Behavior of biometric parameters during clinical hours

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optometry

Background:

• Accurate biometric measurements are crucial for successful intraocular lens (IOL) power calculation in cataract surgery.
• Previous studies have not fully quantified the diurnal variation of key ocular biometric parameters.

Purpose of the Study:

• To evaluate and quantify the diurnal variation of axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), and white-to-white (WTW) distance.
• To assess the potential impact of these diurnal changes on refractive outcomes after cataract surgery.

Main Methods:

• A retrospective cohort study analyzed 21,975 biometry examinations from 8611 patients undergoing pre-cataract surgery measurements using the IOL Master 700.
• Ocular parameters (AL, ACD, CCT, WTW) were assessed hourly and grouped into morning (7-9 AM) and afternoon (12-3 PM) time slots.
• Statistical analysis, including a generalized linear mixed model, was used to determine the significance of diurnal changes.

Main Results:

• All measured biometric parameters (AL, ACD, CCT, WTW) demonstrated a statistically significant diurnal increase (P<0.001).
• Axial length (AL) exhibited the most significant diurnal change, increasing from 23.64±1.5 mm to 24.01±1.76 mm.
• The observed diurnal variations remained significant even after adjusting for potential confounding factors in the mixed-effects model.

Conclusions:

• Significant diurnal fluctuations exist in key ocular biometric parameters measured during standard office hours.
• The timing of biometry measurements may influence refractive predictability and effective lens position (ELP) calculations.
• Further investigation is warranted to establish optimal timing for biometry to enhance refractive accuracy in cataract surgery.