Assessment of corneal backward light scattering in the healthy cornea and factors affecting corneal transparency

Abstract

Purpose: To quantify normative corneal optical density (COD) values of healthy individuals and to investigate alterations in the COD in relation to their ocular and demographic characteristics.

Study design: Prospective, cross-sectional, and observational.

Methods: In total, 588 eyes from 588 healthy participants with clear corneas were consecutively enrolled. Corneal densitometry values expressed in standardized grayscale units (GSU) from different corneal layers and zones obtained using the rotating Pentacam Scheimpflug system were analyzed.

Results: The mean (SD) COD over the 12-mm diameter area was 14.4 ± 2.74 GSU. A significant positive correlation was found between the participants' age and the total COD (r = 0.756, P < .001). No significant differences were found between males and females with respect to COD (P = .51). No significant correlation was found between the COD measurements and refractive error, pachymetry, and keratometry (P > .05 for all comparisons). On the other hand, COD was negatively correlated with white-to-white (WTW) corneal diameter (r = - 0.415, P < .001). Moreover, the WTW corneal diameter was correlated with the COD in any zone and layer of the cornea (P < .05 for all comparisons).

Conclusions: Wide variations in COD can be detected even in corneas deemed clinically clear. Age and corneal diameter that seem to influence corneal transparency should be taken into account when evaluating corneal backscatter.

Keywords: Corneal backscattering; Corneal transparency; Densitometry; Scheimpflug imaging system.