Heritability of Choroidal Thickness in the Amish

Longitudinal Retinal and Choroidal Image Analysis in a Set of Monozygotic Twins

We analyzed multimodal retinal and choroidal imaging, including optical coherence tomography (OCT) and OCT angiography (OCTA), to assess differences and characterize variations in the retinal and choroidal structure and microvasculature between healthy monozygotic twins without ocular or systemic pathology over a five-year period. Retinal imaging of both subjects revealed normal age-related changes. There was up to an 11% difference in OCT and OCTA variables within the subjects, both at baseline and at five years, and there was up to an 18% difference in OCT and OCTA parameters between the subjects for both time points. Larger changes in subfoveal choroidal thickness and foveal avascular zone area were observed. Our observations suggest that the parafoveal superficial capillary plexus, choroidal vascularity index, central subfield thickness, retinal nerve fiber layer thickness, and ganglion cell-inner plexiform layer thickness may be more heavily influenced by genetic, rather than environmental, factors. In contrast, subfoveal choroidal thickness and the foveal avascular zone area may be more heavily influenced by environmental factors. The environmental impact on retinal and choroidal structure and microvasculature is increasingly important to characterize, as such imaging parameters are being explored as potential biomarkers of systemic disease. These differences, as seen in these identical twin subjects, may be important considerations in supporting the security of biometric identifiers.

Co occurrance of Macular Telangiectasia type 2 with hemorrhagic polypoidal choroidal vasculopathy and response to anti-vascular endothelial growth factor

We report the case of a 57-year-old female patient who presented with defective vision in the right eye due to large hemorrhagic pigment epithelial detachment with subretinal hemorrhage near the arcades with scattered retinal pigment epithelium (RPE) alteration at the macula and minimal vitreous hemorrhage inferiorly. The left eye showed right angle perifoveal dipping venule with RPE alteration temporal to the fovea, intraretinal RPE stellate plaque at the macula area. Multimodal imaging features including color fundus photo, red-free photograph, optical coherence tomography (OCT), enhanced depth imaging OCT, fundus fluorescein angiography, indocyanine green angiography, and OCT angiography were studied along with treatment response. One eye showed features of macular telangiectasia Type 2 (MacTel 2) with polypoidal choroidal vasculopathy (PCV) (hemorrhagic type) and the other eye showed features of MacTel 2 with pachychoroid pigment epitheliopathy. This report highlights the hitherto undescribed co-occurrence of MacTel 2 with bilateral pachychoroid and with unilateral hemorrhagic PCV in one eye and its favorable outcome with anti-vascular endothelial growth factor therapy.

Genetic Variability of Complement Factor H Has Ethnicity-Specific Associations With Choroidal Thickness

Purpose

To identify genetic alleles associated with differences in choroidal thickness (CT) in a population-based multiethnic Asian cohort.

Methods

A population-based multiethnic Asian cohort without retinal pathology was subjected to spectral-domain OCT (SD-OCT) and genotyping of risk alleles in CFH, VIPR2, ARMS2, and CETP. Subfoveal choroidal thickness (SFCT) values were assessed from SD-OCT, and associations with the risk alleles were determined for each cohort.

Results

A total of 1045 healthy Asian individuals (550 Chinese, 147 Indians, 348 Malays) were prospectively enrolled in the study. Several CFH alleles (rs800292, rs1061170, and rs1329428) were associated with increased SFCT in Indians (+18.7 to +31.7 µm; P = 0.001-0.038) and marginally associated with decreased SFCT in Malays (-12.7 to -20.6 µm; P = 0.014-0.022). Haplotype analysis of CFH revealed variable associations with SFCT among races, with the H6 haplotype being associated with a 29.08-µm reduction in SFCT in the Chinese cohort (P = 0.02) but a 35.2-µm increase in SFCT in the Indian cohort (P < 0.001). Finally, subfield analysis of the Chinese cohort identified associations between the CFH risk allele rs1061170 and reduced CT in the nasal and superior sectors (-20.2 to -25.8 µm; P = 0.003-0.027).

Conclusions

CFH variants are variably associated with CT among Asian ethnic groups. This has broad implications for the pathogenesis of common diseases such as age-related macular degeneration and central serous choroidopathy, the pathogenesis of which is associated with CT.

BILATERAL MACULAR CHOROIDAL ABNORMALITIES WITH DRUSENOID DEPOSITS IN PATIENTS WITH UNILATERAL PERIPHERAL EXUDATIVE HEMORRHAGIC CHORIORETINOPATHY

PURPOSE

To investigate bilateral macular features on optical coherence tomography in patients with unilateral peripheral exudative hemorrhagic chorioretinopathy (PEHCR).

METHODS

In this cross-sectional study, optical coherence tomography features of affected eyes (PEHCR group, n = 30) and unaffected contralateral eyes (contralateral group, n = 30) were investigated. Age-matched and sex-matched patients with polypoidal choroidal vasculopathy (PCV group, n = 51) and healthy controls (normal group, n = 50) were included to compare choroidal thickness, measured at six points apart from the fovea, with the PEHCR group.

RESULTS

Subretinal drusenoid deposits were the most common feature in the PEHCR (20%) and contralateral (23%) groups, followed by soft drusen. Although the macular choroid was comparably thin in both the PEHCR and contralateral groups, pachyvessels were also observed. The choroids of the PEHCR group were significantly thinner than those of the normal group at the subfovea and 1-mm temporal to the fovea and considerably thinner than those of the polypoidal choroidal vasculopathy group from 3-mm nasal to 3-mm temporal to the fovea.

CONCLUSION

In patients with unilateral PEHCR, bilateral choroidal thinning and drusenoid deposit accumulation were noted in the macula. The pathophysiology of PEHCR may be a rare peripheral complication of age-related macular degeneration with pathologic choroid.

Choroidal Thickness in Early Postnatal Guinea Pigs Predicts Subsequent Naturally Occurring and Form-Deprivation Myopia

Purpose

To identify choroidal characteristics associated with susceptibility to development of naturally occurring and experimentally induced myopia.

Methods

We compared choroidal properties between pigmented and albino guinea pig (GP) strains. Biometry, cycloplegic refractive error (RE), and eye wall sublayer thickness were measured from 171 GPs at postnatal day (P)6, 14, and 28. Forty-three P14 GPs underwent two-week monocular form-deprivation myopia (FDM). En face images of choroidal vasculature were obtained with a customized swept-source optical coherence tomography. Multivariate regression analyses were performed, with P28 RE as the outcome and P14 choroidal thickness (ChT) as the main predictor variable. Proteomic analysis was performed on choroidal tissue from P14 albino and pigmented GPs.

Results

At P14, RE was correlated with thickness of the choroid (β = 0.06), sclera (β = 0.12), and retina (β = 0.27; all P < 0.001). P14 ChT was correlated with P28 RE both with (β = 0.06, P = 0.0007) and without FDM (β = 0.05, P = 0.008). Multivariate regression analysis, taking into account FDM (versus physiological growth) and strain, revealed that for every 10-µm greater ChT at P14, P28 RE was 0.50D more positive (P = 0.005, n = 70). En face images of choroidal sublayers showed that albino choroids were relatively underdeveloped, with frequent avascular regions. Consistent with this finding, proteomic analysis suggested abnormalities of the nitric oxide system in the albino GP choroid.

Conclusions

Current results are consistent with the notion that greater ChT could protect from or delay the onset of myopia, while lower ChT is associated with greater susceptibility to myopia development. The underlying mechanism could be related to dysfunction of the choroidal vascular system.

Consequences of a Rare Complement Factor H Variant for Age-Related Macular Degeneration in the Amish

Purpose

Genetic variants in the complement factor H gene (CFH) have been consistently implicated in age-related macular degeneration (AMD) risk. However, their functional effects are not fully characterized. We previously identified a rare, AMD-associated variant in CFH (P503A, rs570523689) in 19 Amish individuals, but its functional consequences were not investigated.

Methods

We performed genotyping for CFH P503A in 1326 Amish individuals to identify additional risk allele carriers. We examined differences for age at AMD diagnosis between carriers and noncarriers. In blood samples from risk allele carriers and noncarriers, we quantified (i) CFH RNA expression, (ii) CFH protein expression, and (iii) C-reactive protein (CRP) expression. Potential changes to the CFH protein structure were interrogated computationally with Phyre² and Chimera software programs.

Results

We identified 39 additional carriers from Amish communities in Ohio and Indiana. On average, carriers were younger than noncarriers at AMD diagnosis, but this difference was not significant. CFH transcript and protein levels in blood samples from Amish carriers and noncarriers were also not significantly different. CRP levels were also comparable in plasma samples from carriers and noncarriers. Computational protein modeling showed slight changes in the CFH protein conformation that were predicted to alter interactions between the CFH 503 residue and other neighboring residues.

Conclusions

In total, we have identified 58 risk allele carriers for CFH P503A in the Ohio and Indiana Amish. Although we did not detect significant differences in age at AMD diagnosis or expression levels of CFH in blood samples from carriers and noncarriers, we observed modest structural changes to the CFH protein through in silico modeling. Based on our functional and computational observations, we hypothesize that CFH P503A may affect CFH binding or function rather than expression, which would require additional research to confirm.

The genetic architecture of Alzheimer disease risk in the Ohio and Indiana Amish

Alzheimer disease (AD) is the most common type of dementia and is currently estimated to affect 6.2 million Americans. It ranks as the sixth leading cause of death in the United States, and the proportion of deaths due to AD has been increasing since 2000, while the proportion of many other leading causes of deaths have decreased or remained constant. The risk for AD is multifactorial, including genetic and environmental risk factors. Although APOE ε4 remains the largest genetic risk factor for AD, more than 26 other loci have been associated with AD risk. Here, we recruited Amish adults from Ohio and Indiana to investigate AD risk and protective genetic effects. As a founder population that typically practices endogamy, variants that are rare in the general population may be of a higher frequency in the Amish population. Since the Amish have a slightly lower incidence and later age of onset of disease, they represent an excellent and unique population for research on protective genetic variants. We compared AD risk in the Amish and to a non-Amish population through APOE genotype, a non-APOE genetic risk score of genome-wide significant variants, and a non-APOE polygenic risk score considering all of the variants. Our results highlight the lesser relative impact of APOE and differing genetic architecture of AD risk in the Amish compared to a non-Amish, general European ancestry population.

Genomewide Association Study of Retinal Traits in the Amish Reveals Loci Influencing Drusen Development and Link to Age-Related Macular Degeneration

Purpose

The purpose of this study was to identify genetic risk loci for retinal traits, including drusen, in an Amish study population and compare these risk loci to known risk loci of age-related macular degeneration (AMD).

Methods

Participants were recruited from Amish communities in Ohio, Indiana, and Pennsylvania. Each participant underwent a basic health history, ophthalmologic examination, and genotyping. A genomewide association analysis (GWAS) was conducted for the presence and quantity of each of three retinal traits: geographic atrophy, drusen area, and drusen volume. The findings were compared to results from a prior large GWAS of predominantly European-ancestry individuals. Further, a genetic risk score for AMD was used to predict the presence and quantity of the retinal traits.

Results

After quality control, 1074 participants were included in analyses. Six single nucleotide polymorphisms (SNPs) met criteria for genomewide significance and 48 were suggestively associated across three retinal traits. The significant SNPs were not highly correlated with known risk SNPs for AMD. A genetic risk score for AMD provided significant predictive value of the retinal traits.

Conclusions

We identified potential novel genetic risk loci for AMD in a midwestern Amish study population. Additionally, we determined that there is a clear link between the genetic risk of AMD and drusen. Further study, including longitudinal data collection, may improve our ability to define this connection and improve understanding of the biological risk factors underlying drusen development.

Evaluation of choroidal thickness in light-coloured eyes

OBJECTIVE

The aim of this study was to determine whether iris colour is related to the choroidal thickness of healthy individuals.

METHODS

Healthy participants were divided into two groups. Group 1 had light-coloured eyes (blue and green), and group 2 had dark-coloured eyes (brown). The main outcome measures were iris thickness, subfoveal choroidal thickness and nasal and temporal choroidal thicknesses 500 µm away from the fovea.

RESULTS

Group 1 comprised 31 subjects with light-coloured eyes, and group 2 had 31 subjects with dark eyes. The mean ages of groups 1 and 2 were 26.7 ± 7.5 years and 24.1 ± 5.8 years, respectively (p = 0.14). The choroidal thicknesses of the subfoveal, nasal and temporal regions were 336.3 ± 52.1 µm, 321.9 ± 43.6 µm and 318.4 ± 49.2 µm, respectively, in group 1 and 396.5 ± 76.9 µm, 372 ± 79.3 µm and 379.6 ± 82.4 µm, respectively, in group 2. All the values in group 1 were statistically lower than those in group 2 (p = 0.001, p = 0.001 and p = 0.003, respectively). The iris thickness in group 1 (493.73 ± 95.44 µm) was thinner than in group 2 (524.61 ± 69.74 µm) but not statistically significant (p = 0.141).

CONCLUSION

The results showed that a thinner choroid can be seen in disease-free light-coloured eyes. The iris colour should be considered among the factors affecting the choroidal thickness, such as age, sex, race and refractive error.

Genetic Influence on Choroidal Volume

PURPOSE

To evaluate the degree of genetic influence on macular choroidal volume.

DESIGN

A cross-sectional twin and family study.

METHODS

In total, 353 Korean adults with healthy eyes from 78 households with 2 or more family members were included in the study. Macular choroidal volume was measured using spectral-domain optical coherence tomography with enhanced depth imaging at 9 macular subfields defined by the ETDRS. Demographics and clinical characteristics were investigated, including age, sex, axial length, hypertension, diabetes, drinking habits, and smoking status. The associations of these factors with macular choroidal volume were assessed using univariate and subsequent multivariate regression analyses while accounting for family structure. The heritability estimates of macular choroidal volume in total and at each of the 9 macular subfields were calculated after adjusting the covariates.

RESULTS

Patients who were younger, male, and had a shorter axial length showed associations with greater choroidal volume (P < .001 for all 3 independent variables). The covariates-adjusted heritability (±standard error) of the total macular choroidal volume was 0.76 ± 0.06, and the heritabilities of choroidal volume at each subfield ranged from 0.55 ± 0.09 (inner temporal subfield) to 0.77 ± 0.08 (inner superior subfield).

CONCLUSION

The macular choroidal volume is highly heritable.

The GGLEAM Study: Understanding Glaucoma in the Ohio Amish

Glaucoma leads to millions of cases of visual impairment and blindness around the world. Its susceptibility is shaped by both environmental and genetic risk factors. Although over 120 risk loci have been identified for glaucoma, a large portion of its heritability is still unexplained. Here we describe the foundation of the Genetics of GLaucoma Evaluation in the AMish (GGLEAM) study to investigate the genetic architecture of glaucoma in the Ohio Amish, which exhibits lower genetic and environmental heterogeneity compared to the general population. To date, we have enrolled 81 Amish individuals in our study from Holmes County, Ohio. As a part of our enrollment process, 62 GGLEAM study participants (42 glaucoma-affected and 20 unaffected individuals) received comprehensive eye examinations and glaucoma evaluations. Using the data from the Anabaptist Genealogy Database, we found that 80 of the GGLEAM study participants were related to one another through a large, multigenerational pedigree containing 1586 people. We plan to integrate the health and kinship data obtained for the GGLEAM study to interrogate glaucoma genetics and pathophysiology in this unique population.

Quantitative Assessment of Asymmetric Choroidal Outflow in Pachychoroid Eyes on Ultra-Widefield Indocyanine Green Angiography

Purpose

To quantitatively demonstrate asymmetric choroidal outflow in pachychoroid (central serous chorioretinopathy [CSC]/pachychoroid pigment epitheliopathy [PPE]) eyes using mid-phase, ultra-widefield indocyanine green angiography (UWF ICGA) images.

Methods

Eyes with a clinical diagnosis of CSC/PPE were imaged with multimodal imaging including UWF ICGA (Optos California). Quadrant brightness was measured by manually segmenting based on vortex vein location, calculating the brightness “max-min” value to assess nonuniformity between quadrants, and comparing between CSC/PPE and control eyes. A multivariate linear regression was performed to determine, across individual eyes, which specific quadrants have the greatest brightness in pachychoroid eyes, after taking into account patient-eye-specific variability.

Results

Thirty-three eyes (18 patients) with CSC/PPE along with 16 eyes of 9 controls had a mean age of 51.94 ± 9.72 vs. 53.78 ± 17.92 years (P = 0.731), respectively. Max-min analysis showed significantly increased likelihood of nonuniform drainage between vortex veins in both CSC/PPE and control eyes. Multivariate linear regression in control eyes showed that on average, the inferotemporal quadrant was significantly brighter than the superonasal quadrant (9.72 units, P < 0.001). Among CSC/PPE eyes, adjusting for the preferential, nonuniform drainage in control eyes, the inferonasal and inferotemporal quadrants in CSC/PPE eyes remained significantly brighter than the reference quadrant by 5.36 units (P = 0.034) and 7.51 units (P = 0.008), respectively.

Conclusions

Asymmetric choroidal venous outflow occurs in both control and CSC/PPE eyes based on UWF ICGA quantitative brightness levels in each quadrant. Increased brightness levels along inferior quadrants in mid-phase ICGA images suggest venous outflow congestion among eyes with CSC or PPE.

AMISH EYE STUDY: Baseline Spectral Domain Optical Coherence Tomography Characteristics of Age-Related Macular Degeneration

PURPOSE

To describe spectral domain optical coherence tomography (SD-OCT) findings in an Amish cohort to assess SD-OCT markers for early age-related macular degeneration (AMD).

METHODS

The authors performed a family-based prospective cohort study of 1,146 elderly Amish subjects (age range 50-99 years) (2,292 eyes) who had a family history of at least 1 individual with AMD. All subjects underwent complete ophthalmic examinations, SD-OCT using both Cirrus and Spectralis (20 × 20° scan area) instruments, fundus autofluorescence, infrared imaging, and color fundus photography. Spectral domain optical coherence tomography characteristics were analyzed in subjects with AMD (with and without subretinal drusenoid deposits [SDDs]) and normal healthy cohorts.

RESULTS

Participants' mean age was 65.2 years (SD ± 11). Color fundus photographic findings in 596 (53%) subjects (1,009 eyes) were consistent with AMD; the remaining 478 (43%) subjects showed no signs of AMD. The choroid was significantly thinner on OCT (242 ± 76 µm, P < 0.001) in those with AMD compared with those without (263 ± 63 µm). Subretinal drusenoid deposits were found in 143 eyes (7%); 11 of the 143 eyes (8%) had no other manifestations of AMD. Drusen volume (P < 0.001) and area of geographic atrophy (P < 0.001) were significantly greater, and choroid was significantly (P < 0.001) thinner in subjects with SDDs versus those without SDDs.

CONCLUSION

The authors describe spectral domain optical coherence tomography characteristics in an elderly Amish population with and without AMD, including the frequency of SDD. Although relatively uncommon in this population, the authors confirmed that SDDs can be found in the absence of other features of AMD and that eyes with SDDs have thinner choroids.

Heritability of Inner Retinal Layer and Outer Retinal Layer Thickness: The Healthy Twin Study

The purpose of the study is to evaluate the heritability of inner retinal layer (IRL) and outer retinal layer (ORL) thicknesses in the healthy Korean population. This was a cross-sectional, twin and family study. We included 374 Korean adults with healthy eyes from 89 families. IRL thickness (from the internal limiting membrane to the external limiting membrane) and ORL thickness (from the external limiting membrane to the outer border of the retinal pigment epithelium layer) were measured in the nine macular subfields as defined by the Early Treatment of Diabetic Retinopathy Study using optical coherence tomography. The heritability on IRL and ORL thicknesses were investigated using a variance decomposition model. The heritability of IRL thickness was 0.87, 0.58, 0.85, 0.89, and 0.74 for the central, inner superior, inner inferior, inner temporal, inner nasal subfields, respectively; and 0.62, 0.83, 0.62, and 0.60 for the outer superior, outer inferior, outer temporal, outer nasal subfields, respectively. The heritability of ORL thickness was 0.56, 0.75, 0.66, 0.72, and 0.56 for the central, inner superior, inner inferior, inner temporal, inner nasal subfields, respectively; and 0.64, 0.63, 0.73, 0.54 for the outer superior, outer inferior, outer temporal, and outer nasal subfields, respectively. The heritability estimates of IRL thickness and ORL thickness ranged from moderate to high. The IRL thickness at the central, inner temporal, and inner inferior subfields had particularly high heritability.

Genetic influence on macular retinal nerve fibre layer thickness according to retinal subfield

Background/aim

Characterising genetic effect on macular retinal nerve fibre layer (RNFL) is needed to obtain better understanding of various retinopathies and optic neuropathies. The purpose of this study was to evaluate genetic influence on macular RNFL thickness.

Methods

This is a cross-sectional, twin and family study. Three hundred and sixty-two Korean adults with healthy eyes were included in the study from 79 households with two or more family members. Macular RNFL thickness was measured with optical coherence tomography at nine macular subfields defined by the ETDRS. Intraclass correlation coefficients (ICCs) were estimated to assess intrafamilial resemblance of RNFL thickness by different types of family relationship. Heritability of RNFL thickness was evaluated using variance decomposition model.

Results

RNFL thickness increased from central subfield to outer subfields. Temporal quadrant RNFL was thinner compared with other quadrants. Monozygotic twin pairs showed the highest ICCs of RNFL thickness, although the ICC level varied across different subfields. Heritability of RNFL thickness was the highest at central subfield (0.81). RNFL thicknesses of outer subfields were moderately to highly heritable: 0.53, 0.71, 0.47 and 0.66 for superior, inferior, temporal and nasal fields, respectively. RNFL thicknesses at inner subfields showed the lowest heritability: 0.21, 0.24, 0.27 and 0.27 for superior, inferior, temporal and nasal subfields, respectively.

Conclusion

Macular RNFL thickness is significantly influenced by genetic factors. It varies largely by subfields with the highest heritability at the central subfield and a relatively lower heritability at inner subfields.

Rare variants and loci for age-related macular degeneration in the Ohio and Indiana Amish

Age-related macular degeneration (AMD) is a leading cause of blindness in the world. While dozens of independent genomic variants are associated with AMD, about one-third of AMD heritability is still unexplained. To identify novel variants and loci for AMD, we analyzed Illumina HumanExome chip data from 87 Amish individuals with early or late AMD, 79 unaffected Amish individuals, and 15 related Amish individuals with unknown AMD affection status. We retained 37,428 polymorphic autosomal variants across 175 samples for association and linkage analyses. After correcting for multiple testing (n = 37,428), we identified four variants significantly associated with AMD: rs200437673 (LCN9, p = 1.50 × 10⁻¹¹), rs151214675 (RTEL1, p = 3.18 × 10⁻⁸), rs140250387 (DLGAP1, p = 4.49 × 10⁻⁷), and rs115333865 (CGRRF1, p = 1.05 × 10⁻⁶). These variants have not been previously associated with AMD and are not in linkage disequilibrium with the 52 known AMD-associated variants reported by the International AMD Genomics Consortium based on physical distance. Genome-wide significant linkage peaks were observed on chromosomes 8q21.11–q21.13 (maximum recessive HLOD = 4.03) and 18q21.2–21.32 (maximum dominant HLOD = 3.87; maximum recessive HLOD = 4.27). These loci do not overlap with loci previously linked to AMD. Through gene ontology enrichment analysis with ClueGO in Cytoscape, we determined that several genes in the 1-HLOD support interval of the chromosome 8 locus are involved in fatty acid binding and triglyceride catabolic processes, and the 1-HLOD support interval of the linkage region on chromosome 18 is enriched in genes that participate in serine-type endopeptidase inhibitor activity and the positive regulation of epithelial to mesenchymal transition. These results nominate novel variants and loci for AMD that require further investigation.

Retinal and Cerebral Microvasculopathy: Relationships and Their Genetic Contributions

Purpose

Retinal microvasculopathy may reflect small vessel disease in the brain. Here we test the relationships between retinal vascular parameters and small vessel disease, the influence of cardiovascular risk factors on these relationships, and their common genetic background in a monozygotic twin cohort.

Methods

We selected 134 cognitively healthy individuals (67 monozygotic twin pairs) aged ≥60 years from the Netherlands Twin Register for the EMIF-AD PreclinAD study. We measured seven retinal vascular parameters averaged over both eyes using fundus images analyzed with Singapore I Vessel Assessment. Small vessel disease was assessed on MRI by a volumetric measurement of periventricular and deep white matter hyperintensities. We calculated associations between RVPs and WMH, estimated intratwin pair correlations, and performed twin-specific analyses on relationships of interest.

Results

Deep white matter hyperintensities volume was positively associated with retinal tortuosity in veins (P = 0.004) and fractal dimension in arteries (P = 0.001) and veins (P = 0.032), periventricular white matter hyperintensities volume was positively associated with retinal venous width (P = 0.028). Intratwin pair correlations were moderate to high for all small vessel disease/retinal vascular parameter variables (r = 0.49-0.87, P < 0.001). Cross-twin cross-trait analyses showed that retinal venous tortuosity of twin 1 could predict deep white matter hyperintensities volume of the co-twin (r = 0.23, P = 0.030). Within twin-pair differences for retinal venous tortuosity were associated with within twin-pair differences in deep white matter hyperintensities volume (r = 0.39, P = 0.001).

Conclusions

Retinal arterial fractal dimension and venous tortuosity have associations with deep white matter hyperintensities volume. Twin-specific analyses suggest that retinal venous tortuosity and deep white matter hyperintensities volume have a common etiology driven by both shared genetic factors and unique environmental factors, supporting the robustness of this relationship.

Pachychoroid disease

Pachychoroid is a relatively novel concept describing a phenotype characterized by attenuation of the choriocapillaris overlying dilated choroidal veins, and associated with progressive retinal pigment epithelium dysfunction and neovascularization. The emphasis in defining pachychoroid-related disorders has shifted away from simply an abnormally thick choroid (pachychoroid) toward a detailed morphological definition of a pathologic state (pachychoroid disease) with functional implications, which will be discussed in this review. Several clinical manifestations have been described to reside within the pachychoroid disease spectrum, including central serous chorioretinopathy, pachychoroid pigment epitheliopathy, pachychoroid neovasculopathy, polypoidal choroidal vasculopathy/aneurysmal type 1 neovascularization, focal choroidal excavation, peripapillary pachychoroid syndrome. These conditions all exhibit the characteristic choroidal alterations and are believed to represent different manifestations of a common pathogenic process. This review is based on both the current literature and the clinical experience of our individual authors, with an emphasis on the clinical and imaging features, management considerations, as well as current understanding of pathogenesis of these disorders within the context of the recent findings related to pachychoroid disease.

IMPROVING THE AGE-RELATED MACULAR DEGENERATION CONSTRUCT: A New Classification System

Previous models of disease in age-related macular degeneration (AMD) were incomplete in that they did not encompass subretinal drusenoid deposits (pseudodrusen), subtypes of neovascularization, and polypoidal choroidal vasculopathy. In addition, Type 3 neovascularization starts in the retina and may not necessarily involve the choroid. As such, the term choroidal neovascularization is not appropriate for these eyes. The new aspects in the AMD construct are to include specific lipoprotein extracellular accumulations, namely drusen and subretinal drusenoid deposits, as early AMD. The deposition of specific types of deposit seems to be highly correlated with choroidal thickness and topographical location in the macula. Late AMD includes macular neovascularization or atrophy. The particular type of extracellular deposit is predictive of the future course of the patient. For example, eyes with subretinal drusenoid deposits have a propensity to develop outer retinal atrophy, complete outer retinal and retinal pigment epithelial atrophy, or Type 3 neovascularization as specific forms of late AMD. Given Type 3 neovascularization may never involve the choroid, the term macular neovascularization is suggested for the entire spectrum of neovascular disease in AMD. In contrast to older classification systems, the proposed system encompasses the relevant presentations of disease and more precisely predicts the future course of the patient. In doing so, the concept was developed that there may be genetic risk alleles, which are not necessarily the same alleles that influence disease expression.

Quantitative genetic methods depending on the nature of the phenotypic trait

A consequence of the assumptions of the infinitesimal model, one of the most important theoretical foundations of quantitative genetics, is that phenotypic traits are predicted to be most often normally distributed (so-called Gaussian traits). But phenotypic traits, especially those interesting for evolutionary biology, might be shaped according to very diverse distributions. Here, I show how quantitative genetics tools have been extended to account for a wider diversity of phenotypic traits using first the threshold model and then more recently using generalized linear mixed models. I explore the assumptions behind these models and how they can be used to study the genetics of non-Gaussian complex traits. I also comment on three recent methodological advances in quantitative genetics that widen our ability to study new kinds of traits: the use of "modular" hierarchical modeling (e.g., to study survival in the context of capture-recapture approaches for wild populations); the use of aster models to study a set of traits with conditional relationships (e.g., life-history traits); and, finally, the study of high-dimensional traits, such as gene expression.

CONCURRENT IDIOPATHIC MACULAR TELANGIECTASIA TYPE 2 AND CENTRAL SEROUS CHORIORETINOPATHY

PURPOSE

To describe cases presenting with features of idiopathic macular telangiectasia (MacTel) Type 2 and central serous chorioretinopathy (CSC).

METHODS

Databases from four tertiary retina centers were searched for cases copresenting CSC and MacTel Type 2.

RESULTS

Five cases were identified (4 men, 1 woman; mean age: 67.2 years). Four patients were referred for chronic or nonresolving CSC, and the diagnosis of MacTel Type 2 was made based on multimodal imaging findings. One patient had advanced MacTel Type 2, and developed acute CSC. Regarding the MacTel Type 2 findings, all subjects presented perifoveal telangiectasia on fluorescein angiography, and four subjects showed intraretinal cavitations typical of MacTel Type 2 on optical coherence tomography, in one or both eyes. Regarding the CSC findings, fluorescein angiography identified focal or extended retinal pigment epithelium alteration in all eyes, and an active leakage in two eyes. Indocyanine green angiography showed choroidal vascular hyperpermeability in four subjects. On optical coherence tomography, pigment epithelial detachments were detected in five eyes (four subjects), and foveal detachments were present in five eyes (three subjects), which spontaneously resolved (two eyes), responded to photodynamic therapy (two eyes), or persisted (one eye). Mean choroidal thickness was 402 ± 99 μm.

CONCLUSION

The codiagnosis of CSC and MacTel Type 2 should be considered in atypical presentations associating features from both disorders.