{'fraction_non_alphanumeric': 0.020555767034640272, 'fraction_numerical': 0.003806623524933384, 'mean_word_length': 4.615384615384615, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Measurement of intraocular lens tilt with ultrasound biomicroscopy – authors reply

Editor, W e thank Kothari, Shukri and Ranade (Kothari et al. 2011) for their interest in our article (Ang et al. 2010). The authors do raise some interesting points about the measurement of intraocular lens (IOL) tilt with ultrasound biomicroscopy (UBM). While our technique of measuring IOL tilt is by no means perfect, we believe that it is nevertheless useful in the clinical and research setting. Ultrasound biomicroscopy scanning with the Paradigm Ultrasound Biomicroscope Model P40 UBM Workstation (Paradigm Medical Industries Inc., Salt Lake city, UT, USA) requires the use of a coupling agent (Viscotears for our study), and so, there is no direct contact between the UBM probe and the cornea. To obtain a good UBM scan with the image in the centre of the screen, the UBM probe has to be at an optimum distance away from the anterior corneal surface. It is therefore very unlikely that there would have been any indentation effect on the cornea because of the UBM probe. It is true that it may be difficult to find the exact centre of the posterior corneal surface with only one UBM scan, especially one which is tilted or decentred. We, therefore, take multiple scans and choose the best scan for measurement. The best scan was the one where the IOL optic and pupil were oriented centrally, with the pupil at its largest size and with symmetry of ocular structures. By doing this, we minimized any potential errors and inaccuracies and were thus able to take the highest point of the corneal curvature to represent the centre of the posterior corneal surface. We agree that the cord length lines do not represent the axis of the IOL optic. However, we contend that calculating the angle subtended by the cord length line and line of reference at the point of reference remains valid as one method of measuring of IOL tilt. This may be useful in cases where there is a local deformity or defect (of any aetiology) in the IOL optic. Additionally, the authors also describe an alternative way of measuring IOL tilt. This method has its merits and also its potential drawbacks, one of which is the difficulty in identifying the scleral spur in some patients. Another is the requirement to first print or export the scan image to a separate computer before the IOL optic tilt can be measured. We are unable to comment upon the reliability or reproducibility of this technique compared with ours. We thank the authors again for this interesting discussion, and we look forward to reading more about developments in this field in the future.