[Accuracy of immersion B-scan ultrasound biometry in high myopic patients with cataract].

OBJECTIVE

To compare the accuracy of axial length measurement with three methods, that is, immersion B-scan, contact A-scan, and IOLMaster in high myopia with cataract.

METHODS

To analyze the data of the 40 patients (66 eyes), who were all high myopia with cataract and accepted the phacoemulsification and fold-able lens implantation surgery in our hospital from Jan 2012 to May 2012. The measurement of axial length was performed respectively in 66 eyes by immersion B-scan, contact A-scan and IOLMaster. Keratometric power was measured preoperatively by IOLMaster. The IOL power calculation was carried out according to SRK/T formula in the basis of IOLMaster. Their refraction outcome was follow-up three months after operation.

RESULTS

The axial length was (27.91 ± 1.96) mm, (27.71 ± 2.15) mm, (27.88 ± 2.04) mm respectively by immersion B-scan, A-scan and IOLMaster. There was no significant difference between immersion B-scan and IOLMaster method (t = 0.726, P = 0.473). But the axial length measured by contact A-scan was shorter than that tested by immersion B-scan(t = 2.223, P = 0.003) and IOL Master (t = 2.614, P = 0.014) significantly. There was significant difference between immersion B-scan and contact A-Scan method in those patients whose mean absolute refractive error (MARE) was within ± 0.50 Diopter three months after operation (χ(2) = 5.67, P < 0.05) , while there was no significant difference between immersion B-scan and IOLMaster measurement (χ(2) = 0.06, P > 0.05). The same situation happened in those patients whose MARE was within ± 1.00 Diopter. That means, there was significant difference between immersion B-scan measurement and contact A-scan measurement (χ(2) = 4.19, P < 0.05) , while there was no significant difference between immersion B-scan and IOLMaster measurement(χ(2) = 0.36, P > 0.05).

CONCLUSIONS

The immersion B-Scan measurement is better than A-scan, and it is as accurate as the IOL Master measurement, which is another good choice for the axial length measuring in high myopia with cataract cases.