Iol Master 700 Diurnal Variations Of Biometric Parameters

Biometric parameters measured during the biometry exam are critical factors used to determinate the effective lens position (ELP) in order to predict the optimal power of the Intra ocular Lens (IOL) implanted during cataract surgery. Variations of the biometric parameter’s values can influence and change the IOL calculation and by that the IOL selection. The aim of this study is to evaluate and quantify diurnal variation of biometric parameters - Axial length (AL), Anterior chamber depth (ACD), Central corneal thickness (CCT) and White to white (W2W).

A population-based cohort of patients who underwent a Biometry test prior to cataract surgery using the IOL-Master700 (Carl Zeiss Meditec, Jena, Germany) between the years 2017-2021. 

Differences in mentioned parameters were evaluated between scans executed at different time of the day.

21,975 examinations of 8,611 patients were included in the study. Mean age was 70.50±12.56. The mean hour conducting the biometry test was 9.37±1.4 am. Measurements of AL, ACD, CCT, W2W were taken between 07:00 am to 03:00 pm. Between 7:00-9:00 am and 12:00-3:00 pm mean AL was 23.64±1.5mm and 24.01±1.76mm, mean ACD was 3.29±0.67 and 3.35± 0.64mm, mean CCT was 0.53±0.04 and mean W2W was 11.83±0.46 and 11.90±0.51mm respectively (p<0.001).

The differece remained significant in a generalized linear mixed model analysis with standardization for multiple distractors, controlling for repeated measures in the same subject (P<0.001)

Different parameters of IOLMaster 700 biometry exam were assessed for diurnal variations. We can conclude that there are fluctuations in AL, ACD, CCT and WTW measurements during the day. These results arise questions about the significance of timing of the biometry exam and the effect on the ELP calculation.  Further studies should be made to investigate the refractive outcome after cataract surgeries based on the time of the primary biometry exam.