Systemic and Ocular Determinants of Peripapillary Retinal Nerve Fiber Layer Thickness Measurements in the European Eye Epidemiology (E3) Population

Effects of Deep Optic Nerve Head Structures on Bruch's Membrane Opening- Minimum Rim Width and Peripapillary Retinal Nerve Fiber Layer

PURPOSE

To explore the effects of deep optic nerve head (ONH) structures on Bruch's membrane opening (BMO)-minimum rim width (MRW) and peripapillary retinal nerve fiber layer thickness (pRNFLT) in healthy eyes.

DESIGN

Prospective cross-sectional study.

METHODS

Two hundred five healthy eyes of 141 subjects (mean ± standard deviation of age and axial length (AXL): 46.9 ± 10.0 years and 24.79 ± 1.15 mm) were enrolled. Best fit multivariable linear mixed models identified factors associated with BMO-MRW and pRNFLT. Explanatory variables included age, gender, AXL, BMO and anterior scleral canal opening (ASCO) area and ovality, magnitude of BMO and ASCO shift, peripapillary choroidal thickness, lamina cribrosa (LC) parameters, prelaminar thickness, and peripapillary scleral (PPS) angle.

RESULTS

Thinner BMO-MRW was associated with older age, smaller ASCO/BMO offset magnitude, larger BMO area, thinner prelaminar thickness, deeper LC, and thinner pRNFLT (P = .011, <.001, .004, <.001, <.001, <.001 respectively). Thinner pRNFLT was associated with shorter AXL, smaller ASCO area, a more posteriorly bowed PPS, shallower LC and thinner BMO-MRW. (P = .030, .002, .035, .012, <.001 respectively) CONCLUSIONS: BMO-MRW and pRNFLT were influenced by several deep ONH structures such as BMO and ASCO position shift, BMO or ASCO area, prelaminar thickness, PPS bowing and LC depth in addition to patient characteristics such as age and AXL. The degree and/or direction of associations varied between deep ONH structures and BMO-MRW or pRNFLT. Despite both BMO-MRW and pRNFLT being surrogate parameters for RGC loss, a complex relationship with ONH deep-layer morphology was indicated.

[Retinal optical coherence tomography biomarkers in dementia]

BACKGROUND

Due to the general aging of society, the prevalence and incidence of dementia are expected to increase considerably. In order to timely identify patients and assess their need for treatment and/or supportive measures, comprehensive and easy access screening methods are required, which, however, are yet to be developed. To date, several biomarkers for the presence of dementia on high-resolution spectral domain optical coherence tomography (OCT) and OCT angiography (OCT-A) images were identified.

AIM

To summarize previously identified OCT biomarkers in dementia and to assess their suitability for comprehensive screening examinations.

MATERIAL AND METHODS

A literature search was conducted on PubMed until March 2023 for the keywords "dementia", "mild cognitive impairment", "OCT", "OCT angiography" and "retinal biomarkers". Relevant publications were identified and summarized.

RESULTS

Numerous unspecific alterations on OCT imaging and OCT‑A were identified in patients with (predementia) dementia according to many population and clinical studies. These include a reduced thickness of the peripapillary retinal nerve fiber layer, the ganglion cell complex and the central retinal region. Additionally, a reduced vascular density and an enlarged foveal avascular zone (FAZ) were identified on OCT‑A imaging.

CONCLUSION

The currently known OCT biomarkers are too unspecific, and there is to date no OCT or OCT-A-based signature distinguishing between different types of dementia. Further longitudinal studies with larger sample sizes are warranted to develop and evaluate such distinct OCT signatures for different types of dementia and their respective early disease stages and to assess their prognostic value. Only then is the inclusion in comprehensive screening investigations feasible.

[Retinal OCT biomarkers and neurodegenerative diseases of the central nervous system beyond Alzheimer's disease]

BACKGROUND

Optical coherence tomography (OCT) biomarkers are increasingly used by neurologists, psychiatrists, and ophthalmologists for the diagnosis, prognosis, and follow-up of neurodegenerative diseases. Long-term data on OCT biomarkers of selected primary and secondary neurodegenerative diseases of the central nervous system (CNS), such as multiple sclerosis (MS) or Parkinson's disease, are already available in part. In addition, there are rare neurodegenerative diseases with early disease onset that may show OCT abnormalities.

METHODS

A literature review on the association of OCT biomarkers with neurodegenerative diseases of the CNS beyond Alzheimer's disease is presented. Parkinson's disease, MS, Friedreich's ataxia, Huntington's disease, spinocerebellar ataxia, and lysosomal storage diseases are addressed.

RESULTS

Relevant OCT biomarkers of neurodegenerative diseases are the macular ganglion cell inner plexiform layer (GCIPL) and the peripapillary retinal nerve fiber layer (pRNFL) thickness. Different sectors may be affected depending on the disease entity in addition to global pRFNL reduction. OCT‑angiography (OCT-A) is also increasingly used as a biomarker in neurodegenerative diseases.

CONCLUSION

Optical coherence tomography biomarkers are used in an interdisciplinary context. Retinal pathologies should be excluded by an ophthalmologist. While OCT biomarkers are increasingly used clinically in MS, the benefit in other neurodegenerative diseases, especially the rare ones, is less well documented. Further longitudinal studies are required.

Segregation of neuronal and vascular retinal damage in patients with hypertension and diabetes

This study aimed to examine the impact of diabetes and hypertension on retinal nerve fiber layer (RNFL) thickness components. Optical coherence tomography (OCT) measurements do not consider blood vessel contribution, which this study addressed. We hypothesized that diabetes and/or hypertension would lead to thinner RNFL versus controls due to the vascular component. OCT angiography was used to measure the RNFL in 121 controls, 50 diabetes patients, 371 hypertension patients, and 177 diabetes patients with hypertension. A novel technique separated the RNFL thickness into original (vascular component) and corrected (no vascular component) measurements. Diabetes-only (98 ± 1.7 µm; p = 0.002) and diabetes with hypertension (99 ± 0.8 µm; p = 0.001) patients had thinner original RNFL versus controls (102 ± 0.8 µm). No difference was seen between hypertension-only patients (101 ± 0.5 µm; p = 0.083) and controls. After removing the blood vessel component, diabetes/hypertension groups had thinner corrected RNFL versus controls (p = 0.024). Discrepancies in diabetes/hypertension patients were due to thicker retinal blood vessels within the RNFL thickness (p = 0.002). Our findings suggest that diabetes and/or hypertension independently contribute to neurodegenerative thinning of the RNFL, even in the absence of retinopathy. The differentiation of neuronal and vascular components in RNFL thickness measurements provided by the novel technique highlights the importance of considering vascular changes in individuals with these conditions.

Arterial hypertension and retinal layer thickness: the Beijing Eye Study

PURPOSE

To investigate relationships between blood pressure and the thickness of single retinal layers in the macula.

METHODS

Participants of the population-based Beijing Eye Study, free of retinal or optic nerve disease, underwent medical and ophthalmological examinations including optical coherence tomographic examination of the macula. Applying a multiple-surface segmentation solution, we automatically segmented the retina into its various layers.

RESULTS

The study included 2237 participants (mean age 61.8±8.4 years, range 50-93 years). Mean thicknesses of the retinal nerve fibre layer (RNFL), ganglion cell layer (GCL), inner plexiform layer, inner nuclear layer (INL), outer plexiform layer, outer nuclear layer/external limiting membrane, ellipsoid zone, photoreceptor outer segments (POS) and retinal pigment epithelium-Bruch membrane were 31.1±2.3 µm, 39.7±3.5 µm, 38.4±3.3 µm, 34.8±2.0 µm, 28.1±3.0 µm, 79.2±7.3 µm, 22.9±0.6 µm, 19.2±3.3 µm and 20.7±1.4 µm, respectively. In multivariable analysis, higher systolic blood pressure (SBP) and diastolic blood pressure (DBP) were associated with thinner GCL and thicker INL, after adjusting for age, sex and axial length (all p<0.0056). Higher SBP was additionally associated with thinner POS and higher DBP with thinner RNFL. For an elevation of SBP/DBP by 10 mm Hg, the RNFL, GCL, INL and POS changed by 2.0, 3.0, 1.5 and 2.0 µm, respectively.

CONCLUSIONS

Thickness of RNFL, GCL and POS was inversely and INL thickness was positively associated with higher blood pressure, while the thickness of the other retinal layers was not significantly correlated with blood pressure. The findings may be helpful for refinement of the morphometric detection of retinal diseases.

Association of lipid-lowering drugs and antidiabetic drugs with age-related macular degeneration: a meta-analysis in Europeans

BACKGROUND/AIMS

To investigate the association of commonly used systemic medications with prevalent age-related macular degeneration (AMD) in the general population.

METHODS

We included 38 694 adults from 14 population-based and hospital-based studies from the European Eye Epidemiology consortium. We examined associations between the use of systemic medications and any prevalent AMD as well as any late AMD using multivariable logistic regression modelling per study and pooled results using random effects meta-analysis.

RESULTS

Between studies, mean age ranged from 61.5±7.1 to 82.6±3.8 years and prevalence ranged from 12.1% to 64.5% and from 0.5% to 35.5% for any and late AMD, respectively. In the meta-analysis of fully adjusted multivariable models, lipid-lowering drugs (LLD) and antidiabetic drugs were associated with lower prevalent any AMD (OR 0.85, 95% CI=0.79 to 0.91 and OR 0.78, 95% CI=0.66 to 0.91). We found no association with late AMD or with any other medication.

CONCLUSION

Our study indicates a potential beneficial effect of LLD and antidiabetic drug use on prevalence of AMD across multiple European cohorts. Our findings support the importance of metabolic processes in the multifactorial aetiology of AMD.

From randomised controlled trials to real-world data: Clinical evidence to guide management of diabetic macular oedema

Randomised clinical trials (RCTs) are generally considered the gold-standard for providing scientific evidence for treatments' effectiveness and safety but their findings may not always be generalisable to the broader population treated in routine clinical practice. RCTs include highly selected patient populations that fit specific inclusion and exclusion criteria. Although they may have a lower level of certainty than RCTs on the evidence hierarchy, real-world data (RWD), such as observational studies, registries and databases, provide real-world evidence (RWE) that can complement RCTs. For example, RWE may help satisfy requirements for a new indication of an already approved drug and help us better understand long-term treatment effectiveness, safety and patterns of use in clinical practice. Many countries have set up registries, observational studies and databases containing information on patients with retinal diseases, such as diabetic macular oedema (DMO). These DMO RWD have produced significant clinical evidence in the past decade that has changed the management of DMO. RWD and medico-administrative databases are a useful resource to identify low frequency safety signals. They often have long-term follow-up with a large number of patients and minimal exclusion criteria. We will discuss improvements in healthcare information exchange technologies, such as blockchain technology and FHIR (Fast Healthcare Interoperability Resources), which will connect and extend databases already available. These registries can be linked with existing or emerging retinal imaging modalities using artificial intelligence to aid diagnosis, treatment decisions and provide prognostic information. The results of RCTs and RWE are combined to provide evidence-based guidelines.

Cardiovascular disease and thinning of retinal nerve fiber layer in a multi-ethnic Asian population: the Singapore epidemiology of eye diseases study

Introduction

Our study aimed to examine the relationship between cardiovascular diseases (CVD) with peripapillary retinal fiber layer (RNFL) and macular ganglion cell-inner plexiform layer (GCIPL) thickness profiles in a large multi-ethnic Asian population study.

Methods

6,024 Asian subjects were analyzed in this study. All participants underwent standardized examinations, including spectral domain OCT imaging (Cirrus HD-OCT; Carl Zeiss Meditec). In total, 9,188 eyes were included for peripapillary RNFL analysis (2,417 Malays; 3,240 Indians; 3,531 Chinese), and 9,270 eyes (2,449 Malays, 3,271 Indians, 3,550 Chinese) for GCIPL analysis. History of CVD was defined as a self-reported clinical history of stroke, myocardial infarction, or angina. Multivariable linear regression models with generalized estimating equations were performed, adjusting for age, gender, ethnicity, diabetes, hypertension, hyperlipidaemia, chronic kidney disease, body mass index, current smoking status, and intraocular pressure.

Results

We observed a significant association between CVD history and thinner average RNFL (β = -1.63; 95% CI, -2.70 to -0.56; p = 0.003). This association was consistent for superior (β = -1.79, 95% CI, -3.48 to -0.10; p = 0.038) and inferior RNFL quadrant (β = -2.14, 95% CI, -3.96 to -0.32; p = 0.021). Of the CVD types, myocardial infarction particularly showed significant association with average (β = -1.75, 95% CI, -3.08 to -0.42; p = 0.010), superior (β = -2.22, 95% CI, -4.36 to -0.09; p = 0.041) and inferior (β = -2.42, 95% CI, -4.64 to -0.20; p = 0.033) RNFL thinning. Among ethnic groups, the association between CVD and average RNFL was particularly prominent in Indian eyes (β = -1.92, 95% CI, -3.52 to -0.33; p = 0.018). CVD was not significantly associated with average GCIPL thickness, albeit a consistent negative direction of association was observed (β = -0.22, 95% CI, -1.15 to 0.71; p = 0.641).

Discussion

In this large multi-ethnic Asian population study, we observed significant association between CVD history and RNFL thinning. This finding further validates the impact of impaired systemic circulation on RNFL thickness.

Association of retinal nerve layers thickness and brain imaging in healthy young subjects from the i-Share-Bordeaux study

Given the anatomical and functional similarities between the retina and the brain, the retina could be a "window" for viewing brain structures. We investigated the association between retinal nerve fiber layers (peripapillary retinal nerve fiber layer, ppRNFL; macular ganglion cell-inner plexiform layer, GC-IPL; and macular ganglion cell complex, GCC), and brain magnetic resonance imaging (MRI) parameters in young health adults. We included 857 students (mean age: 23.3 years, 71.3% women) from the i-Share study. We used multivariate linear models to study the cross-sectional association of each retinal nerve layer thickness assessed by spectral-domain optical coherence tomography (SD-OCT) with structural (volumes and cortical thickness), and microstructural brain markers, assessed on MRI globally and regionally. Microstructural MRI parameters included diffusion tensor imaging (DTI) and Neurite Orientation Dispersion and Density Imaging (NODDI). On global brain analysis, thicker ppRNFL, GC-IPL and GCC were all significantly associated with patterns of diffusion metrics consistent with higher WM microstructural integrity. In regional analyses, after multiple testing corrections, our results suggested significant associations of some retinal nerve layers with brain regional gray matter occipital volumes and with diffusion MRI parameters in a region involved in the visual pathway and in regions containing associative tracts. No associations were found with global volumes or with global or regional cortical thicknesses. Results of this study suggest that some retinal nerve layers may reflect brain structures. Further studies are needed to confirm these results in young subjects.

Retinal Functional and Structural Neural Indices: Potential Biomarkers for the Monitoring of Cerebral Neurodegeneration: The Maastricht Study

BACKGROUND

If retinal indices of neurodegeneration are to be biomarkers for the monitoring of cerebral neurodegeneration, it is important to establish whether potentially modifiable risk factors for dementia are associated with retinal neurodegenerative changes.

OBJECTIVE

To study associations of dementia risk factors with retinal sensitivity, an index of retinal neural function, and retinal nerve fiber layer (RNFL) thickness, an index of retinal neural structure.

METHODS

We used cross-sectional data from The Maastricht Study (up to 5,666 participants, 50.5% men, mean age 59.7), and investigated associations with regression analyses (adjusted for potential confounders).

RESULTS

Most risk factors under study (i.e., hyperglycemia, unhealthy diet, lower cardiorespiratory fitness, smoking, alcohol consumption, and hypertension) were significantly associated with lower retinal sensitivity and lower RNFL thickness.

CONCLUSION

Findings of this population-based study support the concept that retinal neural indices may be biomarkers for the monitoring of therapeutic strategies that aim to prevent early-stage cerebral neurodegeneration and, ultimately, dementia.

Application of big data in ophthalmology

The advents of information technologies have led to the creation of ever-larger datasets. Also known as big data, these large datasets are characterized by its volume, variety, velocity, veracity, and value. More importantly, big data has the potential to expand traditional research capabilities, inform clinical practice based on real-world data, and improve the health system and service delivery. This review first identified the different sources of big data in ophthalmology, including electronic medical records, data registries, research consortia, administrative databases, and biobanks. Then, we provided an in-depth look at how big data analytics have been applied in ophthalmology for disease surveillance, and evaluation on disease associations, detection, management, and prognostication. Finally, we discussed the challenges involved in big data analytics, such as data suitability and quality, data security, and analytical methodologies.

Effects of Blood Pressure and Arterial Stiffness on Retinal Neurodegeneration: Cross-Sectional and Longitudinal Evidence From UK Biobank and Chinese Cohorts

BACKGROUND

Hypertension might be a modifiable risk factor for neurodegeneration diseases. However, the associations between blood pressure (BP), arterial stiffness index and retinal neurodegeneration remain unclear.

METHODS

This study used cross-sectional data from the United Kingdom BioBank (UKB) and longitudinal data from the Chinese Ocular Imaging Project (COIP). The macular ganglion cell-inner plexiform layer thickness (mGCIPLT) and macular retinal nerve fiber layer thickness were measured using spectral domain optical coherence tomography imaging. Swept-source optical coherence tomography was performed to obtain the longitudinal trajectory of the mGCIPLT and peripapillary retinal nerve fiber layer thickness in the COIP cohort. Multivariable linear models were used to analyze the associations between BP and retinal measurements.

RESULTS

In a cross-sectional analysis of 22 801 participants from UKB, thinner mGCIPLT was related to higher systolic BP (β: -0.103 [-0.146 to -0.061]; P<0.001), and higher diastolic BP (β: -0.191 [-0.265 to -0.117]; P<0.001), and was significantly associated with higher mean arterial pressure (β: -0.174 [-0.238 to -0.109]; P<0.001) and higher mean pulse pressure (β: -0.080 [-0.139 to -0.020]; P=009). In a longitudinal analysis of 2012 eligible COIP participants, higher levels of baseline systolic BP, diastolic BP, mean arterial pressure, and mean pulse pressure were associated with faster thinning in mGCIPLT and peripapillary retinal nerve fiber layer thickness (all P<0.001). The strongest association was the effect of mean arterial pressure on mGCIPLT (β: -0.118 [-0.175 to -0.061]; P<0.001). The results of the analysis of macular retinal nerve fiber layer thickness and peripapillary retinal nerve fiber layer thickness were consistent with those of mGCIPLT.

CONCLUSIONS

BP levels were independently and consistently associated with various retinal neurodegenerative exacerbations.

Retinal parameters, cortical cerebral microinfarcts, and their interaction with cognitive impairment

BACKGROUND

Quantitative changes in retinal vessels and thinning of optic nerves have been associated with subclinical (atherosclerosis, inflammation) and clinical age-related brain pathologies (stroke and neurodegeneration). However, data on the association between both retinal vascular and neuronal parameters with cortical cerebral microinfarcts (CMIs) and how these factors jointly influence cognition are lacking.

AIM

We investigated the association of retinal vascular and neuronal changes with CMIs on 3 T MRI and explored their interaction with cognitive impairment in a memory-clinic population.

METHODS

A total of 538 participants were included. Retinal vascular parameters (caliber, tortuosity, and fractal dimension) were measured from retinal fundus photographs using a semi-automated computer-assisted program. Retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL) thicknesses were obtained from optical coherence tomography. Cortical CMIs were defined as hypointense on T1-weighted MRI, <5 mm in diameter and restricted to the cortex. Cognition was assessed using Clinical Dementia Rating Sum-of-Boxes (CDR-SoB) score and detailed neuropsychological test. Multivariable regression analysis was conducted adjusting for age, sex, hypertension, hyperlipidemia, diabetes mellitus, smoking, diagnosis, white matter hyperintensities volume, lacunes, and cerebral microbleeds.

RESULTS

Larger venular caliber (Rate ratios (RR): 1.15, 95% CI: 1.01-1.38, p = 0.014), increased venular fractal dimension (RR: 1.58, 95% CI: 1.31-1.91, p ⩽ 0.001), increased venular tortuosity (RR: 1.54, 95% CI: 1.35-1.75, p ⩽ 0.001), and thinner GC-IPL (RR: 1.24, 95% CI: 1.13-1.36, p ⩽ 0.001) were associated with CMI counts. Among individuals in highest tertile of retinal parameters, a significant interaction was observed between venular tortuosity (RR: 1.12, 95% CI: 1.02-1.22, p-interaction = 0.014) and GC-IPL (RR: 1.05, 95% CI: 1.01-1.11, p-interaction < 0.001) with CMIs on CDR-SoB.

CONCLUSION

Retinal vascular and neuronal parameters are associated with cortical CMIs, and persons with both pathologies are likely to have cognitive impairment. Further studies may be warranted to evaluate the clinical utility of retinal parameters and CMI in risk prediction for cognitive dysfunction.

Concordance of Objectively Detected Retinal Nerve Fiber Bundle Defects in En Face OCT Images with Conventional Structural and Functional Changes in Glaucoma

PURPOSE

To assess how objectively detected defects in retinal nerve fiber bundle (RNFB) reflectance on en face OCT images relate to circumpapillary retinal nerve fiber layer thickness (cpRNFLT) and visual field defects.

DESIGN

Cross-sectional study.

PARTICIPANTS

Sixteen participants with early glaucoma and 29 age-matched healthy controls, of whom 22 had usable en face images for the establishment of normative levels of RNFB reflectance.

METHODS

All the participants underwent cpRNFLT scans, visual field examination, and wide-field OCT. En face reflectivity was assessed objectively using the Summary of Multiple Anatomically Adjusted Slabs method. En face defects were deemed concordant with cpRNFLT when they had at least 1 cpRNFLT point with P < 0.01, within ± 15° of the predicted insertion on the optic disc. Visual fields were examined using custom suprathreshold perimetry and SITA Standard 24-2. For each visual field location, the corresponding reflectance was deemed abnormal if any en face superpixel within ± 1° was abnormal. The overall, positive, and negative agreements were measured in each participant.

MAIN OUTCOME MEASURES

Proportion of concordant defects between en face reflectance analysis and cpRNFLT (%) as well as overall, positive, and negative agreements between en face reflectance analysis and visual field results.

RESULTS

Most en face abnormalities had concordant cpRNFLT defects in the mapped sector (median proportion concordant, 0.85; interquartile range, 0.74-0.95). In eyes with glaucoma, a median of 8.1% (range, 2.4%-23.7%) and 14.9% (range, 3.5%-29.1%) locations showed corresponding en face and visual field defects using 24-2 and custom perimetry, respectively. Both the perimetric strategies had moderate-to-good raw agreement with en face analysis (0.66-0.68), with stronger agreement on normal findings than on defects (0.77-0.78 and 0.4-0.44).

CONCLUSIONS

Objectively extracted reflectance defects showed strong concordance with conventional cpRNFLT damage and good agreement with perimetry, which could be enhanced by further minimization of image artifacts.

Retinal Examinations Provides Early Warning of Alzheimer's Disease

Patients with Alzheimer's disease have difficulty maintaining independent living abilities as the disease progresses, causing an increased burden of care on family caregivers and the healthcare system and related financial strain. This patient group is expected to continue to expand as life expectancy climbs. Current diagnostics for Alzheimer's disease are complex, unaffordable, and invasive without regard to diagnosis quality at early stages, which urgently calls for more technical improvements for diagnosis specificity. Optical coherence tomography or tomographic angiography has been shown to identify retinal thickness loss and lower vascular density present earlier than symptom onset in these patients. The retina is an extension of the central nervous system and shares anatomic and functional similarities with the brain. Ophthalmological examinations can be an efficient tool to offer a window into cerebral pathology with the merit of easy operation. In this review, we summarized the latest observations on retinal pathology in Alzheimer's disease and discussed the feasibility of retinal imaging in diagnostic prediction, as well as limitations in current retinal examinations for Alzheimer's disease diagnosis.

Accelerated Peripapillary Retinal Nerve Fiber Layer Degeneration in Patients With Chronic Kidney Disease: A 2-Year Longitudinal Study

Purpose

To evaluate the longitudinal changes in the peripapillary retinal nerve fiber layer (pRNFL) in patients with chronic kidney disease (CKD).

Methods

In this prospective cohort study, the CKD group consisted of patients with CKD stage ≥ 3. Age-matched healthy controls were enrolled at a 1:4 ratio. Spectral-domain optical coherence tomography was used to measure the pRNFL at baseline, 1 year, and 2 years. Within-group longitudinal changes and between-group comparisons were performed using linear mixed models.

Results

Overall, 152 patients with CKD and 40 controls were included (mean ages, 62.8 ± 9.1 years vs. 63.0 ± 9.3 years; P = 0.931). The CKD group showed faster loss of pRNFL than the control group (-0.87 µm/y vs. -0.26 µm/y; P = 0.004). Subgroup analysis found that the rate of pRNFL change was -0.41 µm/y in stage 3a CKD, -0.74 µm/y in stage 3b, -0.98 µm/y in stage 4/5, and -1.38 µm/y in end-stage renal disease. Multiple linear regression analysis revealed that CKD stage (coefficient = -0.549; 95% confidence interval [CI], -0.966 to -0.131; P = 0.010), hypertension (coefficient = -1.557; 95% CI -3.013 to -0.101; P = 0.036), and rim area (coefficient = -1.505; 95% CI, -2.940 to -0.070; P = 0.040) were factors associated with the pRNFL change over 2 years.

Conclusions

Patients with CKD experienced faster pRNFL loss than healthy controls did. Severity of CKD, hypertension, and rim area were independent factors associated with the loss of pRNFL.

Translational Relevance

This study contributes to our understanding of retinal neurodegeneration in normal aging and in patients with chronic kidney diseases.

(Pre)diabetes, glycemia, and daily glucose variability are associated with retinal nerve fiber layer thickness in The Maastricht Study

Retinopathy and neuropathy in type 2 diabetes are preceded by retinal nerve fibre layer (RNFL) thinning, an index of neurodegeneration. We investigated whether glucose metabolism status (GMS), measures of glycaemia, and daily glucose variability (GV) are associated with RNFL thickness over the entire range of glucose tolerance. We used cross-sectional data from The Maastricht Study (up to 5455 participants, 48.9% men, mean age 59.5 years and 22.7% with type 2 diabetes) to investigate the associations of GMS, measures of glycaemia (fasting plasma glucose [FPG], 2-h post-load glucose [2-h PG], HbA1c, advanced glycation endproducts [AGEs] assessed as skin autofluorescence [SAF]) and indices of daily GV (incremental glucose peak [IGP] and continuous glucose monitoring [CGM]-assessed standard deviation [SD]) with mean RNFL thickness. We used linear regression analyses and, for GMS, P for trend analyses. We adjusted associations for demographic, cardiovascular risk and lifestyle factors, and, only for measures of GV, for indices of mean glycaemia. After full adjustment, type 2 diabetes and prediabetes (versus normal glucose metabolism) were associated with lower RNFL thickness (standardized beta [95% CI], respectively - 0.16 [- 0.25; - 0.08]; - 0.05 [- 0.13;  0.03]; P_trend = 0.001). Greater FPG, 2-h PG, HbA1c, SAF, IGP, but not CGM-assessed SD, were also associated with lower RNFL thickness (per SD, respectively - 0.05 [- 0.08; - 0.01]; - 0.06 [- 0.09; - 0.02]; - 0.05 [- 0.08; - 0.02]; - 0.04 [- 0.07; - 0.01]; - 0.06 [- 0.12; - 0.01]; and - 0.07 [- 0.21; 0.07]). In this population-based study, a more adverse GMS and, over the entire range of glucose tolerance, greater glycaemia and daily GV were associated with lower RNFL thickness. Hence, early identification of individuals with hyperglycaemia, early glucose-lowering treatment, and early monitoring of daily GV may contribute to the prevention of RNFL thinning, an index of neurodegeneration and precursor of retinopathy and neuropathy.

Reticular Pseudodrusen Are Associated With More Advanced Para-Central Photoreceptor Degeneration in Intermediate Age-Related Macular Degeneration

Purpose

The purpose of this study was to examine retinal topographical differences between intermediate age-related macular degeneration (iAMD) with reticular pseudodrusen (RPD) versus iAMD without RPD, using high-density optical coherence tomography (OCT) cluster analysis.

Methods

Single eyes from 153 individuals (51 with iAMD+RPD, 51 with iAMD, and 51 healthy) were propensity-score matched by age, sex, and refraction. High-density OCT grid-wise (60 × 60 grids, each approximately 0.01 mm2 area) thicknesses were custom-extracted from macular cube scans, then compared between iAMD+RPD and iAMD eyes with correction for confounding factors. These "differences (µm)" were clustered and results de-convoluted to reveal mean difference (95% confidence interval [CI]) and topography of the inner retina (retinal nerve fiber, ganglion cell, inner plexiform, and inner nuclear layers) and outer retina (outer plexiform/Henle's fiber/outer nuclear layers, inner and outer segments, and retinal pigment epithelium-to-Bruch's membrane [RPE-BM]). Differences were also converted to Z-scores using normal data.

Results

In iAMD+RPD compared to iAMD eyes, the inner retina was thicker (up to +5.89 [95% CI = +2.44 to +9.35] µm, P < 0.0001 to 0.05), the outer para-central retina was thinner (up to -3.21 [95% CI = -5.39 to -1.03] µm, P < 0.01 to 0.001), and the RPE-BM was thicker (+3.38 [95% CI = +1.05 to +5.71] µm, P < 0.05). The majority of effect sizes (Z-scores) were large (-3.13 to +1.91).

Conclusions

OCT retinal topography differed across all retinal layers between iAMD eyes with versus without RPD. Greater para-central photoreceptor thinning in RPD eyes was suggestive of more advanced degeneration, whereas the significance of inner retinal thickening was unclear. In the future, quantitative evaluation of photoreceptor thicknesses may help clinicians monitor the potential deleterious effects of RPD on retinal integrity.

Ocular changes in nephrotic syndrome patients with preserved renal functions

BACKGROUND

Optical coherence tomography (OCT) measurements of central choroidal thickness (CCT) and retinal thickness have been proposed as inflammatory indicators for a variety of systemic disorders, particularly those with a vascular component. The relationship between nephrotic syndrome (NS) and visual impairment is not clear. The aim of this study was to evaluate the ocular changes in primary NS patients with preserved renal functions.

METHODS

A total of 60 participants (30 NS patients, 30 healthy control subjects) was recruited in this cross-sectional and comparative study. Retinal and choroidal examinations were performed via the spectral domain OCT. Enhanced depth imaging (EDI) mode of the OCT was used for choroidal analysis.

RESULTS

Although not statistically significant, CCT was found to be higher in the NS group compared to the control group (p=0.07). Central foveal thickness (CFT) and retinal arteriolar caliber (RAC) values were statistically significantly lower in the patients with nephrotic syndrome, whereas retinal venular caliber (RVC) and choroidal vascularity index (CVI) values were similar in both groups. RAC and RVC were not statistically significantly correlated with CCT or CFT in both groups (p>0.05).

CONCLUSION

The results of the current study showed a significant difference between the NS group and the control group in terms of some ocular changes (i.e., CFT and RAC). As a result, CCT, CFT and RAC measurements with OCT may be used as a marker of inflammation in NS patients.

Asian Race and Primary Open-Angle Glaucoma: Where Do We Stand?

Primary open-angle glaucoma (POAG) is an optic neuropathy characterized by irreversible retinal ganglion cell damage and visual field loss. The global POAG prevalence is estimated to be 3.05%, and near term is expected to significantly rise, especially within aging Asian populations. Primary angle-closure glaucoma disproportionately affects Asians, with up to four times greater prevalence of normal-tension glaucoma reported compared with high-tension glaucoma. Estimates for overall POAG prevalence in Asian populations vary, with Chinese and Indian populations representing the majority of future cases. Structural characteristics associated with glaucoma progression including the optic nerve head, retina, and cornea are distinct in Asians, serving as intermediates between African and European descent populations. Patterns in IOP suggest some similarities between races, with a significant inverse relationship between age and IOP only in Asian populations. Genetic differences have been suggested to play a role in these differences, however, a clear genetic pattern is yet to be established. POAG pathogenesis differs between Asians and other ethnicities, and it may differ within the broad classification of the Asian race. Greater awareness and further research are needed to improve treatment plans and outcomes for the increasingly high prevalence of normal tension glaucoma within aging Asian populations.

Retinal nerve fibre layer thickness measured with SD-OCT in a population-based study: the Handan Eye Study

PURPOSE

To examine the normative profile of retinal nerve fibre layer (RNFL) thickness and ocular parameters based on spectral-domain optical coherence tomography (SD-OCT) and its associations with related parameters among the Chinese population.

METHODS

This population-based cohort Handan Eye Study (HES) recruited participants aged≥30 years. All subjects underwent a standardised ophthalmic examination. Peripapillary RNFL thickness was obtained using SD-OCT. Mixed linear models were adopted to evaluate the correlation of RNFL thickness with ocular parameters as well as systemic factors. R V.3.6.1 software was used for statistical analysis.

RESULTS

3509 subjects (7024 eyes) with the average age of 55.54±10.37 were collected in this analysis. Overall mean RNFL thickness measured was 113.46±10.90 µm, and the thickest quadrant of parapapillary RNFL was the inferior quadrant, followed by the superior quadrant, the nasal quadrant and the temporal quadrant. In the multivariate linear regression model, thinner RNFL thickness was remarkable association with male (p<0.001), older age (p<0.001), increased body mass index (>30, p=0.018), absence of diabetes (p=0.009), history of cataract surgery (p=0.001), higher intraocular pressure (p=0.007), lower spherical equivalent (p<0.001) and increased axial length (p=0.048).

CONCLUSIONS

In non-glaucoma individuals, this difference of RNFL thickness in Chinese population should be noted in making disease diagnoses. Meanwhile, multiple ocular and systemic factors are closely related to the thickness of RNFL. Our findings further emphasise the need to demonstrate ethnic differences in RNFL thickness and the specificity of associated ocular and systemic factors, as well as to develop better normative databases worldwide.

TRIAL REGISTRATION NUMBER

HES was registered in Chinese Clinical Trial Registry website, and the registry number was ChiCTR-EOC-17013214.

Retinal layer assessments as potential biomarkers for brain atrophy in the Rhineland Study

Retinal assessments have been discussed as biomarkers for brain atrophy. However, available studies did not investigate all retinal layers due to older technology, reported inconsistent results, or were based on small sample sizes. We included 2872 eligible participants of the Rhineland Study with data on spectral domain-optical coherence tomography (SD-OCT) and brain magnetic resonance imaging (MRI). We used multiple linear regression to examine relationships between retinal measurements and volumetric brain measures as well as fractional anisotropy (FA) as measure of microstructural integrity of white matter (WM) for different brain regions. Mean (SD) age was 53.8 ± 13.2 years (range 30-94) and 57% were women. Volumes of the inner retina were associated with total brain and grey matter (GM) volume, and even stronger with WM volume and FA. In contrast, the outer retina was mainly associated with GM volume, while both, inner and outer retina, were associated with hippocampus volume. While we extend previously reported associations between the inner retina and brain measures, we found additional associations of the outer retina with parts of the brain. This indicates that easily accessible retinal SD-OCT assessments may serve as biomarkers for clinical monitoring of neurodegenerative diseases and merit further research.

Retinal Nerve Fiber Layer Thickness and Rim Area Profiles in Asians: Pooled Analysis from the Asian Eye Epidemiology Consortium

PURPOSE

To evaluate ethnic variations, ocular and systemic determinants of retinal nerve fibre layer (RNFL) thickness and neuroretinal rim area among Asians, using a large consortium of population-based eye studies.

DESIGN

Cross-sectional pooled-analysis.

PARTICIPANTS

22436 participants (22436 eyes) from 10 population-based studies (China, Hong Kong, India, Japan, Russia and Singapore) of the Asian Eye Epidemiology Consortium.

METHODS

Participants aged ≥40 years without glaucoma were included. All participants underwent spectral domain optical coherence tomography (OCT) imaging, systemic and ocular examinations. Data were pooled from each study. Multivariable regression analysis was performed to evaluate inter-ethnic, inter-machine variations, ocular and systemic factors associated with RNFL thickness and rim area, adjusting for age, gender, diabetes, intraocular pressure (IOP), spherical equivalent (SE), ethnicity, OCT model, and study group. When evaluating body mass index, smoking, and hypertension as exposures, these factors were additionally adjusted in the model.

MAIN OUTCOME MEASURE

Average RNFL thickness (μm) and rim area (mm²) RESULTS: Indian and Japanese eyes showed thinner RNFL, compared to other Asian ethnicities (β values ranging 7.31-12.76μm, P<0.001 for all pair-wise comparisons). Compared to measurements by Cirrus HD-OCT, RNFL was on average 7.29μm thicker when measured by Spectralis, 12.85μm thicker by Nidek, and 17.48μm thicker by Optovue (all P<0.001). Additionally, older age (per decade, β=-2.70; 95% confidence interval [CI], -2.85 to -2.55), diabetes (β=-0.72; 95%CI, -1.20 to -0.24), ), higher IOP (per mmHg, β=-0.07; 95% CI, -0.10 to -0.04), more myopic SE (per dioptre, β=-1.13; 95% CI, -1.19 to -1.07), cardiovascular disease (CVD, β=-0.94; 95% CI, -1.49 to -0.40), and hypertension (β=-0.68; 95% CI, -1.04 to -0.32), were associated with thinner RNFL (all P≤0.003). Similarly, older age (β=-0.019; 95% CI, -0.028 to -0.009), higher IOP (β=-0.010; 95% CI, -0.013 to -0.008) and more myopic SE (β=-0.025; 95% CI, -0.029 to -0.021) were associated with smaller rim area (all P<0.001).

CONCLUSIONS

In this large pooled-analysis of multiple Asian population studies, Indian and Japanese eyes were observed to have thinner RNFL profiles. In addition to previously known determinants, hypertension and CVD were associated with thinner RNFL. These findings further suggest the need of ethnic-specific normative database to improve glaucoma detection.

Effect of Systemic Hypertension on Peripapillary RNFL Thickness in Patients With Diabetes Without Diabetic Retinopathy

Type 2 diabetes mellitus (T2DM) and hypertension (HTN) are both relatively common systemic diseases and cause damage to the retina, such as inner retina reduction and microvascular impairment. The purpose of this study was to identify peripapillary retinal nerve fiber layer (pRNFL) damage by diabetic neurodegeneration and the effects of HTN on the pRNFL thickness in patients with T2DM without clinical diabetic retinopathy. Subjects were divided into three groups: healthy control subjects (group 1), patients with T2DM (group 2), and patients with both diabetes and HTN (group 3). The pRNFL thickness was measured using optical coherence tomography and compared among each group. Linear regression analyses were performed to identify factors associated with pRNFL thickness. A total of 325 eyes were included: 143 eyes in the group 1, 126 eyes in group 2, and 56 eyes in group 3. The mean pRNFL thicknesses of each group were 96.1 ± 7.7, 94.4 ± 8.6, and 91.6 ± 9.6 μm, respectively (P = 0.003). In multivariate linear analyses, diabetes duration (β = -0.236; P = 0.018) and HTN (β = -3.766; P = 0.008) were significant factors affecting the pRNFL thickness in groups 2 and 3. Additionally, the HTN duration was significantly correlated with pRNFL thickness in group 3 (R ² = 0.121; P = 0.008). In conclusion, patients with T2DM with HTN showed thinner pRNFL thickness than those with T2DM only. Additionally, the duration of HTN was significantly correlated with pRNFL thickness in patients with both diabetes and HTN.

Association of Retinal Nerve Fiber Layer Thickness, an Index of Neurodegeneration, With Depressive Symptoms Over Time

IMPORTANCE

Whether neurodegeneration contributes to the early pathobiology of late-life depression remains incompletely understood.

OBJECTIVE

To investigate whether lower retinal nerve fiber layer (RNFL) thickness, a marker of neurodegeneration, is associated with the incidence of clinically relevant depressive symptoms and depressive symptoms over time.

DESIGN, SETTING, AND PARTICIPANTS

This is a population-based cohort study from the Netherlands (The Maastricht Study) with baseline examination between 2010 and 2020 and median (IQR) follow-up of 5.0 (3.0-6.0) years. Participants were recruited from the general population. Individuals with type 2 diabetes were oversampled by design. Data analysis was performed from September 2020 to January 2021.

EXPOSURES

RNFL, an index of neurodegeneration, assessed with optical coherence tomography.

MAIN OUTCOMES AND MEASURES

Depressive symptoms were assessed with the Patient Health Questionnaire (PHQ)-9 (continuous score, 0-27) at baseline and over time via annual assessments. The presence of clinically relevant depressive symptoms was defined as a PHQ-9 score of 10 or higher.

RESULTS

We used data from 4934 participants with depressive symptoms over time (mean [SD] age, 59.7 [8.4] years; 2159 women [50.8%]; 870 had type 2 diabetes [20.5%]). Lower RNFL thickness was associated with higher incidence of clinically relevant depressive symptoms (per 1 SD, hazard ratio 1.11; 95% CI, 1.01-1.23) and more depressive symptoms over time (per 1 SD, rate ratio, 1.04; 95% CI, 1.01-1.06), after adjustment for demographic, cardiovascular, and lifestyle factors.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that lower RNFL thickness is associated with higher incidence of clinically relevant depressive symptoms and more depressive symptoms over time. Hence, neurodegeneration may be associated with the early pathobiology of late-life depression.

Enhanced Objective Detection of Retinal Nerve Fiber Bundle Defects in Glaucoma With a Novel Method for En Face OCT Slab Image Construction and Analysis

Purpose

To introduce and evaluate the performance in detecting glaucomatous abnormalities of a novel method for extracting en face slab images (SMAS), which considers varying individual anatomy and configuration of retinal nerve fiber bundles.

Methods

Dense central retinal spectral domain optical coherence tomography scans were acquired in 16 participants with glaucoma and 19 age-similar controls. Slab images were generated by averaging reflectivity over different depths below the inner limiting membrane according to several methods. SMAS considered multiple 16 µm thick slabs from 8 to 116 µm below the inner limiting membrane, whereas 5 alternative methods considered single summary slabs of various thicknesses and depths. Superpixels in eyes with glaucoma were considered abnormal if below the first percentile of distributions fitted to control data for each method. The ability to detect glaucoma defects was measured by the proportion of abnormal superpixels. Proportion of superpixels below the fitted first percentile in controls was used as a surrogate false-positive rate. The effects of slab methods on performance measures were evaluated with linear mixed models.

Results

The ability to detect glaucoma defects varied between slab methods, χ2(5) = 120.9, P < 0.0001, with SMAS showing proportion of abnormal superpixels 0.05 to 0.09 greater than alternatives (all P < 0.0001). No slab method found abnormal superpixels in controls.

Conclusions

SMAS outperformed alternatives in detecting abnormalities in eyes with glaucoma. SMAS evaluates all depths with potential retinal nerve fiber bundle presence by combining multiple slabs, resulting in greater detection of reflectance abnormalities with no increase in surrogate false positives.

Translational Relevance

SMAS may be used to objectively detect glaucoma defects in en face optical coherence tomography images.

Renal function and lipid metabolism are major predictors of circumpapillary retinal nerve fiber layer thickness-the LIFE-Adult Study

BACKGROUND

Circumpapillary retinal nerve fiber layer thickness (cpRNFLT) as assessed by spectral domain optical coherence tomography (SD-OCT) is a new technique used for the detection and evaluation of glaucoma and other optic neuropathies. Before translating cpRNFLT into clinics, it is crucially important to investigate anthropometric, biochemical, and clinical parameters potentially affecting cpRNFLT in a large population-based dataset.

METHODS

The population-based LIFE-Adult Study randomly selected 10,000 participants from the population registry of Leipzig, Germany. All participants underwent standardized systemic assessment of various cardiometabolic risk markers and ocular imaging, including cpRNFLT measurement using SD-OCT (Spectralis, Heidelberg Engineering). After employing strict SD-OCT quality criteria, 8952 individuals were analyzed. Multivariable linear regression analyses were used to evaluate the independent associations of various cardiometabolic risk markers with sector-specific cpRNFLT. For significant markers, the relative strength of the observed associations was compared to each other to identify the most relevant factors influencing cpRNFLT. In all analyses, the false discovery rate method for multiple comparisons was applied.

RESULTS

In the entire cohort, female subjects had significantly thicker global and also sectoral cpRNFLT compared to male subjects (p < 0.05). Multivariable linear regression analyses revealed a significant and independent association between global and sectoral cpRNFLT with biomarkers of renal function and lipid profile. Thus, thinner cpRNFLT was associated with worse renal function as assessed by cystatin C and estimated glomerular filtration rate. Furthermore, an adverse lipid profile (i.e., low high-density lipoprotein (HDL) cholesterol, as well as high total, high non-HDL, high low-density lipoprotein cholesterol, and high apolipoprotein B) was independently and statistically significantly related to thicker cpRNFLT. In contrast, we do not observe a significant association between cpRNFLT and markers of inflammation, glucose homeostasis, liver function, blood pressure, or obesity in our sector-specific analysis and globally.

CONCLUSIONS

Markers of renal function and lipid metabolism are predictors of sectoral cpRNFLT in a large and deeply phenotyped population-based study independently of previously established covariates. Future studies on cpRNFLT should include these biomarkers and need to investigate whether incorporation will improve the diagnosis of early eye diseases based on cpRNFLT.

Impacts of Systemic Hypertension on the Macular Microvasculature in Diabetic Patients Without Clinical Diabetic Retinopathy

Purpose

To identify the impact of hypertension (HTN) on macular microvasculature in type 2 diabetes (T2DM) patients without clinical diabetic retinopathy.

Methods

In this retrospective cross-sectional study, subjects were divided into three groups: controls (control group), patients with T2DM (DM group), and patients with both T2DM and HTN (DM + HTN group). The vessel length density (VD) was compared among the groups. Linear regression analyses were performed to identify factors associated with VD.

Results

The VD in the control, DM, and DM + HTN groups was 20.43 ± 1.16, 19.50 ± 1.45, and 18.19 ± 2.06 mm⁻¹, respectively (P < 0.001). The best-corrected visual acuity (B = −9.30; P = 0.002), duration of T2DM (B = −0.04; P = 0.020), HTN (B = −0.51; P = 0.016), signal strength (B = 1.12; P < 0.001), and ganglion cell–inner plexiform layer thickness (B = 0.06; P < 0.001) were significant factors affecting VD in patients with T2DM. Additionally, the hemoglobin A1c (HbA1c) (B = −0.49; P = 0.016) was significantly associated with VD in patients with both T2DM and HTN.

Conclusions

Patients with T2DM had impaired macular microvasculature, and patients with T2DM with HTN exhibited greater impairment of the microvasculature than did patients with T2DM only. Additionally, physicians should be aware that the macular microvasculature would be more vulnerable to hyperglycemic damage under ischemic conditions by HTN.

Association of high myopia with peripapillary retinal nerve fiber layer in patients with hypertension

Purpose

To identify the impacts of hypertension (HTN), high myopia, and the combination thereof on peripapillary retinal nerve fiber layer (pRNFL) thickness.

Methods

All subjects were divided into four groups: control (group 1); patients with HTN without high myopia (group 2); patients with high myopia without HTN (group 3); and patients with both HTN and high myopia (group 4). The pRNFL thicknesses were compared using a one-way analysis of variance. Univariate and multivariate linear regression analyses were used to identify factors affecting pRNFL thickness in subjects with and without HTN.

Results

The mean pRNFL thicknesses were 93.9±8.8, 88.7±6.8, 86.4±8.1, and 82.5±9.6 μm in group 1, 2, 3, and 4, respectively, and differed significantly (P<0.001). On multivariate linear regression analyses, age (β = -0.181, P = 0.044), axial length (β = -1.491, P<0.001), and HTN (β = -4.876, P = 0.044) significantly affected pRNFL thickness. Additionally, age and axial length affected the pRNFL thickness in subjects with HTN (age, β = -0.254, P = 0.020; axial length, β = -1.608, P<0.001) much more than in subjects without HTN (age, β = -0.028, P = 0.712; axial length, β = -1.324, P<0.001).

Conclusions

High myopia and HTN affected pRNFL reduction and a combination of the 2 diseases exacerbated pRNFL damage. This could be a confounding factor in interpreting pRNFL thickness in patients with ophthalmic diseases affecting the pRNFL thickness when combined with the 2 diseases.

Distribution and Classification of Peripapillary Retinal Nerve Fiber Layer Thickness in Healthy Young Adults

Purpose

To report the distribution of peripapillary retinal nerve fiber layer (RNFL) thickness in healthy young adults, investigate factors associated with RNFL thickness, and report the percentage of outside normal limits (ONL) and borderline (BL) RNFL thickness classifications based on the optical coherence tomography (OCT) manufacturer reference database.

Methods

Participants of the Raine Study Generation 2 cohort (aged 18–22 years) underwent spectral domain OCT imaging with an RNFL circle scan. Eyes with inadequate scans or optic nerve pathology were excluded. Linear mixed models were used to analyze associations.

Results

Data were available for 1288 participants (mean age, 20.0 years). Mean RNFL thicknesses in right and left eyes, respectively, were global = 100.5 µm, 100.3 µm (P = 0.03); temporal = 73.1 µm, 68.9 µm (P < 0.001); superotemporal = 140.6 µm, 136.3 µm (P < 0.001); superonasal = 104.9 µm, 115.1 µm (P < 0.001); nasal = 79.7 µm, 79.1 µm (P = 0.09); inferonasal = 109.8 µm, 111.5 µm (P < 0.001); and inferotemporal = 143.2 µm, 143.6 µm (P = 0.51). Longer axial length was associated with thinner RNFL globally, nasally, inferotemporally, superotemporally, superonasally, and inferonasally, as well as thicker RNFL temporally. The prevalence of ONL and BL classifications was generally higher than the expected rates of 1% and 4%, respectively, in temporal sectors and lower than expected in nasal sectors. The prevalence of global BL classifications was lower than expected (right eye, 2.3%; left eye, 2.6%).

Conclusions

Measured RNFL thickness differs with axial length and between right and left eyes. More reference data are needed to better define the normal limits of RNFL variation in different populations.

Translational Relevance

This study provides an improved understanding of normal variation in RNFL thickness in young adults.

Retinal biomarkers in Alzheimer's disease and mild cognitive impairment: A systematic review and meta-analysis

BACKGROUND

Retinal changes may reflect the pathophysiological processes in the central nervous system and can be assessed by imaging modalities non-invasively. We aim to localize candidate retinal biomarkers in Alzheimer's disease (AD), mild cognitive impairment (MCI), and preclinical AD.

METHODS

We systematically searched PubMed, EMBASE, Scopus, and Web of Science from inception to January 2021 for observational studies that investigated retinal imaging and electrophysiological markers in AD, MCI, and preclinical AD. Between-groups standardized mean differences (SMDs) with 95 % confidence intervals were computed using random-effects models.

RESULTS

Of 19,727 citations identified, 126 articles were eligible for inclusion. Compared with healthy controls, the thickness of peripapillary retinal nerve fiber layer (pRNFL; SMD = -0.723, p < 0.001), total macular (SMD = -0.612, p < 0.001), and subfoveal choroid (SMD = -0.888, p < 0.001) were significantly reduced in patients with AD. Compared with healthy controls, patients with MCI also had lower thickness of pRNFL (SMD = -0.324, p < 0.001), total macular (SMD = -0.302, p < 0.001), and subfoveal choroid (SMD = -0.462, p = 0.020). Other candidate biomarkers included the optic nerve head morphology, retinal amyloid deposition, microvascular morphology and densities, blood flow, and electrophysiological markers.

CONCLUSIONS

Retinal structural, vascular, and electrophysiological biomarkers hold great potential for the diagnosis, prognosis and risk assessment of AD and MCI. These biomarkers warrant further development in the future, especially in diagnostic test accuracy and longitudinal studies.

Intraocular pressure and circumpapillary retinal nerve fibre layer thickness in the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA): distributions and associations

AIMS

To describe the distributions of and associations with intraocular pressure (IOP) and circumpapillary retinal nerve fibre layer (cRNFL) thickness in a population-based study.

METHODS

Northern Ireland Cohort for the Longitudinal Study of Ageing participants underwent a computer-assisted personal interview, a self-completion questionnaire and a health assessment (HA). At the HA, participants underwent IOP measurement using Ocular Response Analyser and spectral-domain optical coherence tomography with Heidelberg Spectralis. Participants also underwent a range of anthropometric, ophthalmic, cardiovascular, cognition and blood tests. Participants who attended the HA and had a vertical cup-to-disc ratio (VCDR) measurement in at least one eye were eligible for the study. Participants without any IOP or cRNFL measurements were excluded from the respective analyses.

RESULTS

There were 3221 participants eligible for this study (5753 eyes included in the IOP analysis and 5461 eyes included in the cRNFL analysis). The mean (SD) Goldmann correlated IOP (IOPg) was 15.39 mm Hg (3.55 mm Hg). The mean (SD) average global cRNFL thickness was 94.39 µm (11.18 µm). Increased IOPg was associated with increased age, male sex, hypertension, refractive error (myopic decrease in spherical equivalent) and increased corneal resistance factor, while beta-blocker drug use was associated with lower IOPg in the fully adjusted multivariate analysis. Thinner average global cRNFL was associated with Alzheimer's disease in the age-adjusted and sex-adjusted model. In the fully adjusted multivariate analysis, increased age, male sex, left eyes, hypertension, increased VCDR, refractive error (myopic decrease in spherical equivalent) and increased IOPg were associated with thinner average global cRNFL, while Parkinson's disease and current (vs never) smoking status were associated with thicker average global cRNFL.

CONCLUSIONS

Increased IOP and reduced cRNFL were associated with increased age, myopic refractive error, male sex and hypertension. Alzheimer's disease was associated with thinner average global cRNFL, while Parkinson's disease was associated with thicker average global cRNFL.

Past, present and future role of retinal imaging in neurodegenerative disease

Retinal imaging technology is rapidly advancing and can provide ever-increasing amounts of information about the structure, function and molecular composition of retinal tissue in humans in vivo. Most importantly, this information can be obtained rapidly, non-invasively and in many cases using Food and Drug Administration-approved devices that are commercially available. Technologies such as optical coherence tomography have dramatically changed our understanding of retinal disease and in many cases have significantly improved their clinical management. Since the retina is an extension of the brain and shares a common embryological origin with the central nervous system, there has also been intense interest in leveraging the expanding armamentarium of retinal imaging technology to understand, diagnose and monitor neurological diseases. This is particularly appealing because of the high spatial resolution, relatively low-cost and wide availability of retinal imaging modalities such as fundus photography or OCT compared to brain imaging modalities such as magnetic resonance imaging or positron emission tomography. The purpose of this article is to review and synthesize current research about retinal imaging in neurodegenerative disease by providing examples from the literature and elaborating on limitations, challenges and future directions. We begin by providing a general background of the most relevant retinal imaging modalities to ensure that the reader has a foundation on which to understand the clinical studies that are subsequently discussed. We then review the application and results of retinal imaging methodologies to several prevalent neurodegenerative diseases where extensive work has been done including sporadic late onset Alzheimer's Disease, Parkinson's Disease and Huntington's Disease. We also discuss Autosomal Dominant Alzheimer's Disease and cerebrovascular small vessel disease, where the application of retinal imaging holds promise but data is currently scarce. Although cerebrovascular disease is not generally considered a neurodegenerative process, it is both a confounder and contributor to neurodegenerative disease processes that requires more attention. Finally, we discuss ongoing efforts to overcome the limitations in the field and unmet clinical and scientific needs.

OCT Variability Prevents Their Use as Robust Biomarkers in Multiple Sclerosis

Objective

To evaluate the agreement between the peripapillary retinal nerve fiber layer (pRNFL) and foveal thickness (FT) measurements among three different spectral domain-optical coherence tomography (SD-OCT) instruments in a sample of multiple sclerosis (MS) patients and a healthy age-matched control group.

Methods

An observational cross-sectional study with three groups: healthy subjects and MS patients w/w a previous clinical diagnosis of optic neuritis (ON) was conducted. The pRNFL and FT were measured using three different SD-OCT instruments (OCT PRIMUS 200 and OCT CIRRUS 500 SD-OCT [Carl Zeiss Meditec] and OCT 3D 2000 [Topcon]).

Results

Twenty eyes from 10 healthy subjects matched in age with MS patients without a previous history of eye disease and 62 MS eyes from 31 MS patients (29 eyes without history of ON and 33 eyes with history of ON) were enrolled. Healthy subjects and MS patients without ON did not show differences between the pRNFL and FT thickness (P>0.99) with any of the instruments. However, MS eyes with a previous episode of ON showed thinner pRNFL and FT (P<0.01). PRIMUS and CIRRUS OCT showed better agreement of the pRNLF and FT in both healthy and MS eyes. However, 3D OCT showed less agreement in the pRNFL measurement with CIRRUS in both healthy and MS eyes.

Interpretation

Although OCT is a valuable technology to improve MS patient assessment, differences between devices must be taken into account. It is necessary to create an international group that standardizes the measurement conditions and above all that provides reference bases for normal subjects.

Effects of prolonged type 2 diabetes on changes in peripapillary retinal nerve fiber layer thickness in diabetic eyes without clinical diabetic retinopathy

To identify the effects of prolonged type 2 diabetes (T2DM) on changes in peripapillary retinal nerve fiber layer (pRNFL) thickness in patients without clinical diabetic retinopathy. Subjects were divided into two groups: controls and patients with T2DM (DM group). After the initial visits, the pRNFL thicknesses were measured three more times at 1-year intervals. Subgroup analyses were performed in patients with T2DM duration ≥ 10 years. The mean pRNFL thickness at each visit was 95.8 ± 8.1, 95.4 ± 8.3, 94.9 ± 8.1, and 94.5 ± 8.3 μm in the control group (P = 0.138) (n = 55); and 93.4 ± 9.1, 92.1 ± 9.3, 90.9 ± 9.3, and 89.5 ± 9.2 μm in the DM group (P < 0.001) (n = 85). The estimated rate of reduction in mean pRNFL thickness was - 0.45 μm/year in the control group and - 1.34 μm/year in the DM group, respectively. In the DM group, the BCVA and HbA1c (both P = 0.001) were significant factors associated with pRNFL reduction. In patients with T2DM duration ≥ 10 years, the estimated pRNFL reduction rate was - 1.61 μm/year, and hypertension was a significant factor affecting the pRNFL reduction (P = 0.046). We confirmed rapid pRNFL reduction over time in T2DM, and the reduction rate was higher in patients with T2DM ≥ 10 years. Additionally, BCVA and HbA1c levels were significantly associated with the change in pRNFL thickness in T2DM patients.

Retinal Neurodegeneration in Diabetic Peripheral Neuropathy by Optical Coherence Tomography: A Systematic Review and Meta-analysis

PURPOSE

The optical coherence tomography (OCT) has been used to evaluate the changes of retinal degeneration in patients with diabetic peripheral neuropathy (DPN) in recent years, but the results of previous studies were controversial. Therefore, systematic review and meta-analysis were performed to evaluate the degree of retinal neurodegeneration in DPN measured by OCT.

METHODS

A comprehensive search of PubMed, Embase, Web of Science, Scopus, China Biomedical Literature (CBM), China National Knowledge Infrastructure (CNKI), VIP, and Wanfang databases were performed to identify studies that evaluate retinal neurodegeneration in DPN by using OCT. The included studies were critically reviewed and meta-analyses were performed to evaluate differences of the OCT-derived parameters between the DPN and non-DPN patients.

RESULTS

Twelve studies were included in the final meta-analysis, involving a total of 1,807 eyes (573 in the DPN group and 1,229 in the non-DPN group). The mean peripapillary retinal nerve fiber layer (pRNFL) thickness was significantly lower in the DPN group than in the non-DPN group (weighted mean difference [WMD] = -8.37 μm; 95% CI: -11.00, -5.74). The reduction of pRNFL thickness was the most pronounced in the inferior quadrant, and the differences in the nasal and temporal quadrants were also statistically significant, with WMD (95% CI) being -4.63 μm (-7.51, -1.76) and -3.92 μm (-6.86, -0.98), respectively. Similar results were observed for macular parameters, with WMD and 95% CI being -1.0 μm (-1.5, -0.5) for macular retinal nerve fiber layer (mRNFL), -2.7 μm (-10.7, -5.3) for macular ganglion cell-inner plexiform layer (mGCIPL), and -2.2 μm (-4.4, -0.04) for macular ganglion cell complex (mGCC), respectively.

CONCLUSIONS

Patients with DPN present with significant retinal neurodegeneration, with reduced pRNFL, mRNFL, mGCIPL, and mGCC thickness. Measurements of OCT parameters may serve as a biomarker for diagnosing and monitoring DPN.

Diagnostic ability of spectral-domain optical coherence tomography peripapillary retinal nerve fiber layer thickness to discriminate glaucoma patients from controls in an elderly population (The MONTRACHET study)

PURPOSE

To evaluate the capacity of retinal nerve fibre layer (RNFL) thickness measured by SD-OCT to discriminate glaucoma patients from controls in an elderly population.

METHODS

The MONTRACHET (Maculopathy, Optic Nerve, nuTRition, neurovAsCular and HEarT diseases) Study is a population-based study including participants aged 75 years and over. All participants underwent a complete eye examination with optic nerve photographs, visual field testing and OCT peripapillary RNFL thickness measurement. Glaucoma was defined according to the ISGEO (International Society for Epidemiologic and Geographical Ophthalmology) classification. Performance indicators were calculated including area under the receiver operating characteristics curves (AUC), likelihood ratios (LR) and diagnostic odds ratios (DOR).

RESULTS

In total, 1061 participants were included in the study, of whom 89 were classified as having glaucoma and 972 were classified as normal. The mean (SD) age of the population was 82.3 (3.7) years. The average RNFL thickness was significantly lower in the glaucoma group than in controls 64.0 (14.9) µm versus 88.9 (12.4) µm, respectively, p < 0.001) and in all sectors compared with controls. The average RNFL thickness had the highest AUC (0.901) followed by the temporal-inferior (0.879) and temporal-superior sectors (0.862). When RNFL thickness was classified as abnormal by SD-OCT, the average RNFL thickness had the best sensitivity (83.75%) followed by the temporal-inferior sector (75.64%). The specificity for these two parameters was 87.34% and 91.08%, respectively. The highest DOR was 28.70 for average RNFL thickness and reached 34.84 when using the reference database of the OCT manufacturer.

CONCLUSION

This study confirms that SD-OCT could be useful as an additional test to discriminate glaucoma patients from controls in an elderly population.

Retinal Nerve Fiber Layer Thickness in Healthy Eyes of Black, Chinese, and Latino Americans: A Population-Based Multiethnic Study

PURPOSE

To compare peripapillary retinal nerve fiber layer (RNFL) thickness among healthy adults by race and ethnicity and to identify determinants of RNFL thickness.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Data from 6133 individuals (11 585 eyes) from 3 population-based studies in Los Angeles County, California, 50 years of age or older and of self-described African, Chinese, or Latin American ancestry.

METHODS

We measured RNFL thickness and optic nerve head parameters using the Cirrus HD-OCT 4000. Multivariate linear mixed regression was used to evaluate factors associated with RNFL thickness among participants without ocular diseases.

MAIN OUTCOME MEASURES

Determinants and modifiers of RNFL thickness.

RESULTS

The mean age of the participants was 60.1 years (standard deviation, 7.4 years). Black Americans showed the lowest RNFL thickness and smallest cup-to-disc ratio (CDR), and Chinese Americans showed the largest CDR and disc area after adjusting for age and gender (all P < 0.05). Per each 10-year older age group, the average RNFL thickness was 2.5 μm (95% confidence interval [CI], 1.8-3.1 μm), 2.8 μm (95% CI, 2.3-3.3 μm), and 3.5 μm (95% CI, 2.9-4.1 μm) thinner for Black, Chinese, and Latino Americans, respectively (age trend P < 0.05 and interaction P = 0.041). Black Americans compared with Chinese Americans, older age, male gender, hypertension, diabetes, greater axial length (AL), bigger disc area, and lower scan signal strength were associated with thinner average RNFL. Race, age, AL, disc area, and scan signal strength consistently were associated with RNFL thickness in all quadrants, whereas gender, hypertension, and diabetes were associated with RNFL thickness in select quadrants. Age and race explained the greatest proportion of variance of RNFL thickness.

CONCLUSIONS

Clinically important differences in RNFL thickness are present in healthy adults 50 years of age or older from different racial and ethnic groups of the same age, with the thinnest measures observed in Black Americans. This difference remains after accounting for disc size and AL. Furthermore, age-related RNFL thinning differs by race and ethnicity. Longitudinal studies are needed to verify our findings and to assess the influence of race and ethnicity in the clinical application of RNFL thickness.

Association between the retinal vascular network and retinal nerve fiber layer in the elderly: The Montrachet study

PURPOSE

To investigate the association between the characteristics of the retinal vascular network in the elderly and retinal nerve fiber layer (RNFL) thickness in a population-based study.

METHODS

We conducted a population-based study, the Montrachet study (Maculopathy Optic Nerve, nuTRition neurovAsCular, and HEarT disease), in participants aged ≥ 75 years. RNFL thickness was assessed with spectral-domain optical coherence tomography (SD-OCT). Analysis of the retinal vascular network was performed by means of the Singapore "I" Vessel Assessment (SIVA) software based on fundus photography.

RESULTS

Data from 970 participants were suitable for analysis. Patients with optic neuropathy were excluded. In multivariable analysis, each standard deviation (SD) decrease in the caliber of the six largest arterioles and veins in zone B and the six largest arterioles and veins in zone C was associated with a decrease in global RNFL thickness (β = -1.62 μm, P = 0.001; β = -2.39 μm, P < 0.001; β = -1.56 μm, P = 0.002; and β = -2.64 μm, P < 0.001, respectively).

CONCLUSIONS

Our study found that decreased retinal vessels caliber were associated with a decreased RNFL thickness in the elderly without optic neuropathy.

Peripapillary Retinal Nerve Fiber Layer Profile in Relation to Refractive Error and Axial Length: Results From the Gutenberg Health Study

Purpose

To investigate the retinal nerve fiber layer profile measured by optical coherence tomography and its relation to refractive error and axial length.

Methods

The Gutenberg Health Study is a population-based study in Mainz, Germany. At the five-year follow-up examination, participants underwent optical coherence tomography, objective refraction and biometry. Peripapillary retinal nerve fiber layer (pRNFL) was segmented using proprietary software. The pRNFL profiles were compared between different refraction groups and the angle between the maxima, i.e., the peaks of pRNFL thickness in the upper and lower hemisphere (angle between the maxima of pRNFL thickness [AMR]) was computed. Multivariable linear regression analysis was carried out to determine associations of pRNFL profile (AMR) including age, sex, optic disc size, and axial length in model 1 and spherical equivalent in model 2.

Results

A total of 5387 participants were included. AMR was 145.3° ± 23.4° in right eyes and 151.8° ± 26.7° in left eyes and the pRNFL profile was significant different in the upper hemisphere. The AMR decreased with increasing axial length by −5.86°/mm (95% confidence interval [CI]: [−6.44; −5.29], P < 0.001), female sex (−7.61°; 95% CI: [−8.71; −6.51], P < 0.001) and increased with higher age (0.08°/year; 95% CI: [0.03; 0.14], P = 0.002) and larger optic disc size (2.29°/mm²; 95% CI: [1.18; 3.41], P < 0.001). In phakic eyes, AMR increased with hyperopic refractive error by 2.60°/diopters (dpt) (95% CI: [2.33; 2.88], P < 0.001).

Conclusions

The pRNFL profiles are related to individual ocular and systemic parameters.

Translational Relevance

Biometric parameters should be considered when pRNFL profiles are interpreted in diagnostics, i.e., in glaucoma.

Association of retinal layer measurements and adult cognitive function: A population-based study

OBJECTIVE

To quantify the associations of peripapillary retinal nerve fiber layer (pRNFL) thickness and macular ganglion cell layer (mGCL) volume with cognitive functioning and to investigate how demographic and vascular health factors affect these associations in a population-based sample of adults.

METHODS

The sample included the first 3,000 participants (age range 30-95 years) of the Rhineland Study (recruited from March 2016 to December 2018) who underwent spectral-domain optical coherence tomography and cognitive assessment at 1 of 2 identical study centers in Bonn, Germany. We used multiple linear regression models to examine the relationships between retinal layer measurements and cognitive functioning after adjustment for confounders, and we examined the moderating effects of demographic and vascular health factors.

RESULTS

The analytical sample included 2,483 participants who were 54.3 years old (SD 13.8 years) on average. After full adjustment, each 1-SD decrease in mGCL volume was associated with a greater decrease in global function than that of pRNFL thickness (β = -0.048 [95% confidence interval (CI) -0.077 to -0.018] vs β = -0.021 [95% CI -0.049 to 0.007]). These relationships increased in strength with advancing age, were stronger in participants with hypertension, and were reversed in current smokers relative to nonsmokers.

CONCLUSIONS

mGCL volume is more strongly related to adult cognitive functioning than pRNFL thickness, making it a better potential biomarker of neurodegeneration. Age and vascular health factors play important roles in determining the strength and direction of this association.

Personalising surgical treatments for glaucoma patients

Surgical treatments for glaucoma have relied for decades on traditional filtering surgery such as trabeculectomy and, in more challenging cases, tubes. Antifibrotics were introduced to improve surgical success in patients at increased risk of failure but have been shown to be linked to a greater incidence of complications, some being potentially vision-threatening. As our understanding of glaucoma and its early diagnosis have improved, a more individualised management has been suggested. Recently the term "precision medicine" has emerged as a new concept of an individualised approach to disease management incorporating a wide range of individual data in the choice of therapeutic modalities. For glaucoma surgery, this involves evaluation of the right timing, individual risk factors, targeting the correct anatomical and functional outflow pathways and appropriate prevention of scarring. As a consequence, there is an obvious need for better knowledge of anatomical and functional pathways and for more individualised surgical approaches with new, less invasive and safer techniques allowing for earlier intervention. With the recent advent of minimally invasive glaucoma surgery (MIGS) a large number of novel devices have been introduced targeting potential new sites of the outflow pathway for lowering intraocular pressure (IOP). Their popularity is growing in view of the relative surgical simplicity and apparent lack of serious side effects. However, these new surgical techniques are still in an era of early experiences, short follow-up and lack of evidence of their superiority in safety and cost-effectiveness over the traditional methods. Each year several new devices are introduced while others are withdrawn from the market. Glaucoma continues to be the primary cause of irreversible blindness worldwide and access to safe and efficacious treatment is a serious problem, particularly in the emerging world where the burden of glaucoma-related blindness is important and concerning. Early diagnosis, individualised treatment and, very importantly, safe surgical management should be the hallmarks of glaucoma treatment. However, there is still need for a better understanding of the disease, its onset and progression, the functional and structural elements of the outflow pathways in relation to the new devices as well as their long-term IOP-lowering efficacy and safety. This review discusses current knowledge and the future need for personalised glaucoma surgery.

Objectives, design and main findings until 2020 from the Rotterdam Study

The Rotterdam Study is an ongoing prospective cohort study that started in 1990 in the city of Rotterdam, The Netherlands. The study aims to unravel etiology, preclinical course, natural history and potential targets for intervention for chronic diseases in mid-life and late-life. The study focuses on cardiovascular, endocrine, hepatic, neurological, ophthalmic, psychiatric, dermatological, otolaryngological, locomotor, and respiratory diseases. As of 2008, 14,926 subjects aged 45 years or over comprise the Rotterdam Study cohort. Since 2016, the cohort is being expanded by persons aged 40 years and over. The findings of the Rotterdam Study have been presented in over 1700 research articles and reports. This article provides an update on the rationale and design of the study. It also presents a summary of the major findings from the preceding 3 years and outlines developments for the coming period.

Primary Open Angle Glaucoma and Vascular Risk Factors: A Review of Population Based Studies from 1990 to 2019

Glaucoma is one of the leading causes of blindness worldwide, and as the proportion of those over age 40 increases, so will the prevalence of glaucoma. The pathogenesis of primary open angle glaucoma (POAG) is unclear and multiple ocular risk factors have been proposed, including intraocular pressure, ocular perfusion pressure, ocular blood flow, myopia, central corneal thickness, and optic disc hemorrhages. The purpose of this review was to analyze the association between systemic vascular risk factors (including hypertension, diabetes, age, and migraine) and POAG, based on major epidemiological studies. Reports presenting the association between POAG and systemic vascular risk factors included a total of over 50,000 patients. Several epidemiological studies confirmed the importance of vascular risk factors, particularly hypertension and blood pressure dipping, in the pathogenesis and progression of glaucomatous optic neuropathy. We found that diabetes mellitus is associated with elevated intraocular pressure, but has no clear association with POAG. No significant correlation between migraine and POAG was found, however, the definition of migraine varied between studies.

Longitudinal Changes in the Peripapillary Retinal Nerve Fiber Layer Thickness in Hypertension: 4-Year Prospective Observational Study

Purpose

To determine longitudinal changes in the peripapillary retinal nerve fiber layer (pRNFL) thickness in patients with hypertension (HTN).

Methods

Participants without any ophthalmic disease were divided into two groups: an HTN group (50 eyes) that included patients with HTN for ≥5 years and a control group. After the initial visit, pRNFL thicknesses were measured four more times at 1-year intervals using spectral-domain optical coherence tomography. The pRNFL thickness was fitted using linear mixed models. Univariate and multivariate generalized linear mixed models were used to determine factors associated with pRNFL reductions over time.

Results

The mean ages of the HTN and control groups were 62.9 ± 6.2 and 60.7 ± 6.1 years, respectively, and they were not significantly different (P = 0.089). The baseline mean pRNFL thicknesses were 90.50 ± 8.31 and 93.90 ± 8.77 μm; they were significantly different (P = 0.049). The mean pRNFL reduction rate was -0.99 and -0.40 μm/y in the HTN and control groups, respectively; the interaction between group and duration was significant (P < 0.001). In the linear mixed model determination of factors associated with pRNFL reduction, there was no significant factor in the control group. In the HTN group, age, and axial length showed significant results in both univariate and multivariate analyses (estimate: -0.362 and -2.618; P = 0.042 and 0.026, respectively).

Conclusions

Patients with HTN had a significantly greater decrease in pRNFL than normal individuals. Additionally, age and axial length significantly affected the reduction in pRNFL in HTN patients.

Clinical Role of Epigenetics and Network Analysis in Eye Diseases: A Translational Science Review

Network medicine is a molecular-bioinformatic approach analyzing gene-gene interactions that can perturb the human interactome. This review focuses on epigenetic changes involved in several ocular diseases, such as DNA methylation, histone and nonhistone post-translational modifications, and noncoding RNA regulators. Although changes in aberrant DNA methylation play a major role in the pathogenesis of most ocular diseases, histone modifications are seldom investigated. Hypermethylation in TGM-2 and hypomethylation in MMP-2/CD24 promoter genes may play a crucial role in pterygium development; hypermethylation in regulatory regions of GSTP1 and OGG1 genes appear to be diagnostic biomarkers of cataract; hypomethylation of TGF-β1 promoter may trigger glaucoma onset; hypermethylation of the LOXL1 gene might be associated with pseudoexfoliation syndrome. A large panel of upregulated micro-RNAs (miRNAs), including hsa-hsa-miR-494, hsa-let-7e, hsa-miR-513-1, hsa-miR-513-2, hsa-miR-518c, hsa-miR-129-1, hsa-miR-129-2, hsa-miR-198, hsa-miR-492, hsa-miR-498, hsa-miR-320, hsa-miR-503, and hsa-miR-373, ^∗ may have a putative role in the development of retinoblastoma. Hypermethylation of H3K4 and hypomethylation of H3K27 at the TGFBIp locus are putative pathogenic mechanisms involved in corneal dystrophies. Determining how, where, and when specific epigenetic changes trigger ocular diseases may provide useful clinical biomarkers for their prevention, diagnosis, and management, as well as innovative drug targets. PF-04523655, a 19-nucleotide methylated double-stranded siRNA targeting the RTP80 gene, showed a dose-related improvement in best-corrected visual acuity (BCVA) in patients affected by diabetic macular edema. The observed results support a clinical network-based research program aimed to clarify the role of epigenetic regulators in the development of ocular diseases and personalized therapy.

Age-Related Decline of Retinal Oxygen Extraction in Healthy Subjects

Purpose

To investigate the age-dependence of total retinal blood flow and total retinal oxygen extraction in healthy subjects and determine their possible correlations with structural optical coherence tomography (OCT) parameters.

Methods

This observational cross-sectional study consisted of 68 healthy subjects (mean ± SD age, 45.6 ± 16.3 years; 47% female). Total retinal oxygen extraction was calculated based on measurement of total retinal blood flow using bi-directional Doppler OCT and measurement of oxygen saturation using spectroscopic reflectometry. Retinal nerve fiber layer thickness was measured using OCT, and the total number of retinal ganglion cells was estimated based on a previous published model. Correlation of these parameters with age was studied and the association between structural OCT parameters and hemodynamic vascular parameters was calculated.

Results

Both structural and vascular parameters showed a significant decline with increasing age. The correlation coefficients were between r = -0.25 and r = -0.41. Furthermore, structural and vascular parameters were significantly correlated with each other. The strongest association was found between the level of total retinal oxygen extraction and the number of retinal ganglion cells (r = 0.75, P < 0.001).

Conclusions

We showed that there was an age-related decline of retinal oxygen extraction. Levels of retinal oxygen extraction are correlated to retinal nerve fiber layer thickness and number of retinal ganglion cells. Our data partially explain the wide inter-individual variability in retinal blood flow values in healthy subjects. Longitudinal studies are required to study the time course of vascular and neuronal loss in humans.

Determining Possible Shared Genetic Architecture Between Myopia and Primary Open-Angle Glaucoma

Purpose

To determine genetic correlations between common myopia and primary open-angle glaucoma (POAG).

Methods

We tested the association of myopia polygenic risk scores (PRSs) with POAG and POAG endophenotypes using two studies: the Australian & New Zealand Registry of Advanced Glaucoma (ANZRAG) study comprising 798 POAG cases with 1992 controls, and the Rotterdam Study (RS), a population-based study with 11,097 participants, in which intraocular pressure (IOP) and optic disc parameter measurements were catalogued. PRSs were derived from genome-wide association study meta-analyses conducted by the Consortium for Refractive Error and Myopia (CREAM) and 23andMe. In total, 12 PRSs were constructed and tested. Further, we explored the genetic correlation between myopia, POAG, and POAG endophenotypes by using the linkage disequilibrium score regression (LDSC) method.

Results

We did not find significant evidence for an association between PRS of myopia with POAG (P = 0.81), IOP (P = 0.07), vertical cup-disc ratio (P = 0.42), or cup area (P = 0.25). We observed a nominal association with retinal nerve fiber layer (P = 7.7 × 10-3) and a significant association between PRS for myopia and disc area (P = 1.59 × 10-9). Using the LDSC method, we found a genetic correlation only between myopia and disc area (genetic correlation [RhoG] = -0.12, P = 1.8 × 10-3), supporting the findings of the PRS approach.

Conclusions

Using two complementary approaches we found no evidence to support a genetic overlap between myopia and POAG; our results suggest that the comorbidity of these diseases is not influenced by common variants. The association between myopia and optic disc size is well known and validates this methodology.