David Romero-Bascones

The fovea is the small depression at the neurosensory retina that underlies high-resolution central vision. It is vulnerable to disease and disruption of its architecture can lead to visual disability. Foveal morphology varies substantially across individuals but the molecular causes and functional consequences of this variation remain incompletely understood. Here, we analyse six foveal morphological parameters derived from optical coherence tomography (OCT) images of 39,521 UK Biobank participants. We find marked variation in foveal morphology and identify significant associations with sex and genetic ancestry. Genome-wide association studies identify 162 lead loci across the six foveal morphological parameters, implicating genes involved in pigmentation (including TYR , TSPAN10 and GPR143 ) and developmental patterning (including FGFR2 , CYP26C1 and CYP1A1 ). Heritability estimates range from 29 to 43%. Foveal pit volume is associated with future risk of age-related macular degeneration (AMD) (hazard ratio 1.09, p = 0.026), a finding supported by Mendelian randomisation. Given the strong correlations among foveal traits, the specificify of this association to pit volume remains unclear. These results establish foveal morphology as a highly heritable trait that is biologically linked to AMD.

Characterizing the effect of age and sex on macular retinal layer thicknesses and foveal pit morphology is crucial to differentiating between natural and disease-related changes. We applied advanced image analysis techniques to optical coherence tomography (OCT) to: 1) enhance the spatial description of age and sex effects, and 2) create a detailed open database of normative retinal layer thickness maps and foveal pit shapes. The maculae of 444 healthy subjects (age range 21–88) were imaged with OCT. Using computational spatial data analysis, thickness maps were obtained for retinal layers and averaged into 400 (20 x 20) sectors. Additionally, the geometry of the foveal pit was radially analyzed by computing the central foveal thickness, rim height, rim radius, and mean slope. The effect of age and sex on these parameters was analyzed with multiple regression mixed-effects models. We observed that the overall age-related decrease of the total retinal thickness (TRT) (-1.1% per 10 years) was mainly driven by the ganglion cell-inner plexiform layer (GCIPL) (-2.4% per 10 years). Both TRT and GCIPL thinning patterns were homogeneous across the macula when using percentual measurements. Although the male retina was 4.1 μm thicker on average, the greatest differences were mainly present for the inner retinal layers in the inner macular ring (up to 4% higher TRT than in the central macula). There was an age-related decrease in the rim height (1.0% per 10 years) and males had a higher rim height, shorter rim radius, and steeper mean slope. Importantly, the radial analysis revealed that these changes are present and relatively uniform across angular directions. These findings demonstrate the capacity of advanced analysis of OCT images to enhance the description of the macula. This, together with the created dataset, could aid the development of more accurate diagnosis models for macular pathologies.

Disentangling the cellular anatomy that gives rise to human visual perception is one of the main challenges of ophthalmology. Of particular interest is the foveal pit, a concave depression located at the center of the retina that captures light from the gaze center. In recent years, there has been a growing interest in studying the morphology of the foveal pit by extracting geometrical features from optical coherence tomography (OCT) images. Despite this, research has devoted little attention to comparing existing approaches for two key methodological steps: the location of the foveal center and the mathematical modelling of the foveal pit. Building upon a dataset of 185 healthy subjects imaged twice, in the present paper the image alignment accuracy of four different foveal center location methods is studied in the first place. Secondly, state-of-the-art foveal pit mathematical models are compared in terms of fitting error, repeatability, and bias. The results indicate the importance of using a robust foveal center location method to align images. Moreover, we show that foveal pit models can improve the agreement between different acquisition protocols. Nevertheless, they can also introduce important biases in the parameter estimates that should be considered.

Local content insertion and viewer segmentation with proximity service information is a critical business case for broadcasting operators. This personalized service delivery will open up an opportunity for new use cases, such as local service delivery, local advertisement insertion and local emergency warning. In practice, single frequency networks (SFNs) offer a better spectrum efficiency when compared with traditional Multiple Frequency Network (MFN) approaches. Nevertheless, the addition of local content delivery can dramatically reduce that efficiency. Recently, the Layered Division Multiplexing (LDM) based Local Service Insertion (LSI) solution has been proposed as an interesting alternative for including local content in single frequency networks. Nonetheless, the required channel estimation procedure has been considered a major drawback for its successful implementation. In this work, a new semi-blind channel estimation algorithm is proposed. The algorithm takes advantage of the LDM structure and it is based on the statistical properties of the time domain Orthogonal Frequency Division Multiplexing (OFDM) frame. It proposes a solution for the major challenges that have remain unsolved so far. The paper also includes the first simulation results for this new approach.

Recent advances in broadband communications have led to the first standardization phase of 5G (Rel’ 15). Several works present this novel standard as the main solution in order to cover all the new requirements that have arisen in the multimedia delivery industry. However, the latest 5G release does not include the option of transmitting traditional broadcast services. That is why, in this paper, Non-Orthogonal Multiple Access (NOMA) is presented as a promising candidate in order to boost the implementation of the broadcast/multicast communications within the 5G NR standard. Therefore, a 5G New Radio (NR) fully compliant simulation tool has been developed and NOMA multiplexing schemes have been added, introducing as few modifications as possible. The simulation platform and proposed techniques have been tested within two different use cases. Results present a better overall reliability performance of the communications by using NOMA. In fact, both services performance is improved when compared to traditional TDMA schemes, with a maximum gain around 4 dB.