Pellucid-like keratoconus

Area of Science:

• Ophthalmology
• Corneal Imaging
• Refractive Surgery

Background:

• Pellucid marginal degeneration (PMD) and pellucid-like keratoconus (PLK) are corneal ectatic disorders that can present with similar tomographic features.
• Differentiating between PMD and PLK is crucial for appropriate patient management and treatment planning.

Purpose of the Study:

• To investigate the tomographic characteristics of PLK using Scheimpflug-based tomography.
• To identify and report a novel diagnostic sign on the pachymetry map (PM) for PMD.

Main Methods:

• A retrospective analysis of 15 eyes (9 patients) with a "claw" pattern on the anterior sagittal map (ASM) was conducted.
• Patients were classified into PMD (inferior corneal thinning) and PLK (no inferior thinning) groups.
• Slitlamp biomicroscopy and Pentacam HR tomography (ASM, anterior elevation map, PM) were used for analysis.

Main Results:

• The "claw" pattern on the ASM was observed in both PMD and PLK groups.
• The "bell" sign on the PM was present in all PMD cases (100%) but absent in PLK cases.
• Cone location varied, with no clear correlation to the diagnosis.

Conclusions:

• The "claw" pattern on the ASM is not pathognomonic for PMD and can be present in PLK.
• The "bell" sign on the pachymetry map serves as a distinguishing diagnostic feature for PMD.
• Cone location is not a reliable factor in differentiating PMD from PLK.