Vol. 20 No. 1, March 2005
Tanzania Medical Journal
1
SURGICAL INDUCED ASTIGMATISM AND SURGICAL OUTCOMES OF 3.2MM CLEAR CORNEAL
SUTURELESS SELF-SEALING INCISION VS. 5.5MM FOR CATARACT OPERATION.
Summary
HU hai-peng and ZHANG xiu-ping
Key wards: Cataract surgery, Astigmatism, Sutureless
selfsealing
Objective: To evaluate the surgical induced astigmatism and other
surgical outcomes in 3.2mm and 5.5mm clear corneal sutureless
self-sealing incision for cataract operation.
Methods: Prospective study was conducted on 68 eyes of 58 patients
out of which 35 eyes were in 3.2mm and 33 eyes in 5.5mm incision
groups. Except the incision size, lens type, and implantation
technique, the surgical methods were identical. Uncorrected visual
acuity, keratometry were measured preoperatively, one day, one
week, one month and three months postoperatively.
Results: Eyes in 3.2mm clear corneal incision group had
significantly less surgical induced astigmatism than 5.5mm incision
group. One day after surgery, the surgical induced
astigmatism(vector analysis, keratometry)was 1.44/2.79 (P<0.01),
one week1.28/2.58(P<0.01),one month 1.20/1.92 (P<0.01), and three
months 1.10/1.89 (P<0.01) In the 3.2mm clear corneal incision and
5.5mm sclera tunnel incision group, respectively. The visual acuity
was also better and stable in 3.2mm group starting from the first
day of operation. Visual acuity one day postoperation was
0.73±0.22/0.51±0.20 (P=0.002), one week 0.75±0.24/0.53±0.21
(P=0.001), one month 0.71±0.24/0.57±0.23 (P=0.005), three months
73±0.26/0.60±0.18 (P=0.003) in the two group, respectively.
Conclusion: The 3.2mm clear corneal incision cataract surgery led
to early recovery of visual function in short term and less induced
astigmatism. But the 5.5mm group the surgically induced
astigmatism decreased and the visual acuity increased progressively
with time.
Introduction
Cataract surgery techniques have improved in the
past decades. Self-sealing incision are recognized to
improve intraoperative safety and reduce postoperative
inflammation and complications. The small incision
surgery has a number of surgical advantages: It is easy to
perform, is faster, offer's better visualization and
cosmetically attractive because there is minimal bleeding
and no need of retrobulbar or pribulbar injection for
anesthesia. Sutureless clear corneal incisions are the
preferred approach for phacoemulsification; that is
3.2mm for foldable lens and 5.5mm for ridged PMMA
lens implantation. In this prospective study we were
trying to compare the surgical outcomes using some
parameters, it corneal changes measuring astigmatism
keratometry by, visual performance preoperative and
postoperative by.
Materials and Methods
Sixty-eight eyes of 58 patients with cataract, mean age of
16men and 14 women in the 3.2mm incision group was
66+8.8(SD), 13 men and 15women in the 5.5mm incision
group was 68+9.8(SD) and preexising astigmatism 0.11.8D as measured by keratometry. All surgery was
performed by
Correspondence to: HU hai-peng and Muhimbili National Hospital Dar es Salaam,
Tanzania.
Department of Ophthalmology, The Fourth People’s Hospital of Jinan, China
one experienced surgeon. Superior temporal and superior
nasal clear corneal incisions were made for right and left
eyes respectively using topical anesthesia of 0.05%
Alcaine eye drops. A 2.8mm clear corneal incision was
made at surgical limbus using 2.8mm steel keratom.
(Alcon com) Anterior chamber entry was made after 1.52mm corneal tunneling. In both groups small side port
incision was made for insertion of chopper or lens hook,
which supported the nucleus during phacoemulsification.
Except for difference in incision size, the surgical
method in each group was identical. After continuous
curvilinear capsulorhexis and hydrodissection, the nucleus
was phacoemulsified within the capsular bag using a
bimanual technique(stop and chop)with an ultrasonic
probe and hook, and the residual cortical material was
removed with an automated irrigation/aspiration(I/A)unit.
The ultrasonic probe was manipulated carefully to avoid
damaging the wound structure, then the corneal incision
extended to approximately 3.2mm or 5.5mm for
intraocular lens implantation. Viscoelatic substance
(Methylcellulos) was injected into the capsular bag, and a
foldable acryl-soft lens was implanted through 3.2mm
self-sealing and ridged PMMA lens implanted through
5.5mm self-sealing incisions. Balanced salt solution was
injected from the corneal side port at the end of each
procedure to control intraocular pressure and check for
wound leakage. At the end of the operation TobraDex
(Tobramycin and Dexamethasone) eye ointment were
applied. The standard postoperative dosage of topical
dexamethasone and ofloxacin was instilled six times daily
during the first 1to 2 weeks then four times a day for the
next 2 weeks.
Keratometry (Tocon OM-4) and uncorrected distant
Snellen’s visual acuities were measured preoperatively
and postoperatively at 1 day, 1week, 1 and 3months.
The amount of surgically induced astigmatic changes
was calculated using the vector analysis method described
by Jaffe. Numerical data were compared between the two
groups using an paired, two tailed student’s t-test. P< 0.05
was considered significant.
Results
The mean age, preoperative visual acuity and sex
distribution in the two groups were similar. And the mean
preoperative astigmatism 0.73±0.67 for 3.2mm group
and 0.94±0.84 for 5.5mm group did not differ
significantly between the groups (P>0.05)(table1). All
eyes were followed for 3 months. Table 2 shows the mean
surgically induced cylinder using Jaffe’s vertor analysis.
Vol. 20 No. 1, March 2005
Tanzania Medical Journal
At all postoperative period, the mean induced astigmatism
was large in the CCI-5.5mm group (P<0.01).
Mean preoperative uncorrected visual acuity (UCVA)
were 0.15±0.12/0.13±0.12 (P>0.05) for 3.2mm and
5.5mm groups respectively. The postoperative
uncorrected visual acuity was much better in CCI-3.2mm
group from the first day of operation till the third month
follow up time (P<0.01). In the CCI-3.2mm group the
mean UCVA at day one and three months postoperative
was almost the same, but in CCI-5.5mm group, there was
progressive increment from postoperative day one till the
third month of follow up (table-3). No intraoperative
complications were observed in either group. No suture
was needed because the wounds were self-sealing. Other
complications such as fibrin formation, prolonged
inflammation, secondary glaucoma, IOL dislocation were
not seen.
Table 1. 1-age, preoperative vusual acuity (VA) and
astigmatisms (AS)
Age
Preop VA
Preop AS
CCI-3.2.mm
66±8.8(SD)
0.13±0.14
0.93±0.67
CCi-5.5.mm
68± 9.8(SD
0.12±0.17
094±0.84
P-value
P>0.05
P>0.05
P>0.05
*CCI=velar corneal incision
Table 2. Mean surgical induced astigmatism (vertor
analysis) through time from keratometry data
1 –day
1 – week
1 – mont
3 - months
CCI-3.2.mm
1.68±1.30
1.44±1.20
1.35±0.96
1.16±0.84
CCi-5.5.mm
2.86±1.6
2.68±1.5
2.36±1.2
1.76±1.6
P-value
P =0.0067
P = 0.00078
P = 0.0007
P = 0.004
Table 3. Mean Pre and postoperative UCVA
Pre
1 day
1 week
1 mont
3 months
CCI-3.2mm
0.15±0.12
0.73±0.22
0.75±0.24
0.71±0.24
0.73±0.26
CCi-5.5.mm
0.13±012
0.15±0.20
0.53±0.21
0.57±0.23
0.60±0.18
P-value
0.21
0.02
0.001
0.005
0.003
corneal astigmatism could be minimized, as K-Muller and
B.Barlin corneal tunnel incision at 12o’clock only in eyes
with preoperative WTR astigmatism of more than 1.0D, in
eyes with preoperative WTR astigmatism between 0.5and
1.0D to use corneoscleral incision which induces
considerably less astigmatism， in eyes WTR
astigmatism of 0.5D or less, ATR astigmatism and
spherical cornea lateral corneal tunnel incision. However
the superior 5.5mm clear corneal incision for ridged
PMMA lens implantation compare to other incision type
such as sclera tunnel or corneoscleral incision of classic
ECCE, it has obvious advantages: it could be done using
topical anesthesia with minimal or no bleeding, less
discomfort, short operation time, fast recovery of wound
and visual performance. Xie lixin’s study showed that
surgical induced astigmatism was very small after a
corneal incision in phacoemultification without a suture. If
the incision was placed on the steepest meridian, the
corneal
astigmatism
was
significantly reduced
postoperatively.
From our study, though of small sample size and
short duration of followup we can conclude that 3.2mm is
superior in every aspect the 5.5mm incision group except
it is expensive. But 5.5mm clear corneal incision is also a
good alternative for normal PMMA lens based on its
many advantages. Furthermore it is better to consider
preoperative astigmatism the dioptre and direction from
keratometry readings to determine the incision site on the
cornea and its size (3.3mm and 5.5mm). So, the patient
can choose which incision (3.2mm or 5.5mm), he or she
prefer depending on their financial capability because
foldable lens were expensive than ridged lens.
Finally we suggest long term comparative study
between different types of clear corneal incision and
sclerrocorneal tunnel or scleral incision to see which
incision type has minimal induced astigmatism and less
complications.
Reference
1.
Discussion
Our results showed a significantly higher amount of
surgically induced astigmatism with 5.5mm sclera tunnel
incision than 3.2mm corneal incision based on vector
analysis of keratometric data. The uncorrected visual
acuity was also significantly better in the 3.2mm group
than in 5.5mm group throughout the follow time. In
3.2mm the mean visual acuity become stable after oneweek postoperatively. Whereas in 5.5mm group the visual
acuity progressively improves with time though not
statistically significant.
Keratometric change induced by a 3.2mm incision
was not related to uncorrected visual rehabilitation. The
relatively poor uncorrected visual acuity in the 5.5mm
incision group might be due to high-induced astigmatism,
produced by relatively big wound gap.
It is known that different incision types have
beneficiary effect if they are in accordance with
preexisting astigmatism because the final post operative
2
2.
3.
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Xie lixin, ZHU Gang, WANG Xu. Clinical observation of astigmatism induced
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