is normal, though pigmentary mottling and atrophic changes may be observed at the macula. Incomplete achromatopsia: Patients in this group have somewhat better visual acuity, about 20/80 to 20/120, with some residual functioning of cone photoreceptors. This milder form allows some color discrimination. Complete achromatopsia: It occurs in about 4-10% of Pingelapese islanders, who live on one of the Eastern Caroline Islands of Micronesia.

VCAN Canonical Splice Site Mutation is Associated With Vitreoretinal Degeneration and Disrupts an MMP Proteolytic Site

Purpose

To gain insight into the pathophysiology of vitreoretinal degeneration, the clinical course of three family members with Versican Vitreoretinopathy (VVR) is described, and a canonical splice site mutation in the gene encoding for versican (VCAN) protein was biochemically analyzed.

Methods

A retrospective chart review, human eye histopathology, Sanger DNA sequencing, protein structural modeling, and in vitro proteolysis assays were performed.

Results

The proband (II:1), mother (I:2), and younger sibling (II:2) suffered retinal degeneration with foveal sparing and retinal detachments with proliferative vitreoretinopathy, features that were confirmed on histopathologic analysis. All affected members carried a heterozygous adenine to guanine variant (c.4004-2A>G) predicted to result in exon 8 skipping or the deletion of 13 amino acids at the beginning of the GAGβ chain (VCAN p.1335-1347). This deleted region corresponded to a putative MMP cleavage site, validated using fluorescence resonance energy transfer (FRET)-based proteolysis assays. Proteomic network analysis identified 10 interacting partners in the human vitreous and retina linked to retinal detachment and degeneration.

Conclusions

VVR causes significant ocular disease, including retinal detachment and retinal dystrophy. The intronic VCAN mutation removes an MMP cleavage site, which alters versican structure and results in abnormal vitreous modeling. Disruption of a versican protein network may underlie clinicopathologic disease features and point to targeted therapies.

Correlation between B-scan optical coherence tomography, en face thickness map ring and hyperautofluorescent ring in retinitis pigmentosa patients

OBJECTIVE

To evaluate and compare the B-scan OCT loss of ellipsoid zone, OCT en face thickness map constriction, and hyperautofluorescent ring constriction in RP patients.

METHODS

Retrospective case series study. Forty-eight eyes of 24 RP patients with a parafoveal hyperautofluorescent ring were studied. The diagnosis of RP was established by the presence of rod response impairment and a prevalent decrease of scotopic over photopic responses on electroretinography. The FAF and spectral-domain optical coherence tomography (SD-OCT) images were obtained from 24 patients with RP. The measurements of the EZ line width on B-scan OCT, hyperautofluorescent ring area on FAF, and hyperautofluorescent ring area on en face thickness map were performed by two independent graders. The measurements of these three parameters were correlated.

RESULTS

The mean age of study patients was 46 years old (sd = 19). The external and internal FAF rings involving the fovea were identified in all study eyes. The area of the thickness ring decreased at an average rate of 0.5 (sd 0.4) mm² per year (P < 0.001). The average rate of EZ-line constriction was estimated to be 123 (sd 63) μm per year (P < 0.001). The hyperautofluorescent ring area decreased at an average rate of 0.9 (sd 0.98) mm² per year (P < 0.001). The strongest correlation was observed between hyperautofluorescent ring area and EZ-line width (r = 0.78).

CONCLUSIONS

We observed that the hyperautofluorescent ring area exhibits a faster progression rate than the area of the thickness ring. In addition, we found that the EZ-line width had a high positive correlation with the hyperautofluorescent ring area and a moderate positive correlation with area of the thickness ring.

Insights into Retinal Development Using Live Imaging in Female Carriers of Choroideremia

Lineage tracing can provide key insights into the development of tissues, such as the retina. Yet it is not possible to manipulate human cells during embryogenesis. The authors observed a distinct phenotype in female carriers of X-linked disorders, in particular, carriers of choroideremia caused by mutations in CHM, encoding Rab escort protein-1. The authors found that X chromosome inactivation provides a method for retinal lineage tracing in human patients. Live imaging of female carriers displays a developmental pattern that is different within the peripheral retina compared with the posterior retina and provides important insights into the development and migration of retinal cells. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e158-e162.].

Multi-platform imaging in ABCA4-Associated Disease

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

Optical Coherence Tomography Angiography of RPGR-Associated Retinitis Pigmentosa Suggests Foveal Avascular Zone is a Biomarker for Vision Loss

RPGR-associated retinitis pigmentosa (RP) is a progressive disease with retina degeneration. Optical coherence tomography angiography (OCTA) is an imaging technique that provides novel insights. The authors report two affected male siblings who underwent OCTA imaging. The area of the foveal avascular zone (FAZ) was measured. Although the younger sibling exhibited more advanced clinical disease, his visual acuity was superior to his older sibling. OCTA imaging revealed a better preserved FAZ in the younger sibling as the reason for this. It also highlighted attenuation of choriocapillaris / choroid layers as biomarkers for disease severity. This provides new insights into retinal degeneration in RPGR-associated RP. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e44-e48.].