Quantitative assessment of corneal clarity in keratoconus: a case control study of corneal densitometry

To evaluate corneal clarity quantitatively by corneal densitometry measurement in treatment-naive keratoconus patients and to compare these results with those of healthy control subjects.

Corneal densitometry measurement of consecutive treatment-naive keratoconus patients and healthy control subjects was performed by Scheimpflug corneal topography (Pentacam®HR). Corneal densitometry measurements were expressed in gray scale unit (GSU) and the data from the right eyes of subjects were used for statistical analysis.

A total of 102 subjects (51 patients with keratoconus [27 male, 24 female] and 51 healthy control subjects [24 male, 27 female]) were included in the study. There was no statistically significant difference with regard to the mean age (p = 0.910) or distribution of sex (p = 0.552) between the groups. There were significant differences in corneal densitometry values of the groups in central 2 mm (17.95 ± 0.33 GSU in keratoconus and 16.43 ± 0.24 GSU in controls, p<0.001) and in annulus of 2 to 6 mm in diameter (15.88 ± 0.26 GSU in keratoconus and 15.02 ± 0.22 GSU in controls, p = 0.015). When considering the measurements in different depths, the anterior layer displayed the highest densitometry value compared to that of both the central and posterior layers. Corneal densitometry of anterior 0-2 mm was positively correlated with simulated K value (r = 0.446, p = 0.001), whereas it was negatively correlated with central corneal thickness (r = -0.361, p = 0.016) in keratoconus patients.

Treatment-naive keratoconus patients have significantly higher corneal densitometry values in central cornea when compared to healthy control subjects. The clinical relevance should be further studied in detail.