Assessing and predicting the effective addition power of multifocal intraocular lenses

Session Details

Session Title: Multifocal IOLs I

Session Date/Time: Sunday 15/09/2019 | 16:30-18:00

Paper Time: 17:06

Venue: Free Paper Forum: Podium 1

First Author: : E.Law UK

Co Author(s): :    H. Buckhurst   R. Aggarwal   H. Kasaby   P. Buckhurst                    

Abstract Details

Purpose:

Manufacturers of multifocal intraocular lenses (MIOLs) describe the near addition at the IOL plane. However, the effective addition power at the spectacle plane is a better clinical description to describe the actual working distance that a MIOL provides to a patient. The effective addition power is dependent on both the power of the IOL and an individual’s ocular biometry. This study was designed to explore the relationship between the theoretical add power at the spectacle plane and the effective addition power at the spectacle plane. In addition, a simple clinical technique for predicting the post-operative add power was evaluated.

Setting:

BMI Southend Hospital University of Plymouth

Methods:

A prospective study involving 42 subjects implanted with a MIOL with addition power +3.50D. Pre- and post-operative biometry measurements were attained using the LenStar. Binocular defocus curves from +1.5D to -5.0D in 0.5D randomised steps were measured. Polynomial curves fitted to the data derived the inflection points and thus the distance and near focal points were identified. Effective add power was defined as dioptric distance between distance and near inflection points. Post-operative biometry was used to calculate the theoretical add by paraxial ray tracing. Pre-operative biometry was used to predict the add power according to Haigis, Holladay and SRK/T formulae.

Results:

The mean effective addition derived from defocus curves was 2.730D 0.269 and ranged from 1.90D to 3.11D. This effective add was greater than that predicted by the formulae, Haigis 2.538D 0.411, Holladay 2.422D 0.400 or SRK/T 2.421D 0.420 and that determined by ray tracing 2.504D 0.111. There was a significant difference between the effective add and all the predicted methods (p <0.01). There was no significant difference between the theoretical ray tracing results and the Holladay (p = 0.386) and SRK/T (p = 0.474). There was a significant correlation (R = 0.726, p <0.01) between Holladay and SRK/T predicted results.

Conclusions:

The results of this study demonstrate the possibility to predict the effective addition power using pre-operative ocular biometry measurements and conventional IOL formula, However, this does appear to underestimate/overestimate the add power in individual cases. There was wide variation in addition powers between individuals, suggesting that factors such as anterior chamber depth and base IOL power influence the outcome.

Financial Disclosure:

None