When Should We Repeat Biometry Readings?

Current practice in our trust is to repeat biometry readings if greater than 18 months old. Royal College of Ophthalmology guidelines suggest patients should have repeat biometry readings if there is a history of ocular disease or biometry readings are greater than 4 years old. The aim of this study was to establish if over time the axial length (AL) and average keratometry (KER) changes, and to assess the necessity of repeat biometry readings.

A retrospective departmental note review was performed for all patients undergoing repeat biometry between August 2019 to April 2023.

Biometry data was collected via IOL Master 700. Inclusion criteria included adult patients with two biometry measurements over 6 months apart. Patients were separated into two groups; those that had ocular co-morbidities (Group A) and those that did not (Group B). Axial length, K1 and K2 readings, and anterior chamber depth (ACD) data was collected.

A total of 430 eyes were included (234 eyes in group A, 196 eyes in group B). Median time between biometry readings was 118 weeks (IQR 75 - 241 weeks) in group A and 117 weeks (IQR 66 – 240 weeks) in group B.

Mann Whitney U-test was used to compare mean difference in AL and KER over time. Group A showed significant change in AL (p=0.023 and p=0.011), and significant change in KER between readings less than 18 months and 18 months – 4 years (p=0.04).  In group B, there was significant change in mean AL between those with readings at less than 18 months, 18 months - 4 years and >4 years (p=0.026 and p=0.0000036 respectively), however, mean change in KER was not significant (p=0.19 and p=0.97).

Our findings suggest AL and KER in our cohort changed over time.  Repeat biometry should be considered in patients with or without ocular co-morbidities if older than 18 months. Larger studies are required to review guidance around repeating biometry.  Further research into possibilities of refractive outcomes related to repeated biometry would be beneficial.