Hyperopia and presbyopia - part 10 doc

Mean Technique and Loss of best of follow-up microkeratome corrected visualStudy Year eyes months used Complications acuity BCVA Nidek EC-5000Excimer LaserAutomated CornealShaper8.5-mm f

Table 2 Complications of LASIK for Correction of Spherical Primary Hyperopia

No of follow-up Technique and corrected visualStudy Year eyes (months) microkeratome used Complications acuity (BCVA)

Keracor 116 ExcimerLaser

Automated CornealShaper8.5-mm flap diameter

Keracor 117 ExcimerLaser

Automated CornealShaper8.5-mm flap diameterKeracor 117CTExcimer LaserAutomated CornealShaper8.5-mm flap diameter

VISX STAR S2Excimer LaserHansatome9.5-mm flap diameter

• 1.3% corneal ectasia

• Epithelial invasion ofthe interface

• Traumatic flapdisplacement

• Bilateral haze

• 15% epithelialingrowth

• 2.3% haze

• 7.5% scars

• 4.7% verticaldecentration

• 2.3% central island

• 4.7% free cap

• 11.6% flapdislocation

• 11.6% flap folds

• 31.4% epithelialingrowth

• 13%

corrected

regressed/under-• 9.3% glare at 9months

• 3.7% transientdiplopia that resolvedentirely

• 1.8% irregular flapcut

• 1.8% decentration

• 3.7% irregularastigmatism

• No significantcomplications noted

• 6% epithelialingrowth into theinterface

• 4% scars on nasalside

• 2% ablationdecentration

• 2% transient diplopia

• 5% flap folds

• 6.5% transientepithelial defect

• 4.3% diffuse lamellarkeratitis

• 2% lost 1 line

• 1.3% lost 2lines

• 9% lost 1 line

• 4.7% lost 3lines

• 5.6% lost 2lines

• 63% of lowhyperopes lost

1 line

• 50% of highhyperopes lost

1 line

• 6% lost 1 line

at 1 yearfollow-up

• 6% lost 2 lines

at 1 yearfollow-up

• 5% lost 2 lines

at 2 yearfollow-up

• 11% lost 1 line

• 2.2% lost 2lines

Table 2 Continued

No Mean Technique and Loss of best

of follow-up microkeratome corrected visualStudy Year eyes (months) used Complications acuity (BCVA)

Nidek EC-5000Excimer LaserAutomated CornealShaper8.5-mm flap diameterLasersight 200Excimer Laserwith 9.0 softwareAutomated CornealShaper9.0- to 9.5-mm flapdiameterKeracor 117CExcimer LaserHansatome5.9-mm optical zonediameter, flapdiameter notreportedVISX STAR S2Excimer LaserHansatome9.5-mm flap diameterVISX S2 SmoothscanExcimer LaserHansatome9.5-mm flap diameter

• 4.3% epithelial cells

in the interface

• 2.2% haze

• 2.2% mild irreg astig

• 0.6% had a free cap

• 0.6% sterile keratitis,(Note: Complicationrates combine the

192 sphericalhyperopes with the

164 toric hyperopes.)

• No significantcomplications noted

• 2% epithelialingrowth in thewould edgesassociated with freecaps, not requiringsurgical removal

• 8.2% transientepithelial ulcer

• 4.5% stromalinfiltrates

• No significantcomplications noted

• No significantcomplications noted

• 13% of highhyperopes lost

2 lines or more

• 1.4% lost 2lines or more

• No eyes lostBCVA

• Less than 5.8%lost 1 line

• 19% lost 1 line

• 7.7% lost 2lines

The larger ablation areas necessary for H-LASIK require larger flaps Extra caremust be taken with the larger flaps because a large flap may be more prone to wrinkles

or misalignment, which may lead to irregular astigmatism When pannus exists, a largeflap may cause bleeding, which must be cleared from the bed prior to ablation.

Appropriate preoperative examinations can help one identify and discourage patients

at greater risk for flap complications Preplaced surgical landmarks that straddle the flapedge will help with accurate repositioning of the flap in the operative and postoperativeperiod In addition, the newer microkeratomes and suction rings create fewer flap complica-tions

If epithelial cells under the flap progress toward the visual axis or induce stromalmelting, the flap should be lifted, the stromal bed and flap undersurface should be thor-oughly irrigated and scraped, and the flap should then be repositioned (37)

With larger flaps of 9 to 10 mm, the risk of epithelial ingrowth is greatly reduced,most likely because this avoids ablation of epithelium beyond the edge of the flap (38).Other measures one may take to prevent epithelial ingrowth include using dedicated instru-ments exclusively for interface manipulation, so that these instruments do not come incontact with the surrounding epithelium Also, one should be careful to avoid flap folds,

as these may provide a conduit for cell infiltration (13)

c Decentration

Decentration or small optical zones may lead to irregular astigmatism, causing loss ofBCVA, glare, monocular diplopia or halos, and halo effects The same principles of de-centration described above for PRK apply here For example, whether with PRK or LASIK,

a larger optical zone is more forgiving of a slight decentration More sophisticated LASIKablation profiles may also diminish the risk of decentration: a more gradual transitionzone between ablated and unablated tissue helps minimize epithelial and stromal regenera-tion, with its subsequent regression

Figure 3 Epithelial ingrowth after LASIK (A) Stable epithelial ingrowth at the LASIK interface.(B) Retroillumination used to view the same area of epithelial ingrowth (From Ref 13.)

Figure 4 Diffuse lamellar keratitis following LASIK (A) Diffuse lamellar keratitis 2 days afterLASIK (B) Diffuse lamellar keratitis, 5 days after LASIK, with central coalescence, scarring, andstromal melt (From Ref 13.)

d Diffuse Lamellar Keratitis

Although diffuse lamellar keratitis (DLK) is a recently described syndrome, not yet mented after H-LASIK, it has been reported in approximately 0.2 to 3.2% of cases ofmyopic LASIK (13,39–42) DLK is characterized by a proliferation of inflammatory cells

docu-at the LASIK interface (Fig 4) It can lead to loss of BCVA due to irregular astigmdocu-atismand may also cause stromal corneal melting with induced hyperopia or hyperopic astigma-tism

The cause of DLK is still unclear; thus, prevention remains a challenge Whenpresent, however, DLK must be treated immediately with hourly topical prednisoloneactate 1% and broad-spectrum topical antibiotic coverage It has been observed that if theDLK is not resolved by the fifth postoperative day, there is typically central coalescence

of the inflammatory cells, which may lead to central stromal melting and scarring Thus,

if inflammation progresses despite the steroid/antibiotic treatment, the flap should be lifted,scraped, and irrigated by the fourth postoperative day at the latest (13) The use of topicalintrastromal steroid during LASIK has been proposed as a way of reducing the incidenceand severity of DLK (43)

e Late Flap Dislocation

One rare, potential H-LASIK complication is traumatic flap dislocation, occasionally seenmonths or years after LASIK (44,45) One might expect a slightly greater risk of flapdislocation in H-LASIK because the flap tends to be wider than that created for myopicLASIK For this reason, it would be wise to avoid performing H-LASIK on high-riskpatients, such as boxers One should also encourage patients to wear safety glasses whenengaging in high-risk sports activities after H-LASIK

from the anterior stroma, with subsequent weakness of the cornea Denervation of the flap

or subclinical epithelial ingrowth may exacerbate this mechanical uncoupling Other tors that may predispose to corneal ectasia include excessive ablation with less than 250

fac-␮m of residual stromal bed, a thicker than normal flap with consequent ablation at a deeperthan planned level, and irregular corneal thickness (46) One can attempt to prevent cornealectasia with preoperative pachymetry maps to detect borderline cases One must alsoidentify patients with keratoconus and prevent them from undergoing H-LASIK becausethey, of course, would be at great risk for postoperative corneal ectasia

g Loss of Best Corrected Visual Acuity

Loss of BCVA is more likely to occur after H-LASIK performed on high hyperopes Choinotes that 50% of eyes with attempted corrections greater than 5 D lost two lines of BCVA.These high rates of loss of BCVA in eyes with high hyperopia may be due to inducedirregular astigmatism (27–28,30–31,35) Irregular astigmatism can result from poor cen-tration of the ablation Even small levels of decentration can cause irregular astigmatism,leading to degraded vision quality or monocular diplopia

Knorz performed a pilot study on eyes with hyperopia and hyperopic astigmatism

In eyes withⳭ5.1 D to Ⳮ10 D of hyperopia (15 eyes), 53% had lost one line at 1 month,and 20% had lost two or more lines of BCVA at 1 month For 12-month follow-up, 6eyes were available, and 50% of these had lost one line while none had lost two or morelines of BCVA No significant intraoperative or postoperative complications were noted.However, it was felt that the loss of acuity was due to image degradation by significantoptical aberrations caused by the new corneal surface Knorz concluded his study bysuggesting that LASIK should not be used for hyperopia⬎Ⳮ5 D.(28) Studies of myopicLASIK procedures have identified other causes of loss of BCVA to include flap folds,epithelial defects, lamellar keratitis, and epithelial ingrowth (30)

3 Conclusion

As we gather more experience with hyperopic PRK and LASIK, we can achieve higherrates of predictability and accuracy by creating nomograms adjusted for preoperative re-fraction, keratometry, and age Also, more sophisticated equipment can decrease complica-tion rates for both PRK and LASIK: more sophisticated ablation profiles and better eye-tracking systems can reduce decentrations For LASIK, newer, larger microkeratomes thatproduce flap diameters of at least 9.0 mm should be used

C COMPLICATIONS OF NONCONTACT LASER THERMAL

KERATOPLASTY

1 Background

Thermal keratoplasty (TK) was first performed in 1898 by the Dutch ophthalmologistLendert Jan Lans in an attempt to treat astigmatism (47) Lans demonstrated that thermalenergy, applied with a cautery, altered the structure of the corneal stromal collagen andchanged the anterior corneal curvature Unfortunately, using simple cauteries and probes,

it was difficult to control the amount of energy applied, and TK resulted in unpredictableresults and regression (48,49) Interest in TK was rekindled with the development of lasersthat could heat the cornea in a more controlled manner

Figure 5 Slit-lamp photograph of a cornea immediately after treatment with noncontact holmium:YAG laser thermal keratoplasty (From Ref 55.)

In 1990, Seiler first described laser thermal keratoplasty (LTK), which utilizes theholmium:yttrium aluminum garnet (Ho:YAG) laser to correct hyperopia (50) Ho:YAGLTK avoids damage to the corneal epithelium by delivering infrared radiation to the mid-stroma LTK changes the anterior corneal curvature because corneal collagen shrinks by

30 to 45% of its original length at temperatures of 55 to 60⬚C (51) Local, peripheralflattening causes central steepening, which corrects for hyperopia Initially, both contactand noncontact LTK were performed However, contact LTK, performed by directly appla-nating the cornea with a probe, tended to cause irregular astigmatism, regression andundercorrection; this form of LTK was withdrawn from U.S Food and Drug Administra-tion (FDA) trials (52–54)

Noncontact LTK, on the other hand, has been approved by the FDA It is traditionallyperformed by projecting one to three concentric rings of eight laser spots each onto thecornea through a slit lamp–mounted, fiberoptic delivery system (Fig 5) FDA phase IIAclinical trials with 2 years of follow-up showed the uncorrected visual acuity (UCVA)was improved by one or more lines in 19 (73%) of 26 treated eyes (55)

2 Complications

While a variety of complications may occur following LTK, the most common is regression

of effect (Table 3) Short-term complications include discomfort immediately after LTKtreatment or for 1 to 3 days post-LTK; some patients complain of mild pain (18–20%),tearing (41–43%), mild photophobia (33–41%), mild foreign-body sensation (41–54%),and other mild discomfort (29%) These side effects of laser-induced epithelial injurytypically resolve within 3 days of treatment (56,58) Corneal opacities and epithelial hazeand staining are common in the first week post-LTK treatment However, by 2 years aftertreatment, corneal opacities at the treated sites and golden-brown intraepithelial deposits(presumably iron deposits) in or adjacent to inferior treatment spots are typically the onlyevidence of change to the cornea (56) Long-term damage to the central cornea has notbeen reported as a complication

Clearly, the principal limitation of noncontact LTK is regression Reported rates ofregression vary from 27 to 45% (55–58) In one study, 70.1% had an UCVA of 20/20 at

Table 3 Complications of Noncontact LTK for Correction of Spherical, Primary Hyperopia

No of follow-up Technique corrected visualStudy Year eyes (months) used Complications acuity (BCVA)Koch (56)

1 ring of 8 spotsper ringSunriseTechnologiesdelivery system1–2 rings of 8spots per ringSunriseTechnologiesdelivery system2–3 rings of 8spots per ringSunriseTechnologiesdelivery system1–3 rings of 8spots per ringSunriseTechnologiesdelivery system

3 rings of 8 spotsper ring

• 27% had 0.5 to 1.0

D of inducedastigmatism

• 27% regression

• 29% regression inthe 1-ring group

• 31.5% had totalregression

• 45% regression

• 0.55% decenteredtreatment ring

• 0.55% with 1 D ofinduced astigmatism

• 25% complained ofhalos or ghostimages at 12-monthfollow-up

• 6% lost 2 lines

of BCVA

• 7% lost 1 line

of corrected nearvisual acuity

spectacle-• No loss ofBCVA

• No loss ofBCVA

• No loss ofBCVA

3 months, but only 50.8% maintained this level at 15 months In fact, by 15 months, only57.8% were within Ⳳ1.00 D of the intended refraction (57) In addition to regression ofeffect, astigmatism may occur as a result of noncontact LTK

3 Etiology of Regression

Some researchers feel that regression is inherent to the current technique for LTK TheHo:YAG LTK technique delivers pulses of energy to the cornea The pulses themselvesmay trigger a mixed shrinkage/relaxation pattern For example, if the energy pulses aretoo low, an insufficient amount of collagen shrinkage is achieved, and the initial refractivechange may gradually be lost On the other hand, if the laser heats the collagen fibrils to

65 to 70⬚C, collagen relaxation occurs

Regression after noncontact LTK is more common in younger patients and patientswith thicker central corneas (57) Regression may be due to the elasticity of Bowman’smembrane and stromal collagen in younger patients, which causes the cornea to return toits previous shape Similarly, thicker corneas may be more likely to resume their previousconfiguration At least in rabbit models, noncontact LTK provokes procollagen synthesis

by fibroblastic keratocytes, causing stromal remodeling which can produce irregularities

in the anterior corneal surface leading to epithelial hyperplasia This in turn, results in an

altered corneal curvature (60) While the precise wound healing response to noncontactLTK in humans is not known, it is possible that both regression and astigmatism mayresult from a similar response.

4 Prevention

Investigators are speaking optimistically about a new continuous-wave diode laser thatcan change the shape of the cornea without the peaks and troughs of the pulsed Ho:YAGlaser (61,62) The continuous-wave diode laser is expected to avoid tissue overheating,thereby improving long-term refractive stability In addition, FDA trials are under way

on a device that uses radiofrequency energy to the peripheral cornea; this may producemore controlled shrinkage of collagen lamellae (63)

5 Conclusion

One point to remember is that while regression and, less frequently, astigmatism mayresult from noncontact LTK, it is rare for patients to lose even one line of BCVA Noeyes have been reported to have lost two or more lines of BCVA from noncontact LTK(55–58) For risk-averse low hyperopes (Ⳮ0.75 to Ⳮ2.50 D), noncontact LTK is a proce-dure to consider because it causes very few BCVA-threatening complications

D COMPLICATIONS OF PHAKIC INTRAOCULAR LENSES AND

CLEAR LENS EXTRACTIONS WITH INTRAOCULAR LENS

Intraocular lenses being made today are of much better quality than those used inthe 1950s A recent study used a scanning electron microscope to analyze the surfacequality of new-generation phakic IOLs; the study showed that these lenses did not haveany defects that would contraindicate their use as phakic IOLs (66) This study examinedthe three major types of lenses currently used as phakic IOLs: anterior chamber lenses(currently used only in myopic eyes), iris-fixated anterior chamber lenses, and posteriorchamber lenses

2 Complications

Even when perfectly constructed IOLs with smooth surfaces are placed, there is still arisk of progressive corneal endothelial cell loss secondary to phakic IOLs (67–71) Other

Table 4 Complications of Phakic Intraocular Lens Implantation for Correction of Hyperopia

No of follow-up IOL corrected visualStudy Year eyes (months) Implanted Complications acuity (BCVA)Davidorf (76)

• 12.5% pupillaryblock glaucoma

• 8% IOLdecentration ofmore than 1 mm

• 12.5% underwentremoval of theirIOL

• 11% pupillary blockglaucoma, requiringsurgical iridectomyand removal of IOL

• 1.4% lensdislocationsecondary topostoperativetrauma

• 3% uveitis, cornealedema, andglaucoma

• 13% pupillary blockglaucoma

• 6.7% anterior

• No complications

• 6% anteriorsubcapsular cataract

• 3% lensreplacement wasrequired due tocalculation error

• 9% pigmentdispersion withoutIOP elevation

• 4% lost 3lines

• 22% lost 1line

• No loss ofBCVA

• 6.7% lost

2 lines

• No loss ofBCVA

• No loss ofBCVA

potential complications of IOL implantation include cataract formation, pupillary-blockglaucoma, endophthalmitis, and retinal detachments (Table 4) (72–75)

Currently the most popular phakic IOL for the treatment of hyperopia is the CollamerStaar Posterior Chamber IOL, also called the implantable contact lens (ICL) (Fig 6) Arecent phase I trial of silicone plate posterior chamber lenses, implanted in hyperopes,reported that 100% of patients had 20/40 or better UCVA, and 70% had 20/20 or betterUCVA (80)

In one study of hyperopes with phakic IOLs 1 year after implantation, opacities inthe area of lens contact with the capsule developed in two eyes (6%) Pigment dispersionoccurred in three eyes (9%), but without intraocular pressure elevation One eye (3%)required a lens replacement because of a calculation error (81) Another study reported

Figure 6 The STAAR Collamer posterior chamber phakic intraocular lens implant (From Ref.79.)

an anterior subcapsular cataract developing immediately after surgery in one eye (6.7%),causing a loss of two lines of BCVA (79)

Because hyperopic eyes tend to be shorter, they are more prone to pupillary blockafter implantation of posterior chamber lenses One study using the Staar Collamer Im-plantable Contact Lens (ICL) reported 2 of 15 eyes (13%) developing a severe pupillaryblock despite two iridotomies that had been performed 2 weeks prior to surgery Theincreased intraocular pressures due to the pupillary block necessitated removal of theimplants (79) Another study of the Staar ICL reported a 12.5% incidence of postoperativepupillary block In addition, IOL decentration of more than 1 mm occurred in 2 of the 24eyes (76)

Sight-threatening complications such as endophthalmitis have been reported to occur

in phakic IOL procedures for myopia and could theoretically occur for hyperopic phakicIOL implantation procedures as well (75) Occasionally, silicone plate phakic intraocularlenses need to be removed due to incorrect sizing of the lens and poor fixation within thesulcus (82) Retinal detachments after phakic IOL implantation have been reported in4.8% of myopic eyes (74) This complication has not yet been reported in hyperopic eyes.Iris-fixated phakic IOLs for the correction of high hyperopia can be associated withserious complications such as corneal decompensation and glaucoma (Fig 7) (78) Otherrisks include cataract formation and glaucoma (pupillary block glaucoma, pigmentaryglaucoma, narrow-angle glaucoma, and malignant glaucoma) (76) Peripheral iridotomiescan treat or prevent pupillary-block glaucoma Shallow anterior chambers should be acontraindication to performing an ICL because of the risk of narrow-angle glaucoma Lensdecentration may also occur

3 Clear Lens Extraction with IOL Implantation

Clear lens extraction (CLE) with IOL placement has been studied as a surgical correction

of hyperopia Some of the disadvantages associated with this procedure as a treatment formyopia are not as a relevant when it is considered as a hyperopic treatment For example,

Figure 7 The Fechner iris-claw intraocular lens implant (From Ref 78.)

myopes are more prone to retinal detachments (RDs) But the increased risk of an RDafter clear lens extraction surgery is less relevant in hyperopes In addition, the loss ofaccomodation that accompanies removal of the crystalline lens is a moot point in the highhyperope, who can see neither at distance nor at near without correction One problem ofCLE with IOL placement encountered with hyperopes, which is not relevant in myopes, isthe potential need to implant more than one IOL (piggyback IOLs) to correct for hyperopia.Several recent studies on clear lens extraction for hyperopia demonstrate that this

is a safe and effective procedure Kolahdouz-Isfahani performed clear lens extraction on

18 eyes Two eyes lost two lines of BCVA, but no reason for the loss of BCVA wasfound after a complete ocular examination was performed Complications included onecase of postcapsular opacification requiring one YAG capsulotomy, one case of a lensdislocation requiring an IOL exchange, and one case of malignant glaucoma (83) Anotherstudy of 35 eyes reported that no eyes lost BCVA postoperatively Additional proceduresconsisted of one IOL exchange and one PRK for overcorrection, both due to IOL miscalcu-lations Posterior capsular opacification developed in 19 eyes (54.2%), requiring 19 YAGcapsulotomies (84) One study of 20 eyes that underwent clear lens extraction and IOLimplantation reported no complications; there was no loss of BCVA and no need forfurther procedures The authors did find, however, that the procedure was less accurateand less predictable for less thanⳭ3.00 D of hyperopia (85)

Pop et al performed CLE with IOLs followed by PRK or LASIK The only CLE complication in this study was interlenticular opacification (ILO), which occurred

post-in 14 eyes that had piggyback polyacrylic lenses Of the post-initial 65 eyes post-in the study, 40eyes received two IOLs (piggyback IOLs) because the lens power needed was higher than

30 D Thus, 35% of all the piggybacks developed interlenticular opacification There were

no other reported complications from the CLE surgery (86)

Other potential risks of clear lens extraction surgery with IOL implants include therisks associated with any cataract surgery, such as hemorrhage, retinal detachment, cystoidmacular edema, and endophthalmitis Approximately 10% of high hyperopes have axiallengths of less than 21 mm, predisposing them to choroidal effusions.

4 Prevention

As with any type of surgery, many surgical complications of phakic IOL surgery or CLE/IOL surgery decrease with surgeon experience Visual complications such as halo andglare are significantly reduced with increased optic size from 5.0 to 6.0 mm

When iris-claw lenses are used, the risk of corneal decompensation can be decreased

by using adequate viscoelastic during surgery, so that the IOL does not touch the cornea;ensuring sufficient anterior chamber depth; and providing long-term monitoring of thecorneal endothelium (78)

Glaucoma is always a potential problem associated with IOL implantation in small,hyperopic eyes During clear lens extraction with IOL implantation, peripheral iridectomiesshould be performed in eyes with corneal diameters of 11.0 mm or less or axial lengths

of 20 mm or less Peripheral iridotomies should be performed prior to the implantation

of phakic IOLs

5 Conclusion

While many daunting complications may occur secondary to phakic IOL implantation orCLE/IOL implantation, there are certainly many advantages to treatment of hyperopiawith either of these techniques First, IOL implantation is the only refractive procedurethat can correct higher degrees of hyperopia Second, it uses skills that physicians whoperform cataract surgery have honed and polished Finally, it does not require expensiveequipment, such as lasers Hopefully, more long-term data will be available in the future

to help decrease the rate of potential complications associated with phakic IOL surgery

E COMPLICATIONS OF INTRACORNEAL SEGMENTS AND LENSES

1 Background

Intacs, the intrastromal corneal ring segment (ICRS), consists of two 160-degree methyl methacrylate (PMMA) segments placed in two pockets of the peripheral stroma(Fig 8) The procedure is unique in that it retains the potential to be adjusted or reversed

poly-Figure 8 The Intrastromal corneal ring (From Ref 91.)

In April 1999, the FDA approved Intacs for myopic correction ofⳮ1.00 to ⳮ3.00

D withⳭ1.00 D or less of astigmatism Intacs can also be used to create central cornealsteepening to correct for hyperopia Studies are currently investigating the use of smalllinear segments placed in the peripheral cornea to create shortening of the peripheral length

of the corneal arc, with subsequent central corneal steepening By altering the thickness

of the insert, one can titrate the refractive effect

Although there have been no published studies on Intacs for hyperopia, clinical trialsare currently under way in Germany and Spain These trials have produced promisingpreliminary results: study噛1 enrolled 19 patients, and at 1 year 95% (18 of 19) achieved

an UCVA of 20/40 or better Of note, an induced astigmatism of 1.00 D or greater wasseen in 32% (6 of 19) of the cases Eleven patients were enrolled in study 噛2, with 6months of follow-up Ten of the 11 eyes (91%) were 20/40 or better, and 4 eyes (36%)experienced an induced astigmatism of 1.00 D or more Finally, study 噛3 enrolled 9patients with 6 months follow up All patients had an UCVA of 20/40 or better; only 1patient had an induced astigmatism equal to or greater than 1.00 D (87)

2 Complications

Published studies of Intacs today are for the correction of myopia However, the tions of Intacs would be similar whether the segments were placed for the correction ofmyopia or for hyperopia In the FDA phase II and III studies, the incidence of adverseevents was 2% of the 452 eyes enrolled Complications of the ICRS procedure includeaccidental perforation into the anterior chamber (2 eyes), surface perforation of the epithe-lium anteriorly (3 eyes), significant decentration of the rings requiring removal or reposi-tioning (5 eyes), and infectious keratitis (1 eye) All eyes in the group of patients withcomplications returned to preoperative BCVA by their 6-month follow-up appointment(88)

complica-Schanzlin reported no serious complications in the 125 eyes that received ICRS inhis study Minor postoperative problems included one case of transient conjunctivitis,three cases of filamentary keratitis, and one case of transient iritis One patient, whoseincision had gone into a region of superior pannus, developed deep stromal blood vessels

At 12 months follow-up, four patients had a two-line loss of BCVA, from 20/12.5 to 20/

20 All four of these patients had a substantial improvement in their UCVA (89).Postoperative astigmatism is clearly a significant potential problem, with 20 of 102patients in one group experiencing post-ICR astigmatism of 1.0 D or more at 3 monthsfollow-up Various theories exist as to the cause of the astigmatism; it may be related tosuture tightness (90) Induced astigmatism may also result from postoperative movement

of the intracorneal ring segments Finally, Intacs-induced astigmatism can result fromirregular stromal and epithelial thickening between the Intacs rings (91)

Reports describe one patient with persistent focal edema due to a small Descemet’stear from a lamellar dissection that was too deep Although the edema necessitated ICRremoval, the patient’s BCVA was 20/20 at exit from the study One of 102 patients incurred

an intraoperative perforation of Descemet’s membrane, requiring an ICRS explantation(90) Channel deposits associated with Intacs are occasionally seen but are not associatedwith impaired visual acuity (88,89)

3 Prevention

One can attempt to prevent postimplant complications through meticulous attention topositioning, proper incision depth and pocketing, and sterile technique In addition, proper

attention to wound architecture along with adequate closure and tissue approximation withsuturing can minimize the frequency of wound-related complications such as wound gapeand epithelial cysts One can prevent corneal neovascularization status post-ICRS by avoid-ing incisions that make contact with pannus or a limbal blood vessel and by warningagainst eye rubbing so as to prevent wound dehiscence.

4 Conclusion

Intacs may prove to be a valuable tool for the correction of hyperopia Advantages overprocedures such as LASIK and PRK include the fact that the Intacs insert is placed in theperipheral cornea and the central cornea is never violated during the surgical procedure

In addition, the Intacs devices can easily be removed if necessary Finally, the refractiveeffect can be adjusted by replacement of any of the implanted radial segments The compli-cation of induced astigmatism may become less of an issue as more Intacs devices areimplanted: the cause of induced astigmatism may become better understood and thus betterprevented In addition, surgical technique will be improved as more of these surgeries areperformed

F CONCLUSION

Clearly, since hyperopic refractive surgery is entirely elective, the surgeon must have athorough understanding of any potential complications of each type of procedure Therisk/benefit balance is tipping in favor of H-PRK, H-LASIK, or noncontact LTK for low

to moderate hyperopes and toward intraocular lens implantation with or without clear lensextraction for moderate to high hyperopes The use of ICRS for hyperopia may be usefulfor low to moderate hyperopes; however, long-term results of current studies have yet to

be reported

Thorough preoperative evaluations and preventive techniques such as those scribed above can help to avoid complications However, even with the most preparedsurgeon and in the best of hands, complications may occur Thus, it is essential to providepatients with a clear understanding of the potential risks of a procedure before proceeding

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