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AM Fea, F Annetta, S Cirillo, M DeGiuseppe, D Regge, FM Grignolo; MR Evaluation of the Anterior Segment . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4172.
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Purpose: Although in the last few years, low ametropias (< 8 D) have been successfully corrected by corneal surgery (excimer laser), higher ametropias still rely on the use of phakic intraocular lenses (PIOLs). In particular posterior chamber PIOLs have gained wide acceptance and guarantee optimal refractive characteristics. The most frequent complications following this surgical correction are due to improper measuring of the PIOL diameter. A larger PIOL can determine acute glaucoma, whereas a shorter IOL invariably determines cataract in the short or medium term. Untill now the PIOL diameter is obtained considering the white to white size assessed by topographic or by caliper measures. MR is the only method to study the site of PIOL implantation and to determine the whole diameter of the PIOL. We decided to study the reproducibility and the correlation of the MR estimates with the standard method of white to white measuring. Method: High resolution MR (T1 and T2) was used to measure the diameter of a PIOL in 50 healthy subjects aged 23 to 50 years. Two scans were taken and the measures were taken by two independent observers to assess the reliability of the method. In the same subjects the white to white measure was taken by caliper and by reading two corneal maps. The correlation between the methods and whithin the methods was evaluated using the Spearmann correlation coefficient. Results: MR measures proved to be highly correlated either when the same operator read the two scans obtained by the same subject (r=0.85) and when two different operators read the same scan (r=0.80). Similar results were obtained considering the correlation of the topographic white to white diameters. MR correlated well when compared to the white to white determination (r=0.79), although in some cases (3) a difference as high as 2 mm was detected. All those cases were long soft contact lens users.≷ Conclusion: The topographic measure of the white to white diameter seems a reasonable method of assessing the PIOL size, but in some cases further analysis may be necessary in order to avoid complications
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