Which type of illumination would MOST likely be used to diagnose a patient with EBMD?

• A. Sclerotic scatter
• B. Optic section
• C. Conical beam
• D. Indirect illumination

Answer: (D)

Illuminating the corneal surface from an oblique angle to highlight surface irregularities is what makes EBMD patterns visible. EBMD produces map-like and fingerprint patterns in the epithelial layer, and these subtle changes are best seen when light is directed to skim the surface rather than straight on. Indirect illumination provides that angled, shadow-promoting lighting, which enhances the contrast of the epithelial irregularities so the maps and fingerprint lines stand out during the slit-lamp exam. Other illumination modes either emphasize overall corneal clarity, give only cross-sectional detail, or don’t create the shadowing needed to reveal these surface changes, so they’re less effective for diagnosing EBMD.