Transcript . Limbal relaxing incision for corneal astigmatism

Evaluation of “C” Limbal Relaxing Incisions for Astigmatism
Correction in Eyes Submitted to Phacoemulsification and
SN6D3 ReSTOR Intraocular Lens Implants
Mario J. Carvalho
Giuliano O. Freitas
The authors have no financial interest on this presentation
Setting
ISO Olhos – Ocular Health Institute - Uberlandia – MG - Brazil
Introduction
Phacoemulsification’s (PHACO) key aim is fast visual recovery associated to minimal
surgical risks (1). Near and distance visual recovery is dependent upon appropriate intraocular
lens (IOL) selection (2-5) and intraoperative astigmatism management. Lower surgically
induced astigmatism derived from currently available incisions, followed by the implantation of
bifocal IOLs have deeply changed cataract surgery focus to a more refractive status,
sometimes being referred to as phacorefrative surgery, or also phacorefractive lensectomy (89). So, spectacle dependence for near and distance vision has been tremendously lessened by
bifocal IOLs, adding an important therapeutic option for cataract surgeons. Fifteen to 20
percent of PHACO patients present topographic astigmatism ranging from 1 to 3 cylinder
diopters (CD). Such patients are not good candidates for such an approach, unless preexisting
astigmatism is appropriately managed (10). In this scenario, limbal realxing incisions (LRIs) are
broadly used to correct corneal topographic astigmatism, due to their easiness to be performed
and low cost. LRIs on the other hand, may determine astigmatism hypocorrection, or induce a
topographic pattern alteration referred to as adjacent coupling. An alternative to minimize
topographic changes sencondary to “conventional” LRIs has been proposed by Carvalho: the
“C” limbal relaxing incisions (CLRIs). The present study’s objective is to evaluate CLRIs
efficiency, safety and stability in terms of corneal astigmatism reduction among eyes submitted
to PHACO followed by bifocal ReSTOR IOL implantation.
Methods
The present study has been conducted from September 2004 to July 2008.
Patients’ selection has been based on the following criteria: age equals to, or
greater than 40 years, cataract occurrence worsening best corrected visual acuity,
regular corneal topographic astigmatism ranging from 1 to 2.5 CD and finally, no
other ocular or systemic disease that could adversely limit final visual outcomes.
Patients’ preoperative evaluation relied on: uncorrected and best corrected visual
acuity measurements, anterior segment biomicroscopy at slit lamp, applanation
tonometry, indirect binocular ophthalmoscopy, computerized videokeratoscopy
(Eye Sys 2000 Corneal Analysis System –Eye Sys/ Premier Laser Systems, Inc.;
Irvine, CA, U.S.A.,Orbscan, Bausch & Lomb, U.S.A) and immersion biometry
(OcuScan XP, Alcon, Forth Worth,TX, U.S.A.). Lens power calculations have took
into account simulated keratometry for the central 3 mm optical zones. Hoffer Q
formula has been used for axial lengths shorter than 22 mm or SRK-T for longer
than 22 mm. All patients had been previously instructed about potential risks and
benefits related to the procedure. Every patient enrolled in this study had read and
assigned an informed consent. All surgeries have been performed by the same
surgeon (M.C.). At first, patients remained sat in the up right position, staring at a
distant point, so that 90 and 180 degrees meridians could be marked. After that,
patients lied on surgical table, and routine antiseptic measures have been
conducted. The steepest meridian could then be identified and the CLRIs
performed. A 9 mm inner diameter and 10 mm outer diameter axis marker with
divisions at every 10 degrees (Duckworth&Kent U.S.A.) has been routinely
employed for the placement of the incisions in accordance to Carvalho’s nomogram
(Table 01).
Methods
CLRIs (degrees)
Age Groups (years)
Preoperative
cylinder
(CD)
41 - 50
51 - 60
61 - 70
71 - 80
0,75 - 1,25
LRIs – 1 pair 40°
“C”- 2 pairs 15°
LRIs – 1 pair 35°
“C”- 2 pairs 15°
LRIs – 1 pair 30°
“C”- 1 pair 15°
LRIs – 1 pair 25°
“C”- 1 pair 15°
1,50 – 2,00
LRIs – 1 pair 50°
“C”- 2 pairs 20°
LRIs – 1 pair 40°
“C”- 1 pair 20°
LRIs – 1 pair 35°
“C”- 1 pair 20°
LRIs – 1 pair 30°
“C”- 1 pair 10°
2,25 – 2,75
LRIs – 1 pair 60°
“C”- 1 pair 20°
LRIs – 1 pair 50°
“C”- 1 pair 25°
LRIs – 1 pair 40°
“C”- 1 pair 20°
LRIs – 1 pair 30°
“C”- 1 pair 25°
LRIs – Limbal Relaxing Incisions
“C” – “C” Incisions
Methods
All PHACOs have been performed through a temporally placed 2.2 mm
incision (Figure 01), limbal biplanar for with-the-rule astigmatism (WTR) and hinge
incision (12-13) for against-the-rule astigmatism (ATR). Bifocal IOL (SN6D3
ReSTOR - Alcon, Fort Worth, TX, U.S.A.) implantation has been accomplished
without cartridge tip insertion to the anterior chamber to avoid any incision
distortions (Royale lens injector). A preset 600 m in depth double-edge blade
diamond knife (KOI – U.S.A.) has been used to perfmorm the CLRIs. For eyes
with WTR astigmatism, CLRIs have been performed previously to PHACO incision.
For eyes with ATR astigmatism, the following steps have been carried on: 1) the
nasal arc of the CLRIs is performed, than a 30 degrees temporally placed arc is
performed (Figure 02. A); 2) PHACO 2.2 mm incision is performed at nearly 300
m in depth in the temporal arc; 3) as IOL implantation is accomplished, the
temporal arc is extended in accordance to nomogram (Figure 02. B).
Methods
PHACO
Incision
“C”
LRI
Figure 01.: Temporal 2.2 mm PHACO incision (WTR astigmatism).
Methods
PHACO
Incision
LRI
“C”
Figure 02. A: Temporal 2.2 mm PHACO
incision
and
nasal
arc
(ATR
astigmatism).
Figure 02.B: Temporal 2.2 mm PHACO
incision and temporal arc elongation
shown by dashed lines (ATR
astigmatism).
Results
In the present study, 30 eyes from 22 patients (04 men and 18 women)
have been evaluated. Patients’ ages ranged from 48 to 81 years (mean age
67.43 +/- 9.32 years).
Graph 01: Percentage of eyes submitted to PHACO, CLRIs and bifocal ReSTOR IOL implants
presenting near uncorrected visual acuity of J1 or J2 from the 1st to 12th POM.
90
Percentage
80
70
60
78,57
68,96
66,67
66,67
50
40
31,04
33,33
33,33
30
20
21,43
10
0
1st POM
3rd POM
6th POM
Period
J1
J2
12th POM
Results
Graph 02: Mean preoperative and postoperative best distance corrected
visual acuity of eyes submitted to PHACO, CLRIs and bifocal ReSTOR IOL
implants from the 1st to 12th POM.
0,3
LogMAR Scale
0,25
0,25
0,2
0,15
0,1
0,1
0,08
0,05
0,08
0,05
0
Preoperative
1st POM
3rd POM
Period
Mean
6th POM
12th POM
Results
Graph 03: Mean preoperative and postoperative topographic and
refractional astigmatism profile of eyes submitted to PHACO, CLRIs and bifocal
ReSTOR IOL implants from the 1st to 12th POM.
1,4
1,32
Cylinder Diopters
1,2
1
1,06
0,9
0,8
0,68
0,6
0,66
0,5
0,49
0,4
0,25
0,24
0,2
0,23
0
Preoperative
1st POM
3rd POM
6th POM
Period
Topographic
Refractional
12th POM
Discussion
The present study demonstrates that CLRIs are a safe and efficient approach to
corneal topographic management. Its association to PHACO has resulted in astigmatism
reduction, at the same time, keeping the spherical equivalent constant during all the
periods studied. These characteristics have allowed bifocal IOL implantation also for eyes
with astigmatism ranging from 1 to 2.5 CD.The CLRIs nomogram adds a modification to
conventional LRIs nomogram, once it adds a pair of incisions to the innermost extremities
of the main incisions. Such a modification is designed to reduce the adjacent coupling
induction, often seen with conventional LRIs. Adjacent coupling effect, as described by
Akura, is thought to be due to misalignment of the LRI to the steepest meridian or to
insufficient LRI length to fully cover the steepest meridian. Since CLRIs have a longer
incision arc, compaired to conventional LRIs, coupling occurrence is brought to a minimum.
Astigmatism hypercorrection, as some might expect, has not been observed in this study
but, some degree of hypocorrection, as also happens to conventional LRIs, is demonstrated
by residual astigmatism.Carvalho’s nomogram is, as Nichamin’s (11) nomogram, ageadjusted, but such a criterion is not a consensus among researchers and must be further
investigated (10, 16, 17 -18). Postoperative topographic astigmatism has been statistically
reduced by CLRIs in all periods studied, although some trend towards hypocorrection may
be observed (28-18). Even hypocorrected, CLRIs may play a key role in postoperative
distance and near uncorrected vision, since residual topographic astigmatism for optimal
bifocal IOL performance must be 0.75 CD or less. Such a residual astigmatism has been
reached by 71.42 percent of eyes in the current study. Low percentage (6.6 percent – 2
eyes) demanding additional refractive procedure is another evidence of CLRIs efficiency.
Emphasis must be given to the fact that CLRIs have not changed simulated central
keratometry. Undesirable spherical residual errors are, then, due to biometrical errors, not
to CLRIs, since the spherical equivalent remains constant.In conclusion, CLRIs broadened
the indication of bifocal IOL implants for cataract patients with astigmatism greater than 1
CD, efficiently and safely, making these patients less dependent on spectacles for good
distance and near vision.
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