Transcript An Analysis of Wound Burns in the United States and Canada

Astigmatism Following 2 IOL Injection Techniques:
Wound Assisted Versus Wound Directed
Jay J. Meyer, MD
Hart B. Moss, MD
Kenneth L. Cohen, MD
University of North Carolina, Dept. of Ophthalmology
The authors have no financial interest in the subject matter
of this E-Poster.
Background
•There has been a trend toward reducing cataract incision size with subsequent reduction
in surgically induced astigmatism (SIA). Bimanual sleeveless phacoemulsification allows
further reduction in the clear corneal incision (CCI) size. Many IOLs available in the US
are directly injected through 2.4 mm CCIs. However, wound-assisted injection of IOLs
through 2.2 mm CCIs, in which the cartridge tip does not project completely into the
anterior chamber, is an alternate method.1
•Some studies suggest that surgical trauma may be different between these two methods
of IOL injection. Intraocular pressure has been found to rise as high as 306 mm Hg using
wound-assisted injection through 2.2 mm CCIs compared to 85 mm Hg using a wounddirected technique.2 Studies of wound sizes before and after wound-assisted IOL
injection have documented enlargement of the original CCI, indicating trauma to the CCI
during injection.3,4
•No studies have compared SIA or endothelial cell loss, important indices of surgical
trauma, following IOL injection by these two techniques.
1. Tsuneoka H, et al. Ultrasmall-incision bimanual phacoemulsification and AcrySof SA30AL implantation through a 2.2 mm incision. J Cataract Refract Surg 2003; 29:1070-1076.
2. Kamae, KK, et al. Intraocular pressure changes during injection of microincision and conventional intraocular lenses through incisions smaller than 3.0 mm. J Cataract Refract Surg
2009; 35:1430-1436.
3. Osher, RH. Microcoaxial phacoemulsification, Part 2: Clinical study. J Cataract Refract Surg 2007; 33:408-412.
4. Thomas Kohnen, et al. Incision sizes before and after implantation of SN60WF intraocular lenses using the Monarch injector system with C and D cartridges. J Catarct Refract
Surg 2008; 34:1748-1753.
Objective
•To compare surgically induced astigmatism (SIA) following 2
techniques of IOL injection:
Wound Assisted (2.2mm)
(Cartridge tip in wound)
Wound Directed (2.4mm)
(Cartridge tip over pupil)
•Secondary outcomes: endothelial cell loss, wound enlargement,
BSCVA, complications
Methods
Prospective randomized trial of patients with cataracts and no other eye disease or prior
surgery
•Pre-operative and one month post-operative refraction, specular microscopy, and corneal topography
were recorded for each eye.
Surgical Technique:
•Two temporal limbal paracentesis incisions were made at 8 and 10 or 2 and 4 o’clock, using a 1.2 x
1.4 mm trapezoid blade, followed by bimanual microincision phacoemulsification by the same surgeon
(KLC) and enlargement of the right hand incision to 2.2 or 2.4mm.
•Patients randomized to receive IOL (Tecnis 1-piece IOL model ZCB00, AMO) insertion using a
wound-assisted (cartridge tip within the wound) technique through a 2.2 mm CCI or a wound-directed
(cartridge tip over pupil) technique with a 2.4 mm CCI.
•The Alcon D-cartridge and Monarch III injector were used.
•Wound size measured using incision gauges (Duckworth and Kent).
•All wounds were sutureless.
Analysis:
•Topographic and Refractive SIA (diopters) were compared between the groups and
a nonsurgical control group composed of 23 fellow eyes.
•SIA was calculated using the Alpins method of vector analysis.1
1. Alpins NA, Goggin M. Practical astigmatism analysis for refractive outcomes in cataract and refractive surgery. Survey of Ophthalmology. 2004, 49(1): 109-122.
Results
•40 patients completed the study: Wound-Assisted (WA,
n=20), Wound-Directed (WD, n=20).
•No significant differences in mean refractive SIA or
topographic (p=0.39) SIA between groups including the
non-surgical control (n=23).
•Mean wound enlargement was 10.2% in the WA and
9.1% in the WD group (p=0.68).
•In the WA group, 90% had BCVA of 20/20 compared to
85% in the WD group at the 1 month follow up (p=0.63).
•Mean endothelial cell loss was 8.1% in the WA and
9.3% in the WD group (p=0.20).
Mean Refractive SIA (D)
Wound Assisted
Wound Directed
P Value
0.60 +/- 0.41
0.92 +/- 0.65
0.09
Mean Topographic SIA (D)
Wound
Assisted
Wound
Directed
Non-Surgical
Control
P Value
0.38 +/- 0.22
0.46 +/- 0.28
0.34 +/- 0.27
0.27
Mean Refractive Astigmatism (D)
Preop
Postop
P Value
Wound
Assisted
0.81 +/- 0.39
0.69 +/- 0.40
0.47
Wound
Directed
0.93 +/- 0.55
0.82 +/- 0.47
0.46
P Value
0.39
0.39
Mean Topographic Astigmatism (D)
Preop
Postop
P Value
Wound
Assisted
0.71 +/- 0.58
0.57 +/ 0.59
0.53
Wound
Directed
1.16 +/- 0.83
0.58 +/- 0.66
0.02
P Value
0.08
0.97
Mean endothelial cell count (cells/mm2)
Preop
Postop
Difference
Wound
Assisted
Wound
Directed
P Value
2273 +/- 328
2089 +/- 416
-184
2254 +/- 452
2044 +/- 425
-210
0.88
0.76
0.82
Mean Incision Size (mm)
Preop
Wound
Assisted
2.21 +/- 0.04
Wound
Directed
2.35 +/- 0.05
Postop
2.44 +/- 0.06
2.57 +/- 0.06
P Value
<0.01
<0.01
P Value
<0.01
<0.01
Conclusions
•Wound-assisted and Wound-directed lens injection at
the studied incision sizes are comparable techniques
with no significant differences in SIA, wound
enlargement, endothelial cell loss, BSCVA, or
complications.
•Amount of SIA was not statistically different from a nonsurgical control group, indicating minimal SIA following
either technique
Discussion
•Wound enlargement was not significantly different
between the two groups in this study although final
wound size was larger in the wound-directed group.
•Even though final wound size was significantly larger in
the WD group (2.57mm) compared to the WA group
(2.44mm), absolute wound enlargement was not
different. There was a trend toward less SIA in the WA
group which did not reach statistical significance. This is
consistent with a previous study that showed no
differences in SIA between 2.2mm and 2.6mm incisions,
although final wound size was not measured.6
6. Wang J, et al. The effect of micro-incision and small incision co-axial phaco-emulsification on corneal astigmatism. Clin and Exper Ophthalmology. 2009; 37:664-69
Discussion (cont’d)
•Mean topographic SIA of the WA and WD groups did
not differ significantly from a non-surgical study group,
suggesting possible astigmatic neutrality following both
methods of lens insertion. The exact minimum wound
size for astigmatic neutrality has yet to be determined,
but is at least less than 2.8 mm based on one study.7,8
•As technological advances allow further reductions in
wound sizes, additional studies are needed to define any
benefits of the reduced incision size.
7. Masket S, Wang L, Belani S. Induced astigmatism with 2.2- and 3.0-mm coaxial phacoemulsification incisions. J Refract Surg. 2009;25:21-24.
8. Kaufmann C, et al. Astigmatic change in biaxial microincisional cataract surgery with enlargement of one incision: a prospective controlled study. Clin and Exper Ophthalmology
2009; 37: 254-61