CATARACT AND REFRACTIVE SURGERY UPDATE
| TOXIC ANTERIOR SEGMENT SYNDROME (TASS)—Lawrence Weisbrod, MD, Clinical Instructor, Department of
Ophthalmology and Visual Sciences, University of Toronto, Faculty of Medicine, Toronto, ON
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| TASS vs infectious endophthalmitis: shared features—pain; decreased, hazy vision; corneal edema, fibrinous uveitis
or hypopyon; distinguishing features—TASS occurs within first 24 hr after surgery (infectious endophthalmitis takes
3-5 days to present); with corneal endothelial destruction from TASS, limbus-to-limbus edema (with infectious endophthalmitis,
possibly less edema, but amount variable); vitreous usually clear in patient with TASS (consider B-scan ultrasonography
[US]), and cultures negative
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Causes of TASS
| Injection into or around eye during cataract surgery: effect of ointment bases injected into anterior chamber
(AC) of rabbit eyes (study)—at volumes ≥0.1 mL, large inflammatory effect; number of eyes lost to corneal edema and
glaucoma; ointment used at conclusion of surgery can enter AC
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| Water implicated in 2 ways: 1) outbreak of TASS linked to softened city water that supplied autoclave system generator;
2) inadvertent injection of water instead of balanced salt solution (BSS) into AC can lead to corneal destruction; autoclave
steam generator should be supplied with deionized ultrafiltered water; never have sterile water in syringe on surgical
table
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| Antibiotic agents: concern about use of intracameral antibiotics and antibiotics in irrigating solutions; potential retinal
or macular toxicity and emergence of resistant organisms; prophylaxis of postoperative endophthalmitis (European Society
of Cataract and Refractive Surgeons)—intracameral cefuroxime after cataract surgery decreased incidence of postoperative
infectious endophthalmitis from 3.5 cases per 1000 to <1 per 1000 (findings in other studies mixed); in most
studies, intracameral cephalosporins safe and nontoxic to endothelium (however, TASS may result from improper administration
of antibiotics due to concentration error, preservatives, or other components in mixture)
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| Detergents used to wash instruments: during aspiration of viscoelastic or ophthalmic viscosurgical device (OVD),
some residue may get trapped in lumen of instrument; when instrument washed, OVD residue may combine with active
detergent or enzymes before autoclaving; with next use, contaminant injected into eye causing inflammation (problem reported
by Kim et al); avoid reusable cannulas, and flush reusable instruments with sterile deionized water through irrigation
and aspiration ports; enzymes not deactivated until steam autoclave reaches 284°F (most sterilizers do not reach this
temperature)
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| More risks related to sterilization: water baths, ultrasonographic (US) baths, and autoclave reservoirs can harbor
gram-negative organisms despite sterilization if water not changed regularly; cell membrane has heat-stable endotoxin,
which can remain enzymatically active; oxidized metal deposits from plasma gas sterilization can also cause toxic inflammation;
limit use of reusable equipment and discard old instrumentation; change water baths and reservoirs frequently to
flush out endotoxins; limit enzymatic detergents
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| Preservatives: benzalkonium chloride (BAC)—common ophthalmic preservative in topical medications; toxic to corneal
endothelium if injected into eye; epinephrine—1 part per 1000 concentration used in irrigating solution; usually
preserved with sodium bisulfite; dilute with irrigating solution (eg, Endosol or BSS; usually not toxic to cornea); avoid
BSS with preservative; other topical medications used intraoperatively—mix with BSS (not water); most ocular structures
tolerate pH 6.5 to 8.5
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Management of TASS
| Prevention: mainstay intervention; communicate with entire surgical team about what is appropriate for use in eye; limit
use of reusable instruments; instruct staff on proper cleaning of irrigation/aspiration (I/A) machine and phacoemulsification
handpieces; limit enzymatic detergents; use sterile deionized ultrafiltered water; if possible, use preservative-free
medications; do not mix intracameral medications with sterile water (use BSS)
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| Treatment: once infection ruled out, topical corticosteroids mainstay of treatment; intraocular pressure (IOP)-lowering
drugs may be indicated; if persistent corneal edema develops, corneal transplantation may be necessary (for intractable
glaucoma, trabeculectomy, or tube shunt)
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| LASIK VS PHAKIC INTRAOCULAR LENSES —Donald M. Miller, MD, Assistant Professor of Surgery (Ophthalmology),
Dartmouth Medical School, Hanover, NH
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| Advantages of laser-assisted in situ keratomileusis (LASIK): low-to-moderate myopia—nearly 90% of patients
achieve 20/20 vision (nearly 100% 20/40); high myopia—correction up to 13 diopters (D), 70% to 80% 20/20
(nearly 100% 20/40; no loss of best-corrected visual acuity [BCVA])
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| Disadvantages of LASIK: problems with higher corrections—poor quality of vision due to glare and haloes; concerns
about biomechanic stability of cornea (some patients experience post-LASIK ectasia); other LASIK risks—infection; inflammation;
flat buttonholes or striae; epithelial ingrowth; basic issues—quality of vision in high ametropias (high prescriptions);
safety (especially if adequate pachymetry not performed or early signs of biomechanic instability present)
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| Verisyse phakic IOL (Allergan Medical Optics [AMO]): iris-fixated polymethylmethacrylate (PMMA) lens
with 5- or 6-mm optic; vaults slightly into AC and attaches to iris; approved by Food and Drug Administration (FDA) in
2004; outside United States, counterpart Artisan lens (>100,000 implanted worldwide); family of lenses (myopic, hyperopic,
toric, and flexible); indications—myopia to 20 D with <2.5 D cylinder (cyl); exclusions—anterior segment pathology
that lens might exacerbate (eg, glaucoma, cataract, cornea problems, inflammation, iritis); pupil too large or
abnormally centered; shallow AC or low endothelial cell count
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| Visian ICL (implantable collamer lens) phakic IOL (STAAR Surgical): sulcus-supported lens; FDA approved
1 yr ago; correction of myopia ≤15 D with ≤2.5 D astigmatism in patients ≤45 yr of age; collamer has attractive
optic and biocompatibility characteristics (lens thin and flexible); newer version vaults slightly farther forward (previous
version tended to rest on lens capsule, causing cataracts); contraindications—similar to Verisyse lens; preexisting corneal
problems, glaucoma, narrow AC, uveitis, or cataract
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| FDA comparison of Verisyse and Visian lenses
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 | Quality of vision: results remarkably similar; BCVA—50% of patients had improvement with implantation of either lens;
uncorrected visual acuity (UCVA)—for Verisyse lens, 84% of patients achieved 20/40 vision or better (up to 20 D);
with Visian lens, 85% 20/40 or better; in most patients, no loss in quality of vision overall
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| Adverse events: ≈3% to 4% of patients needed surgical reintervention for problems created by lens (eg, dislocation of lens);
additional 3% to 4% needed surgery to correct unacceptable refractive result; no corneal edema, yet FDA recommends
ongoing monitoring of corneal endothelium; ongoing endothelial cell loss worrisome finding in both studies (with Visian
lens, current findings predict ≈50% cell loss by 25 years)
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| LASIK vs phakic IOLs (summary): both treatments preserve accommodation (important for younger patients); LASIK
able to treat myopia, hyperopia, and astigmatism (limited by optic and biomechanic considerations); phakic intraocular lenses
able to treat myopia and astigmatism (even high prescriptions); LASIK modifiable using wavefront technology (not yet for
phakic IOLs); LASIK alters corneal asphericity (preserved with phakic lenses); risk in LASIK, damage to cornea (risk with
phakic lenses, damage to anterior segment); with phakic lenses, long-term concerns corneal damage and endothelial cell loss
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| SURFACE ABLATION vs LASIK —Jonathan H. Talamo, MD, Associate Clinical Professor of Ophthalmology, Harvard
Medical School, Boston, MA
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| LASIK most popular refractive procedure available: rapid and relatively painless visual recovery; easy adjustability
with enhancement surgery; and wide acceptance by patients and surgeons
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| Limitations of LASIK: flap problems; abnormal corneal topography; overly thin stromal bed may be too weak to last
long term; bulk of cornea’s biomechanic strength in anterior 140 µm; if only 80 µm removed, flap thin enough to avoid
epithelium in Bowman’s layer; theoretic loss of corneal strength only ≈14%
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| New LASIK technology: femtosecond lasers have improved safety and precision of creating corneal flaps; more predictably
thin flaps possible with IntraLase than with popular microkeratomes; standard deviation with IntraLase ≈50%
(comparable to Moria microkeratomes), and range of flap thickness tighter
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| Reasons for resurgence of surface ablation: 1) increased concern over keratoectasia after LASIK, and role of flap
and residual stromal bed thickness; 2) custom ablations deeper than in past; may have to go 25% or 30% deeper to
achieve desired refractive effect; prophylactic use of antimetabolites helpful; 3) results with surface ablation improving
due to development of low-energy scanning flying-spot systems; 4) improved pain management
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| Problems with surface ablation: visual recovery slower than with LASIK and discomfort greater; occasional cases
of haze and loss of vision
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| Solutions: in speaker’s experience, all 3 procedures similar in utility short and long term
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| 1) Intraoperative use of single-dose mitomycin C in low concentrations: excellent short-to-midterm (ie, 6 mo to 3 yr)
safety in PRK; UCVA and BCVA results for higher corrections improved over PRK alone; optimal dosing regimen—
controversial; trend toward lesser concentrations for shorter times (speaker uses 0.02% for 15 sec prophylactically);
indications—useful prophylactically and after development of haze
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| 2) Laser epithelial keratomileusis (LASEK): alcohol used when removing sheet of epithelium, which is then replaced
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| 3) Epithelial (Epi)-LASIK: microkeratome with dull blade used to remove sheet of epithelium, which is then discarded
or replaced
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| Can surface ablation compete with LASIK? meta-analysis comparing PRK to LASIK—higher incidence of 20/20
vision and better refractive predictability with LASIK at 1 yr; visual recovery slower with surface ablation; prospective fellow-eye
study—patients took >1 wk but <1 mo to regain equal driving vision in both eyes; when patients asked which eye
better, 3 mo before equivalence; for high and low contrast visual acuity, persistent difference between surface ablation and
LASIK at 3 mo
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| CORRECTION OF IOL SURPRISES —Bonnie An Henderson, MD, Assistant Clinical Professor of Ophthalmology, Harvard
Medical School, Boston, MA
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| Etiologies of IOL surprise: case 1 (hyperopic surprise)—preoperatively, patient failed to report that he had had laser
surgery for myopia in 1991 (enrolled in FDA trials for PRK); therefore, keratometric (K)-readings wrong; case 2—
pterygium in cornea; postoperatively, patient remained hyperopic with much cyl; when axial length rechecked by immersion
biometry, extra error contributed to hyperopia and astigmatism; case 3—postoperatively, patient reported wearing
contact lenses during preoperative evaluation; surgical team factors—incorrect measurements; in study of resident surgeries,
30% of errors human error (eg, transposing data between left and right eye); incorrect IOL; patient factors—
previous corneal surgery or disease (eg, pterygia); retinal disease (eg, large staphyloma); very short or long eyes
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Surgical Options
| Keratorefractive surgery: pros—not intraocular surgery; results fairly accurate and reliable; quick recovery; cons—
physician must offer refractive service or have arrangement with refractive surgeon; in older patient, hyperopic treatment
more likely to regress; cons (risks of combined surgery)—same as those for refractive surgery alone; patient population
different from typical 25-yr-old myope having LASIK (problem of prior surgeries); consider health of cornea and endothelium;
in this population, more glaucoma suspects; risk not clear if open-angle glaucoma well controlled; issue whether
IOP 80 mm Hg will cause permanent damage if nerve fiber layer already compromised; most physicians feel procedure
safe; previous retinal holes or detachments additional risks
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| Pros: most cataract surgeons comfortable with intraocular surgery; early in postoperative period, IOL easy to remove (especially
within first month, regardless of lens type); lens power determination easy if original printout at hand;
caveat—acrylic lenses (eg, AcrySof ReSTOR IOL [Alcon]) do not need to be cut for removal
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| Cons: risks of additional intraocular surgery (eg, capsule tear); IOL may be difficult to remove in late postoperative
period
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| Reasons for IOL exchange: Jin et al 2006—22 eyes; incorrect K-readings (most common occurrence, followed by axial
length measurement and wrong IOL); in 91%, same type of lens used (same A-constant); Kora et al 2007—34 eyes;
largest errors axial length determination and wrong IOL; recommendations—use same lens type and consider Sanders-Retzlaff-Kraff
(SRK) formula II or SRK/T formula for IOL exchange
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| Pros: IOL not removed; refraction known; technically easier than IOL exchange for most surgeons
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| Cons: risks of additional intraocular surgery; 2 acrylic IOLs not ideal because of risk for late sequelae
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| Late sequelae: greatest risk interlenticular opacification (ILO); fibrosis between lenses can cause hyperopic shift; pigmentary
dispersion, glaucoma, and pupillary block; Werner et al 2006—in rabbit eyes, more ILO with acrylic lenses
(with silicone lenses, less or none)
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| Recommendations: use different materials (silicone and acrylic) or silicone/silicone (not acrylic/acrylic); do not use square-
edged lens in sulcus (can cause iris chafing and increased pigment dispersion); speaker positions haptics at 90° vis-à-vis
each other; polish capsule to decrease risk for fibrosis
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Suggested Reading
Abad JC et al: A prospective evaluation of alcohol-assisted versus mechanical epithelial removal before photorefractive
keratectomy. Ophthalmology 104:1566, 1997; Hellinger WC et al: Outbreak of toxic anterior segment syndrome following
cataract surgery associated with impurities in autoclave steam moisture. Infect Control Hosp Epidemiol 27:294,
2006; Ament CS, Henderson BA: Instructions after routine phacoemulsification cataract surgery with clear corneal
incision. J Cataract Refract Surg 33:352, 2007; Claramonte PJ et al: Conductive keratoplasty to correct residual hyperopia
after cataract surgery. J Cataract Refract Surg 32:1445, 2006; Grosser S: Association of TASS with ointment in
the anterior chamber following cataract surgery. J Cataract Refract Surg 32:1979, 2006; Habot-Wilner Z et al: Refractive
results with secondary piggyback implantation to correct pseudophakic refractive errors. J Cataract Refract Surg
31:2101, 2005; Hawker MJ et al: Refractive expectations of patients having cataract surgery. J Cataract Refract Surg
31:1970, 2005; Jehan FS et al: Postoperative sterile endophthalmitis (TASS) associated with the memorylens. J Cataract
Refract Surg 26:1773, 2000; Jin GJ et al: Analysis of intraocular lens power calculation for eyes with previous myopic
LASIK. J Refract Surg 22:387, 2006; Kim JK et al: Laser in situ keratomileusis versus laser-assisted subepithelial
keratectomy for the correction of high myopia. J Cataract Refract Surg 30:1405, 2004; Kora Y et al: Intraocular lens
power calculation for lens exchange. J Cataract Refract Surg 27:543, 2007; Lovisolo CF, Reinstein DZ: Phakic intraocular
lenses. Surv Ophthalmol 50:549, 2005; Mamalis N: Anatomy of a TASS outbreak. J Cataract Refract Surg
33:357, 2006; Qazi MA et al: Development of late-onset subepithelial corneal haze after laser-assisted subepithelial
keratectomy with prophylactic intraoperative mitomycin-C case. Case report and literature review. J Cataract Refract Surg
32:1573, 2006; Tahzib NG et al: Functional outcome and patient satisfaction after Artisan phakic intraocular lens implantation
for the correction of myopia. Am J Ophthalmol 142:31, 2006; Talamo JH et al: Reproducibility of flap thickness
with IntraLase FS and Moria LSK-1 and M2 microkeratomes. J Refract Surg 22:556, 2006; Werner L et al:
Interlenticular opacification: dual-optic versus piggyback intraocular lenses. J Cataract Refract Surg 32:655, 2006.
Resources
tassfacts.com
doctor-hill.com
Educational Objectives
| The goal of this program is to improve—through knowledge and utilization of recent advances—cataract and refractive
surgery. After hearing and assimilating this program, the clinician will be better able to:
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| 1. Manage and prevent toxic anterior segment syndrome (TASS).
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| 2. Compare the benefits and risks of laser-assisted in situ keratomileusis (LASIK) to implantation of phakic intraocular
lenses (IOLs).
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| 3. Recognize advantages and disadvantages of surface ablation in comparison to LASIK.
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| 4. Identify causes of poor refractive outcomes after IOL implantation.
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| 5. Correct poor refractive outcomes after IOL implantation.
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Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty members to disclose relevant
financial relationships within the past 12 months that might create any personal conflicts of interest. Any identified
conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business
or commercial interest. For this program, the following has been disclosed: Dr. Talamo has been a consultant to IntraLase
Corporation.
Acknowledgements
Dr Weisbrod was recorded at Update in Medicine and Ophthalmology, presented December 8-9, 2006, in Toronto, ON,
by the University of Toronto, Faculty of Medicine, Departments of Ophthalmology and Vision Sciences, and Continuing
Education; Drs. Miller, Talamo, and Henderson were recorded at New Options for Treatment of Refractive Error
, presented December 8, 2006, in Boston, MA, by the New England Ophthalmologic Society. The Audio-Digest
Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.
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