Abstract: Objective To compare corneal densitometry(CD) between keratoconus(KC) and normal cornea, and to investigate the correlation between CD and topographic parameters. Design Cross-sectional study. Participants A total of 162 keratoconic patients (162 eyes) (KC group) and 41 normal subjects (41 eyes) (NL group) were included from Beijing Tongren Hospital from 2017 to 2019. Methods CD values were obtained for the 0~2 mm, 2~6 mm, 6~10 mm, 10~12 mm and 0~12 mm zones of the anterior (up to 120 μm), posterior (posterior 60 μm), central (between the anterior and posterior) and total cornea by Pentacam HR. The Pentacam provides a topographic keratoconus classification for staging the disease in grades 1 to 4. Cases were divided into mild, grade 1; moderate, from grades 1 to 2 and grade 2; and severe, grade 3, from grades 3 to 4 and grade 4. Bonferroni multiple comparisons test or Kruskal-Wallis test was used to compare CD between different groups. Pearson’s correlation test or Spearman’s correlation test was used to determine the correlations between CD and topographic parameters. Main Outcome Measures CD values over different corneal annular concentric zones and depths, maximum keratometry (Kmax), corneal central thickness (CCT) and thinnest corneal thickness (TCT). Results The CD values of the anterior 0 to 2 mm layer for the NL group, KC group, KC mild, KC moderate and KC severe were 21.67±1.60, 21.90（18.70~98.70）, 21.6（18.70~24.80）, 21.60（19.30~29.10） and 22.80（20.00~98.70）, respectively. There were significant differences between KC group and NL group for the CD of the anterior 0 to 2 mm layer (P=0.043). There were no significant differences between KC mild, KC moderate and NL group for the CD of the anterior 0 to 2 mm layer(all P＞0.05). There were significant differences between KC severe and the other groups for the CD of the anterior 0 to 2 mm layer (all P＜0.05). There were no significant differences between groups for the CD of the remaining corneal annuluses and layers(all P＞0.05). The CD values of the anterior 0 to 2 mm layer significantly and positively correlated with the Kmax values (R=0.181，P=0.03), and significantly and negatively correlated with CCT and TCT values (R=-0.172, P=0.03 and R=-0.171, P=0.04, respectively). Conclusion The CD values of the anterior 0 to 2 mm layer are higher for the keratoconic cornea than in the normal cornea. The CD level is higher in more advanced stages. There are significant correlations between the CD values of the anterior 0 to 2 mm layer of the keratoconic cornea and the Kmax, CCT and TCT values. CD may be a useful index of KC progression. (Ophthalmol CHN, 2020, 29: 278-283)

Key words: corneal densitometry, keratoconus, maximum keratometry, corneal thickness