COMPARISON OF HORIZONTAL ANTERIOR CHAMBER ANGLE-TO-ANGLE MEASUREMENTS OBTAINED USING OPTICAL COHERENCE TOMOGRAPHY AND HIGH-FREQUENCY ULTRASONIC BIOMETRY Paul “Butch” Harton, MD Harbin Clinic Eye Center Rome, GA USA ASCRS Boston Poster, 2010 The Author has no financial interest in the subject matter of this poster
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Paul “Butch” Harton , MD Harbin Clinic Eye Center Rome, GA USA ASCRS Boston Poster, 2010
Comparison of Horizontal Anterior Chamber Angle-to-Angle measurements obtained using optical coherence tomography and high-frequency ultrasonic biometry. Paul “Butch” Harton , MD Harbin Clinic Eye Center Rome, GA USA ASCRS Boston Poster, 2010 - PowerPoint PPT Presentation
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COMPARISON OF HORIZONTAL ANTERIOR CHAMBER ANGLE-TO-
ANGLE MEASUREMENTS OBTAINED USING OPTICAL COHERENCE
TOMOGRAPHY AND HIGH-FREQUENCY ULTRASONIC
BIOMETRY
Paul “Butch” Harton, MDHarbin Clinic Eye Center
Rome, GA USAASCRS Boston Poster, 2010
The Author has no financial interest in the subject matter of this poster
Purpose
Accurate Horizontal Anterior Chamber Angle-to-Angle (ATA) measurements are necessary for the implantation of both phakic and aphakic IOLs.
The general purpose of this pilot study
was to determine the degree of correlation between the OCT and UBM methods of measuring ATA
Methods – UBM ATA 30 Eyes of 15 healthy volunteers
Each eye was scanned with the Sonomed VuMaxII High Resolution Ultrasound (UBM) by a single Technician
The Author, blind to the on-screen identity of each eye analyzed the UBM video
Using the on-screen calipers, the best visible ATA dimension was recorded
UBM - ATA
Methods – OCT ATA Each eye was also scanned with the Visante OCT
by a single Technician. The Author, again blind to the identity of each eye, used the on-screen calipers to measure OCT ATA
However the OCT ATA was measured 2 ways. The first was similar to UBM, the second used a rule developed for this study
This rule was suggested after personal communications indicated OCT might over-estimate ATA when measured with similar landmarks as UBM (This theory has been subsequently supported by Kim, Kim and Song in J Refract Surg. 2010;26:120-126)
Methods OCT - ATA The two values of OCT recorded are
described below: One caliper line simply measured the visible
extent of ATA in a manner similar to the UBM (OCT ATA – Visible Margins or VM)
The other method determined OCT ATA using a rule where the caliper line was always drawn tangential to the anterior lens surface. The ATA was determined where this line then intersected the inner aspect of the cornea. (OCT ATA-Lens Plane or LP)
OCT - ATA
Results Mean ATA in millimeters (N=30)
UBM OCT VM OCT LP 11.76 12.26 11.86 (SD 0.47) (SD 0.48) (SD 0.58)
UBM OCT VM OCT LP11.5
11.6
11.7
11.8
11.9
12
12.1
12.2
12.3
Chart Title
Mean (mm) N=30
Results Mean Difference (mm)
UBM-OCT VM -0.494*UBM-OCT LP -0.097OCT VM – OCT LP +0.397*
Correlation Coefficient (r)UBM-OCT VM 0.865UBM-OCT LP 0.873OCT VM-OCT LP 0.902 Mea
n Differe
nce (m
m)
Corre
lation
C
oefficie
nt
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
UBM - OCT VMUBM - OCT LPOCT VM - OCT LP
* Statistically Significant p< .0001
Conclusions OCT and UBM show close correlation with
one another in their determination of the horizontal anterior chamber angle-to-angle measurement (ATA)
The absolute value of ATA is however significantly different between the two technologies when measuring from the visible margins of ATA. OCT VM consistently gives larger ATA values vs. UBM.
Conclusions These findings are similar to the recent
article by Kim, Kim and Song in the Journal of Refractive Surgery. This article found a high degree of correlation
between UBM and OCT ATA measurements The OCT measurements defined in their study
were the same as theVisible Margin (VM) type in our study and similarly showed the OCT ATA to be consistently larger than the UBM ATA.
This may indicate the OCT overestimates ATA using this criteria
Conclusions Our adjustment in the OCT ATA measurement (OCT
LP) has close correlation with UBM and produces similar absolute values as UBM
Further studies are needed to better define the degree of correlation and the accuracy of these technologies with respect to phakic and aphakic IOL sizing.
Further studies are needed to confirm which technology provides a better determination of the actual ATA value.