Anterior segment optical coherence tomography versus ultrasound pachymetry to measure corneal thickness in endothelial keratoplasty donor corneas.

PURPOSE

To analyze corneal thickness (CT) by anterior segment optical coherence tomography and ultrasound pachymetry in precut endothelial keratoplasty (EK) donor corneas at the eye bank.

METHODS

Thirty-six corneas were analyzed. All corneas were dissected to create lamellar grafts for EK using the standard eye bank protocol. We measured central and peripheral (3 mm from center) CT by ultrasound after lamellar tissue processing and by optical coherence tomography after the tissue was transferred to a viewing chamber. We performed paired t tests and Pearson correlation analyses to compare ultrasound and optical coherence tomography measurements.

RESULTS

Central CT measurements by optical coherence tomography versus ultrasound in donor corneas were not statistically different (mean: 169 vs. 177 µm, respectively, P = 0.09). There was a strong correlation between measurements of central CT (r = 0.73, P < 0.0001). There was a statistically significant difference in mean peripheral CT measurements by optical coherence tomography and ultrasound (mean: 190 vs. 236 µm, respectively, P < 0.0001); at peripheral locations, measurements correlated moderately (r = 0.52, P = 0.002).

CONCLUSIONS

Optical coherence tomography measurements of EK-prepared tissue averaged 8 μm thinner than the ultrasound measurements, similar to clinical measurements of central CT. Given the growing interest in the effect of EK graft thickness on patient outcomes, it is important to understand the differences in measurements obtained by different devices used to assess donor corneas.