In Vivo Confocal Microscopy Demonstration Of The Formation Of A Keratocytic Separation Plane Along The Pre-Descemet Stroma In Post-Penetrating Keratoplasty Eyes

Tertiary Eye Care Referral Center (Ospedali Privati Forlì “Villa Igea”, Forlì, Italy)

The study included 13 eyes of 13 patients who previously underwent PK for keratoconus. All patients underwent IVCM (Heidelberg Retina Tomogram III-Rostock Cornea Module; HRTIII-RCM; Heidelberg Engineering GmbH, Heidelberg, Germany) with sequential and volumetric scans of the central cornea including the stroma, Descemet membrane (DM), and endothelium. The findings were compared with a group of 13 age-matched controls with no ocular disease.

In all post-PK eyes, IVCM demonstrated a distinct plane of densely distributed keratocytes within the pre-Descemet stroma which represents the most posterior confocal image with countable cells. These keratocytes appear as hyperreflective oval to kidney-shaped figures within a hyporeflective extracellular matrix. In control corneas, keratocytes are sparsely distributed within the stroma with a decreasing density from anterior to posterior. No distinct plane of dense keratocytes could be identified within the pre-Descemet stroma. The mean keratocyte cell count of the most posterior confocal image with countable cells was 506 ± 191 cells/mm² which was significantly higher than in control eyes (238 ± 35 cell/mm²) (p< 0.001).

Within the pre-Descemet stroma of post-PK eyes, IVCM demonstrates a dense cellular plane which is not observed in keratoplasty-naïve corneas. The presence of this distinct keratocytic layer separates posterior stroma from pre-Descemet layer, Descemet membrane and endothelium, thereby accounting for the technical ease of stromal peeling in post-PK eyes with stromal disease.