Abstract
Purpose :
It is standard practice to repeat biometry every 1-2 years prior to cataract surgery. The goal of this study was to assess if axial length (AL) and average keratometry (KER) (vital in lens calculation) change over time and question the clinical necessity of regularly repeating biometry.
Methods :
Retrospective study of biometry data collected via IOL Master 700 (Zeiss, Germany) at Northwestern Memorial Hospital from January 1, 2016 through September 15, 2020. Inclusion criteria were patients over 35 years old, with two biometry measurements over 6 months apart. Patients were excluded if they had any other intraocular surgery, other than cataract. This analysis focused on AL and KER variables. To compare AL measurements among timepoints, a paired t-test was used. P-values were adjusted using the Bonferroni correction. Data was also stratified into four groups by axial length: hyperopia (<22mm), average (22 – 24.5mm), mild myopia (24.5 – 26.0mm), and high myopia (>26.0mm).
Results :
A total of 201 patients (402 eyes) were included (average age 73.3, 59.3% female). Average time between biometry measurements was 21.5 months, average AL was 24.08 mm, and average KER was 43.73 D. The mean change in AL was 0.04 mm (95% CI: 0.03 to 0.05). The mean change in KER was 0.10 D (95% CI: -0.10 to 0.30, p=0.33). At the 6mo to 1 year interval (n=73), mean change in AL was 0.04 mm. Mean change in AL did not increase at the 1 to 2 year interval (n=204, ΔAL=0.05), the 2 to 3 year interval (n=87, ΔAL=0.03) or the 3 to 4 year interval (n=38, ΔAL=0.04). Using a linear regression model, there was no correlation between time and change in AL (p=0.06), nor between time and KER (p=0.15).
Eyes with high myopia showed a ΔAL of 0.07 (n=23; 95% CI: 0 to 0.15, p=0.06). This subgroup had the highest mean change in AL; compared to hyperopia (ΔAL = 0.04), average length eyes (ΔAL = 0.04) and moderate myopia (ΔAL of 0.03).
Conclusions :
AL and KER change minimally over time between biometry readings. The mean change in AL was 0.04 mm (95% CI: 0.03 to 0.05). Change in AL did not increase with longer intervals of time between measurements. High myopes had a larger change in AL compared to shorter eyes, however, ΔAL was still low at 0.07 mm. These results suggest repeating biometry at a 1 to 2-year interval during surgical workup may not be a necessity, rather can be used selectively – for example, in high myopes.
This is a 2021 ARVO Annual Meeting abstract.