title: Accuracy of axial length measurements from immersion B-scan ultrasonography in highly myopic eyes.
abstract: OBJECTIVE
  To evaluate the accuracy of axial length (AL) measurements obtained from immersion B-scan ultrasonography (immersion B-scan) for intraocular lens (IOL) power calculation in patients with high myopia and cataracts.
  
  
  METHODS
  Immersion B-scan, contact A-scan ultrasonography (contact A-scan), and the IOLMaster were used to preoperatively measure the AL in 102 eyes from 102 patients who underwent phacoemulsification and IOL implantation. Patients were divided into two groups according to the AL: one containing patients with 22 mm≤AL<26 mm(group A) and the other containing patients with AL≥26 mm (group B). The mean error (ME) was calculated from the difference between the AL measurement methods predicted refractive error and the actual postoperative refractive error.
  
  
  RESULTS
  In group A, ALs measured by immersion B-scan (23.48±1.15) didn't differ significantly from those measured by the IOLMaster (23.52±1.17) or from those by contact A-scan (23.38±1.20). In the same group, the standard deviation (SD) of the mean error (ME) of immersion B-scan (-0.090±0.397 D) didn't differ significantly from those of IOLMaster (-0.095±0.411 D) and contact A-scan (-0.099±0.425 D). In group B, ALs measured by immersion B-scan (27.97±2.21 mm) didn't differ significantly from those of the IOLMaster (27.86±2.18 mm), but longer than those measured by Contact A-scan (27.75±2.23 mm, P=0.009). In the same group, the standard deviation (SD) of the mean error (ME) of immersion B-scan (-0.635±0.157 D) didn't differ significantly from those of the IOLMaster (-0.679±0.359 D), but differed significantly from those of contact A-scan (-0.953±1.713 D, P=0.028).
  
  
  CONCLUSIONS
  Immersion B-scan exhibits measurement accuracy comparable to that of the IOLMaster, and is thus a good alternative in measuring AL in eyes with high myopia when the IOLMaster can't be used, and it is more accurate than the contact A-scan.
authors: Department of Ophthalmology, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China.
authors: Qing-Hua
authors: QH
authors: Yang
authors: Department of Ophthalmology, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China.
authors: Bing
authors: B
authors: Chen
authors: Department of Ophthalmology, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China.
authors: Guang-Hua
authors: GH
authors: Peng
authors: Department of Ophthalmology, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China.
authors: Zhao-Hui
authors: ZH
authors: Li
authors: Department of Ophthalmology, Chinese PLA General Hospital, 28 Fuxing Road, Haidian District, Beijing 100853, China.
authors: Yi-Fei
authors: YF
authors: Huang
keywords: axial length; high myopia; immersion; measurement; ultrasonography