Paul "Butch" Harton conducted a pilot study to determine the correlation between optical coherence tomography (OCT) and ultrasound biomicroscopy (UBM) for measuring the horizontal anterior chamber angle-to-angle (ATA). Thirty eyes of 15 healthy volunteers were scanned using both UBM and OCT. While OCT and UBM showed close correlation, the absolute ATA values differed between the two when measured from the visible margins, with OCT giving larger values. Adjusting the OCT measurement method produced values with close correlation and similarity to UBM values.

1. Paul “Butch” Harton, MD
Harbin Clinic Eye Center -Rome, GA USA
ESCRS 2010 - Paris, France
pharton@harbinclinic.com
The Author has no financial interest in the subject matter of this poster

2.  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
 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
Paul “Butch” Harton, MD

3.  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
 OCT ATA was recorded two ways as 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)
 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)
Paul “Butch” Harton, MD

4. UBM ATA
OCT – LP OCT VM

5.  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)
Mean (mm) N=30
12.3
12.2
12.1
12
11.9
Mean (mm) N=30
11.8
11.7
11.6
11.5
UBM OCT VM OCT LP
Paul “Butch” Harton, MD

6.  Mean Difference (mm) 1
UBM-OCT VM -0.494* 0.8
UBM-OCT LP -0.097 0.6
OCT VM – OCT LP +0.397* 0.4
UBM - OCT VM
0.2 UBM - OCT LP
 Correlation Coefficient (r) 0
OCT VM - OCT LP
UBM-OCT VM 0.865 Mean Difference
(mm)
Correlation
Coefficient
-0.2
UBM-OCT LP 0.873
-0.4
OCT VM-OCT LP 0.902
-0.6
* Statistically Significant p< .0001
Paul “Butch” Harton, MD

7.  OCT and UBM show close correlation when
measuring 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 and our adjustment in the OCT ATA
measurement (OCT LP) has close correlation
with UBM and produces similar absolute
values as UBM
Paul “Butch” Harton, MD