Understanding Pellucid Marginal Degeneration: A Retrospective Case Series

Pellucid marginal degeneration (PMD) is a rare, progressive corneal disorder characterized by a peripheral inferior band of corneal thinning in a crescent-shaped pattern. This idiopathic condition is non-inflammatory and ectatic in nature, affecting the cornea in a way that is distinct from other corneal disorders.

In this retrospective case series, we analyzed the clinical and tomographic findings of 15 eyes (9 patients) with the claw pattern on the anterior sagittal map (ASM). Our goal was to study the tomographic features of pellucid-like keratoconus (PLK) and report a new sign on the pachymetry map (PM) in PMD.

Our results show that the 'bell' sign is a deferential diagnostic sign in PMD, with 4 out of 4 eyes exhibiting this characteristic. In contrast, none of the eyes diagnosed with PLK showed the bell sign. We also found that cone location does not relate to diagnosis, as cones were central, paracentral, or peripheral in both PMD and PLK cases.

Furthermore, our analysis revealed that the 'kissing birds' sign was present in 18.2% of eyes diagnosed with PLK, whereas none of the PMD eyes exhibited this sign. The cone location in these eyes was central (9.1%), paracentral (72.7%), or peripheral (18.2%).

In conclusion, our study highlights the importance of the bell sign on the PM as a diagnostic feature of PMD, distinct from PLK. Additionally, our findings suggest that the claw pattern on the ASM is not a hallmark of PMD and can be seen in PLK cases.

The patients were studied using slitlamp biomicroscopy and Scheimpflug-based tomography (Pentacam HR), allowing us to analyze the corneal thickness and topography. The results of our study provide valuable insights into the diagnosis and management of PMD and PLK, two conditions that are often confused with each other.

Lynden pellucid marginal degeneration