Validation of optical coherence tomography-based crystalline lens thickness measurements in children

To evaluate the validity and repeatability of crystalline lens thickness measurements obtained by anterior segment optical coherence tomography (OCT).

Forty-seven normal children (mean age, 11.06 +/- 2.30 yr) had their crystalline lens thickness measured with the Visante anterior segment OCT (Carl Zeiss Meditec, Dublin, CA) and with conventional corneal touch A-scan ultransonography (ultrasound) (Humphrey 820). The subjects' right corneas were anesthetized, and their right eyes were cyclopleged. Five ultrasound measurements were recorded per eye, and three Visante OCT measurements were recorded per eye. Thirty-eight subjects had measurements at a second visit where three additional Visante OCT measurements were recorded.

The mean of the differences between the Visante OCT and ultrasound was -0.045 mm (p = 0.017) with 95% limits of agreement from -0.29 to 0.20 mm, indicating that the measurement of crystalline lens thickness was slightly thinner with the Visante OCT. When validity was assessed using only Visante OCT images that contained the corneal reflex, the mean of the differences was 0.019 mm (p = 0.11) with 95% limits of agreement from -0.091 to 0.13 mm. For the repeatability of the Visante OCT, the mean of the differences between visit one and visit two was -0.008 mm (p = 0.25) with 95% limits of agreement from -0.088 to 0.072 mm. Repeatability improved when reassessed using only images that contain the corneal reflex; the mean of the differences was -0.0001 mm (p = 0.97) with 95% limits of agreement from -0.030 to 0.030 mm.

The Visante OCT is a non-contact instrument that is simple to use, and it provides valid crystalline lens thickness measurements with excellent repeatability. Validity and repeatability are optimized when the Visante OCT images contain the corneal reflex and a consistent corneal index refraction is applied to the entire image.