Influence of brightness artefacts on corneal densitometry.

Abstract

Purpose: To quantify objectively the influence of brightness artefacts inherent in Scheimpflug tomography on corneal densitometry (CD) estimates.

Methods: Fifty-seven healthy participants aged 30.9 ± 13.7 years (range 17-60 years) were examined with a Ziemer Galilei G2 Scheimpflug tomographer. Images were automatically segmented to isolate the cornea, iris, crystalline lens and corneoscleral lateral brightness regions. CD was calculated as the corneal mean pixel intensity (MPI). Statistical analysis explored the relationship between brightness artefacts and CD across different corneal layers, while also considering age and biometric parameters such as anterior chamber depth and pupil size.

Results: Brightness artefacts accounted for 6.56 ± 1.93% of the pixels in the images, with lateral brightness being the largest source of noise (4.19 ± 0.97%). A strong positive correlation was found between CD and overall brightness artefacts (r = 0.57, p < 0.001). Age was also significantly correlated with both CD (r = 0.65, p < 0.001) and brightness (r = 0.29, p = 0.01). Mediation analysis revealed that age accounts for 60.0% of CD variability, while brightness artefacts contributed 40.0%. Brightness artefacts had the strongest effect on the corneal periphery beyond 7.5 mm as well as the stromal layer.

Conclusion: Brightness artefacts significantly influence CD estimates, particularly in the peripheral cornea. Accurate quantification of these artefacts is essential for proper clinical assessment of corneal transparency, especially in older populations. Future research should focus on identifying the specific sources of artefacts to refine CD measurement techniques.