Corneal Densitometry in Keratoconus
To compare corneal densitometry measured by Scheimpflug tomography in normal and keratoconic eyes and to assess the difference in densitometry among the stages of keratoconus.
Keratoconic and normal corneas were examined by Pentacam (Oculus). Corneal densitometry was measured over 12mm diameter area, divided by annular concentric zones and depths. Keratoconus was classified according to topographic keratoconus classification (TKC). Were enrolled one eye randomly selected from 172 patients with normal corneas (N) and from 98 patients with bilateral keratoconus (KC).
There were significant differences between the groups for densitometry measurements in 2 annuli: central 2.0mm in diameter (N=16.85 ± 2.42, KC=18.93 ± 2.78, p=0.0001) and annulus 2.0mm to 6.0mm in diameter: (N=15.18 ± 2.18, KC=16.16 ± 1.71, p=0.005), and total diameter (N=24.89 ± 6.18, KC=16.71 ± 2.3, p=0.033). Divided by layers, the inner part of anterior (120µm), central (from 120µm to the last 60µm) and posterior (last 60µm) layers were also higher in KC group (p<0.001). There were differences according to the stages of keratoconus for corneal densitometry of the central annuli at total thickness, anterior and central layers. More advanced cases presented the higher backscatter (p<0.05). Anterior layer presented the smallest overlap between groups and KC stages.
The densitometry map reveals that light backscatter was higher in central portion of anterior keratoconic cornea than normal cornea. Considering the stage of the disease, the densitometry level is higher in more advanced stages.