Robert M. Kershner, MD, FACS
Ophthalmic
Practice
Vol. 20, No. 7, August 2002
R.M.
Kershner — Director of Cataract and Refractive Surgery, Eye Laser Center,
Tucson, Arizona; Clinical Professor of Ophthalmology, University of Utah School
of Medicine, Salt Lake City, Utah; Ik Ho Visiting Professor of Ophthalmology,
Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
Correspondence to: Dr. Robert M. Kershner, Eye Laser
Center, Suite 303, 1925 West Orange Grove Road, Tucson, Arizona USA 85704-1152;
E-mail: Kershner@EyeLaserCenter.com; Web site: http://www.asiteforeyes.com
Dr. Kershner has no financial or
proprietary interest in any of the techniques or instruments described in this
article. This article received the "Best Paper of Session" award at
the 2001 American Society of Cataract and Refractive Surgery Symposium held in
San Diego, California.
Abstract
The growing popularity of refractive surgical procedures
that eliminate or reduce the need for eyeglasses has led to the use of small
(less than 2.5 mm) incisions, which, along with the insertion of an intraocular
lens allows for correction of preexisting myopia, hyperopia and
astigmatism during cataract surgery.
Procedure:
This paper describes a clear corneal cataract surgery technique using a
single-incision, single-instrument approach. This technique consists of
using the smallest possible clear corneal microincision, and involves simultaneous
correction of spherical and astigmatic errors with refractive keratotomy and
toric intraocular lenses. In-the-bag phacoemulsification is performed and
the intraocular lens is injected through the unenlarged microincision.
Results:
Microincision cataract surgery has all but eliminated the complications of
wound leak, uveal prolapse, and surgically-induced astigmatism, and has
optimized the refractive results for the patient while providing immediate
recovery without restrictions in normal postoperative activities. The
refractive outcomes of these techniques, as performed in our Eye Laser
Center in Tucson, Arizona, are the best we have ever achieved.
Lens
extraction with implantation of an intraocular lens (IOL) is the most common
refractive procedure in the world today. Since the invention of the IOL by the
late Mr. Harold Ridley, in England in 1949, lens implantation has been the
primary means to correction of the most common refractive error, aphakia, which
occurs as a result of cataract extraction. In 1994, I published results of
clear corneal cataract surgery with simultaneous correction of myopia,
hyperopia and astigmatism.1 The results then, as today, demonstrated
that ophthalmologists can do a good job of improving a patient’s visual acuity
by performing cataract surgery with the simultaneous correction of refractive
errors. Today, cataract surgery is looked upon as a refractive procedure that
improves pre-existing refractive error and optimizes uncorrected visual acuity
rather than solely as a means to treat a clouded crystalline lens.
Background
Today's
cataract procedure has enabled the use of small (less than 3.0 mm) incisions.
With the development of laser phacoemulsification, phakonit, and newer
technologies, surgeons will soon be able to use incisions as small as 1 mm
or even smaller. These microincisions are placed through the clear cornea,
which precludes the need for conjunctival dissection, cautery, sutures,
injection anesthetics, bandaging and restriction of normal postoperative
activities. Microincision cataract surgery has all but eliminated the
complications of wound leak, uveal prolapse, and surgically-induced
astigmatism. These advances have paved the way for faster, more efficient
surgery, with less instruments, less intervention and faster visual recovery
for the patient.
In 1994, I
coined the term “keratolenticuloplasty” (KLP) to describe the simultaneous
reshaping of the cornea (kerato) and replacing the lens with an IOL to correct
refractive error (lenticuloplasty).1,2 Smaller-incision surgery has
motivated IOL manufacturers to develop new intraocular silicone, acrylic,
thermoplastic, and hydrogel lenses that can be injected through microincisions,
replacing the rigid polymethylmethacrylate (PMMA) lenses of yesterday.
Along with
these advances in microincision cataract surgery, have been the increasingly
superior visual results patients have achieved.3,4 Myopia and
hyperopia can be eliminated with IOL implantation, and astigmatism can be
corrected with the use of a toric IOL with or without arcuate keratotomy
incisions (the so-called limbal or peripheral corneal-relaxing incisions).
Smaller-incision surgery has meant better results, fewer complications for
patients, and fewer worries for surgeons.
I have
developed and adhered to a single-incision single-instrument approach to
cataract surgery,5-12 which has benefited my patients over the
years. I use a clear corneal microincision, in-the-bag phacoemulsification with
a mini-phaco flip maneuver, and injection of the IOL through the unenlarged
incision.
Clear Corneal Refractive
Surgical Procedure
Preoperative Evaluation and Surgical Plan
All
cataract surgery patients undergo a comprehensive ophthalmic evaluation. In
devising the surgical plan, cycloplegic refraction, combined with corneal
topography and ultrasonic biometry, is used to select the best approach with
the IOL for complete refractive correction. The aim is to fully correct the
sphere for distance and to eliminate less than one diopter (D) of astigmatism
with a single incision that doubles as the cataract incision, and to supplement
the astigmatic correction for over 1 D with the toric IOL. The goal is to fully
correct or slightly undercorrect the cylinder, and not overcorrect or shift the
cylinder axis. To achieve the proper correction, preoperative data is entered
on a worksheet (Fig. 1) and a surgical plan is developed.
Patients
are administered topical 1% tropicamide in combination with 2.5% phenylephrine
drops into the operative eye; 1 drop every 5 minutes is given 3 times, starting
15 minutes prior to surgery. When patients are called to surgery, they receive
a single drop of 4% topical Betadine suspension. The surgical scrub is
performed, and a sterile adhesive drape that excludes the eyelids and lashes is
applied. Several drops of 2.5% tetracaine anesthetic are instilled; (if
anesthetic drops are used prior to the procedure there may be excessive drying
or sloughing of the corneal epithelium making visualization difficult).13,14
The Kershner reversible eyelid speculum (Rhein Medical, Tampa, Florida) is
positioned under the eyelids and rotated out of the way so as to not interfere
with the various steps of the procedure. The cornea is kept dry while the
proper meridian of the cylinder is identified and marked with the inkless
marker. The globe can be fixated with the disposable fixation ring if
necessary, and the incisions are created.
Measuring Astigmatism
A
preoperative corneal topography scan is extremely valuable in both determining
the qualitative appearance of the astigmatism as well as the location of the
cylinder. This scan is also helpful for choosing whether to use symmetrical or
asymmetrical incisions. Newer methods of corneal and intraocular analysis using
wavefront analysis may also provide insight into higher-order aberrations that
could affect postoperative refractive results. If the astigmatic correction is
regular, clear, and present on a single meridian, then it is correctable. Surgeons
should not correct irregular astigmatism, keratoconus, corneal scars and
higher-order aberrations, in order to avoid corrections that could
result in undesirable postoperative irregular corneas.
To assure a precise method to
achieve better refractive outcomes, surgeons need to follow three rules: 1)
Accurately measure astigmatism, 2) Apply the astigmatic correction on the
proper meridian, and 3) Do not overcorrect the cylinder or shift from the
pre-existing axis.
Prior to
surgery, note in the patient’s chart the position of the patient’s
steepest meridian on the cornea (Fig. 2). As all transverse or arcuate corneal
incisions flatten the dome of the cornea, locate the incision on the steepest
meridian.
Corneal Incision(s)
Placing the
incision anywhere other than the steepest part of the cornea will make the
astigmatism worse. Since most elderly patients have against-the-rule
astigmatism, temporal incisions typically work well for most, but not all,
patients. These incisions are also best if the patient has a spherical cornea. Compared
with the superior limbus, the temporal limbus is located further away from
the optical center and is furthest away from the influence of the recti
muscles. As a result, temporal incisions will create less induced
corneal astigmatism.
Patients
with significant pre-existing astigmatism will benefit from astigmatic
keratotomy (keratolenticuloplasty) at the time of surgery. Limbal-relaxing
incisions, because they are placed far peripherally in the corneal scleral
limbus, have less flattening effect for a given length. As a result, they must
be large to have any substantial effect on corneal curvature. When limbal
incisions traverse 120 degrees of arc, they effectively denervate the cornea.
In an elderly patient, this can mean an anesthetic cornea, severe dry eye, and
corneal breakdown. Smaller, arcuate incisions have more effect with less
surgery, and as long as they do not approach the central optical zone of the
cornea, are less problematic.
For
astigmatically-neutral clear-corneal incisions, a one-step, plane-parallel
clear-corneal incision is used. A 2.4-mm disposable keratome can be used to
create the proper architecture for a clear-corneal incision that will be
self-sealing and maintain a width-to-height ratio of 3:2. If the width of the
incision is 3 mm, the tunnel length through the cornea should be approximately
2 mm. In the KLP technique, the cataract incision is used for all the
subsequent surgical steps in order to optimize the refractive results. The
cataract incision itself can correct up to 1.5 D of astigmatism alone when used
in a length of approximately 3 mm or less (Table
I)
For an
astigmatically-neutral incision, a single-plane incision is created with the
keratome (Fig. 2a). For less than 1 D of astigmatism, a two-step clear-corneal
incision is utilized to flatten in the meridian in which it is placed (Fig.
2b). By using an accurate depth blade set at a depth of 550 to 600 microns, the
incision is made vertically, perpendicular to the cornea. Position the blade
handle towards the center of the globe to create a deep groove approximately
85% of the corneal depth. The keratome is selected to fit the
phacoemulsification tip and the IOL injector. (I usually use a 2.6 mm blade). The
blade is positioned at the base of the incision and enters the eye in a
plane-parallel fashion. This creates a two-step clear-corneal self-sealing
incision with maximal flattening effect.
To correct astigmatism greater than
2 D (Fig. 2c), the cataract incision is coupled with an additional arcuate
incision on the opposite meridian from the cataract incision (at an optical
zone of 9, 10, or 11 mm to induce further flattening), or combined with the
implantation of the toric IOL (Table
II) (Staar Surgical, Monrovia, California). The toric IOL is presently
available in two cylinder powers with the anterior surface of the lens
delivering the refractive torus. The 2 D lens will deliver approximately 1.4 D
of astigmatic correction at the spectacle plane, and the 3.5 D lens will
provide approximately 2.3 D of correction.
The incisions are constructed15
using the disposable Becton Dickinson clear cornea incision system (Becton
Dickinson Ophthalmic Surgery, Waltham Massachusetts), which is comprised of a
hinged fixation ring, an accurate depth blade to make the vertical component of
the incision, and a slit blade to make the proper architecture for corneal
entry (Figs. 3, 4).
Next, the
cornea is coated with several drops of 2.5% hydroxypropylmethylcellulose
(HPMC), which covers the cornea, keeps it moist, protects it, eliminates the
need for irrigation during the procedure, and provides 1.5 X magnification.
Hyaluronate viscoelastic (Healon or Healon 5, Pharmacia, Peapack, New Jersey)
is instilled into the anterior chamber.
The Kershner one-step forceps (Rhein
Medical, Tampa, Florida) is used to create a 5-mm, round, central capsulotomy
(Fig. 5).15,16 Hydrodissection is carried out using a Binkhorst
cannula and balanced salt solution irrigation (Fig. 6), beginning with
subincisional cortex to make sure that this is loosened prior to the
phacoemulsification procedure.17
Phacoemulsification
Today's
techniques of topical anesthesia, clear corneal cataract surgery, and injection
of elastic IOLs through small microincisions have placed new constraints on the
ability of the surgeon to perform phacoemulsification. Introducing the phacoemulsification
tip through a small, clear corneal refractive microincision limits access to
the cataract and can restrict the surgeon's ability to manipulate the lens
within the capsular bag (Fig. 7).
Many
surgeons make two incisions through the cornea and use two instruments for
phacoemulsification, one for the phacoemulsification tip and one for a sideport
lens-manipulating instrument. I do not believe that a second-handed instrument
is necessary for effective and efficient phacoemulsification of the cataract.
There are distinct advantages of maintaining the phacoemulsification incision
to one incision. Placing an additional incision in the eye is not only
unnecessary but it increases the likelihood of incisional leaks, introduces an
additional portal for infection and synechiae, and results in excessive
instrumentation in the eye.
Single-Incision Phacoemulsification — Three-Step
Keyhole Technique
The single
incision/single instrument phacoemulsification technique is also known as a
"one-handed" phaco technique. The maneuvers of lens rotation and
segmental removal of the cataract can be performed with a single hand on the
instrument, thus freeing the other hand for manipulating the eye, stabilizing
of the globe, retrieving instruments, or stabilizing the phacoemulsification
handle and tubing. It is important that the surgeon masters the ability to
perform efficient phacoemulsification through a small corneal microincision
before he or she adopts a single-incision technique. Single
incision/single instrument phacoemulsification is a three-step method
that I call the “keyhole” technique.
Step
1: central sculpting. When performing central sculpting, occlusion of the
phacoemulsification tip rarely occurs. The goal of central sculpting is to
remove the densest, hardest part of the nucleus at the beginning of the
procedure when it is easiest to do so. The lens is kept entirely within the
capsular bag. Using the phacoemulsification tip, gentle sculpting of the
central nucleus is completed. If the lens nucleus is dense, a deep and wide
sculpting is performed. If the lens is soft, a narrow and shallow sculpting is
performed.
Step 2: segmental removal of the cortical rim — the
keyhole method. Once central sculpting is completed, a cortical bowl
remains. To remove the cortical bowl, a notch of the cortical rim is
aspirated to release the tension on the cortical ring of the cataract in the
peripheral cortex. Using the phacoemulsification tip as a fulcrum, the
remaining cortical rim can be gently rotated clockwise. Two “clock-hours” of
cortical rim are then gently aspirated into the central “triangle of safety,”
and with minimal phacoemulsification are removed.
Step 3: removal of the nuclear plate. Following
complete removal of the cortical rim, a small, flat section of the posterior
nucleus remains. To remove this without risking injury of the posterior
capsule, I use a mini phaco-flip technique. The phacoemulsification tip is used
to push the tip of the nucleus plate against the equator of the capsule and
flip it over. Using short bursts of phacoemulsification power, the final piece of
the posterior nucleus can be safely elevated off the posterior capsule and
removed. The clear corneal irrigation-aspiration tip is introduced to remove
residual cortex and to irrigate the capsular bag.
Insertion of the IOL
The
capsular bag is inflated with enough viscoelastic to open the capulorrhexis
while being careful not to overfill the chamber (Fig. 8). Next, the 911A Tecnis
aspheric IOL (Pharmacia, Peapack, New Jersey) or the silicone toric IOL (STAAR
Surgical, Monrovia, California) is selected and loaded into the injector
cartridge. The IOL is then passed through the incision into the capsular bag at
the proper meridian, where it is allowed to position itself without additional
manipulation (Fig. 9).
The injector is then withdrawn from
the incision. Irrigation and aspiration are used to remove residual
viscoelastic. The lens position is checked for proper centration, and the eye
is reinflated to 20 mm Hg. A subconjunctival injection of 0.1 mL of
betamethasone (Celestone) and 0.1 mL of cefazolin (Ancef) is injected.18
The patient is given artificial tear drops to be used as needed. No bandage is
provided, but the patient is given a pair of sunglasses to be used outdoors.
The patient is seen on day 1, and at 2 weeks, 3 months, 6 months, and 1 year postoperatively and annually thereafter. If a
yittrium-aluminum-garnet (YAG) laser capsulotomy is required, it is not
performed until after the 3-month postoperative visit.
A Prospective Study of 690
Patients
Data were
analyzed prospectively for 690 consecutive clear corneal cataract procedures
between March 1993 and March 1995 with follow-up from 24 months to 5 years. Each patient underwent cataract
removal with topical anesthesia, clear corneal incision fashioned as an arcuate
keratotomy to correct preexisting astigmatism, intercapsular
phacoemulsification, and microinjection of a single-piece elastic IOL into the capsular
bag to correct spherical error. Preoperatively, best corrected visual acuity
was less than 20/50 (6/15) in all patients; 58% were myopic, 32% were
hyperopic, and 57% had astigmatism of greater than 1 D.
Of the 690 patients who were
included in the prospective study, postoperative spectacle independence was
achieved with uncorrected vision of 20/40 (6/12) or better in 600 patients (87%
of eyes). A total of 200 patients (29%) could read without the need for near
correction. The sphere was fully corrected in 538 patients (78%), and was
corrected within 1 D in 117 patients (17%) and within 2 D in 34 patients (5%).
No patients were overcorrected. The cylinder was fully corrected in 497
patients (72%), and was corrected within 1 D in 194 patients (26%) and within 2
D in 14 patients (2%). In patients with residual astigmatism, there was no
significant postoperative shift in cylinder axis. There were no
sight-threatening complications. All patients were able to resume normal
unrestricted activities within 24 hours of undergoing surgery.
Discussion
The
refractive outcomes achieved by following these techniques are the best we have
ever achieved, and with incision sizes approaching 1 mm, this technology holds
promise for even greater advances in the not-too-distant future. Both the
sphere and the cylinder can be predictably corrected with clear corneal
cataract surgery. Most patients can return to normal activities the same day.
Because the incision size is so small, the need for long-term, postoperative
eye-drop therapy is unnecessary. As a result, this procedure lowers costs, decreases
the number of postoperative visits that are required, reduces patient
inconvenience, reduces dependence on sunglasses, and increases patient
satisfaction.
Although
surgeons can deliver superior uncorrected visual acuity following cataract
surgery using microincisions and insertion of toric IOLs to correct
astigmatism,19-21 there have been few surgical options to
correct presbyopia. Multifocal or bifocal IOLs are plagued with optical
aberrations and loss of contrast sensitivity, and therefore should not be used
in any but the simplest cases. Most cataract patients who need refractive
correction for near tasks will need to use low-power reading spectacles.
Perhaps in the future, a high-quality refractive correction for both near and
far vision will be achievable with surgery. Work on the aspheric IOL is
presently underway (Tecnis Z-9000 IOL-Pharmacia, Peapack, New Jersey) and appears
promising.
I would encourage surgeons to
consider switching to topical anesthesia and small clear corneal incisions. This
surgical approach saves time. Patients love the fact that their eyes are fully
functional and appear normal almost as soon as they leave the operating room.22-24
Because the results are better, more surgeons are mastering the finesse of this
technique and more patients are demanding the rapid recovery and clear
uncorrected vision that this procedure provides. By incorporating the surgical
steps described earlier, surgeons will save time, avoid complications, and allow
their patients to benefit from the advantages of clear corneal cataract
surgery.
Many
surgeons have been slow to accept the techniques of astigmatism management
combined with cataract surgery. This may be due to resistance in acquiring new
skills or to the unavailability of new instruments. Some of us may wrongly
assume that better uncorrected vision following cataract surgery is difficult
to achieve. In the United States, there is no extra reimbursement for taking
the time to create better visual outcomes for patients, so some surgeons may feel
that there is no benefit to surgeons. I believe that these techniques
should be embraced by all surgeons. Astigmatism should be corrected, because it
improves patients’ quality of life, and because it can be predictably
and easily be accomplished using techniques that are currently available.
By simply adopting a few sound fundamental principals and making a minimal
investment in new instruments, surgeons can offer better refractive results for
their patients.
Conclusion
Today’s
modern techniques of microincision cataract surgery have enabled surgeons to
fully correct refractive error at the time of cataract removal and IOL
implantation. Smaller, more flexible, injectable, IOLs combined with more
efficient methods of phacoemulsification have made it possible to use incision
sizes that are smaller than 2.5 mm (and as small as 1 mm). Judicious selection
of the IOL type (such as the use of toric and aspheric IOLs ) combined with
astigmatic correction, can maximize refractive outcomes for cataract patients.
This translates into more satisfied patients with fewer postoperative
complications, less need for postoperative care, and less need for multiple
refractive measurements following surgery.
Today’s surgeons have within their
grasp the techniques for optimizing the refractive results of cataract surgery.
Full refractive correction at the time of cataract surgery can and should be
accomplished, and should be the goal of every cataract surgeon. Our patients
should expect nothing less.
References
1. Kershner
RM. ed. Refractive keratotomy for cataract surgery and the correction of
astigmatism. Thorofare, NJ: Slack, 1994.
2. Kershner
RM. Keratolenticuloplasty: arcuate keratotomy for cataract surgery and
astigmatism. J Cataract Refract Surg 1995; 21: 274-277.
3. Kershner
RM. Clear corneal cataract surgery and the correction of myopia, hyperopia and
astigmatism. Ophthalmology 1997; 104(3): 381-389.
4. Kershner
RM. How to be a hero to your patients: refractive cataract surgery. Rev
Ophthalmol June1996: 50-54.
5. Kershner
RM. Clinical consultation - single instrument phaco and continuous curvilinear
capsulorhexis. Ophthalmic Practice 1994; 12(1):
6.
Kershner, RM. “Single-Incision Phacoemulsification-The Three-Step Keyhole
Technique” Cataract and Refractive Surgery Today November/December 2001, 21-24.
7. Kershner
RM. Sutureless one-handed intercapsular phacoemulsification: the keyhole
technique. J Cataract Refract Surg 1991; 17(suppl): 719-725.
8. Kershner
RM. "Phacoemulsification Through a Clear Corneal Microincision"
Phacoemulsification, Laser Cataract Surgery and Foldable IOLs Eds. Agarwal,
Agarwal, Sacedev, Fine and Agarwal. New Dehli, India: Jaypee Brothers,1998, pp.
118-114.
9. Kershner
RM. The case for one-handed clear corneal cataract surgery. Rev Ophthalmol
1998; 3: 68-73.
10.
Kershner RM. "Single Instrument Phacoemulsification"
Phacoemulsification, Laser Cataract Surgery and Foldable IOLs 2nd Edition, Eds.
Agarwal, Agarwal, Sacedev, Fine and Agarwal. New Delhi, India: Jaypee Brothers,
2000, pp. 146-150
11.
Kershner RM. Six tips to clear cornea cataract surgery. Rev Ophthalmol 1999;
VI(4): 120
12. Kershner RM. “Clear Corneal Incision System for
Cataract Surgery” Refractive Surgery Eds Agarwal, Agarwal, Agarwal. New Delhi,
India: Jaypee Brothers, 1999
13.
Kershner RM. Topical anesthesia for small incision self-sealing cataract
surgery - a prospective study of the first 100 patients. J Cataract Refract
Surg 1993; 19(3): 290-292.
14.
Kershner RM. Topical anesthesia cataract surgery. Ophthalmic Practice 1993;
11(4): 160-165.
15.
Kershner RM. One-step forceps for capsulorhexis. J Cataract Refract Surg 1990;
16: 762-765.
16.
Kershner RM. Embryology, anatomy and needle capsulotomy. In: Koch PS, Davison
JA, eds. Textbook of Advanced Phacoemulsification Techniques. Thorofare, NJ:
Slack, 1991;35-48.
17.
Kershner RM. Capsular rupture at hydrodissection. J Cataract Refract Surg 1992;
18: 201.
18.
Kershner RM. Antibacterial prophylaxis before, during and after routine
cataract surgery. In: Masket S, ed. Consultative Section. J Cataract Refract
Surg 1993; 19(1): 110.
19.
Kershner RM. Toric lenses for correcting astigmatism in 130 eyes (Discussion).
Ophthalmology 2000; 107: 1776-1782.
20.
Kershner, RM "Refractive Keratotomy and the Toric IOL for the Correction
of Astigmatism in Clear Cornea Cataract Surgery " in James Gills, M.D.,
Editor A Complete Guide to Astigmatism
Management Slack, Inc. 2002.
21.
Kershner, RM. "Clear Cornea Cataract Surgery and the Collamer IOL",
Vision and Aging, October, 2001.
22.
Kershner RM. Refractive cataract surgery. Curr Opin Ophthalmol 1998; 9(1):
46-54.
23.
Kershner RM. Patient's adaptation to cataract surgery. Ophthalmology 1998;
105(1): 6-7.
24.
Kershner, RM "Optimizing the Refractive Outcomes of Clear Cornea Cataract
Surgery" Highlights of Ophthalmology-Phaco, Phakonit and Laser Phaco, Benjamin
Boyd, MD, Eds. Agarwal, S, Agarwal, A, Agarwal, A. Chapter 9, 2002.
Figure
Legends
Fig. 1 The
Kershner clear corneal cataract surgery preoperative worksheet
Fig. 2 Location and architecture of clear
corneal arcuate astigmatic incisions. Reprinted
from: Kershner, RM. “Clear Cornea Cataract Surgery and the Correction of
Myopia, Hyperopia and Astigmatism.” Ophthalmology 1997;104:381-389.
a. Single, clear corneal, 2.5 mm planar, stab incision
on the oblique or temporal limbus for astigmatic neutrality, to correct less
than 1 D of astigmatism.
b. Single, clear corneal, 2.5 mm arcuate incision on the
steepest axis at the 10 mm optical zone to correct 1 D or less of astigmatism
or a single 3.0 mm arcuate incision on the steepest axis at a 9 mm optical
zone, to correct 1 to 2 D of astigmatism.
c. Two arcuate keratotomy incisions are placed according
to the nomograms to correct greater than 2 D of astigmatism.
Fig. 3 A disposable Clear Cornea Incision
System (Becton Dickinson) can be used to create the ideal corneal incisions for
refractive cataract surgery.
Fig. 4 The location is marked and the
incision created.
Fig. 5 The
one-step capsulorrhexis forceps creates a round central 5.0mm capsulorrhexis.
Fig. 6 Hydrodissection
loosens sub-incisional cortex.
Fig. 7 Phacoemulsification
is carried out within the capsular bag with a 3-step technique.
Fig. 8 The capsular bag is inflated with
viscoelastic.
Fig. 9 The IOL is loaded into the
injection cartridge and injected.
Table I Incision guideline for clear
corneal cataract surgery
Correction Optical
Zone Number of Arcuate Incision
(Diopters) (mm) Incisions Length (mm)
<1.0 10 1 2.5
1.0 9 1 2.5
1.5 9 1 3.0
2.0 8 2 2.5
2.5 8 2 3.0
3.0 7 2 2.5
3.5 7 2 3.0
4.0 6 1 2.5
10 1 2.5
4.5 6 1 3.0
10 1 2.5
5.0 6 1 3.0
10 1 2.5
5.5 5 1 2.5
10 1 2.5
6.0 5 1 3.0
10 1 3.0
This
nomogram is to be used when incisions alone are utilized to correct the
cylinder. They are a guideline only, surgeons should adjust for the desired
result. Corrected for age 60+. Arcs placed on steepest axis of astigmatism
(plus cylinder). Pachymetry at incision site, keratome set to 95% of pachymetry
(550-600 microns). Mark arcuate incisions and optical zone with Kershner
One-Step Marker. Cataract keratotomy at 10 mm, 9 mm, or 8 mm only.
Table II Incision guideline for clear
corneal cataract surgery with a toric IOL.
Correction Optical
Zone Number of Arcuate Incision Toric
(Diopters) (mm) Incisions Length (mm) IOL
<1.0 10 1 2.5
1.0 9 1 2.5
1.5 9 1 3.0 +2.00 toric
2.0 9 1 3.0 +2.00 toric
2.5 9 1 3.0 +3.50 toric
3.0 9 2 3.5 +3.50 toric
3.5 8 1 3.0 +3.50 toric
10 1 3.0 +3.50 toric
4.0 8 1 3.5 +3.50 toric
10 1 3.5
4.5 8 1 4.0 +3.50 toric
10 1 4.0
5.0 8 1 4.5 +3.50 toric
10 1 4.5
5.5 8 1 5.0 +3.50 toric
10 1 5.0
6.0 8 1 5.5 +3.50 toric
10 1 5.5
This
nomogram is to be used when incisions are utilized in combination with the
toric IOL to correct the cylinder. They are to be used a a guideline only,
surgeons should adjust for the desired result. Corrected for age 60+. Arcs
placed on steepest axis of astigmatism (plus cylinder). Pachymetry at incision
site, keratome set to 95% of pachymetry (550-600 microns). Mark arcuate
incisions and optical zone with Kershner One-Step Marker. Cataract keratotomy
at 10 mm, 9 mm, or 8 mm only.