WHAT’S NEW IN REFRACTIVE SURGERY?
From What’s New in Anterior Segment Disorders, presented by the Ocular Immunology and Uveitis Foundation at
the Massachusetts Eye Research and Surgery Institute
| INTACS FOR KERATOCONUS —Jonathan H. Talamo, MD, Associate Clinical Professor of Ophthalmology, Harvard
Medical School, Cambridge, MA
|
| Intacs inserts: approved in 1999 to treat low spherical myopia; also decrease asymmetric and irregular astigmatism associated
with early keratoconus (off-label use); semicircular implants with 150° arc made of polymethyl methacrylate
(PMMA), available in various thicknesses; current practice for keratoconus is implantation of single segment in weakest
area; goal to improve contact lens fit and tolerance (warn patients not to expect perfect vision); best candidates people
with keratoconus who cannot tolerate contact lenses; improved spectacle tolerance possible in selected cases; may
help avoid penetrating keratoplasty
|
 | Surgical techniques: prolate system—early technique; employs mechanical suction and trephination to make tunnels in
cornea and insert implants; femtosecond yttrium-aluminum-garnet (YAG) laser—newer technique; can vary depth
and width of tunnels to allow snugger fit and possibly improve effect; associated with less epithelial trauma
|
| Patient 1: 34-yr-old man intolerant of rigid gas-permeable lens; met criteria for Intacs (clear corneas; best spectacle-corrected
visual acuity >20/40, and adequate corneal thickness at incision site); implants exerted selective flattening effect
on cornea; also promoted central migration of corneal apex; outcome—decreased refractive astigmatism, better visual
acuity with glasses and better contact lens fit; after 2 yr, patient had 20/15 vision with soft toric lens
|
| Patient 2: 54-yr-old man with stable moderate keratoconus, anisometropia, and anisoiconia; severe astigmatism in operative
eye (other eye also astigmatic); selective flattening effect caused decrease from 5.5 (at start) to 3.0 diopters (D) of
refractive astigmatism; spectacle-corrected visual acuity improved; corneal cone shrank and apex centered
|
| Patient 3: 40-yr-old woman rejected for laser surgery; wore soft contact lenses; spectacle-corrected vision approached 20/
20, but disliked glasses; significant against-the-rule astigmatism and topographic features consistent with mild keratoconus;
good outcome with asymmetric implants
|
| Summary of speaker’s data on 26 eyes: 35% of patients experienced significantly improved spectacle-corrected vision
(Snellen chart improvement >2 lines); most striking finding improved contact lens tolerance (seen in ≈90% of patients);
however, patients need vigilant follow-up
|
| CONDUCTIVE KERATOPLASTY: AN UPDATE —Helen K. Wu, MD, Director of Refractive Surgery, New England
Eye Center, and Assistant Professor of Ophthalmology, Tufts University School of Medicine, Boston, MA
|
| Background: conductive keratoplasty (CK) option for people 40 to 58 yr of age with presbyopia (plano to +1 range);
current options include spectacles, contact lenses, and laser vision correction (may exacerbate dry eye [concomitant problem];
stereo acuity issues also of concern in monovision); accommodating intraocular lenses (IOL) another choice, but
involves invasive surgery
|
| Conductive keratoplasty: requires monovision tolerance; advantages—proven benefit; no worsening of dry eye
symptoms; excellent safety profile, and no loss of corneal tissue; attractive to patients who fear laser
|
| Approved indications: temporary induction of myopia (1-2 D) in nondominant eye of patients >40 yr of age with presbyopic
hyperopia or emmetropia, or spherical hyperopia up to ≈3 D
|
| Potential off-label use: enhancement of visual outcomes from laser or pseudophakic procedures; correction of astigmatism;
neutral or light-pressure CK; keratoconus (adjunctive to Intacs and collagen cross-linking)
|
| Mechanism of CK: applies radiofrequency energy (350 kHz) to corneal stroma with 450 x 90 µm contact probe for 0.6
sec; temperature and duration optimal for collagen shrinkage; produces 4 corneal zones (apex, periapical steep zone, treatment
belt zone, and peripheral flat zone); increases central power of cornea in more prolate shape, with slightly less increase
of power in the central 1 mm; creates multifocal, modified prolate surface with no change at 5- to 6-mm ring (CK
not performed within this zone); in ≈80% of patients, design of modified prolate surface utilizes pupil and corneal shape
to reduce distance vision 2 lines on average (20/20 to 20/30), but with corresponding gain in near vision of 7 to 9 lines (20/
200 to 20/25); compared to monovision, improvement in near acuity disproportionate to myopia induced; generally produces
less anisometropia than comparable monovision systems, with no loss of contrast sensitivity and no subjective loss
of depth perception reported
|
| Technique (conventional): heat created by corneal impedance to radiofrequency energy (probe cool); heat begins at posterior
aspect of cornea, then travels up surface and back to unit through lid speculum (≈3 min process); after topical anesthesia
instilled, insert lid speculum; mark eye, apply treatment, confirm application (1 additional spot if necessary),
and remove speculum
|
| Light touch technique: probe tip seated with sufficient pressure to indent cornea, but cornea then permitted to relax and
resume normal curvature (or indent by ≈1 mm) before applying energy; permits greater aplanation of cornea, larger
leukomas, greater effect, and fewer spots; preliminary results indicate good stability
|
| What to tell patients: in study by Food and Drug Administration (FDA), ≈85% of patients achieved 20/20 binocular vision
at distance, J3 at near; procedure safe (only side effect induced astigmatism), with “reasonable” effect stability
|
| Ideal candidate: >45 yr of age with significant presbyopic symptoms; healthy spherical corneas and no visually significant
cataracts; no previous corneal incisional surgery; reasonable expectations; able to tolerate monovision and accept
functional end point
|
| Contraindications: decentered apex; peripheral astigmatism; decentered pupil; keratoconus (unless specifically treating);
autoimmune or collagen vascular disease; visually significant cataracts
|
| Effect stability: loss of 0.02-0.03 D/mo after first yr (procedure sometimes criticized for “wearing off”); underlying
presbyopia also worsens; seen with all laser procedures for hyperopia
|
| Indications for use after photorefractive keratectomy (PRK) or laser in situ keratomileusis
(LASIK): consecutive hyperopia or induced or residual astigmatism; dry eyes; thin or irregular flap; borderline stromal bed
thickness; ectasia; epithelial ingrowth
|
| NEW IOL TECHNOLOGY —James P. Gills, Jr, MD, Founder and Director, St. Luke’s Cataract and Laser Institute; Clinical
Professor of Ophthalmology, University of South Florida, Tampa
|
| Patient considerations: lifestyle, hobbies, expectations; comorbidities (eg, diabetes); refractive status; astigmatism
(axial length may determine IOL selection)
|
| Dr. Gills’ protocol for IOL selection: STAAR Collamer 1-piece—first choice for most patients (3-piece for sulcus);
good biocompatibility; predictable outcomes; excellent optical quality; STAAR Implantable Collamer Lens
(ICL)—produces good results in patients with large pseudophakic refractive errors; Technis—complements positive
spherical corneal aberration, but causes serious glare in post-hyperopic LASIK patients; blue-blocking lenses
(Acrysof monofocal)—easy to insert; excellent centration; questionable in patients with macular degeneration
|
| Multifocal lenses (Crystalens): much patient dissatisfaction and require close follow-up; best candidate is high hyperope
with significant cataract; insertion may be time-consuming; capsularhexis must be 5.5 mm and perfectly round; posterior
capsulotomy may result in hyperopic shift
|
| Presbyopic IOLs: mix of ReZoom and ReStor works well; require a lot of office “chair time” (staff must be specially
trained); speaker considers “not worth the money”
|
| Astigmatism management: acrylic toric (Acrysof) lenses—cost prohibitive; lens of future; STAAR ICL—first
choice for now; good results and satisfied patients; risk for retinal detachment low (good choice for high myopia); best
candidates relatively young and still accommodating; if performing clear lens extraction and replacement (CLEAR), minimize
risk for retinal detachment by maintaining eye pressure during surgery; STAAR toric ICL—awaiting FDA approval;
until then, can combine STAAR ICL with LASIK or limbic-relaxing incision to manage residual astigmatism
|
| Single-lumen phacoemulsification sleeve: lumen goes posteriorly; prevents iris from bubbling up and causing turbulence;
speaker uses for patients taking tamsulosin (Flomax) or those with small pupils; also good for people with
Fuchs’dystrophy
|
| THE PROS AND CONS OF BETADINE —Dr. Gills
|
| Background on povidone iodine (PVP; Betadine): in wide use since World War II; proven effective at reducing
endophthalmitis; works faster and lasts longer than most antibiotics, without bacterial resistance; however, highly
acidic (pH 3.4); unbuffered solution can damage endothelium and corneal epithelium; may dry eyes permanently or
temporarily; also associated with superficial punctate keratitis; patients frequently complain of foreign body sensation
after cataract surgery; unbuffered Betadine tantamount to “assault and battery on the cornea and conjunctiva”; neutralization
associated with dramatic decrease in cases of tear deficiency syndrome (TDS); otherwise, Betadine-associated
TDS can take months to clear
|
| Solution strength: dilution of 0.5% to 5%, with pH slightly >7 recommended; Centers for Disease Control and Prevention
has shown solutions as dilute as 1:1000 retain efficacy; neutralize before and after surgery
|
| ADVANCES IN SURFACE ABLATION —Dr. Wu
|
| Disadvantages of surface ablation: postoperative pain; prolonged visual recovery; possible prolonged need for topical
corticosteroids; potential for delayed-onset corneal haze; eyes usually done sequentially
|
| Advantages: no flap, so no risk for LASIK flap complications; greatly reduced risk for keratectasia; results equal to those
of LASIK in low and moderate myopia; no flap-induced higher-order aberrations, with results potentially superior to
LASIK after wavefront-guided ablation
|
| Current practice patterns: LASIK still preferred, but popularity of surface ablation growing; concerns remain over
potential for postoperative discomfort and haze
|
| Modern surface ablation: epithelium removed with alcohol, laser scrape, brush, or mechanical epikeratome; cornea
cooled with balanced saline solution to avoid thermal damage; newer-generation lasers minimize risk for thermal damage
and have smoother ablation profiles; bandage contact lenses, oral and topical nonsteroidal agents, and topical dilute anesthetic
drops improve patient comfort
|
| Epithelial removal: blades and spatulas work well at scraping cornea, as does rotating brush; epitome or alcohol removes
epithelium in 1 sheet; laser also removes epithelium; in study of human eye-bank eyes, brushed eyes had better
uncorrected vision and less haze, compared to those undergoing blunt scraping
|
| Alcohol-assisted laser epithelial keratomileusis (LASEK): excises at level of hemidesmosomal attachments, including superficial
lamina lucida; results in fragmentation of basal epithelial cells, discontinuity in basement membrane, and dose- and
time-dependent death of cultured corneal epithelial cells; studies comparing LASEK to PRK vary in their findings (sometimes
LASEK associated with more pain and longer time to bandage lens removal, sometimes associated with less); alternatives
to traditional LASEK include “butterfly” LASEK (epithelial flaps created to preserve connection to limbal stem
cells), lifting epithelium with gel, or replacing alcohol with sodium chloride to minimize epithelial cell damage
|
| Epi-LASIK: employs plastic-edged separator, theoretically to preserve lamina densa and lamina lucida; preserves more
normal hemidesmosomal morphology; associated with less trauma to basal epithelial cells (no alcohol-induced damage);
tears from eyes treated with LASEK contain more transforming growth factor (TGF)-ß than eyes treated with
epi-LASIK; in at least one study, epi-LASIK eyes also had less haze
|
| Post-PRK haze: generated by activated keratocytes that produce proteoglycans, collagen, and hyaluronic acid; more common
and severe in patients with higher degrees of ametropia, especially if ablations deep or high; usually peaks at 1 to
3 mo postsurgery, but may appear as long as 17 to 18 mo after surgery; reticular and subepithelial; associated with UV
light exposure; possible genetic predisposition in dark-skinned people; associated with prolonged re-epithelialization;
smoother stromal bed seems to decrease incidence; corneal chilling decreases haze, pain, and myopic regression
|
| Vitamin C: may help protect from effects of UV light; major antioxidant in tears; after transepithelial PRK or LASIK,
level of ascorbic acid in tears drops; in retrospective study, 1 g vitamin C for 1 wk before and 3 wk after treatment
shown to decrease haze up to 6 mo
|
| Mitomycin C: prophylactic use after PRK inhibits haze formation in humans and animals (possibly through inhibition of
keratocyte proliferation in anterior stroma); optimal dose unknown; most commonly used dose 0.1 to 0.2 mg/mL for 12
sec to 2 min
|
| Managing postoperative discomfort: choices include topical nonsteroidal anti-inflammatory drops; dilute anesthetic
drops (0.05% tetracaine); oral nonsteroidal anti-inflammatory drugs (NSAIDs; eg, celecoxib [Celebrex]) taken just before
and after procedure; oral narcotic agents; oral corticosteroids; or gabapentin (Neurontin) 300 mg 3 times daily
|
Educational Objectives
| The goal of this program is to review new developments in refractive surgery. After hearing and assimilating this program,
the listener will be able to:
|
| 1. List the advantages and disadvantages of Intacs inserts.
|
| 2. State the indications and optimal candidates for conductive keratoplasty.
|
| 3. Discuss the pros and cons of some widely used intraocular lenses.
|
| 4. Explain why it is important to buffer povidone iodine for refractive surgery.
|
| 5. Describe ways of minimizing haze and pain after surface ablation.
|
Discussed on this Program
Celecoxib [Celebrex]
Gabapentin [Neurontin]
Meperidine HCl [Demerol]
Meperidine HCl and promethazine HCl
Mitomycin (mitomycin-C; MTC) [Mutamycin]
Oxycodone and acetaminophen [Percocet, others]
Promethazine HCl [Phenadoz, Phenergan]
Rofecoxib [Vioxx] (withdrawn from market 09/30/04)
Tamsulosin HCl [Flomax]
Tetracaine HCl [Pontocaine, Pontocaine HCl, Cepacol Viractin]
Suggested Reading
Ambrosio R Jr, Wilson S: LASIK vs LASEK vs PRK: advantages and indications. Semin Ophthalmol 18:2,
2003; Bartels MC et al: Toric phakic intraocular lens for the correction of hyperopia and astigmatism. J Cataract
Refract Surg 32:243, 2006; Camellin M: Laser epithelial keratomileusis for myopia. J Refract Surg 19:666, 2003;
Chiam PJ et al: ReSTOR intraocular lens implantation in cataract surgery: quality of vision. J Cataract Refract
Surg 32:1459, 2006; Claramonte PJ et al: Conductive keratoplasty to correct residual hyperopia after cataract surgery.
J Cataract Refract Surg 32:1445, 2006; Ertan A et al: Intacs insertion with the femtosecond laser for the
management of keratoconus. One-year results. J Cataract Refract Surg 32:2039, 2006; Lackner B et al: Long-term
results of implantation of phakic posterior chamber intraocular lenses. J Cataract Refract Surg 30:2269, 2004; Lai
WW et al: Prevention of endophthalmitis. J Cataract Refract Surg 31:1683, 2005; Leccisotti A: Laser-assisted
subepithelial keratectomy (LASEK) without alcohol versus photorefractive keratectomy (PRK). Eur J Ophthalmol
13:676, 2003; McDonald MB: Conductive keratoplasty: a radiofrequency-based technique for the correction of hyperopia.
Trans Am Ophthalmol Soc 103:512, 2005; Rabinowitz YS: INTACs for keratoconus. Int Ophthal Clin
46:91, 2006; Stahl JE: Conductive keratoplasty for presbyopia: 1-year results. J Refract Surg 22:137, 2006.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant financial
relationship with the manufacturer or provider of any commercial product or service discussed. The following
has been disclosed: Dr. Talamo has received honoraria from Refractec and Alcon, and is a member of the Alcon
Speakers’ Bureau.
This program was recorded at What’s New in Anterior Segment Disorders, held October 21, 2006, in Cambridge,
MA, presented by the Ocular Immunology and Uveitis Foundation and sponsored by the Massachusetts Eye Research
and Surgery Institute. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the
production of this program.
|
