Predict and Protect: Evaluating the Double-Layer Sign in Age-Related Macular Degeneration

Advanced age-related macular degeneration (AMD) is a major cause of vision loss. Therefore, there is interest in precursor lesions that may predict or prevent the onset of advanced AMD. One such lesion is a shallow separation of the retinal pigment epithelium (RPE) and Bruch’s membrane (BM), which is described by various terms, including double-layer sign (DLS). In this article, we aim to examine and clarify the different terms referring to shallow separation of the RPE and BM. We also review current evidence on the outcomes associated with DLS: firstly, whether DLS is predictive of exudative neovascular AMD; and secondly, whether DLS has potential protective properties against geographic atrophy. The range of terms used to describe a shallow separation of the RPE and BM reflects that DLS can present with different characteristics. While vascularised DLS appears to protect against atrophy but can progress to exudation, non-vascularised DLS is associated with an increased risk of atrophy. Optical coherence tomography (OCT) angiography (OCTA) is the principal method for identifying and differentiating various forms of DLS. If OCTA is unavailable or not practically possible, simplified classification of DLS as thick or thin, using OCT, enables the likelihood of vascularisation to be approximated. Research is ongoing to automate DLS detection by applying deep-learning algorithms to OCT scans. The term DLS remains applicable for describing shallow separation of the RPE and BM. Detection and classification of this feature provides valuable information regarding the risk of progression to advanced AMD. However, the appearance of DLS and its value in predicting AMD progression can vary between patients. With further research, individualised risks can be confirmed to inform appropriate treatment. Age-related macular degeneration (AMD) is an eye disease that may develop in older people, usually those aged over 60 years. Early in the disease, people often do not show any symptoms, but as the disease progresses, vision loss may occur. The advanced forms of AMD are called neovascular AMD (also called “wet” AMD) and advanced dry AMD (called geographic atrophy; GA). It is important to identify features and signs on eye scans that can help to predict if someone with AMD will develop an advanced form of the disease because this will help doctors plan the most appropriate treatment. One such feature on eye scans is the double-layer sign (DLS). In this article, we summarise the different names used for DLS, and assess if having a DLS increases the likelihood of someone with early AMD developing wet AMD or GA. We conclude that how DLS looks varies between people, which leads to DLS being called by various names. Someone with early AMD and a DLS containing blood vessels may be more likely to develop wet AMD; whereas someone with early AMD and a DLS without blood vessels may be more likely to develop GA. Taking photos of the eye using optical coherence tomography angiography imaging is the main method of identifying DLS and confirming whether it contains blood vessels.