Mirataollah Salabati MD
Retina Research Fellow
Wills Eye Hospital
The unicorn: expert consensus on OCT-A nomenclature in exudative AMD
Usha Chakravarthy, Belfast, United Kingdom
In this session, Dr.Usha Chakravarthy, professor of ophthalmology and vision sciences at the Queen’s University of Belfast, discussed the recent findings from the Unified Expert Commentary on OCTA in Neovascular AMD (UNICORN) project. The rationale for the UNICORN group was the inconsistency in definitions and descriptive nomenclature of optical coherence tomography angiography (OCTA) technology in neovascular AMD (nAMD). As a result, disparities exist in delineating tissue boundaries, contradictory findings, and a wide variety in the estimates of diagnostic accuracy using OCTA for nAMD.
With alterations in the OCTA slab segmentation, the appearance of an nAMD lesion could vary widely. Even when boundary segmentation is applied consistently, the lesion extent, the morphology, and the vessel density can vary between instruments because of the differences in the manufacturer-supplied processing algorithms for the imaging data.
UNICORN was a collaborative group based in the UK and USA. The first step of the UNICORN group was unifying definitions and descriptions based on literature review of OCTA studies. The systematic review confirmed the absence of consistency of descriptive and quantitative OCTA metrics in nAMD.
The UNICORN group aimed to:
- To construct a dictionary of terms/definitions from the published sources.
- To identify the most consistent features of nAMD under a unified nomenclature.
- To create a publicly available repository to act as a core training set for clinical and academic use.
The first version of the dictionary was created, which intuited commonly encountered clinically relevant terms in OCTA literature and technical terminology. In addition to technical and quantitative terms, the dictionary provided definitions for algorithms used in OCTA machines and various artifacts which may lower the quality of images. In the next step, an international group of experts reviewed the preliminary results and aimed to test the robustness and agreement of the selected terms amongst experts. The overlapping terms from the first UNICORN consensus and those without a clear definition were excluded by the panel of experts, and the most reproducible qualitative and quantitative terms were retained.
In the next step, an agreement study was performed to test the consistency of the nomenclature. Eleven experts graded 23 OCTA image sets and answered 13 dichotomized questions. Intra-class correlation coefficient (ICC), which was calculated based on mixed effect logistic regression models, evaluated the agreement between the graders. ICC ranged from 0.079 to 0.55, and the highest agreement was achieved for type 1 macular neovascularization (MVN) and polypoidal choroidal vasculopathy (PCV) lesions. However, the ICC only minimally improved when the number of evaluated images was restricted to 11 sets. The results of this study were published in Ophthalmology (https://pubmed.ncbi.nlm.nih.gov/33359557/).
Currently, UNICORN group is completing their full-scale systematic review and constructing the complete inventory of terms with definitions. They are planning to have their next face-to-face meeting by early 2022.
BEAVRS data about silicone oil visual loss in GRTs and retinal detachments. Functional and anatomical results
Jonathan Smith, Sunderland, United Kingdom
The topic of this session was an analysis of the EURETINA/BEAVRS retinal detachment dataset for silicone oil-related visual loss in patients with giant retinal tear (GRT). Silicone oil tamponade is widely used in the treatment of GRT-related detachment, however the effect of tamponade choice on visual outcome has not been evaluated.
This analysis included the 152 GRT related detachments (84 [55.3%] were macula-on, and 68 [44.7%] were macula-off). Silicone oil tamponade was utilized in 44% of the macula-on and 79% of the macula-off patients. Analysis of visual acuity (VA) outcomes in patients with primary success showed that the median LogMAR VA significantly improved from 2.3 pre-operatively to 0.30 post-operatively in macula-off patients. In patients with macula-on detachment, the median logMAR VA before surgery was 0.18 which remained the same after surgery.
Evaluating post-operative VA based on the type of the tamponade showed that in macula-on patients, those who were treated with gas had a median LogMAR VA of 0.18 (same as the overall postoperative VA in macula-on patients); however, patients who were treated with silicone oil had significantly worse postoperative VA (0.33, p=0.002). Also, 95% of the eyes in the gas groups achieved postoperative VA ≤ 0.30 LogMAR (Snellen equivalent better than 20/40), compared to only 50% of the eyes in the silicone oil group (p=0.002). There was no significant difference in postoperative visual outcomes between the gas and silicone oil within the macula-off group. (0.30 for gas, 0.55 for silicone oil, p=0.278). For macula-on patients treated with silicone oil, 12/47 (25.5%) of the eyes lost 0.2 logMAR (2 lines of vision on Snellen chart) after oil removal compared to baseline.
In summary, silicone oil-related visual loss is a significant phenomenon affecting a subset of patients. Several theories have been proposed as the underlying cause, and future studies are underway to evaluate the potential impact of oil impurities.