Symptomatic abnormalities of dark adaptation in patients with EFEMP1 retinal dystrophy (Malattia Leventinese/Doyne honeycomb retinal dystrophy)

Electrophysiological Evaluation of Macular Dystrophies

Macular dystrophies are a heterogeneous group of genetic disorders that often severely threatens the bilateral central vision of the affected patient. While advances in molecular genetics have been instrumental in the understanding and diagnosis of these disorders, there remains significant phenotypical variation among patients within any particular subset of macular dystrophies. Electrophysiological testing remains a vital tool not only to characterize vision loss for differential diagnosis but also to understand the pathophysiology of these disorders and to monitor the treatment effect, potentially leading to therapeutic advances. This review summarizes the application of electrophysiological testing in macular dystrophies, including Stargardt disease, bestrophinopathies, X-linked retinoschisis, Sorsby fundus dystrophy, Doyne honeycomb retina dystrophy, autosomal dominant drusen, occult macular dystrophy, North Carolina macular dystrophy, pattern dystrophy, and central areolar choroidal dystrophy.

The second Japanese family with Malattia Leventinese/Doyne honeycomb retinal dystrophy

PURPOSE

To describe the clinical and genetic findings of patients in the second Japanese family with Malattia Leventinese/Doyne honeycomb retinal dystrophy (ML/DHRD).

METHODS

Two patients (a 41-year-old male proband and his third son) underwent comprehensive ophthalmic examinations, including full-field and multifocal electroretinography (ERG). Sanger sequencing was performed to detect an EFEMP1 gene variant (p.Arg345Trp), which was identified as the only causative pathogenic variant.

RESULTS

Genetic analysis revealed that both patients carried the heterozygous variant, but the other unaffected family members did not. Although the proband exhibited innumerable radially distributed drusen in both the posterior poles and good visual acuity at initial presentation, bilateral choroidal neovascularization (CNV) developed during the 15-year follow-up. The proband received 15 intravitreal anti-vascular endothelial growth factor (VEGF) injections in the left eye (LE) and two injections in the right eye (RE). At 56 years of age, his decimal best-corrected visual acuity was 0.1 and 1.2 in the LE and RE, respectively. Full-field ERG showed that while the rod and combined responses were within normal amplitudes, the cone and 30-Hz flicker responses had slightly decreased amplitudes. Multifocal ERG revealed attenuated central responses in the LE and decreased temporal responses in the RE. In the 20-year-old son, multifocal ERG showed normal responses in both eyes.

CONCLUSION

This is the first report of ML/DHRD in a patient who developed bilateral CNV and received anti-VEGF treatment in both eyes. Although multifocal ERG exhibited worsening of macular function, the generalized photoreceptor function was preserved until middle age.

Impaired cholesterol efflux in retinal pigment epithelium of individuals with juvenile macular degeneration

Macular degeneration (MD) is characterized by the progressive deterioration of the macula and represents one of the most prevalent causes of blindness worldwide. Abnormal intracellular accumulation of lipid droplets and pericellular deposits of lipid-rich material in the retinal pigment epithelium (RPE) called drusen are clinical hallmarks of different forms of MD including Doyne honeycomb retinal dystrophy (DHRD) and age-related MD (AMD). However, the appropriate molecular therapeutic target underlying these disorder phenotypes remains elusive. Here, we address this knowledge gap by comparing the proteomic profiles of induced pluripotent stem cell (iPSC)-derived RPEs (iRPE) from individuals with DHRD and their isogenic controls. Our analysis and follow-up studies elucidated the mechanism of lipid accumulation in DHRD iRPE cells. Specifically, we detected significant downregulation of carboxylesterase 1 (CES1), an enzyme that converts cholesteryl ester to free cholesterol, an indispensable process in cholesterol export. CES1 knockdown or overexpression of EFEMP1R345W, a variant of EGF-containing fibulin extracellular matrix protein 1 that is associated with DHRD and attenuated cholesterol efflux and led to lipid droplet accumulation. In iRPE cells, we also found that EFEMP1R345W has a hyper-inhibitory effect on epidermal growth factor receptor (EGFR) signaling when compared to EFEMP1WT and may suppress CES1 expression via the downregulation of transcription factor SP1. Taken together, these results highlight the homeostatic role of cholesterol efflux in iRPE cells and identify CES1 as a mediator of cholesterol efflux in MD.

Age-related macular degeneration masqueraders: From the obvious to the obscure

Age-related macular degeneration (AMD) is one of the leading causes of blindness worldwide with increasing prevalence owing to increased life expectancy. Intravitreal injections of antivascular endothelial growth factor agents are commonly used in exudative AMD and oral antioxidant medication for nonexudative AMD; however, many disorders mimic exudative and nonexudative AMD, and misdiagnosis can seriously affect the management of these patients. We summarize the demographics and clinical and imaging characteristics of each of the conditions that masquerade as AMD. As some of the conditions have features of AMD, a short update on the classical features of AMD is also included.

Late-onset night blindness with peripheral flecks accompanied by progressive trickle-like macular degeneration

PURPOSE

To report the clinical and genetic characteristics of 6 cases with late-onset night blindness with peripheral flecks accompanied by progressive trickle-like macular degeneration.

METHODS

Clinical and genetic data were collected from 6 independent patients who complained of night blindness in their fifth to eighth decade of life. The ophthalmological examinations included ophthalmoscopy, fundus autofluorescence (FAF), and full-field electroretinography (ERG). Whole exome sequencing with target gene analysis was performed to determine the causative genes and variants.

RESULTS

All of the patients first complained of night blindness at the ages of 40-71 years. Funduscopic examinations demonstrated white or atrophic flecks scattered in the posterior pole and peripheral retina bilaterally. FAF showed patchy hypo-autofluorescence spots in the posterior pole similar to that of the trickling type of age-related macular degeneration (AMD). The region of abnormal FAF rapidly expanded with age, and one eye developed a choroidal neovascularization. The full-field scotopic ERGs with 20 min of dark adaptation were severely reduced or extinguished in all cases. There was partial recovery of the ERGs after 180 min of dark adaptation. The cone ERGs were reduced in all cases. Whole exome sequencing revealed no pathogenic variants of 301 retinal disease-associated genes.

CONCLUSIONS

The six cases had some common features with the flecked retina syndrome, familial drusen, and late-onset retinal degeneration although none had pathogenic variants causative for these disorders. These cases may represent a subset of severe trickling AMD or a new clinical entity of acquired pan-retinal visual cycle deficiency of unknown etiology.

Doyne honeycomb retinal dystrophy/malattia leventinese induced by EFEMP1 mutation in a Chinese family

Background

Doyne honeycomb retinal dystrophy (DHRD)/malattia leventinese (ML) is a rare allelic condition with massive drusen in the posterior fundus caused by EFEMP1 gene mutation. Patients showed decreased vision when the lesion affected the macular area. At present, the treatment efficiency is not satisfactory.

Case presentation

In this study, we presented a family with DHRD/ML disease and analyzed the pathological and genetic information. A 28-year-old female patient presented to our department due to impaired visual acuity for 10 years especially in the right eye with deterioration for 5 months. Gene sequencing was performed by MyGenostics (Peking, China). Gene sequencing results revealed heterozygous mutations in EFEMP1 gene, which were consistent with the DHRD/ ML. Single heterozygous mutation (c.1033C > T) was observed in each of the three blood samples. This missense mutation triggered p.R345W.

Conclusions

DHRD/ML is a rare disease associated with EFEMP1 gene mutation. Up to now, we are not sure whether these lesions are associated with the onset of DHRD/ML. In future, we hope to find out the exact relationship between them.

Acquired color vision deficiency

Acquired color vision deficiency occurs as the result of ocular, neurologic, or systemic disease. A wide array of conditions may affect color vision, ranging from diseases of the ocular media through to pathology of the visual cortex. Traditionally, acquired color vision deficiency is considered a separate entity from congenital color vision deficiency, although emerging clinical and molecular genetic data would suggest a degree of overlap. We review the pathophysiology of acquired color vision deficiency, the data on its prevalence, theories for the preponderance of acquired S-mechanism (or tritan) deficiency, and discuss tests of color vision. We also briefly review the types of color vision deficiencies encountered in ocular disease, with an emphasis placed on larger or more detailed clinical investigations.

Correlation of Type 1 Neovascularization Associated With Acquired Vitelliform Lesion in the Setting of Age-Related Macular Degeneration

PURPOSE

To correlate postmortem histology with previously recorded multimodal imaging from a patient with type 1 neovascularization (NV) associated with an acquired vitelliform lesion in the setting of age-related macular degeneration (AMD).

DESIGN

Case study.

METHODS

Multimodal imaging that was obtained antemortem was matched with ex vivo and high-resolution histologic images of the preserved donor macula. Anatomic correlates for multimodal imaging findings were then defined.

RESULTS

Spectral-domain optical coherence tomography (OCT) revealed a split in the retinal pigment epithelium-Bruch membrane band. Type 1 NV in this case was composed of 6 layered components: (1) retinal pigment epithelium, (2) basal laminar deposits, (3) fibrovascular membrane, (4) fibrocellular scar, (5) hemorrhage, and (6) Bruch membrane. The anatomic correlates for the hyporeflective band on spectral-domain OCT included a thick basal laminar deposit. Not all structures could be readily separated on the basis of their reflectivity patterns.

CONCLUSIONS

This is an important clinicopathologic correlation of NV secondary to AMD in the spectral-domain OCT era. Our findings of 6 layers include and extend the anatomic framework encapsulated by the double-layer and triple-layer signs. The resolution of current devices does not always permit distinction of the different layers of NV tissue. Thick basal laminar deposits may appear hyporeflective on spectral-domain OCT and may be confused with fluid from a neovascular process. It will be important to perform a larger clinicopathologic series to aid our anatomic interpretation of spectral-domain OCT images.

Best vitelliform macular dystrophy: literature review

Best vitelliform macular dystrophy (BVD) is a slowly progressive form of macular dystrophy. In most cases this disease begins in childhood although sometimes it can develop in later age. The diagnosis of BVD is based on family history, clinical and electrophysiological findings. Clinical signs are variable, yet the majority of patients have a typical yellow yolk-like macular lesion in the eye fundus. Lesions are usually bilateral, but in rare cases can be unilateral. Atrophy of the macula may develop after many years. The mutations responsible for Best vitelliform macular dystrophy are found in a gene called VMD2, which encodes a transmembrane protein named bestrophin-1 (hBest1) that is a Ca2+-sensitive chloride channel. Most reported cases causing the disease are in exons 2, 4, 6 and 8 in patients with BVD. In this article we discuss the etiology of Best’s vitelliform macular dystrophy, clinical presentation, diagnostics, genetic and current treatment possibilities.

A CTRP5 gene S163R mutation knock-in mouse model for late-onset retinal degeneration

Late-onset retinal macular degeneration (L-ORD) is an autosomal dominant inherited disorder caused by a single missense mutation (S163R) in the CTRP5/C1QTNF5 protein. Early phenotypic features of L-ORD include: dark adaptation abnormalities, nyctalopia, and drusen deposits in the peripheral macular region. Apart from posterior segment abnormalities, these patients also develop abnormally long anterior lens zonules. In the sixth decade of life the rod and cone function declines, accompanied by electroretinogram (ERG) abnormalities. Some patients also develop choroidal neovascularization and glaucoma. In order to understand the disease pathology and mechanisms involved in retinal dystrophy, we generated a knock-in (Ctrp5(+/-)) mouse model carrying the disease-associated mutation in the mouse Ctrp5/C1QTNF5 gene. These mice develop slower rod-b wave recovery consistent with early dark adaptation abnormalities, accumulation of hyperautofluorescence spots, retinal pigment epithelium abnormalities, drusen, Bruch's membrane abnormalities, loss of photoreceptors, and retinal vascular leakage. The Ctrp5(+/-) mice, which have most of the pathological features of age-related macular degeneration, are unique and may serve as a valuable model both to understand the molecular pathology of late-onset retinal degeneration and to evaluate therapies.

A novel haplotype with the R345W mutation in the EFEMP1 gene associated with autosomal dominant drusen in a Japanese family

PURPOSE

To describe ophthalmic and molecular genetic findings in a family of Japanese patients with Malattia leventinese (ML)/Doyne honeycomb retinal dystrophy (DHRD), also known as autosomal dominant drusen.

METHODS

Four patients with ML/DHRD, including a 42-year-old female proband, were ascertained. The proband underwent complete ophthalmic examinations, including fundus and electrodiagnostic investigations, and Humphrey visual field (VF) perimetry. Mutation screening of the EFEMP1 gene and haplotype analysis were performed in the family, an Indian ML/DHRD family, and a branch of 1 of 39 ML/DHRD families in the United States, in which all affected patients shared a common haplotype.

RESULTS

A heterozygous missense mutation (p.R345W) was identified in all four Japanese patients and in affected patients of the other two families. This mutation was the only mutation that has been exclusively found in the gene. The disease haplotype in the Japanese family was different from those of the other two families. Clinically, central retinas were prominently affected in the proband and her mother, and subsequently the proband developed subfoveal choroidal neovascularization in the left eye, whereas her younger sister with the mutation, who was asymptomatic, exhibited only fine macular drusen. Long-term follow-up of Humphrey VF and multifocal-electroretinography (mfERG) in the proband also revealed progressive attenuation of macular function in the right eye.

CONCLUSIONS

This is the first report to describe a Japanese family with variable expressivity of ML/DHRD, in which a novel disease haplotype was identified. Humphrey VF and mfERG testing may be helpful in determining the long-term outcome of macular function.

ABCA4-associated retinal degenerations spare structure and function of the human parapapillary retina

PURPOSE

To study the parapapillary retinal region in patients with ABCA4-associated retinal degenerations.

METHODS

Patients with Stargardt disease or cone-rod dystrophy and disease-causing variants in the ABCA4 gene were included. Fixation location was determined under fundus visualization, and central cone-mediated vision was measured. Intensity and texture abnormalities of autofluorescence (AF) images were quantified. Parapapillary retina of an eye donor with ungenotyped Stargardt disease was examined microscopically.

RESULTS

AF images ranged from normal, to spatially homogenous abnormal increase of intensity, to a spatially heterogenous speckled pattern, to variably sized patches of low intensity. A parapapillary ring of normal-appearing AF was visible at all disease stages. Quantitative analysis of the intensity and texture properties of AF images showed the preserved region to be an annulus, at least 0.6 mm wide, surrounding the optic nerve head. A similar region of relatively preserved photoreceptor nuclei was apparent in the donor retina. In patients with foveal fixation, there was better cone sensitivity at a parapapillary locus in the nasal retina than at the same eccentricity in the temporal retina. In patients with eccentric fixation, approximately 30% had a preferred retinal locus in the parapapillary retina.

CONCLUSIONS

Human retinal degenerations caused by ABCA4 mutations spare the structure of retina and RPE in a circular parapapillary region that commonly serves as the preferred fixation locus when central vision is lost. The retina between fovea and optic nerve head could serve as a convenient, accessible, and informative region for structural and functional studies to determine natural history or outcome of therapy in ABCA4-associated disease.