Transcript Partial Coherence Interferometry Compared with Immersion

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
Purpose
To determine whether measurements obtained by
partial coherence interferometry (PCI) correlate well
with measurements obtained using immersion
ultrasonography (IUS) in children
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.
Data
OD=Right eye; OS=Left eye
PCI=Partial coherence interferometry; IUS=Immersion Ultrasonography
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.
Results
Mean axial length PCI: 22.14
Mean axial length IUS: 22.27
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.
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.
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.
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
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.
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 Multiethnic 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.