How long after cataract surgery can we use biometry measurements for the second eye: never, 1 year, 2 years, 3 years or more? A retrospective analysis of over 5,000 repeated biometry measurements

Session Details

Session Title: Cataract Surgery Outcomes: IOL Power Calculations

Session Date/Time: Sunday 08/10/2017 | 14:30-16:00

Paper Time: 15:06

Venue: Meeting Center Room I

First Author: : L.Lai UK

Co Author(s): :    P. Ursell                    

Abstract Details

Purpose:

It is common for surgeons to request repeat biometries in patients who had biometries in the past for intraocular lens (IOL) calculation. The time interval of when a biometry is valid for is not established, with different surgeons accepting biometries of different historical age. The current Royal College of Ophthalmologists (RCOphth) Cataract Surgery Guidelines do not advise on this. The purpose of this retrospective analysis is to ascertain if repeat biometry measurements change over time, whether that impacts on final intraocular lens power selection and for how long we can safely reuse biometry measurements before they need repeating.

Setting:

UK NHS District General Hospital.

Methods:

Anonymised data on patients with repeated biometry performed over the last 10 years were obtained from our electronic medical record. Only biometries obtained using partial coherence interferometry were included. Biometries of eyes with previous cataract operations were excluded. Data analysis was performed on change in axial length (AL), mean corneal power (K), Steep axis (K2 axis), and power of intraocular lens (IOL) calculated using SRK/T formula for emmetropia, over time. Time interval between repeat biometries were divided into 0-1 year, 1-2 years, 2-3 years, 3-4 years, >4 years, to allow enough biometries in each category for statistical analysis using Bootstrapping.

Results:

A total of 5448 biometries, of 2628 eyes in 1891 patients were included in the analysis. Over time, mean change in AL was 0.03mm increasing to 0.06mm; mean change in mean K was 0.17D increasing to 0.30D; mean change in steep axis was 23 degrees increasing to 45 degrees; mean change in IOL power was 0.22D increasing to 0.37D. This results in less than 0.5D change in IOL power selection in 89% patients in 0-1year, 84.2% in 1-2years, 83.2% in 2-3years, 80% in 3-4years, and 70.4% in >4years. The results are statistically significant for biometries less than 3 years (p=0.04).

Conclusions:

This retrospective analysis of repeat biometries performed over time demonstrates minimal mean change in AL, mean K, steep axis and IOL power selection. As IOL power comes in 0.5D increments, for biometries performed less than 3 years ago, 80% patients will not require change in IOL selection. The mean change of axis also does not exceed 45 degress, therefore should not impact the choice of surgical axis. It is therefore reasonable to propose that it is not necessary to repeat biometry measurements unless they are more than 3 years old.

Financial Disclosure:

NONE