Delving into the distribution of retinal biomarkers for insights on disease aetiology and clinical features

Speakers in a Sunday morning symposium session presented their research investigating the spatial distribution of retinal biomarkers and discussed how the information provides insights about the etiology and clinical features of age-related macular degeneration (AMD) and diabetic eye disease.

Leading off the session, Dr Christine A Curcio (United States) described findings from studies done to characterise human photoreceptor topography for informing mechanisms and outcomes of AMD. Summarising her take-away messages, Dr Curcio said that with knowledge of photoreceptor topography, AMD is a mathematically tractable disease, and she proposed that topographically aligned features may be mechanistically related. Dr Curcio’s research also showed that there is a high-risk area centred under the fovea where drusen abundance, progression risk, and macular xanthophyll pigments align.

“These spatial correspondences can be unified with a model of how soft drusen form, which brings together the evolutionary and developmental biology of the fovea,” she concluded.

Dr Ulrike Grünert (Australia) presented findings from research conducted to describe the distribution, density, and connectivity of bipolar and ganglion cells in the human retina. Taking advantage of the fact that different cell types express distinct combinations of molecular markers, immunohistochemical staining was used to identify the different populations. Dr Ulrike showed that the density of midget ganglion and cone bipolar cells peaks near the fovea. Studies focusing on rod cells demonstrated that the spatial resolution of rod vision in the central retina is limited by the AII amacrine cell mosaic.

Dr Chandra Balaratnasingm (Australia) reviewed findings from histological studies done to determine the topologic characteristics and vascular connections within the human retina and to investigate how the topologic properties are affected in eyes with diabetic retinopathy. The evidence he presented indicates that capillary plexuses in the macula are arranged in series and parallel. The studies conducted in eyes from patients with diabetes showed important associations between vascular topology and the location of both ischaemia and microaneurysms.

“From a clinical standpoint, understanding retinal vascular organization is important because we all see patients with diabetic retinopathy and when we review their angiograms, we realise how different patterns of ischaemia are between patients,” Dr Balaratnasingm said.

Bilal Haj Najeeb (Austria) presented findings from several studies conducted to elucidate the regional distribution of exudative biomarkers in NAMD and diabetic macular oedema (DME). Based on research using fluorescein angiography to determine the distribution of leakage in eyes with DME, Dr Najeeb suggested that clinicians should focus on the temporal macular field when carrying out screening in diabetic retinopathy. Discussing an investigation designed to identify a topographic approach to the diagnosis of macular neovascularization type 3 (MNV3), Dr Najeeb said this lesion may be identified inexpensively and noninvasively with colour fundus photography based on a characteristic pattern of distribution of intraretinal haemorrhage. A third study exploring the regional distribution of MNV3 described a band-shaped pattern radiating outward from the perifoveal area with almost 75% of lesions being located in the temporal half of the macula and almost all lesions lying within the inner fields of the ETDRS grids.