# Corneal optical densitometry in transparent corneas and its correlations with corneal higher-order aberrations

## TL;DR

This study finds that increased corneal optical density correlates with higher corneal optical aberrations, even in transparent corneas, possibly due to age-related changes.

## Contribution

The study identifies a novel correlation between corneal optical densitometry and higher-order aberrations in transparent corneas.

## Key findings

- Total COD correlates positively with HOAs, spherical aberration, and coma in both central 4.0 mm and 6.0 mm zones.
- Age and COD show a statistically significant positive correlation.
- Increased COD may compromise corneal sphericity and symmetry due to microstructural changes.

## Abstract

This study aimed to evaluate correlations between corneal optical densitometry (COD) and corneal higher-order aberrations (HOAs).

A prospective cross-sectional study.

A total of 67 participants were enrolled. The Pentacam quantified total COD and corneal HOAs. Coma and trefoil were described using the root mean square (RMS). HOAs measurements, including total HOA, spherical aberration (Z40), vertical coma (Z3-1), horizontal coma (Z31), oblique trefoil (Z3-3), horizontal trefoil (Z33), coma RMS (Z3 ± 1 RMS), and trefoil RMS (Z3 ± 3 RMS) of the total, anterior, and posterior corneas, were calculated for both the central 4.0 mm diameter and the central 6.0 mm diameter zones.

In the central 4.0 mm diameter zone, total COD exhibited significant positive correlations with HOA, Z40, and Z3 ± 1 RMS of the total cornea, HOA and Z40 of the anterior cornea, as well as Z40 and Z31 of the posterior cornea; in the 6.0 mm zone, total COD was positively correlated with HOA, Z40, and Z3 ± 1 RMS of the total cornea, HOA of the anterior cornea, as well as Z40, Z3-1, Z31, and Z3 ± 1 RMS of the posterior cornea (P < 0.05 for each one). Age and COD showed a statistically positive correlation (rs = 0.350, P = 0.004).

An increase in COD may result in elevated levels of corneal HOAs, particularly including total HOA, spherical aberration, and coma. This increase could potentially compromise the sphericity, symmetry, and regularity of the cornea due to age-related changes in corneal microstructure and composition, even in clinically transparent corneas.

The online version contains supplementary material available at 10.1186/s12886-025-04583-x.