Evaluation of C Limbal Relaxing Incisions for Astigmatism Correction in Eyes Submitted to Phacoemulsification and SN6D3 ReSTOR? Intraocular Lens Implants

1
Evaluation of C Limbal Relaxing Incisions for
AstigmatismCorrection in Eyes Submitted to
Phacoemulsification andSN6D3 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
2
Introduction

• Phacoemulsifications (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 (8-9). 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 studys 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.

3
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 (DuckworthKent?
  U.S.A.) has been routinely employed for the
  placement of the incisions in accordance to
  Carvalhos nomogram (Table 01).

4
Methods

LRIs Limbal Relaxing Incisions C C
Incisions
5
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).

6
Methods
PHACO Incision
C
LRI

• Figure 01. Temporal 2.2 mm PHACO incision (WTR
  astigmatism).

7
Methods
LRI
PHACO Incision
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).

8
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.

9
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.

10
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.

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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.Carvalhos nomogram is, as Nichamins
  (11) nomogram, age-adjusted, 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.

12
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