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Partial Coherence Interferometry Compared with Immersion Ultrasound

Partial Coherence Interferometry Compared with Immersion Ultrasound for Axial Length measurement in children. Phoebe D. Lenhart, M.D. 1 , Amy K. Hutchinson, M.D. 1 , Michael J. Lynn, M.S. 2 , Scott R. Lambert M.D. 1

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Partial Coherence Interferometry Compared with Immersion Ultrasound

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  1. Partial Coherence Interferometry Compared with Immersion Ultrasound for Axial Length measurement in children Phoebe D. Lenhart, M.D.1, Amy K. Hutchinson, M.D.1, Michael J. Lynn, M.S.2, Scott R. Lambert M.D.1 1Department of Ophthalmology, Emory University, Atlanta, Georgia, 2Rollins School of Public Health American Society of Cataract and Refractive Surgery Meeting Boston, Massachusetts, April 2010 Financial interests: None  Supported by National Institutes of Health Grants U10 EY13272 and U10 EY013287 and in part by NIH Departmental Core Grant EY06360 and Research to Prevent Blindness, Inc, New York, New York

  2. Purpose To determine whether measurements obtained by partial coherence interferometry (PCI) correlate well with measurements obtained using immersion ultrasonography (IUS) in children

  3. Methods • We reviewed the charts of 18 pediatric patients (ages 4-16 years) who underwent cataract surgery on 27 eyes at the Emory Eye Center from August 2008 to September 2009 • Axial length measurements of the operative eye were obtained for 21/27 (78%) of eyes using PCI during the preoperative clinic visit • Axial length measurements were then obtained using IUS in the operating room prior to surgery • The data were compared to evaluate the degree of agreement Emory University Institutional Review Board approval was obtained and the study was in compliance with the Health Insurance Portability and Accountability Act.

  4. Data OD=Right eye; OS=Left eye PCI=Partial coherence interferometry; IUS=Immersion Ultrasonography

  5. Results • Axial lengths using PCI were, on average, 0.13 mm less than IUS values (95% CI -0.21 to -0.06; p-value 0.002). • For axial lengths  23.5 mm, all patients had PCI values that were less than the IUS value. • For patients with axial lengths  23.5 mm, there was no systematic pattern of one measurement being greater or less than the other.

  6. Results Mean axial length PCI: 22.14 Mean axial length IUS: 22.27

  7. Results • Negative mean (-0.13) indicates PCI values were, on average, 0.13 mm less than the IUS values. • 95% confidence interval (-0.21 to -0.06) • p-value= 0.002 • Points below the line represent patients with PCI < IUS. • For axial lengths ≤ 23.5, all patients had PCI ≤ IUS. • For patients with axial lengths > 23.5, there was no systematic pattern of one measurement being greater or less than the other.

  8. Discussion • There is a systematic difference in axial length measurement between PCI and IUS with PCI tending to give lower values, particularly for children with axial lengths of  23.5 mm. • A 0.13 mm error in axial length measurement, depending on the length of the eye, could result in a 0.33-0.49 D difference in IOL calculation that may be clinically significant in some patients.

  9. strengths Comparison of PCI to IUS in a pediatric population. • In previous studies of adults and children comparing PCI to applanation A-scan ultrasound, the potential for contact-induced distortion of axial length measurements may have limited direct comparison of values obtained by the two devices.

  10. limitations • Small number of eyes (27) • Unable to obtain more than five axial length measurements for multiple children • Difference between PCI and IUS detected in our study using IUS could have been due to suboptimal alignment of scans along anatomic axis of eye or poor gate positioning   

  11. Future directions Further studies are needed to determine the utility of the IOLMaster in honing postoperative refractive outcome in children and to evaluate the IOLMaster as a tool for the longitudinal follow-up of axial length measurement in children.

  12. references • Carkeet A et al. Repeatability of IOLMaster biometry in children. Optometry and Visual Science 2004;81:829-834. • Hussin HM, Spry PGD, Jamid MA, and Gouws P. Reliability and validity of the partial coherence interferometry for measurement of ocular axial length in children. Eye 2006;20:1021-1024. • Quinn GE et al. Highly precise eye length measurements in children aged 3 through 12 years. Arch Ophthalmol 2003;121:985-990. • Narvaez J et al. Comparing immersion ultrasound with partial coherence interferometry for intraocular lens power calculation. Ophthalmic Surg Lasers Imaging 2008;39:30-34. • Borchert M et al. Testability of the Retinomax autorefractor and IOLMaster in preschool children: the Multi-ethnic Pediatric Eye Disease Study. Ophthalmology 2008;115:1422-1425. • Gordon RA, Donzis PB. Refractive development of the human eye. Arch Ophthalmol 1985;103(6):785-9. • Griener ED, Dahan E, Lambert SR. Effect of age at time of cataract surgery on subsequent axial length growth in infant eyes. J Cataract Refract Surg 1999;25(9):1209-13.

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