A simple and accurate method of alignment for toric

Report
A simple and accurate method of
alignment for toric intraocular lens
implantation using anterior segment
optical coherence tomography (OCT).
Kazuno Negishi, MD1, Kazuhiro Watanabe, MD1, Hidemasa Torii,
MD1, Chiyo Kodama,CO1, Murat Dogru, MD2, Kazuo Tsubota, MD1
1. Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
2. J&J Ocular Surface and Visual Optics Department, Keio University School of Medicine,
Tokyo, Japan
The authors have no proprietary interest in any of the devices mentioned in the manuscript.
Purpose
To report a simple method for accurate alignment of
the IOL axis for toric intraocular lens implantation
using anterior segment OCT.
Setting
Department of Ophthalmology,
Keio University Hospital, Tokyo, Japan.
Patients
• 9 consecutive eyes of 7 patients who had cataract
extraction and implantation of an acrylic toric IOL
(SA6AT3, SA6AT4, or SA6AT5, Alcon, FortWorth, TX)
• Inclusion criteria
– Postoperative visual acuity better than 20/20
• Exclusion criteria
– previous or coexisting ocular pathology and intra- or
postoperative complications.
– Eyes with a corneal astigmatism of less than 0.75 D
• All patients provided written informed consent. The
study adhered to the tenets of Declaration of Helsinki.
• IRB approved this study.
METHODS
1. IOL Power calculation and style selection
–
–
–
–
Biometry using the IOL Master (Carl Zeiss, Germany)
SRK/T formula
Specific A constant for the toric IOL : 119.0.
The online Acrysof Toric IOL Calculator
(http://www.acrysoftoric calculator.com).
2. Preoperative acquisition of corneal topography using
the anterior segment OCT (corneal map mode).
3. Determination of the steep meridian of
corneal astigmatism from corneal
topography.
Anterior segment OCT
(CASIA, Tomey, Japan)
METHODS (continued)
4. Eye image acquisition after full pupillary dilatation using the
anterior segment OCT (anterior segment mode).
5. Selection of the characteristic iris pattern on the peripheral
cornea as a reference axis. (Figure 1 in the following page).
– The line of the slice plane direction can be freely rotated
around the corneal apex by mouse on the CCD image,
thus the rotation degree of any point can be displayed on
the rotational view. The rotational degree of reference
axis including the reference point was measured using
this rotational view .
6. Intraoperative marking of the steep axis (Figure 2 in the
following page) and implantation of the toric IOL
7. Evaluation of the rotation error of the implanted toric IOL
(Figure 3 in the following page)
Figure 1
Preoperative determination of the reference point
and the alignment axis using Acrysof Toric Calculator
and the anterior segment OCT
90 degrees
Reference point
53°
Alignment axis 143°
Characteristic iris pattern
as a reference point
CCD image
Rotational view
Figure 2
Intraoperative marking of the steep axis and
implantation of the toric IOL
1. Marking of the reference point
At the beginning of the surgery,
previously determined reference
point was marked by a surgical
marker-pen under the operating
microscope
observing
the
characteristic iris pattern.
2. Marking of the alignment axis
The zero degree of the Wallace Mendez
degree gauge was fit to the reference
point, and the alignment axis was
marked using the DK axis marker
according to the difference between the
reference and the alignment axes.
Figure 3
Postoperative evaluation of the rotation error
of the implanted toric IOL
Dot marks on the toric IOL
Postoperative CCD image (example)
Rotational view
Results
Pre-op
Age(yrs)
Corneal astigmatism(D)
Subjective astigmatism(D)
Subjective refraction(D)
(Spherical equivalent)
UCVA (Log MAR)
BCVA(Log MAR)
Rotation error in the achieved
from the target axis of the
toric IOL (Degree)
Post-op(1w)
Mean (SD)
73.3 ( 7.8)
1.97 ( 0.66)
2.00(0.67)
-1.50(1.88)
1.97(0.43)
0.28 ( 0.25)
0.16(0.48)
0.69(0.37)
0.16(0.17)
N/A
-0.01(0.16)
-0.09(0.11)
1.9 ( 2.0)
N/A: not applicable
Discussion
• Advantages of this method
– Simple and accurate
– Free from the misalignment related to marking the reference
point due to the differences in the head position at the time of
topography and the time when the reference point is marked,
including cyclorotation of the eye during surgery.
– Reference and alignment axis can be marked under the surgical
microscope (only 2 step for marking)
– Not required to take a photo, or to use image analysis software
• Limitation of this method
– Necessity of an apparatus that can obtain images of iris patterns
with the axis scale and the corneal topography at the same time.
– Not applicable for an eye without any characteristic iris pattern
(rare).
Conclusions
• The current method enables a simple and
accurate marking of reference and alignment
axes for toric IOL implantation, and is useful
for correct placement of toric IOLs.

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