Repeatability and Reproducibility of Slit Lamp, Optical Coherence Tomography, and Scheimpflug Measurements of Corneal Scars.

Purpose: To determine the repeatability and reproducibility of anterior segment optical coherence tomography (AS-OCT) and Scheimpflug photography for several measurements of corneal scars, including scar size, scar depth, and corneal thickness.

Methods

A series of patients treated for fungal keratitis at a tertiary eye care center in South India were recalled two years after successful treatment. Eyes with corneal scars had a slit lamp examination performed by two ophthalmologists masked to the other's examination. For AS-OCT and Scheimpflug photography, each eye had two scans taken by one technician and a third scan taken by a separate technician. Scar measurements were subsequently assessed from AS-OCT images by three graders masked to each other's results. Repeatability and reproducibility were assessed by calculating the intra-class correlation coefficient (ICC) from mixed effects linear regression models.

Results

Fifty eyes had all measurements taken. The corneal scar size, measured as the geometric mean of the two longest perpendicular meridians, ranged from 0.8 to 5.4 (mean 2.8 mm, 95%CI 2.6 to 3.1). Scar size measurements taken by two separate individuals were most reproducible when the border of the scar was traced from the OCT (ICC 0.90, 95%CI 0.86 to 0.94), and least repeatable when assessed from slit lamp examination (ICC 0.80, 95%CI 0.70 to 0.90).

Conclusions

AS-OCT and Scheimpflug imaging of corneal scars produced measurements with acceptable reproducibility that could be useful as cornea-specific outcomes for clinical trials.