Cataract and Refractive Surgery - part 7 pptx

108 Complications of Excimer Laser Surgery tients enjoy their improved uncorrected visual acuity, even a slight decrease in visual acuity is unacceptable.. However, the prophy-lactic use

104 Complications of Excimer Laser Surgery

blows nitrogen gas during ablation has decreased

the occurrence of central islands

Central islands are usually characterized by

undercorrection accompanied by monocular

diplopia With topography, the central elevated

area is clear These symptoms often disappear in

3 to 6 months Several attempts have been made

to treat symptomatic central islands [9, 21] The topography-linked or wavefront-guided laser ab-lation is a helpful tool

Fig 8.2 Retinal images Top: wavefront analysis The

higher order aberration is 1.14 μm Bottom: the

reti-nal image evaluated by wavefront areti-nalysis (pupil size,

3 mm) The blurred image left improved after surgery (right)

Fig 8.3 Orbscan (irregular astigmatism) Top:

kera-tometric map shows irregular astigmatism The visual

acuity is 0.7 (1.5 × sphere: –0.5 D; cylinder: –2.0 D;

axis: 153°) The patient complained of monocular

dip-lopia during the day and at night Bottom: after

wave-front-guided laser ablation, the uncorrected visual acuity improved to 1.5

8.3 Intraoperative Complications 105

106 Complications of Excimer Laser Surgery

8.3.4 Undercorrection

Undercorrection is the result of incorrect preop-erative evaluation of refraction, excessive mois-ture in the stromal bed, decentration, and prob-lems with laser calibration If the preoperative refraction is unstable, the refraction should be

Fig 8.4 Retinal images Top: wavefront analysis The

higher order aberration is 0.66 μm Bottom: the

reti-nal image evaluated by wavefront areti-nalysis (pupil size,

3 mm) The blurred image (left) improved after surgery

(right)

repeated after an interval and the ablation

post-poned If the patient uses hard contact lenses, the

refraction should be done at least 2 weeks after

the patient stops wearing them Because the

re-fraction is the key to achieving successful results,

the examination should be repeated until the

sur-geon is comfortable with the status of the

refrac-tion Some patients require more than 2 months

to obtain a stable refraction after wearing contact

lenses If the cycloplegic refraction differs

sub-stantially from the non-cycloplegic refraction,

the refraction should be repeated using both

val-ues at another visit Using uncertain refractive

results will cause unnecessary complications

Excessive moisture in the stromal bed can

re-sult in undercorrection This often happens when

the surgeon is inexperienced Undercorrection

also can result if the patient’s fixation is poor and

the laser is not ideally applied The laser

calibra-tion is also important The laser operator should

be aware of the condition of the laser The laser

should be recalibrated with each use

Enhancement usually results in good

refrac-tive outcomes The timing of the enhancement

surgery depends on the cause of the

undercor-rection If the refraction is stable, retreatment

can be done at any time To avoid repeating the

problems that arose in the initial surgery, the

cause should be well considered In addition,

the postoperative corneal thickness should be

confirmed If the total corneal thickness is less

than 400 μm, further laser ablation should be

avoided to prevent corneal ectasia The patient’s

age also should be considered If the patient is

over 40 years, monovision may be an option

A surgeon can perform unilateral enhancement

and see both far and near visual function Some

patients enjoy unplanned monovision

8.3.5 Overcorrection

The causes of overcorrection are similar to those

of undercorrection: the accuracy of the

refrac-tion, the condition of the stromal bed, and the

laser calibration Dryness of the stromal bed

usu-ally causes overcorrection If the surgeon delays

starting the laser ablation, the cornea becomes

dry and the effect of the laser is intensified

Tran-sient overcorrection after PRK is a well-known

phenomenon Although this problem has de-creased with the latest generations of excimer lasers, the changes in the refraction should be observed over time

Patient age also plays an important role Younger patients can tolerate overcorrection; however, older patients are very sensitive to over-correction Unfortunately, the risk factors for overcorrection are age and attempted correction The higher these factors are, the more frequently patients encounter this complication

If overcorrection occurs after PRK, the admin-istration of steroid eye drops should be stopped Some physicians also recommend stopping the use of artificial tears Regarding hyperopic cor-rection, transient overcorrection is the goal be-cause subsequent regression is common Patients should be well informed about this before sur-gery

The treatment of overcorrection after the treatment of myopia is mandatory Recently, the use of diclophenac eye drops with contact lenses produced good results If the correction meets the desired target, the eye drops should be stopped immediately If this does not change the results, excimer laser with hyperopic correction

or holmium laser thermoplasty is frequently per-formed

Summary for the Clinician

■ Preoperative examination of the refrac-tion and calibrarefrac-tion of the laser are fun-damental to achieving the best visual outcomes

■ Corneal topography should be per-formed even if the patient achieved good visual outcome to confirm the ideal laser ablation

■ Wavefront-guided ablation is a helpful tool in patients with decentered ablation

or irregular astigmatism

8.4 Postoperative Complications

Even though patients achieve good outcomes, some complications can develop later Since

pa-8.4 Postoperative Complications 107

108 Complications of Excimer Laser Surgery

tients enjoy their improved uncorrected visual

acuity, even a slight decrease in visual acuity is

unacceptable However, the cause of decreased

uncorrected visual acuity should be well

evalu-ated and the treatment planned

8.4.1 Regression

Regression is a common problem for any laser

surgery including LASIK If regression occurs,

retreatment is considered Regression

accompa-nied by corneal haze requires a different

treat-ment approach, such as the application of steroid

eye drops, PRK, or phototherapeutic

keratec-tomy (PTK) Recently, the use of beta-blocker

eye drops to decrease the intraocular pressure

has achieved good results The effect of

improv-ing the vision in these cases is still under

dis-cussion Why beta-blocker eye drops work and

Latanoprost eye drops do not is a question for

future research This approach does not work

in every case; however, it is worth trying

beta-blocker eye drops The interval since the time of

laser surgery, patient gender and age, and the

pre-operative refraction are not correlated with the

amount of improvement If this does not produce

a satisfactory result, retreatment is planned after

confirming that the refraction is stable

Gener-ally, enhancements should be planned at least

3 months after the previous surgery If the

cor-rection exceeds 6 D, waiting more than 6 months

may be necessary to achieve a stable refraction

8.4.2 Corneal Haze

Corneal haze is a well-known complication after

PRK Histopathologic and confocal microscopic

studies revealed that haze is induced by

activa-tion and proliferaactiva-tion of corneal keratocytes [3]

The haze usually appears 1–3 months after

sur-gery and gradually resolves within 1 year With

slit-lamp microscopy, subepithelial haze can be

observed in the central area and classified from

grades 0 to 4 [16] Recently, objective scoring

was introduced using digital images and

con-focal microscopy [2, 6, 10] The incidence of

haze was higher with previous laser treatment

[30]; however, the incidence decreased with re-cent technological advances that produced a smoother ablation The risk factors are greater tissue ablation such as in the treatment of high myopia, ultraviolet exposure, atopic dermatitis, and autoimmune conditions [8, 12, 24] Despite the appearance of haze, most cases achieve good visual acuity If the haze becomes substantial, the best-corrected visual acuity decreases with some regression (Fig 8.5) Problems may develop with night vision and decreased contrast sensitivity [13, 18] Most surgeons use steroid eye drops immediately or shortly after laser treatment and gradually taper the drops Although the effects of corticosteroid eye drops used clinically have been positively or negatively reported, theoretical ben-efits have been described in experimental stud-ies Special attention should be paid to the side effects of corticosteroids, especially increased intraocular pressure

Recently, the effects of chilled irrigation solu-tion and mitomycin C were reported Mitomy-cin C is used for glaucoma filtering surgery and pterygium surgery and has been introduced into laser surgery [17, 28, 34] The concentration of mitomycin C and the duration of its application have been discussed; 0.01 mg/ml is the mini-mum concentration reported to be effective and 0.4 mg/ml is the maximum to avoid complica-tions [4] The 0.02% concentration is widely used After laser application, a 6-mm diameter

Fig 8.5 Corneal haze The best corrected visual acuity

decreases

sponge is soaked in 0.02% mitomycin C diluted

with balanced saline solution (BSS) and applied

over the ablated cornea for 2–3 min The eye

then is washed with BSS Complications such as

thinning of the scleral tissue and delayed

epithe-lialization were reported in cases of

glaucoma-fil-trating surgery and pterygium An experimental

study showed dose-dependent corneal edema

and endothelial apoptosis However, the

prophy-lactic use of 0.02% mitomycin C in laser surgery

seems to be safe and effective at preventing haze

[33] and achieved better visual acuity [7]

Mito-mycin C is also used to treat haze [20, 29] in the

same technique used during PRK, or the drug

can be administered as an eye drop Use of

vita-min C and amniotic membranes also have been

reported; however, the effects need to be studied

further [33, 36]

8.4.3 Delayed Epithelialization

Following PRK, LASEK, and Epi-LASIK,

ban-dage contact lenses are applied After 3 days,

most eyes achieve re-epithelialization and the

contact lenses can be removed The preservative

in the eye drops sometimes delays the recovery of

the epithelium The use of eye drops without

pre-servatives is preferable If the eye developed

epi-thelial problems due to the toxicity of eye drops,

the drops should be discontinued

8.4.4 Infections

Infections after refractive surgery are rare, but

can be the most severe complications after any

ophthalmic surgery Regarding laser surgery,

corneal opacity remains even though the

infec-tion was treated with antibiotics The common

cause is staphylococcus and mycobacteria; the

prophylactic application of antibiotics is

recom-mended [15]

An epithelial defect is the optimal site for

the development of a bacterial infection If the

process of re-epithelialization is prolonged,

spe-cial steps should be taken to avoid infections In

LASIK cases, the focus of the infection is under

the flap and the risk of perforation increases

Cultures should be performed to confirm the bacteria in severe cases; however, topical antibi-otics should be started immediately Lifting the flap and irrigation are necessary in certain cases After treatment, PTK can be performed if the opacity remains on the corneal surface Penetrat-ing or lamellar keratoplasty is needed in patients with poor visual acuity Infection usually results

in poor corrected visual acuity

8.4.5 Adverse Effects

on the Corneal Endothelium

Experimental and clinical studies have shown

no side effects from refractive procedures on the corneal endothelium [3, 11] One study reported that the number of endothelial cells decreased af-ter a tranquilizer was adminisaf-tered to the patient before PRK [25]

8.4.6 Corneal Ectasia

After LASIK was introduced, a new complica-tion, keratectasia, was reported [5, 26, 31] in which continuous regression with irregular astigmatism develops The risk factors are form fruste keratoconus, thin cornea with high myo-pia, and pellucid marginal degeneration Preop-erative evaluation with corneal topography and pachymetry are necessary The postoperative corneal condition should be assessed to maintain

a corneal thickness greater than 400 μm or a re-sidual stromal bed greater than 250–300 μm En-hancements performed without measuring the corneal thickness can cause ectasia

Orbscan can be performed to diagnose kera-tectasia The posterior float map shows obvious thinning If this complication occurs, hard con-tact lenses are fitted If the vision cannot be cor-rected with contact lenses, ICR or cross-linking may be performed, followed if not successful by corneal transplantation If the surgeon does not recognize the corneal thinning and continues to treat with the excimer laser to improve the vi-sion, the cornea may be perforated

8.4 Postoperative Complications 109

110 Complications of Excimer Laser Surgery

Summary for the Clinician

■ Some postoperative complications are

well treated with eye drops

■ Regarding postoperative complications

concerning the refractive error,

en-hancement should be considered when

the refraction is confirmed to be stable

■ Before enhancement, the corneal

thick-ness and shape should be considered

■ Some postoperative complications are

related to the failure of the indication

References

1 Alkara N, Genth U, Seiler T Diametral

abla-tion—a technique to manage decentered

photore-fractive keratectomy for myopia J Refract Surg

1999;15:436–440.

2 Allerman N, Charmon W, Silverman RG, et al

High-frequency ultrasound quantitative analysis

of corneal scarring following excimer laser

kera-tectomy Arch Ophthalmol 1993;111:968–973.

3 Amm M, Wertzel W, Winter M, et al

Histopatho-logical comparison of photorefractive

keratec-tomy and laser in situ keratomileusis in rabbits J

Refract Surg 1996;12:758–766.

4 Ando H, Ido T, Kawai Y, et al Inhibition

of corneal wound healing Ophthalmology

1992;99:1809–1814.

5 Argento C, Cosentino MJ, Tytium A, et al

Cor-neal ectasia after laser in-situ keratomileusis J

Cataract Refract Surg 2001;27:1440–1448.

6 Braustein RE, Jain S, McCally RL, et al

Objec-tive measurement of corneal light scattering

af-ter excimer laser keratectomy Ophthalmology

1996;103:439–443.

7 Carons F, Vigo L, Scadola E, Vacchini L Evaluation

of the prophylactic use of mitomycin C to inhibit

haze formation after photorefractive keratectomy

J Cataract Refract Surg 2002;28:2088–2095.

8 Carson CA, Taylor HR Excimer laser treatment

for high and extreme myopia Arch Ophthalmol

1995; 113:431–436.

9 Castill A, Romero F, Martin-Valverde JA, et al

Management and treatment of steep islands after

excimer laser photorefractive keratectomy J

Re-fract Surg 1996;12:15–20.

10 Chew SJ, Beuerman RW, Kaufman HE, et al In vivo confocal microscopy of corneal wound heal-ing after excimer laser photorefractive keratec-tomy CLAO J 1995;25:273–280.

11 Colin J, Cochener B, Le Floch G Corneal en-dothelium after PRK and LASIK J Refract Surg 1996;12:674.

12 Corbett MC, O’Brart DPS, Warburton FG, Mar-shall J Biological and environmental risk factors for regression after photorefractive keratectomy Ophthalmology 1996;103:1381–1391.

13 Corbett MC, Prydol JI, Verma S, et al An in vivo investigation of the structures responsible for cor-neal haze after photorefractive keratectomy and their effect on visual function Ophthalmology 1996;103:1366–1380.

14 Doanne JG, Cavanaugh TB, Durrie DS, Hassa-nein KH Relation of visual symptoms to topo-graphic ablation zone decentration after excimer laser photorefractive keratectomy Ophthalmol-ogy 1995;102:42–47.

15 Donnefeld ED, O’Brien TP, Solomon R, et al Infectious keratitis after photorefractive keratec-tomy Ophthalmology 2003;110:740–747.

16 Fantes FE, Hanna KD, Waring GO III, et al Wound healing after excimer laser keratomileusis (photorefractive keratectomy) in monkeys Arch Ophthalmol 1990;108:665–675.

17 Gambato C, Ghirlando A, Moretto E, et al Mito-mycin C modulation of corneal wound healing af-ter photorefractive keratectomy in highly myopic eyes Ophthalmology 2005;112:208–218.

18 Hersh PS, Stulting RD, Steinert RF, et al The Summit PRK Study Group Results of phase III excimer laser photorefractive keratectomy for myopia Ophthalmology 1997;104:1535–1553.

19 Krueger R, Saedy NF, McDonnell PJ Clinical analysis of steep central islands after excimer laser photorefractive keratectomy Arch Ophthalmol 1996;114:377–381.

20 Majmudar PA, Forstot SL, Dennis RF, et al Topi-cal mitomycin C for subepithelial fibrosis af-ter refractive corneal surgery Ophthalmology 2000;107:89–94.

21 Manch EE, Maloney RK, Smith RJ Treatment of topographic central islands following refractive surgery J Cataract Refract Surg 1998;24:464–470.

22 Mulhern MC, Foley-Nolan A, O’Keefe M, et al

Topographical analysis of ablation centration

after excimer laser photorefractive keratectomy

and laser in situ keratomileusis for high myopia J

Cataract Refract Surg 1997;23:488–494.

23 Nagy ZZ, Hiscott P, Seitz B, et al

Ultraviolet-B enhances corneal stromal response to

193-nm excimer laser treatment Ophthalmology

1997;104:375–380.

24 Nakaya-Onishi M, Kiritoshi A, Hasegawa T, et al

Corneal endothelial cell loss after excimer laser

keratectomy, associated with tranquillizers Arch

Ophthalmol 1996;114:1282–1283.

25 Pallikaris IG, Kymionis GD, Astyrakakis NR

Cor-neal ectasia induced by laser in-situ

keratomileu-sis J Cataract Refract Surg 2001;27:1796–1802.

26 Pande M, Hillman JS Optical zone centration

in keratorefractive surgery; entrance pupil

cen-ter, visual axis, coaxially sighted corneal reflex

Or geometric corneal center? Ophthalmology

1993;100:1230–1237.

27 Porges Y, Ben-Haim O, Hirsh A, et al

Photothera-peutic keratectomy with mitomycin C for corneal

haze following photorefractive keratectomy for

myopia J Refract Surg 2003;19:40–43.

28 Raviv T, Majmudar PA, Dennis RF, et al

Mitomy-cin-C for post-PRK corneal haze J Cataract

Re-fract Surg 2000;26:1105–1106.

29 Seiler T, Holschbach A, Derse M, et al Com-plications of myopic photorefractive keratec-tomy with the excimer laser Ophthalmology 1994;101:153–160.

30 Seiler T, Koufala K, Richter G Iatrogenic keratec-tasia after laser in-situ keratomileusis J Refract Surg 1998;14:312–317.

31 Stojanovic A, Ringvoid A, Nitter T Ascorbate prophylaxis for corneal haze after photorefractive keratectomy J Refract Surg 2003;19:338–343.

32 Suzuki T, Bissen-Miyajima H, Nakamura T, et al Use of mitomycin C for enhancement following photorefractive keratectomy (in Japanese) Jpn J Clin Ophthalmol 2004;58:461–464.

33 Talamo JH, Collamudi S, Green WR, et al Modu-lation of corneal wound healing after excimer la-ser keratomileusis using topical mitomycin C and steroids Arch Ophthalmol 1991;109:1141–146.

34 Tamayo GE, Serrano MG Computerized topo-graphic ablation using the VisX CAP method In: MacRae SM, Krueger RR, Applegate RA, eds Customized corneal ablation Thorofare, NJ: SLACK, 2001.

35 Tsai Y, Lin JM Ablation centration after active eye-tracker-assisted photorefractive keratectomy and laser in situ keratomileusis J Cataract Refract Surg 2000;26:28–34.

36 Wang MX, Gray TB, Park WC, et al Reduction

in corneal haze and apoptosis by amniotic mem-brane matrix in excimer laser photoablation in rabbits J Cataract Refract Surg 2001;27:310–319.

References 111

Core Messages

■ Refractive lens exchange in myopic eyes

carries a significant risk of postoperative

retinal detachment

■ Particular risk factors are:

■ Higher myopia;

■ Younger age, (less then 50 years);

■ Surgical complications (capsule

rup-ture and vitreous loss);

■ Neodymium:YAG capsulotomy

re-lation to rhegmatogenous retinal

detachment after refractive lens

ex-change is controversial and

indeter-minate

9.1 Introduction

About 60 years ago the concept of intraocular lens

implantation was pioneered About 30 years ago,

small incision lens extraction by

phacoemulsifi-cation was realized Both pioneering efforts have

subsequently led to perfecting the respective

pro-cesses Thus, refractive surgery, the correction

of ametropia through lens-based surgery was

initiated The era of corneal laser surgery

com-mencing about 25 years ago focused public and

professional attention on the wider opportunity

for permanent refractive correction and thereby

created in practice the sub-specialty of refractive

surgery Lens-based refractive surgery was

side-tracked for a time as the surgical process matured

until it was able to offer ophthalmic surgeons

with that interest more security and scope for

in-tervention Initially, surgical techniques evolved

more rapidly than lens implant technology The

crystalline lens, whether cataractous or ‘clear,’

could be removed by sub-2.5-mm incisions

However, intraocular lens implants (IOLs), made

of PMMA before the foldable materials were ap-proved, required a 5- to 6-mm incision, not the ideal basis for a refractive surgical procedure Gradually, though, lens implants became more refined and eventually developed spectacularly

in form, effect, and enhanced small incision ca-pability, an essential component of the refractive surgical process Today, modern lens extraction and implant replacement is a safe, predictable, and stable process in general; however, nothing is absolute in this sense All surgeons are aware that

no surgical intervention is absolutely risk-free

As we age, the crystalline lens is the ever-chang-ing element in the eye Its replacement (the lens implant) provides a permanent result in the op-tical sense, leaving the cornea for enhancement

of effect if necessary As with all surgical proce-dures there are risk factors to be weighed against the benefits Refractive surgery in general is about risk management One issue that requires in-depth exploration is retinal complications of refractive surgery This applies in particular to refractive lens exchange (RLE) and especially its application in myopic eyes, which are more vul-nerable in the retinal sense than hyperopic eyes

9.2 RLE: Need to Know

A refractive surgeon needs to know the risks inherent in an RLE procedure, risks for hyper-metropic eyes, and those for myopic eyes The surgeon needs to know the risk odds so that the patient can be reliably informed what they are getting into In the case of myopic eyes, evidence suggests that the degree of myopia or size of the globe is one type of risk that could be graded Age

is another as is surgical complications A study of the literature enables the risks to be quantified,

Refractive Lens Exchange:

Risk Management

Emanuel Rosen

Chapter 9

9

114 Refractive Lens Exchange: Risk Management

despite the significant variations in study profiles

(Tables 9.1, 9.2)

The literature is an aid to learning about the

risk of RLE as well as the outcomes from

cata-ract and lens implant surgery in myopic eyes It

is necessary to define risk factors as well as the

outcome for myopic and hyperopic eyes that

have suffered pseudophakic retinal detachments

Surgical complications are fortunately very rare

in eyes undergoing RLE in experienced surgical

hands However, what are the risks and potential

outcomes if complications do occur?

9.3 Cystoid Macular Edema

There are other retinal risks of RLE apart from

rhegmatogenous retinal detachment (RRD), but

they are of less importance in incidence and

ef-fect Cystoid macular edema, which if

unre-solved will lead to permanent visual impairment

through cystoid macular changes, is fortunately

rare following uncomplicated surgery It tends

to be transient, causing short-term visual

distur-bances Invariably, it will resolve with

appropri-ate anti-inflammatory medication for it is

medi-ated by the post-surgical inflammatory cascade

and temporary loss of the blood–retinal barrier

The incidence and causes of clinical and

angio-graphic cystoid macular edema (CME) after

un-complicated phacoemulsification and

intraocu-lar lens implantation in otherwise normal eyes

were investigated by Mentes et al [31] Clinical

and fluorescein angiographic macular edema

was evaluated 45 days postoperatively in a study

comprising 252 eyes following uncomplicated phacoemulsification with in-the-bag acrylic IOL implantation Clinical CME was not detected

in any eye at any postoperative visit, but angio-graphic macular edema was detected in 9.1% of eyes The visual outcome did not differ between eyes with no clinical edema and those with fun-dus fluorescein angiography-detected edema Treatment of clinically evident and visually dis-abling CME after RLE is by topical application

of steroidal and non-steroidal anti-inflammatory agents coupled with low-dose acetazolamide Only in circumstances where there is a poor re-sponse to topical therapy should systemic high-dose, short course steroid therapy be contem-plated Other aids include sub-Tenon’s steroid or

as a last resort intraocular steroids though this is

a remote requirement

9.4 Risk Management and Rhegmatogenous Retinal Detachment

A meta-analysis of papers concerning the inci-dence of retinal detachment after lens extraction and IOL implantation for 12 years between 1994 and 2005 reveals that these studies are not uni-form in their protocols (Table 9.1) and most were retrospective reviews There were many variables that have to be evaluated in an attempt to isolate the identifiable risk factors for RRD [1–3, 5–7, 9–12, 14, 16, 18–20, 22, 23, 25, 26, 28–30, 32, 36,

39, 40, 43–45, 48, 50, 52–54]

Factors not apparent from this study, but hinted at in some papers, are the consistently influential factor of age of the patient Younger patients, i.e., less than 50 years old, have a dis-proportionately higher risk of RRD according to the general cataract studies of Polkingshorne and Craig [38], e.g less than 50 years related to an in-cidence of 5.1% RRD (which is a more relevant rate for RLE comparisons) whereas over 70 years the rate was less than 0.7% [8] One hundred and forty-one patients presented between May 1997 and April 1998 with an RRD, i.e., an annual inci-dence of 1.18 cases per 10,000 people (0.0118%),

5 of whom presented with bilateral RRD and the mean age at presentation was 53.9 years RRD was more common in males than in females with

a ratio of 1.3:1 Ocular trauma, high myopia, and

Table 9.1 Meta analysis publications on refractive lens

exchange (RLE) and myopic cataract surgery (1994–

2005): variables

Variables include:

Eye axial length

Number of eyes studies

Follow up duration and range

Neodymium:YAG capsulotomy rates

Pre-operative retinal prophylaxis

Patient age range

Operative complications