Comparison Of Reliability And Repeatability Of Intraocular Lens Tilt And Decentration Assessment

The methods used to assess intraocular lens tilt and decentration vary in their fundamental principles; these differences may have a clinical impact and the accuracy of measurement is vital for the assessment of modern intraocular lenses. We investigated the agreement and reproducibility of five methods of assessing tilt and decentration. 

Hospital eye clinic, Plymouth Hospital University NHS Trust, United kingdom and University eye and vision research Unit, University of Plymouth, United Kingdom

Assessment of tilt and decentration was performed on 44 subjects following implantation of the Tecnis monofocal IOL. Subjects were assessed 3-12months post-operatively using; slit lamp image analysis (decentration only), Gyton method (tilt only), phacometry (bespoke purkinje meter), Scheimpflug (Pentacam) image analysis, and optical coherence tomography (Tomy Casia AS-OCT).  A second observer assessed 20 subjects for inter-observer variability. Data was analysed using intra-class correlation coefficient (ICC) for intra-observer variation. Bland-Altman plots, Pearson’s correlation coefficient and repeated measures analysis of variance were used to assess agreement of data produced by the instruments and Inter-observer concordance. 

The number of subjects that could be successfully assessed varied between techniques with slit lamp image analysis being most dependent on pupil size. The authors were unable to assess decentration using the Guyton method and so only tilt was analysed using that technique. There was no significant difference in absolute tilt and decentration values between all techniques  (p < 0.05). Bland and Altman assessment of decentration and tilt demonstrated relatively wide limits of agreement particularly in relation to the values as assessed with the slit lamp. The OCT and Pentacam demonstrated the closest agreement of all the measures.

The widest limits of agreement when the slit lamp was used to assess decentration; the parallax effect caused by power of the cornea creates an artificial decentration result with this method. The values of decentration from the Pentacam and OCT demonstrated the closest agreement with the OCT demonstrating excellent inter and intra-observer repeatability. Agreement with the phacometer was closest with the OCT in comparison with the Pentacam and slit lamp methods.