Prospective Cohort Study Comparing Intraocular Lens (Iol) Stability In Patients With Normal And Long Axial Length Using Ultrasound Biomicroscopy (Ubm)

Patients with high axial lengths present challenges when undergoing cataract surgery. In particular, the stability of an IOL inserted into the capsular bag may be compromised due to atypical anatomy. Studies using AS-OCT have shown correlations between measures of IOL stability, such as rotation and decentration, in patients with higher axial lengths.

Recent studies suggest that UBM may be a superior method compared to AS-OCT for assessing IOL position given its improved visualization of anterior segment structures. However, there is currently a lack of evidence delineating this relationship using UBM.

This study evaluates long term IOL stability using multiple outcomes measures in patients with high axial lengths using UBM.

This is a prospective study of patients who underwent cataract surgery at a single surgical site (University of Ottawa Eye Institute) in Ottawa, Canada. A total of 3 surgeons were included over a 5-year period from Jul 1, 2017, to Nov 15, 2022.

The comparator groups will be those with 1) high axial length (≥26mm) and 2) normal axial length (between 20.5mm and 26mm). Exclusion criteria will include: 1) those receiving IOLs not inserted into the capsular bag; 2) IOLs stabilized using additional methods (ie capsular tension ring); and 3) those with any posterior capsule complication during surgery.

Pre and long term post operative characteristics will be collected on all participants including refractive outcomes and complications.

IOL stability will be measured using UBM. The main stability measures will be degree of tilt (degree), height of tilt (μm), and decentration (μm).

A total of 13 patients were recruited for the study with long (n=4) and normal (n=9) axial length. There were no significant differences in the baseline demographic and pre-operative characteristics between the two groups.

The biometric values between the two cohorts showed trends towards significance with larger WTW (12.35mm vs 11.94mm, p=0.16) and LT (4.77 vs 3.99, p=0.18) amongst those with longer axial lengths.

There was also a trend towards significance in higher measures of IOL instability amongst the higher axial length group. The average IOL degree of tilt was 1.94 vs 1.16 degrees (p=0.31), height of tilt was 181.13 vs 83.11μm (p=0.11) and decentration was 280 vs 178μm (p= 0.24).

These results using UBM suggest potentially lower levels of IOL stability in those with high axial lengths. An improved understanding of this relationship may inform IOL selection or use of capsular support devices in this patient population. Future work will focus on recruiting a larger cohort of patients to establish statistical significance of these trends.