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`EXPERT
`I REVIEWS
`
`Advances in cataract surgery
`
`Expert Rev. Ophthalmol. 8(5), 447 456 (2013)
`
`Majed Alkharashi,
`Walter J Stark and
`YassineJ Daoud*
`The Wimer Eye Institute, Johns Hopkins
`University, ll/humenee 327,
`600 North Wolfe Street, Baltimore
`MD 21287, USA
`‘Author for corrspondence:
`Tel..-+1410 910 2330
`Fax: +1410 910 2393
`ydaoud Iojhmi. edu
`
`Recent advances in cataract surgery have increased the safety and efficacy of this common
`procedure. Cataract surgery has evolved from ‘couching’ with sub-optimal
`rsults to
`phacoemulsification with excellent results Introduction of the femtosecond laser into cataract
`surgery may further the safety and predictability of this procedure. In addition, innovations in
`intraocular lens material have enabled the surgery to be done through a small incision with
`quicker recovery and more predictable refractive outcome. New intraocular lens design
`technologies have helped patients minimize their need for glasses at most distances Further,
`invention of ophthalmic viscosurgical devics reduced the risk of endothelial decompensation
`and corneal edema. These innovations have transformed the goal of cataract surgery from
`purely visual rehabilitation to a refractive procedure as well.
`
`Ksvwons: cataract surgery 0 femtosecond laser 0 intraocular lens 0 ophthalmic viscosurgical devices
`
`Cataract is a leading cause of blindness world
`wide and cataract surgery is one of the most
`frequently
`performed
`operations
`in
`the
`world. Cataracts afiect more than 20 million
`
`than 40 years. By 2020,
`Americans older
`more than 30 million Americans will have vis
`
`ually significant cataract and 9.5 million are
`expected to have pseudophakia or aphakia [1].
`Advancements
`in
`phacoemulsification
`and
`intraocular lens (IOL) technology have ushered
`in a new era of cataract surgery. Innovations
`in IOL design and phacoemulsification instru
`mentation have potentiated improved surgical
`outcomes,
`reduced
`perioperative morbidity
`and increased likelihood of spectacle independ
`ence. As a result, surgeons are attaining unpre
`oedented safety, efficiency and precision. The
`breakthrough of new technology is paralleled
`by patients’ heightened expectations from cata
`ract surgery.
`In this new era, many patients
`arrive to their appointment well researched
`and prepared with anticipation of exceptional
`postoperative visual acuity, both near and
`distance, without correction [2].
`
`History
`record of cataract being surgiatlly
`The first
`treated is from 600 B.C. by Susruta of India [3].
`Cataracts were surgiully addresed by couch
`ing. Basically the surgeon would insert a long
`instrument posterior to the limbus and push
`the lens into the vitreous cavity, thus clearing
`the visual axis of the dense lens. Complication
`rate was high at that time, but it would change
`
`the patient’s life by giving him some ambula
`tory vision and self dependence. Couching is
`still performed by some traditional
`‘healers’
`in some parts of Africa, the Middle East and
`few other parts of the world. 33.3% of patients
`who undergo traditional couching end up
`with no light perception vision [4]. It is likely
`that outcomes of couching would have been
`worse in ancient
`times when there was no
`
`recourse to modern antibiotics for endophthal
`mitis or treatments for glaucoma. The concept
`of cataract extraction rather than pushing the
`lens inside the eye was introduced by Amrnar
`Ibn Ali
`in Choice of Eye Disease: written in
`Egypt in the 10th century. Ibn Ali invented the
`hollow needle and oral suction device, for the
`
`purpose of cataract extraction:
`“Then I constructed the hollow needle, but
`
`I did not operate with it on anybody at all,
`before I came to Tiberias. There came a man
`
`for an operation who told me: Do as you like
`with me, only I cannot lie on my back. Then
`I operawd on him with the hollow needle and
`attracted the cataract; and he saw immediately
`and did not need to lie, but slept as he liked.
`Only I bandaged his eye for seven days. Witt:
`this needle nobody preceded me. I have done
`many operations with it in Egypt [5]."
`As one would expect, this technique would
`not work on dense cataract and couching
`remained the widely performed surgery to treat
`cataract for many decades [3].
`ophthalmologist,
`In
`1747,
`a French
`Jacques Daviel, was
`the first
`to perform
`
`www.expen-revlewseom
`
`10.1586/17469899.20l3.840Z38
`
`© 2013 lnforrna UK Ltd
`
`ISSN 1746-9899
`
`447
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`PAGE 1 OF 10
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`SENJU EXHIBIT 2052
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`LUPIN V SENJU
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`extracapsular cataract extraction through a large corneal
`incision. Then, he would incise the anterior capsule and
`express the nucleus. Because of the incomplete removal of
`the cortex, chronic inflammation with glaucoma and secon
`dary capsular opacification would lead to unsatisfactory out
`come. Thus, the procedure was not widely accepted at that
`time and surgeons tried to remove the lens as a whole with
`the capsular bag. In 1753, Samuel Sharp was among the
`first to successfully perform intracapsular cataract extraction
`(ICCE)
`through limbal
`incision using pressure from his
`thumb.
`
`Lens expression technique was improved over many years
`by using different approaches. In 1957, Joaquin Barraquer
`used (1 chymotrypsin to dissolve the zonules to facilitate lens
`removal. However, glaucoma and clogging the trabecular
`meshwork with zonule fibers remnant was one of the many
`complications of the technique. Cryoprobe was first intro
`duced in 1961 by Tadeusz Krwawia to remove the lens by
`forming iceball and lessen the risk of capsular rupture. ICCE
`was a very successful operation compared to couching and
`early ECCE. However, the rate of potentially blinding com
`plications was 5% apart
`from aphakia related habitation
`problems [6].
`The gradual introduction of operating microscopes during
`the 1970s offered better intraocular visibility and ability to
`safely place multiple cornml sutures. In addition, it had the
`advantages of leaving the posterior capsule intact which reduced
`the risk of potentially blinding complications (e.g., vitreous loss
`or retinal detachment). It also allowed posterior chamber lens
`implantation.
`introduced in 1967 by Dr.
`Phacoemulsification was
`Charles Kelman. Since then,
`there has been significant
`improvement
`in fluidics, energy delivery, efliciency and
`most important, safety of this procedure. Currently, phacoe
`mulsification is the standard of care for cataract extraction
`
`in the western world. The major advantage of phacoemulsi
`fication is that it reduced the morbidity from cataract sur
`gery by reducing the incision size with subsequent faster
`recovery and decreased risk of complications including
`endophthalmitis.
`A major advance in cataract surgery was the invention of
`an intraocular lens that can be implanted to replace the
`extracted cataractous lens. Casaamata is believed to be the
`
`in
`(IOL)
`lens
`surgeon to implant an intraocular
`first
`1795 [7]. The idea of IOL implantation was revived by Har
`old Ridley. Ridley inserted an artificial lens in the form of
`polymethyl methacrylate (PMMA)
`in 1949 [7,8]. However,
`the idea of PMMA IOL did not gain popularity due to mis
`calculation of the postoperative refraction. The cause of this
`miscalculation was later discovered to be due to the difler
`ence in the refractive index of PMMA material in air vs in
`
`fluid inside the eye. Another drawback of the PMMA lenses
`is that they were rigid and could not be folded which neces
`sitated large corneal incisions to insert such lenses. Subse
`quent I015 made of acrylic and silicone, were flexible and
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`44:
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`PAGE 2 OF 10
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`folded and inserted through a
`could be
`smaller incision.
`
`significantly
`
`Ophthalmic vistosurgical devices
`Healon (sodium hyaluronate 1%, Abbott Medical Optics Inc.
`Santa Ana, CA. USA) was the first ophthalmic viscosurgical
`device (OVD) to be introduced in 1979. Since then, a number
`
`of OVDs have been manufactured with varying composition
`and rheologic behavior. OVDs have variety of uses in ophthal
`mic surgery whidl could be summarized in space creation,
`tissue stabilization and corneal endothelial cell protection [9].
`OVDs used to be classified as either dispersive or cohesive.
`Dispersive OVDs (e.g., Viscoat, Alcon. Fort Worth, TX,
`USA) are low in viscosity and molecular mass, have short
`molecular chain length and require longer aspiration time for
`complete removal. Typically, dispersiva remain in the eye during
`phacoemulsification to protect the endotheliurn from turbulent
`flow.
`
`Cohesive OVDs (e.g., Healon, Abbott Medical Optics Inc.)
`are typically more viscous; have a higher molecular mass,
`possess longer chains, result in atcellent space maintenance and
`are easy to remove. Thus, cohesives are used to expand the
`capsular bag for intraocular lens insertion at the end of cataract
`5'-“3°"Y-
`
`The introduction of Healon5 (sodium hyaluronate 23%) in
`1998 heralded a new class of OVDs termed visooadaptive [I0].
`(e.g., HmlonS and DisCoVisc, Alcon.) behave
`similar to superviscous cohesives under low shear stress. With
`change in fluid dynamics,
`the viscoadaptives fracture freeing
`pieces to float around in the balanced salt solution. This bipha
`sic nature has resulted in viscoadaptives being referred to as
`pseudodispersive in ophthalmic surgery because they are well
`retained in the
`anterior
`segment
`similar
`to dispersive
`OVDs [n].
`
`OVDs have led to dramatic improvement in the safety of
`cataract surgery and minimized damage to the ocular structures
`that used to occur previously as a result of cataract surgery.
`Indeed, OVDs are of the most important advances in cataract
`surgery.
`
`Intraoperative floppy iris syndrome
`Intraoperative floppy iris syndrome (IFIS) typically occurs in
`patients receiving (1 1 blocker. Features of IFIS include poor
`pupil dilation; progressive intraoperative pupillary miosis,
`iris
`prolapse and floppy iris. To decrease the risk of complications,
`few peri and intraoperative interventions have been succmsfully
`attempted. Pre operatively, using atropine drops for few days is
`recommended [12]. Intraoperatively, short and posterior corneal
`wound construction should be avoided. Intracameral prtserva
`tive free epinephrine may be utilized and adding prservative
`free epinephrine to a 500 ml BS3 irrigation bottle is recom
`mended (of label). There should be a low threshold for
`
`using pupillary dihtion devices. Because of the ability to place
`an iris retractor subincisionally, we prefer irk retractors to pupil
`expansion rings in IFIS cases with poor pupil dilation. Manual
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`pupillary dilation and stretching should be avoided, so is over
`filling and overly pressurizing the chamber with OVD. Some
`OVD should be removed by pressing on the wound before
`performing hydrodissection. Low fluidic parameters should be
`utilized, and suturing the main corneal incision to avoid iris
`prolapse in case of lmky wound. Arshinoff described modified
`soft shell and ultimate soft shell
`technique (SST USST)
`for
`IFIS [13] which relies solely upon OVDS for iris stabilization by
`using Viscoat (Alcon.) and Healon5 (Abbott Medical Optics
`Inc.) to add a semi rigid OVD roof to stabilize the iris and
`cause some viscomydriasis. Chang et 41., reported that the use
`of preoperative atropine followed by intraoperative Healon5,
`iris retractors and pupil expansion rings ruulted in excellent
`surgical outcome [14].
`Viscoat may be useful in compartmentalization specially in
`cars of localized weaknms of the zonules (e.g., tratuna). The
`reverse soft shell technique (packing Viscoat in a region of
`broken zonules followed by placing cohesive OVD over it to
`prevent vitreous from prolapsing) can be used in arse of poste
`rior capsule rapture to cover and stabilize the tear. Viscoat can
`also partition residual lenticular material from the prolapsed
`vitreous. In july 2012, Hcalon EndoCoat was approved by
`the US FDA as a dispersive OVD.
`
`Capsular staining
`The advent of capsular staining has improved the safety of Cara
`ract surgery by allowing enhanced visualization.
`Indicttions
`for capsular staining include cases with a poor red reflex as in
`mature or white mtaracts, opalesmnt cortical material, dense pos
`terior subtapsular opacification, vitreous hemorrhage, or oomeal
`opacity. In addition, staining is also useful for pediatric cataract
`extraction and for surgeons learning new intraoperative techni
`quts requiring good visualization of the anterior capsule. Nurner
`ous intraocular dyes have been reported in the literature
`including indocyanine green (ICC), fluorescein, crystal violet,
`gentian violet and brilliant blue G (BBC) [15]. However, only try
`pan blue is FDA approved as an adjunct to cataract surgery [16].
`
`lntraocular lenses
`
`have
`advances
`technological
`significant
`In recent years,
`improved our understanding of the abandons of the normal
`hurnaneyeaswellmthehumaneyethathasbeerralteredby
`refractive surgery. New corneal
`imaging techniques such as
`Scheimpflug imaging, placido disk videokeratography and ante
`rior segment optical coherence tomography have enhanced our
`understanding of the shape and functionality of the human
`cornea. These instnrments have shown that the nonnal comea
`
`is flatter in the central 2 mm, with steepening from 2 4 mm,
`and, then, flattening again beyond 4 mm. This correlates well
`with the lact that the spherical aberration value is not a con
`stant throughout the cornea, but rather varies as one moves
`radially li'om the center of the cornea [tot]. Further,
`in the
`young human eye, the positive spherical aberration introduced
`by the cornea is partially corrected by the negative spherical
`aberration inuoduced by the crystalline lens [I7]. However
`
`changes that occur in the lens with age cause the positive spher
`ical aberration of the lens to increase [18]. Thus, the aberration
`compensation is gradually lost, leading to an increase in total
`ocular aberrations. This,
`in turn,
`leads to a corresponding
`loss in optical and visual quality, reduction of scotopic contrast
`sensitivity and increase in optical side eflects such as glare and
`haloes [mo].
`
`This new understanding of ocular optics and aberrations has
`led to the development of new aspheric IO1s to neutralize the
`positive oomeal spheriarl aberration and improve visual qual
`ity [ZI]. This may be due to the improvement
`in contrast
`sensitivity and improved retinal image [22,23]. However, caution
`must be exercked in using aspheric IOLs in patients at risk of
`decentration (e.g., psardoexfoliation and trauma) as this may
`induce further higher order aberrations [24]. Aspheric IOL should
`also be avoided in eya that had hyperopic IASIK treatment as
`this might increase the negative spherical aberration of the eye.
`
`lntraocular lenses for prsbyopia correction
`Presbyopia remains one of the most challenging optical prob
`lems in cataract and refractive surgery. Dilfercnt approaches
`to treat presbyopia have been studied in recent years. These
`include sderal remodeling (scleral expansion and sclerotomy
`techniques) [25]; cornml procedures (presbyLASIK [26], corneal
`inlays [27] and conductive keratoplasty [2x]); and monovision
`techniques
`[at]. Each of these techniques has
`limitatiors,
`advantages and disadvantages. There has been increasing
`interest in correcting presbyopia at the time of cataract surgery
`by
`prrsbyopia correcting IOLs The two major prubyopia
`correcting IOL designs are the accommodating and the multi
`focal IOLs.
`
`The first presbyopia correcting IOL to be FDA approved
`was the Array (Advanced Medical Optic, Santa Ana, CA, USA
`and USA) in 1997. The Array is a refractive multifocal lens
`with five progressive concentric arms on its anterior surface.
`Zones one, three and five are distance dominant, whereas mnes
`two and four are near dominant. In some of the first smdies,
`
`72% of the eyes implanted with the Array could see both 20/
`40 for distance and J3 for near compared with 48% with a
`monolbcal lens [29].
`
`In 2005, the FDA approved two new multifocal desigrs, the
`refractive Reznom IOL (Advanced Medical Optics, Inc.) and
`the dilfractive Aaysof Restor IOL® (Alcon laboratories, Inc.).
`The Rezoom represents new engineering of the Array platform,
`induding a hydrophobic acrylic material and a shift of the
`zonal progression. Aspheric transitions between the zones offer
`intermediate vision. The near dominant zonm provide +3.50 D
`of add power at
`the IOL’s plane for near vision, yielding
`approximately +2.57 D of add power in the spectacle plane.
`The Remom has been shown to provide spectacle independ
`ence in 93.4, 92.6 and 81.4% for distance, intermediate and
`
`respectively [I02]. The major drawbadrs of the
`near vision,
`Rezoom are its moderate dependence on spectacles for near
`tasks and the increased incidence of photic phenomena com
`pared to other multifocal lenses [30].
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`ReSTOR® IOL employs a central 3.6 mm dif
`The
`liactive zone. This area compriss 12 concentri: steps of gradu
`ally decreasing (1.3 0.2 microns) heights, the farther from the
`center. These steps allocate energy based on lighting conditions
`and activity to create a range of vision. The ReSTOR has been
`shown to yield high rates of spectacle freedom with uncorrected
`distance visual acuity of 20/30 or better in 93.8% eyes and an
`uncorrected near visual acuity of 20/30 or better in 75.0% of
`eyes [3132] Clare and halos have been reported as the main com
`plication of this type of lens. Moderate glare was reported by
`21.3% of the patients compared to 7.1% for a monofocal IOL
`In 2007,
`the FDA approved I:he aspheric version of the
`ReSI'OR (AcrySof IQ ReSTOR), which has a negative aspher
`icity, while maintaining its apodization, dilfractive and refrac
`tive components. The AcrySof IQ ReSTOR IOL + 3.0 D
`(SN6AD1) incorporates a +3.0 diopter correction at the lentic
`ular plane (‘+2.5 D at the spectacle plane). It also has nine
`concentric steps (three less steps than the original IOL) farther
`apart
`to improve intermediate vision over the AcrySof IQ
`ReSTOR IOL +4.0 D (SNGAD3), with similar near and dis
`
`tance visual acuity. Halos and ghre are still common com
`plaints of patients implanted with these lenses. Patients
`implanted with the SN6ADl noticed more glare and patients
`implanted with SNGAD3 noticed more halos
`[33,34]. The
`ReSTOR Toric is the newest addition to this lens design. It
`provides a single platform to correct astigmatism and improve
`nmr and intennediate vision. This lens is currently available in
`Europe and Canada, but
`is not yet
`available
`in the
`United States.
`
`In 2009. another dilfractive IOL was approved, the Teatis
`multifocal (Advanced Medical Optic, Inc. Santa Ana, Califor
`nia). The newer version is a single
`acrylic (ZMB00) and
`hm a full diflractive posterior surface that makes it pupil inde
`pendent. It hm an aspheric anterior surlace with +4 D near
`add (+3.0 D at the spectacle plane). A retrospective study on
`the earlier version of this IOL found an uncorrected distance
`
`visual acuity of 20/30 in 85% of eyes and an uncorrected near
`visual aatity of J1 in 93.7% of 2500 eyes, 3 years postopera
`lively [35]. Clare and halos were reported as severe by 6.1 and
`2.12% of patients, respectively.
`Multifocal lenses have the persistent drawback of the poten
`tial for patients to see glare or halos for few weeks or months
`following surgery. Indeed,
`it has been shown that multifocal
`lenses have greater incidence of glare and halos than monofocal
`IOIs [36]. However, it has been shown that glare and halos
`symptoms decrease as most people learn to disregard them
`with time [37]. Another drawback of multifocal IOIs is the
`
`potential for decreased contrast sensitivity specially in dim
`lights. However, contrast sensitivity with multifocal
`IOLs
`improvs over time and may approximate the levels found with
`spherical monolocal lenss by 6 months postoperatively [38].
`Patient selection for multifocal IOL is critical. Patients with
`
`high expectations, or those with significant astigmatism, ocular
`surface disease (e.g., epithelial basement membrane disease and
`severe dry eye), zonular weakness (e.g., pseudoexfoliation ) or
`
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`patients with retinal diseass (e.g., macular degeneration and
`epiretinal membrane) may not be good candidates.
`
`Accommodating lenses
`The Crystalens (Bausch & Lomb, Aliso Viejo, CA. USA) is the
`only FDA approved ‘accommodating’ lem to correct presbyo
`pia in patients with cataracts. The Crystalens has undergone
`several modifications since the original model (AT 45). It has
`silicone optic and two flexible, hinged plate haptics. The latest
`models (HD and A0) have a central 1.5 mm blended bispheric
`optical zone to enhance near vision [39]. The Crystalens has
`been shown to have better uncorrected nmr visual acuity than
`a monolbcal lens [39]. Although it was thought that the Crysta
`lens mode of action is through accommodation, several studies
`have lailed to demonstrate a significant accommodative shift.
`Indeed, the Crystalens have been shown to have poorer uncor
`rected near visual acuity than the multifocal lenses. Thus, many
`Crystalens surgeons may aim for 0.50 D to 0.75 D of myo
`pia in the nondominant eye to induce ‘mini monovision’ in
`their patients [4o—42]. Another drawbadt of the Crystalens has
`been issues with tilting and decentration of the lens catsed by
`capsular contraction and fibrosis [43]. On the other hand, there
`are less complains of glare and halos from Crystalens than
`from the multilbcal lenses. Thus, Crystalem is a good option
`for patients who are willing to accept some compromise in
`near vision but have a low threshold for glare and halos that
`may be present with multilbcal lenses [44].
`One of the new
`lenses currently undergoing
`FDA trials is the Synchrony accommodating IOL (Abbot Medi
`cal Optic, Abbott Park, IL, USA). The Synchrony IOL consists
`of a foldable, single piece, dual optic system. A spring haptic
`joins the high plus anterior optic to a minus powered posterior
`optic [45]. During attempted distance vision, the two optics are
`close together. Near vision is achieved by attempted accommo
`dation with subsequent decrease in capsular bag and zonular
`tension. The in turn moves the front optic forward and changes
`the focal point to intermediate or near vision. In a small pro
`spective study, the Synchrony lens was shown to have equivalent
`uncorrected distance and uncorrected near visual acuity to the
`ReSI'OR lens while providing better unconected intermediate
`visual acuity and less halos and glare [46].
`Another promising technology is the three piece Light Adjust
`able Lens (Calhoun Vision Inc., Pasadena, CA. USA) made of a
`photosensitive silicone material. Within two weeks post opera
`tively, the raidual refractive error could be corrected by shining
`an ultraviolet light on the IOL through a dilated pupil to change
`the shape of the lens. The Light Adjustable Lens corrects sphero
`cylindrical errors as well :5 presbyopia by creating a small near
`zone add according to the pupil diameter [47-49].
`
`Implantable miniature telescope
`In July 2010, the FDA approved the Imphntable miniature tele
`scope TM (IMT, VisionCare Ophthalmic Technologies Inc.,
`Saratoga, CA, USA). The implantable miniature telescope
`(IMT) is a system which magnifies objects to improve vision
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`in patients with end stage age related macular degeneration
`(AMD).
`It
`is
`indicated for monocular
`implantation in
`patients with stable, but severe to profound vision impair
`ment
`(best corrected distance visual acuity 20/160 20/800)
`caused by bilateral central scotomas associated with end stage
`age related macular degeneration, a visually significant cata
`tact and who achieve at least a 5 letter improvement on the
`visual acuity chart tsing a trial external telescope. Two mod
`els are available: one with 2.2 times magnification and the
`other with 2.7 times magnification. The device’s glass qvlin
`der homing the micro optics is 4.4 mm long and 3.6 mm in
`diameter. The rigid haptic loops are 13.5 mm in diameter.
`The device is placed in the capsular bag while the anterior
`aspect protrudes through the pupil by 0.10.5 mm. The
`prosthesis projects an enlarged image of the patient's central
`visual field onto the retina;
`thus reducing the size of the
`scotoma relative to the objects in the central field of vision.
`The implanted eye sees 20 24 wide field of view due to the
`enlarged image projection.
`The IMT has shown promise with 59.5% of 173 IMT
`implanted eyes gaining three lines or more of BCVA compared
`to 10.3% of 174 fellow control eyes (p < 0.0001) after 2 years
`of follow up. Meanwhile, 0.6% of 173 telescope implanted eyes
`lost three lines or more compared to 7.5% of 174 fellow con
`trol eyes (p = 0.0013). Two cases of corneal edema in IMT
`implanted eyes required grafts between 9 and 12 months [so].
`There were no cmes of corneal decompensation between 1 and
`2 years after
`surgery. The mean endothdial
`cell density
`stabilized after the first year through the second year [51].
`
`Zonules-supporting devices
`The anterior approach of removing a cataract with
`zonular weakn used to be ICCE until endocapsular devices
`were introduced in 1991 [57,53]. The capsular
`tension ring
`(CTR) is made of polyrnethyl methaaylare (PMMA) material
`and has an oval shaped cross section with eyelets at both free
`ends. The diameter of CTR is larger than that of the capsular
`bag and comes in different sizes. The CTR expands the capsu
`lar bag and redistributes the forces, providing equal distribution
`of support over the remaining zonules [54]. At minimum, over
`lap of the end terminals is needed to provide complete circum
`ferential support. CTR is indicated when there is evidence of
`severe, but localized zonular dialysis (<4 h) or mild degree of
`generalized zonular weakn [S4]. The CTR can be inserted
`manually with forceps or with injectors into the capsule bag
`before or after lens extraction.
`
`The CTR has intta as well as post operative advantages. By
`expanding the bag it reducm the risk of fiirther zonular dam
`age. Also, it minimizm the risk of potentially aspirating the bag
`during the surgery. Post operatively, CTR reduces the risk of
`IOL decentration and tilting [55]. It oflers the advantage of pre
`venting capsule wrinkling and fadlitate recentering a mildly
`subluxed capsular bag. Further, it may decrease the prevalence
`of posterior capsule opacification or the incidence of capsular
`phimosis [56].
`
`insufficiency and a
`When there is a profound zonular
`severely subluxed capsular bag. a standard CTR may not supply
`enough intraoperative and postoperative support to maintain
`the desired orientation of the capsular
`To deal with these
`problems, scleral fixated devices sud: as the modified CTR
`(M CTR) or the capsular tension segment (CT3) must be
`used [57]. his chafing from the fixation eyelet and chronic uvei
`tis could occur with small capsulorhexis, thus an adequate size
`capsulorhexis (5.5 mm) should be performed [54].
`
`Correction of astigmatism during cataract surgery
`Cornml astigmatism can be mmsured by multiple techniqum
`including manual keratometry, autokeratometry, optical biome
`tery and corneal
`topography. Topographic measuretnent of
`comeal astignatism is currently the standard of care. Corneal
`topographic measurements identify irregular astigmatism that
`may limit optimum results.
`Management of corneal astigmatism at the time of cataract
`surgery is an area of increasing importance and active research.
`Several approaches to correct cornml
`have been suc
`cessfully tried. These include main corneal incision placement on
`the steep axis of the cornea, single or paired peripheral corneal
`relaxing incisions (PCRIS) and/or toric IOL implantation. Cor
`nml incisions do not diange the spheriatl equivalent power of
`the cornea enough to alfect IOL power calculations. Because of
`the coupling effect, they flatten the meridian where they are
`placed and steepen the meridian 90' away.
`For corneal astigmatism <1 D, placing the main corneal inci
`sion on the steep axis could be perfimned. With 1 1.5 D of
`astigmatism, peripheral corneal relaxing incisions may be uti
`lized. Toric IOL is used for >15 D of astigmatism [58].
`
`On axis corneal incision
`
`A full thidcnss corneal incision for cataract surgery flattem the
`comea in the meridian of the incision and therefore an reduce
`
`preexisting
`
`The incision is made on the steep axis of
`This '5 a good approach for correcting small amounts
`of against the rule astigmatism with a temporal incision.
`
`Peripheral corneal relaxing incisions
`Peripheral corneal relaxing inckions (PCRIs) are called Iirnbal
`relaxing inckions (LRIs) in older literature, but this term is inac
`curate bemuse the limbus is not incised. The inckions reduce cor
`
`by flattening the cornea in the steep meridian
`neal
`and steepening the cornea in the flat meridian. PCRIs are usefiil
`for treating 1 1.5 D of regular corneal
`when implant
`ing non toric IOLs. Beyond 1.5 D, the risks associated with PCRI
`use begin to outweigh the potential benefits compared with toric
`IOLS. To achieve conéstent incision depth, PCRIs should be per
`formed at the beginning of surgery belore altering the intraocular
`pressure. Unwanted under corrections may occur if relaxing inci
`sions are made after a globe is penetrated [59]. Also, the axis mark
`ing should be phced while the patient is in the upright position
`to prevent axis misalignment due to cyclorotation of the eye in
`the supine position. An axis misalignment of LRI of
`5° results
`
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`Alkharashi, Stark & Daoud
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`in a 17% reduction in elfect [60]. Because of risk of corneal perlb
`ration or inducing higher order abenations, PCRIs should be
`avoided on comeas with ectasia [58].
`
`PCRIS cotrld be perlormed by laser during femtosecond
`laser assisted cataract surgery with more precision of depth, axk
`and length. Also,
`the epithelium could be left intact to be
`opened postoperativdy if needed.
`
`Toric IOL
`The lirst toric IOL available in the US market was the STAAR
`
`toric IOL (STAAR Surgical Co, Monrovia, CA, USA). The
`lirst version of STAAR toric IOL was approved by the FDA in
`1998. The overall haptic diameter Wm 10.8 mm. The STAAR
`toric IOL sulfered from early postoperative rotational instabil
`ity, particularly when implanted in large myopic eya [61]. The
`newer version has longer haptic length (11.2 mm) and has
`been shown to be more stable than the older version. However,
`
`limited [62,63]. The
`widespread acatptance and usage was
`STAAR toric power at the IOL plane lot both models is 2 and
`3.5 D, corresponding to 1.4 and 2.3 D at the corneal plane.
`In 2005,
`the one piece acrylic Acrysof Toric IOL (Alcon
`laboratories Inc., Fort Worth, TX, USA) was granted approval
`by the FDA. The lens has excellent rotational stability, with
`less than 4' of rotation at 1 year [66]. Poll at al., showed that
`eyes with astigmatism 22.26 D that were implanted with a
`toric lem implant were more likely to achieve 20/40 UDVA
`compared to PCRIs [65].
`Subsequent Acrysof Toric lenses an correct up to 4.11 D of
`astigmatism at the corneal plane. Visser at al. evaluated the
`eflectiveness of Acrysof Toric SN6AT6 to SNGAT9 model
`IOIs to correct cylinder powers rangm from 2.50 to 4.50 D.
`They found that these IOIs were safe and elfective at correct
`ing astigmatism in eyes with >2.25 D of comeal astigma
`tisrn [66]. The use of toric IOLS is controversial in eyes with
`irregular astigmatism, higher order abandons, or zonular
`weakness [67]. Postoperative IOL rotation significantly decreases
`the effectiveness of toric IOI.s. There is a 3.3% loss of astig
`matic correction for every 1' of oi? axis rotation. Patients with
`long axial lengths have a higher risk of postoperative toric lem
`rotation [as].
`
`Femtosecond laser-assisted cataract surgery
`Since the introduction of the Nd:YAG laser in the treatment of
`
`laser technology has proven to be
`posterior capsular opadty,
`sale and effective for the treatment of many ophthalmic dis
`eases. Indeed, laser assisted eye surgery has proven to be safer
`and superior to stugical instrument msisted eye surgery. A good
`example of this is the outcome of lemtosecond laser assisted vs
`microkeratome assisted flap creation in IASIK surgery [69].
`In 2010, the FDA granted clearance to LenSx system (Alcon).
`This marked a new era for liemtosecond laser assisted cataract sur
`
`gery (FLACS). Since then, three other laser systems have been
`granted FDA approval for FLACS. These systems are Catal