Comparison Of Corneal Collagen Fibril Arrangement In Keratoconic Thin Corneas Vs Normal Thin Corneas Using Polarizarion-Sensitive Oct

To study the phase retardation (PR) distribution in thin corneas and keratoconic thin corneas using our custom-built ultrahigh resolution polarization-sensitive optical coherence tomography (PS-OCT).

Narayana Nethralaya, Bangalore

A total of 15 thin corneas (< 500 µm) with no clinical complications and 10 keratoconic thin corneas were imaged using our PS-OCT. PR enface maps (11mm) from posterior cornea were generated. Zonal analysis was performed on PR enface maps in annular zones from center to periphery. Further corneal sublayer thickness profiles were generated.

PR enface maps from thin corneas showed least retardation (18.61 ± 3.4) in the center and increased (44.32 ± 3.14) radially towards the periphery. This closely resembles the preferential arrangement of collagen fibrils as seen in healthy corneas with thickness greater than 500 µm. The keratoconic thin corneas also showed similar arrangement of fibrillar structures, with higher PR values at the center (23.32 ± 3.18) as well as at the periphery (47.01 ± 3.48). In keratoconic corneas the corneal sublayer thickness profiles showed regional thinning in all layers at the cone location while the thin corneas showed uniform thickness profiles for all layers.

Keratoconic thin corneas showed higher phase retardation compared to healthy thin corneas. PR enfaces maps derived from PS-OCT can be used as a screening modality in routine clinical practice for early diagnosis of keratoconic thin corneas.