Optical coherence tomography angiography for identifying choroidal neovascular membranes: a masked study in clinical practice.

BACKGROUND/OBJECTIVES: Optical coherence tomography angiography (OCT-A) allows non-invasive imaging of chorio-retinal vasculature, and is a potential alternative to fluorescein angiography (FA). Sensitivity and specificity of OCT-A for detecting choroidal neovascularisation (CNV) in treatment-naïve neovascular age-related macular degeneration (nAMD) patients is examined, using the Heidelberg Spectralis in a 'real world' setting. SUBJECT/METHODS: Overall, 43 eyes from 26 patients were included in the study. Spectral domain OCT (SD-OCT), OCT-A and FA images were obtained at baseline. Each of the three retinal image modalities was systematically assessed by three masked clinicians. Decisions about the presence/absence of CNV were recorded using an automated segmentation for OCT-A, a manual method, and using both OCT-A and SD-OCT in conjunction. Additional information about the presence of sub-retinal hyper-reflective material (SHRM) and the 'double layer sign' (DLS) were recorded. RESULTS: The average sensitivity and specificity of the OCT-A for the detection of CNV in treatment naïve AMD was 89% and 87% for the combined SD-OCT and OCT-A, 76% and 91% for the automated segmentation and 84% and 85% for the manual segmentation, respectively. Inter-clinician agreement was 0.59-65 kappa. In patients without CNV, SHRM was present in only 6% while DLS was present in 28%. Sensitivity and specificity was >78% for both SHRM and DLS. CONCLUSIONS: OCT-A provides a reliable tool for detecting CNV in treatment naïve nAMD patients, with high sensitivity and specificity. Combined use of SD-OCT images and SHRM as an additional bio-marker, OCT-A could become an alternative to FA in routine clinical practice.

Predicting visual outcomes in patients treated with aflibercept for neovascular age-related macular degeneration: Data from a real-world clinical setting.

BACKGROUND/OBJECTIVES: There is a significant variation in the way neovascular age-related macular degeneration patients respond to anti-vascular endothelial growth factor treatment. Both the financial and time cost of treatment are significant. As such, being able to predict patient response to treatment is valuable. SUBJECTS/METHODS: 72 eyes treated with intravitreal aflibercept were retrospectively included in analysis. For each subject, visual acuity (letters) and central retinal thickness (µm) at baseline, second, third and fourth visits, as well as 12-month visits, were collated; a plot of visual acuity versus time was generated and a slope of the first three (slope3) and first four (slope4) visits was calculated. Differences in visual acuity at each visit compared to baseline were determined, as well as percentage differences in central retinal thickness at each visit compared to baseline. Lesion sub-type and the presence of fluid and haemorrhage were also recorded. RESULTS: The average change in visual acuity over 12 months was +3.2 ± 13.4 letters with 91.2% of patients losing <15 letters. Slope4 was the only significant predictive factor for 'visual acuity change over 12 months' (p < 0.001). Change in central retinal thickness, lesion sub-type, haemorrhage at baseline and the location of fluid at baseline were not useful predictive factors in long-term outcome. CONCLUSION: Aflibercept is an effective treatment option for neovascular age-related macular degeneration; however, the long-term response should not be predicted until at least three loading dose injections have been given. Visual acuity measures at each visit should be examined, as it is the trend in visual acuity across the first four visits (slope4) rather than the difference in visual acuity between two visits that is the predictive factor.

Adaptation reveals multi-stage coding of visual duration.

In conflict with historically dominant models of time perception, recent evidence suggests that the encoding of our environment's temporal properties may not require a separate class of neurons whose raison d'être is the dedicated processing of temporal information. If true, it follows that temporal processing should be imbued with the known selectivity found within non-temporal neurons. In the current study, we tested this hypothesis for the processing of a poorly understood stimulus parameter: visual event duration. We used sensory adaptation techniques to generate duration aftereffects: bidirectional distortions of perceived duration. Presenting adapting and test durations to the same vs different eyes utilises the visual system's anatomical progression from monocular, pre-cortical neurons to their binocular, cortical counterparts. Duration aftereffects exhibited robust inter-ocular transfer alongside a small but significant contribution from monocular mechanisms. We then used novel stimuli which provided duration information that was invisible to monocular neurons. These stimuli generated robust duration aftereffects which showed partial selectivity for adapt-test changes in retinal disparity. Our findings reveal distinct duration encoding mechanisms at monocular, depth-selective and depth-invariant stages of the visual hierarchy.

Object size determines the spatial spread of visual time.

A key question for temporal processing research is how the nervous system extracts event duration, despite a notable lack of neural structures dedicated to duration encoding. This is in stark contrast with the orderly arrangement of neurons tasked with spatial processing. In this study, we examine the linkage between the spatial and temporal domains. We use sensory adaptation techniques to generate after-effects where perceived duration is either compressed or expanded in the opposite direction to the adapting stimulus' duration. Our results indicate that these after-effects are broadly tuned, extending over an area approximately five times the size of the stimulus. This region is directly related to the size of the adapting stimulus-the larger the adapting stimulus the greater the spatial spread of the after-effect. We construct a simple model to test predictions based on overlapping adapted versus non-adapted neuronal populations and show that our effects cannot be explained by any single, fixed-scale neural filtering. Rather, our effects are best explained by a self-scaled mechanism underpinned by duration selective neurons that also pool spatial information across earlier stages of visual processing.